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  1. Aerobic and Anaerobic Gram-positive Cocci

    General
    Clinical significances of extracellular pathogens in genera Enterococcus, Peptococcus, Peptostreptococcus, Staphylococcus and Streptococcus are presented.
  2. Aerobic and Anaerobic Gram-positive Cocci

    Aerobic Genera:
    Enterococcus, Staphylococcus, Streptococcus
  3. Aerobic and Anaerobic Gram-positive Cocci

    Anaerobic Genera:
    Peptococcus, Peptostreptococcus
  4. Aerobic and Anaerobic Gram-positive Cocci

    Genus Enterococcus
    • -Enterococcus species are enteric flora.
    • -Enterococci are isolated from opportunistic infections with a suppurative exudate and/or abscess formation. From these infections, enterococci can be isolated in pure or mixed culture with other facultative anaerobes and/or obligate anaerobes.
    • -Enterococcus species cause urinary tract infections and vegetative endocarditis.
  5. Aerobic and Anaerobic Gram-positive Cocci

    Genus Staphylococcus
    • -Staphylococcus species are flora of external surfaces of the body.
    • -There coagulase-positive species (S. aureus subspecies aureus, S. hyicus subspecies hyicus and S. pseudintermedius) are pathogens and cause a variety of disease conditions. They are commonly isolated from opportunistic infections with a suppurative exudate and/or abscess formation. From these infections, staphylococci can be isolated in pure or mixed culture with other facultative anaerobes and/or obligate anaerobes.
    • -There are over 25 coagulase-negative species. They are considered to be nonpathogens.
  6. Aerobic and Anaerobic Gram-positive Cocci

    Genus Streptococcus
    • -Streptococcus species are flora of external surfaces of the body.
    • -Hemolytic streptococci are generally pathogens and nonhemolytic streptococci are generally nonpathogens.
    • -Selected Streptococcus species are host-adapted and cause specific disease conditions. They are commonly isolated from opportunistic infections with a suppurative exudate and/or abscess formation. From these infections, streptococci are isolated in pure or mixed culture with other facultative anaerobes and/or obligate anaerobes.
  7. Aerobic and Anaerobic Gram-positive Cocci

    Genera Peptococcus and Peptostreptococcus
    • -Peptococcus and Peptostreptococcus species are normal enteric flora and have a low virulence.
    • -They are isolated from opportunistic infections with a suppurative exudate and/or abscess formation. From these infections, peptococci and peptostreptococci are isolated in mixed culture 28 with facultative anaerobes and/or obligate anaerobes.
    • -These bacteria are rarely identified to species level.
  8. Aerobic and Anaerobic Gram-positive Cocci

    Cellular Characteristics
    • -Enterococcus, Peptococcus, Peptostreptococcus, Staphylococcus and Streptococcus species are gram-positive cocci. These cocci are 1 micrometer in diameter.
    • -Staphylococcus species are arranged in grapelike clusters.
    • -Streptococcus species are arranged in chains.
    • -Streptococcus pneumoniae is arranged in pairs.
    • -Enterococcus, Peptococcus and Peptostreptococcus species seldom have a distinctive cellular arrangement.
  9. Aerobic and Anaerobic Gram-positive Cocci

    Cultural Characteristics
    • -Enterococcus, Staphylococcus and Streptococcus species are facultative anaerobes and can be cultured on blood agar under aerobic conditions at 37C.
    • -Peptococcus and Peptostreptococcus species are obligate anaerobes and can be cultured on brain heart infusion blood agar under anaerobic conditions at 37C.
  10. Aerobic and Anaerobic Gram-positive Cocci

    Biochemical Characteristics
    • -Enterococcus species are catalase-negative and saccharolytic.
    • -Staphylococcus species are catalase-positive and saccharolytic.
    • -Streptococcus species are catalase-negative and saccharolytic.
  11. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    General
    Coagulase reactions of Staphylococcus species are correlated with their ability to cause clinical infections. Coagulase-positive staphylococci are pathogens and coagulase-negative staphylococci are nonpathogens.
  12. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Pathogenic Coagulase-positive Staphylococcus Species
    • -S. aureus subspecies aureus causes opportunistic infections in humans and domestic animals.
    • -S. hyicus subspecies hyicus causes porcine exudative epidermitis.
    • -S. pseudintermedius causes canine pyoderma.
  13. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Nonpathogenic Coagulase-negative Staphylococcus Species
    There are over 25 coagulase-negative Staphylococcus species. They are not considered to be pathogens of humans or domestic animals.
  14. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Virulence Factors of Pathogenic Staphylococcus Species
    • -Coagulase-positive staphylococci have carbohydrate capsules, which are antiphagocytic.
    • -Techoic acids have antiphagocytic activity.
    • -Coagulase-positive staphylococci produce alpha, beta, delta and epsilon toxins. These toxins cause the hemolysis of erythrocytes and are produced by a strain in various combinations. Alpha and delta toxins have leukocidal activity.
    • -Selected S. aureus subspecies aureus and S. hyicus subspecies hyicus strains produce exfoliative toxin.
  15. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Bacteriophage Typing
    • -Strains of staphylococci differ in their susceptibility to various lytic bacteriophages and can be distinguished by their patterns of susceptibility.
    • -Bacteriophage typing is used for epidemiological studies of disease producing strains of S. aureus subspecies aureus with multiple antimicrobial resistance patterns. Several hundred phage types have been described.
  16. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Habitat and Ecology
    • -Staphylococci are flora of the skin and other external surfaces of the body.
    • -Humans and animals have a limited resistance to superficial colonization by the staphylococci, 29 but they have a high degree of resistance to deep invasion and progressive disease.
  17. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Cellular Characteristics
    Staphylococcus species are gram-positive cocci and are arranged in grapelike clusters.
  18. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Cultural Characteristics
    • -Staphylococcus species are facultative anaerobes and can be cultured on blood agar under aerobic conditions at 37C. Colonies are medium-sized, convex and opaque with a white or yellow color.
    • -Most pathogenic staphylococci produce complete or double-zone hemolysis.
    • -The nonpathogenic staphylococci are nonhemolytic.
  19. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Biochemical Characteristics
    Staphylococcus species are catalase-positive and saccharolytic.
  20. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Disease Overview
    Human and Domestic Animal Infections
    • -In humans and animals, coagulase-positive staphylococci cause suppurative infections of the body surfaces, respiratory and urinary tracts or mammary gland. Abscesses are common sequelae. Predisposing factors that reduce the innate resistance of the host are often present when disease occurs.
    • -From humans and animals, S. aureus subspecies aureus is commonly isolated. S. hyicus subspecies hyicus and S. pseudintermedius are occasionally isolated.
  21. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Disease Overview
    Human Foodborne Intoxifications
    Enterotoxin producing strains of S. aureus subspecies aureus are the most common cause of human foodborne intoxifications.
  22. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Disease Overview
    Human Skin Infections
    Exfoliative toxin producing strains of S. aureus subspecies aureus cause severe human skin infections.
  23. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Disease Overview
    Bovine Mastitis
    In dairy cows, S. aureus subspecies aureus is a common cause of mastitis. Infection of udder occurs via the teat canal with organisms derived from skin of the teat and udder.
  24. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Disease Overview
    Canine Pyoderma
    S. pseudintermedius is isolated from approximately 90% of canine pyodermas and S. aureus subspecies aureus is isolated from most of the remaining 10%.
  25. Aerobic and Anaerobic Gram-positive Cocci
    Genus Staphylococcus

    Disease Overview
    Porcine Exudative Epidermitis
    S. hyicus subspecies hyicus causes exudative epidermitis.
  26. Aerobic and Anaerobic Gram-positive Cocci
    Human Staphylococcal Foodborne Intoxification

    General
    Enterotoxin toxin producing strains of Staphylococcus aureus subspecies aureus are the most common cause of foodborne intoxifications.
  27. Aerobic and Anaerobic Gram-positive Cocci
    Human Staphylococcal Foodborne Intoxification

    Etiology
    • -Staphylococcal foodborne intoxifications are caused by enterotoxin-producing strains of S. aureus subspecies aureus, which is an aerobic gram-positive coccus.
    • -Six enterotoxins (A, B, C, D, E and G) are plasmid-mediated and have identical modes of action. They are heat-stable at 100C for 30 minutes.
    • -Only selected strains of S. aureus subspecies aureus possess a plasmid that encodes for an enterotoxin. A strain generally produces only one enterotoxin.
  28. Aerobic and Anaerobic Gram-positive Cocci
    Human Staphylococcal Foodborne Intoxification

    Transmission
    Staphylococcal foodborne intoxifications result from ingestion of the preformed enterotoxin.
  29. Aerobic and Anaerobic Gram-positive Cocci
    Human Staphylococcal Foodborne Intoxification

    Clinical Features
    Outbreaks occur when contaminated food is held at inappropriate temperatures such as room 30 temperature long enough to allow an enterotoxin producing strain to proliferate and produce enterotoxin. After ingestion of contaminated food, the incubation is generally less than 4 hours with an abrupt onset of clinical signs that include diarrhea and vomiting. The symptoms persist for 12 to 24 hours.
  30. Aerobic and Anaerobic Gram-positive Cocci
    Human Staphylococcal Foodborne Intoxification

    Pathogenesis
    Enterotoxins are chemically and immunologically related and act as super antigens.
  31. Aerobic and Anaerobic Gram-positive Cocci
    Human Staphylococcal Foodborne Intoxification

    Pathology
    The diarrhea is watery and no blood is observed.
  32. Aerobic and Anaerobic Gram-positive Cocci
    Human Staphylococcal Foodborne Intoxification

    Diagnosis
    • -S. aureus subspecies aureus can be cultured from contaminated food and the isolate must be tested for the production of an enterotoxin. Commercial test kits are available to identify these enterotoxins.
    • -Contaminated food can be tested for the presence of enterotoxin.
  33. Aerobic and Anaerobic Gram-positive Cocci
    Canine Staphylococcal Pyoderma

    General
    Staphylococcus aureus subspecies aureus and S. pseudintermedius are the most commonly isolated pathogens from pyodermas.
  34. Aerobic and Anaerobic Gram-positive Cocci
    Canine Staphylococcal Pyoderma

    Etiology
    S. aureus subspecies aureus and S. pseudintermedius are aerobic gram-positive cocci and are arranged in grapelike clusters.
  35. Aerobic and Anaerobic Gram-positive Cocci
    Canine Staphylococcal Pyoderma

    Transmission
    • -Staphylococci are normal skin flora, and most pyodermas are caused by endogenous skin flora.
    • -Some pyodermas are contracted via direct skin contact with dogs that have clinical pyodermas.
    • -A few pyodermas are acquired from dogs that are asymptomatic carriers of S. aureus subspecies aureus and/or S. pseudintermedius.
  36. Aerobic and Anaerobic Gram-positive Cocci
    Canine Staphylococcal Pyoderma

    Clinical Features
    • -Dogs exhibit little resistance to superficial colonization of the skin by staphylococci, but dogs exhibit a high degree of resistance to deep invasion and progressive disease. Intact skin tends to be resistant to bacterial invasion.
    • -Skin abrasions and other factors that adversely affect the integrity of the skin are commonly incriminated as predisposing factors. Skin lesions are characterized by a suppurative exudate.
  37. Aerobic and Anaerobic Gram-positive Cocci
    Canine Staphylococcal Pyoderma

    Pathogenesis
    S. aureus subspecies aureus and S. pseudintermedius possess various virulence factors, which include carbohydrate capsules, selected cell wall antigens, extracellular enzymes and toxins.
  38. Aerobic and Anaerobic Gram-positive Cocci
    Canine Staphylococcal Pyoderma

    Pathology
    The lesions are generally restricted to the skin and are characterized by a suppurative exudate, but some animals can have a lymphadenitis, particularly the superficial lymph nodes.
  39. Aerobic and Anaerobic Gram-positive Cocci
    Canine Staphylococcal Pyoderma

    Diagnosis
    • -Staphylococcus species can be identified based on their cellular, cultural and biochemical characteristics.
    • -Staphylococcus species are gram-positive nonmotile cocci arranged in grapelike clusters.
    • -Staphylococcus species can be cultured on blood agar under aerobic conditions at 37C. S. aureus subspecies aureus produces double-zone hemolysis and S. pseudintermedius produce complete hemolysis.
    • -Staphylococcus species are catalase-positive and saccharolytic.
    • -Canine S. aureus subspecies aureus and S. pseudintermedius strains coagulate rabbit plasma.
  40. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    General
    Selected pathogenic Streptococcus species are host-adapted of humans or 1 or 2 animal species.
  41. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Pathogenic Streptococcus Species and Subspecies
    • -Selected Streptococcus species and subspecies are opportunistic pathogens of humans and animals.
    • -S. agalactiae causes bovine mastitis.
    • -S. equi subspecies equi causes equine strangles.
    • -S. pneumoniae causes human pneumococcal pneumonia.
    • -S. pyogenes causes human glomerulonephritis, strep throat, rheumatic fever and scarlet fever.
  42. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Lancefield Classification
    • -Lancefield classification includes Enterococcus and Streptococcus species.
    • -Lancefield groups are based on a precipitation test of extractable group-specific carbohydrate cell wall antigens and are designated A to H and K. To extract these soluble antigens, streptococci are placed in dilute acid with pH 2 and heated at 100C for 10 minutes. These antigens are called C carbohydrates.
    • -Enterococcus species are in Lancefield group D.
    • -S. pyogenes is in Lancefield group A.
    • -S. equi subspecies equi is in Lancefield group C.
    • -S. pneumoniae is not included in the Lancefield classification schema.
  43. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Types of Hemolysis
    Hemolytic patterns on aerobic blood agar cultures include complete hemolysis, incomplete hemolysis and no hemolysis. When isolated from clinical specimens, the hemolytic streptococci are considered to be pathogens and the nonhemolytic streptococci are considered to be nonpathogens.
  44. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Virulence Factors
    Capsules
    • -Capsules are antiphagocytic and help bacteria resist phagocytosis, but nonencapsulated streptococci are avirulent or have a low virulence.
    • -Hyaluronic acid capsules are nonantigenic and are present on Lancefield groups A and C.
    • -Carbohydrate capsules are antigenic and are present on other Lancefield groups.
  45. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Virulence Factors
    M-Proteins, R-Proteins and T-Proteins
    • -M-proteins extend through the capsule and often play a significant role in infections. These antigens have an antiphagocytic activity.
    • -M-protein of S. equi subspecies equi helps the bacterium colonize pharyngeal tissues of horses.
    • -Selected M-proteins of S. pyogenes play significant role in human glomerulonephritis and rheumatic fever.
    • -R-proteins and T-proteins are associated with some Streptococcus species, but play a limited role in streptococcal infections.
  46. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Virulence Factors
    Hyaluronidase
    Hyaluronidase hydrolyzes hyaluronic acid and plays a significant role in the spread of streptococci through tissues.
  47. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Virulence Factors
    Streptodornases
    Streptodornases A, B, C and D are deoxyribonucleases that hydrolyze DNA. These enzymes are immunologically distinct.
  48. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Virulence Factors
    Streptokinases
    Streptokinases A and B lyse fibrin by catalyzing the conversion of plasminogen to plasmin. By promoting the lysis of blood clots, streptokinase facilitates the spread of streptococcal infections by preventing the formation of a fibrin barrier around the infection site.
  49. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Virulence Factors
    Streptolysins O and S
    • -Streptolysin S (nonantigenic and oxygen-stable) lyses erythrocytes under aerobic and anaerobic conditions.
    • -Streptolysin O (antigenic and oxygen-labile) lyses erythrocytes under anaerobic conditions.
    • -Streptolysins O and S can lyse macrophages, neutrophils and platelets in some animal species.
  50. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Habitat and Ecology
    • -Streptococci are flora of mucous membranes and skin of humans and animals.
    • -Many Streptococcus species are adapted to humans or one or two domestic animal species.
    • -S. equi subspecies equi is an equine-adapted pathogen.
    • -S. pneumoniae is a human-adapted pathogen and rarely infects animals.
    • -S. pyogenes is a human-adapted pathogen and is rarely isolated from animals.
  51. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Cellular Characteristics
    • -Streptococcus species are gram-positive cocci and are arranged in chains.
    • -S. pneumoniae is arranged in pairs.
  52. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Cultural Characteristics
    • -Streptococcus species can be cultured on blood agar under aerobic conditions at 37C. Colonies are pinpoint-sized and transparent to semiopaque.
    • -Hemolytic streptococci can have complete or incomplete hemolysis, but most pathogenic streptococci produce complete hemolysis.
  53. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Biochemical Characteristics
    Streptococcus species are catalase-negative and saccharolytic.
  54. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Disease Overview
    Human and Domestic Animal Infections
    • -In humans and domestic animals, Streptococcus species are extracellular pathogens and produce suppurative inflammation and abscesses.
    • -Many Streptococcus species tend to be host-adapted pathogens and are frequently associated with specific disease conditions.
    • -Streptococcal diseases are characterized by febrile symptoms, alone or associated with symptoms of septicemia. Septicemia can result from the hematogenous spread from a primary infection.
    • -Primary infections often involve the mammary glands, skin, reproductive tract, respiratory tract and umbilical cord.
    • -Streptococcal mastitis is common in cattle and sheep and occasionally occurs in humans and other domestic animals.
    • -Streptococci are commonly isolated from suppurative lesions of the skin.
    • -Streptococcal infections of the reproductive mucous membranes can result in abortion, infertility and metritis. These infections are common in horses.
    • -Streptococcal infections of the umbilical cord can be localized with draining purulent material and abscesses.
    • -Some streptococcal infections cause a septicemic. Complications of septicemia can result in localization in the joints and brain.
    • -Some streptococcal septicemias result in death of the neonate.
    • -When isolated from a clinical specimen, streptococci with complete or incomplete hemolysis usually have a clinical significance.
    • -Nonhemolytic streptococci are not considered to be clinically significant since they have a low virulence.
  55. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Disease Overview
    Human Glomerulonephritis and Rheumatic Fever
    • -In humans, glomerulonephritis and rheumatic fever are post-immunological sequelae to primary S. pyogenes infections. Glomerulonephritis is associated with only a few S. pyogenes serovars 33 that are based on their M-protein antigens, but rheumatic fever is associated with over 50 serovars. Serovars that cause glomerulonephritis do not cause rheumatic fever and serovars that cause rheumatic fever do not cause glomerulonephritis.
    • -Some S. pyogenes serovars are not associated with either glomerulonephritis or rheumatic fever.
  56. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Disease Overview
    Human Scarlet Fever
    • -Scarlet fever is caused by erythrogenic toxin producing S. pyogenes strains and is characterized by an acute hyperemia of the skin.
    • -Dick test (in vivo toxin neutralization test) is used to determine the presence or absence of humoral antibodies to the erythrogenic toxin when inoculated into the skin. A susceptible individual without antibodies to the erythrogenic toxin develop a reaction at the inoculation site, whereas a resistant individual with antibodies against the erythrogenic toxin do not develop a reaction at the inoculation site.
  57. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Disease Overview
    Human Strep Throat
    S. pyogenes is the most common cause of strep throat.
  58. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Disease Overview
    Human Pneumococcal Pneumonia
    Pneumococcal pneumonia is acquired by the inhalation of S. pneumoniae. Without antibiotic therapy, these bronchopneumonias are a common cause of death, particularly in the elderly.
  59. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Disease Overview
    Bovine Mastitis
    In dairy cows, S. agalactiae is the most common cause of mastitis. These infections are acquired from the endogenous flora of mucous membranes and skin through the teat canal.
  60. Aerobic and Anaerobic Gram-positive Cocci
    Genus Streptococcus

    Disease Overview
    Equine Strangles and Purpura Hemorrhagica
    In horses, S. equi subspecies equi causes strangles. The disease is characterized by inflammation of the upper respiratory tract and abscessation of the regional lymph nodes. Purpura hemorrhagica is an immune-mediated sequela of strangles and is characterized by extensive subcutaneous edema of the face, limbs and muzzle and ecchymotic and petechial hemorrhages of mucous membranes and skin.
  61. Aerobic and Anaerobic Gram-positive Cocci
    Human Pneumococcal Pneumonia

    General
    In the pre-antibiotic era, Streptococcus pneumoniae induced bronchopneumonia was a common cause of death, particularly in the elderly.
  62. Aerobic and Anaerobic Gram-positive Cocci
    Human Pneumococcal Pneumonia

    Etiology
    • -S. pneumoniae is an aerobic gram-positive coccus and the cocci are arranged in pairs.
    • -S. pneumoniae does not have a Lancefield classification.
    • -S. pneumoniae serovars are based on their carbohydrate capsular antigens.
  63. Aerobic and Anaerobic Gram-positive Cocci
    Human Pneumococcal Pneumonia

    Transmission
    • -Inhalation of S. pneumoniae into the lungs causes a bronchopneumonia.
    • -S. pneumoniae is primarily a respiratory tract pathogen of humans, but has been reported occasionally in other mammalian species.
  64. Aerobic and Anaerobic Gram-positive Cocci
    Human Pneumococcal Pneumonia

    Clinical Features
    Clinical infections are characterized by fever, dyspnea and occasionally result in death.
  65. Aerobic and Anaerobic Gram-positive Cocci
    Human Pneumococcal Pneumonia

    Pathogenesis
    • -Polysaccharide capsule of S. pneumoniae is antiphagocytic and the major virulence factor of the bacterium. Smooth strains with a capsule are virulent, but rough strains without a capsule are avirulent.
    • -Over 100 capsular type-specific antigens have been described. Each strain has 1 type-specific capsular antigen.
    • -S. pneumoniae produces extracellular enzymes and toxins.
    • -Recovery from infections generally confers protective immunity to the capsular type of 34 pneumococcus causing the infection for 6 to 12 months, but there is negligible protective immunity produced to the other capsular types.
  66. Aerobic and Anaerobic Gram-positive Cocci
    Human Pneumococcal Pneumonia

    Pathology
    Lungs are the primary organs affected. Infections of the middle ear are also common.
  67. Aerobic and Anaerobic Gram-positive Cocci
    Human Pneumococcal Pneumonia

    Diagnosis
    Clinical
    Clinical diagnoses are based on the clinical signs of a bronchopneumonia.
  68. Aerobic and Anaerobic Gram-positive Cocci
    Human Pneumococcal Pneumonia

    Diagnosis
    Culture and Biochemical Identification
    -S. pneumoniae can be cultured on blood agar under aerobic conditions at 37C. The pinpoint- sized colonies produce incomplete hemolysis. The bacterium is catalase-negative and saccharolytic.
  69. Aerobic and Anaerobic Gram-positive Cocci
    Human Pneumococcal Pneumonia

    Diagnosis
    Optochin Susceptibility Test
    • -Optochin susceptibility test is used to identify S. pneumoniae.
    • -To conduct the test, a paper disk impregnated with optochin is placed on the surface of a blood agar plate streaked with S. pneumoniae. Optochin inhibits the growth of S. pneumoniae adjacent to the disk, but optochin does not inhibit the growth of the other Streptococcus species.
  70. Aerobic and Anaerobic Gram-positive Cocci
    Human Pneumococcal Pneumonia

    Diagnosis
    Quelling Test
    Quelling test is used to identify type-specific carbohydrate capsular antigens of S. pneumoniae. Homologous IgM antibodies react with the carbohydrate antigens producing an antigen-antibody reaction, thereby delineating the capsular surface antigens of the bacterium.
  71. Aerobic and Anaerobic Gram-positive Cocci
    Human Glomerulonephritis and Rheumatic Fever

    General
    All Streptococcus pyogenes serovars can induce suppurative lesions with abscess formation. However, only selected S. pyogenes serovars are associated with glomerulonephritis and rheumatic fever.
  72. Aerobic and Anaerobic Gram-positive Cocci
    Human Glomerulonephritis and Rheumatic Fever

    Etiology
    • -S. pyogenes is an aerobic gram-positive coccus and the cocci are arranged in chains.
    • -S. pyogenes is the only member of Lancefield group A.
    • -S. pyogenes serovars are based on their M-protein antigens.
    • -Only a few S. pyogenes serovars have been associated with glomerulonephritis.
    • -Over fifty S. pyogenes serovars have been associated with rheumatic fever.
    • -S. pyogenes serovars associated with glomerulonephritis are distinct from those associated with rheumatic fever.
  73. Aerobic and Anaerobic Gram-positive Cocci
    Human Glomerulonephritis and Rheumatic Fever

    Transmission
    • -S. pyogenes infections are usually acquired by inhalation.
    • -S. pyogenes is a human-adapted pathogen and rarely causes clinical infections in animals.
  74. Aerobic and Anaerobic Gram-positive CocciHuman Glomerulonephritis and Rheumatic Fever

    Clinical Features
    • -All S. pyogenes strains can induce suppurative lesions with abscess formation.
    • -S. pyogenes is the most common cause of ‘strep throat’. These infections generally occur several weeks prior to the immunological complications of glomerulonephritis and rheumatic fever.
  75. Aerobic and Anaerobic Gram-positive Cocci
    Human Glomerulonephritis and Rheumatic Fever

    Pathogenesis
    • -Hyaluronic acid capsule of S. pyogenes is antiphagocytic and nonantigenic.
    • -Extracellular enzymes and toxins produced by S. pyogenes are similar to the other pathogenic streptococci.
    • -Inhaled bacteria adhere to the epithelial cells of the pharynx via M-protein antigens, which extend through the capsule.
    • -M-protein is antiphagocytic in the absence of anti-M-protein antibodies. Anti-M-protein antibodies provide protective immunity because they act as opsonins to allow the bacterium to be phagocytized and killed.
  76. Aerobic and Anaerobic Gram-positive Cocci
    Human Glomerulonephritis and Rheumatic Fever

    Pathology
    Abscesses and suppurative lesions are characteristic of S. pyogenes infections, rheumatic fever by heart lesions and glomerulonephritis by kidney lesions.
  77. Aerobic and Anaerobic Gram-positive Cocci
    Human Glomerulonephritis and Rheumatic Fever

    Diagnosis
    General
    • -Clinical diagnoses of S. pyogenes induced suppurative lesions are often based on clinical signs.
    • -S. pyogenes can be cultured on blood agar under aerobic conditions at 37C. The pinpoint-sized colonies produce complete hemolysis.
    • -S. pyogenes is catalase-negative and saccharolytic.
  78. Aerobic and Anaerobic Gram-positive Cocci
    Human Glomerulonephritis and Rheumatic Fever

    Diagnosis
    Bacitracin Susceptibility Test
    • -Bacitracin susceptibility test is used to identify S. pyogenes.
    • -To conduct the test, a paper disk impregnated with bacitracin is placed on the surface of a blood agar plate streaked with S. pyogenes. Bacitracin inhibits the growth of S. pyogenes adjacent to the disk, but bacitracin does not inhibit the growth of the other Streptococcus species.
  79. Aerobic and Anaerobic Gram-positive Cocci
    Equine Strangles

    General
    Strangles is an upper respiratory disease condition of horses and purpura hemorrhagica is an immune-mediated sequela to strangles.
  80. Aerobic and Anaerobic Gram-positive Cocci
    Equine Strangles

    Etiology
    • -Streptococcus equi subspecies equi is an aerobic gram-positive coccus and the cocci are arranged in chains.
    • -Streptococcus equi subspecies equi is a member of Lancefield group C.
    • -Streptococcus equi subspecies equi is an equine-adapted pathogen.
  81. Aerobic and Anaerobic Gram-positive Cocci
    Equine Strangles

    Transmission
    • -S. equi subspecies equi is transient flora on mucous membranes of the upper respiratory tract of horses.
    • -S. equi subspecies equi is transmitted in respiratory aerosols and nasal discharges of clinically infected and carrier horses to susceptible horses, which acquire the infection by ingestion or inhalation.
  82. Aerobic and Anaerobic Gram-positive Cocci
    Equine Strangles

    Clinical Features
  83. -Strangles is characterized by inflammation of the upper respiratory tract and abscessation in the regional lymph nodes. After a 3 to 6 day incubation period, affected horses are febrile with a bilateral mucopurulent nasal discharge. The pharyngeal and mandibular lymph nodes often rupture and drain a purulent exudate. In severe infections, a septicemia gives rise to abscess formation in a variety of lymph nodes, organs and tissues. These infections tend to be chronic with varied symptoms. The disease usually affects animals from 1 to 2 years-of-age.
    -Purpura hemorrhagica is a postinfection immune complex disease that is characterized by extensive subcutaneous edema of the face, limbs and muzzle and ecchymotic and petechial hemorrhages of the mucous membranes and skin. The edema pits on pressure.
  84. Aerobic and Anaerobic Gram-positive Cocci
    Equine Strangles

    Pathogenesis
    • -Ingested or inhaled S. equi subspecies equi colonize the buccal and nasal mucous membranes.
    • -Bacteria adhere to the epithelial surfaces via an M-protein antigen, which extends through the hyaluronic acid capsule Bacteria invade the mucous membranes and infection spreads via the lymphatic system to the regional lymph nodes where abscesses develop.
    • -Hyaluronic acid capsule and M-protein antigen are antiphagocytic and prevent phagocytosis of the infective bacteria by professional phagocytic cells. If a septicemia occurs, abscesses can form in a variety of lymph nodes, organs and tissues. This is called bastard strangles.
    • -Purpura hemorrhagica develops several weeks after the primary infection when antibodies to M-protein form immune complexes that localize in the capillary beds and activate complement. An increased vascular permeability allows the exudation of plasma and cells into the tissues.
    • -Recovery from natural disease confers lifelong immunity.
  85. Aerobic and Anaerobic Gram-positive Cocci
    Equine Strangles

    Pathology
    • -Catarrhal rhinitis and abscesses in the mandibular and pharyngeal lymph nodes are the primary lesions in strangles.
    • -Purpura hemorrhagica is characterized by extensive subcutaneous edema of the face, limbs and muzzle and ecchymotic and petechial hemorrhages of the mucous membranes and skin.
  86. Aerobic and Anaerobic Gram-positive Cocci
    Equine Strangles

    Diagnosis
    • -Clinical signs are characteristic for strangles and purpura hemorrhagica.
    • -S. equi subspecies equi can be cultured on blood agar under aerobic conditions at 37C and identified utilizing biochemical criteria.
  87. Aerobic Gram-positive Bacilli

    Aerobic Genera:
    Arcanobacterium, Corynebacterium, Dermatophilus, Erysipelothrix, Nocardia, Rhodococcus, Listeria
  88. Aerobic Gram-positive Bacilli

    Aerobic Genera:
    Genus Arcanobacterium
    • -A. pyogenes is a commensal on mucous membranes of various domestic animals.
    • -A. pyogenes is an opportunistic pathogen of humans and domestic animals.
    • -A. pyogenes is the most common cause of bovine suppurative lesions and abscesses.
    • -A. pyogenes and Fusobacterium necrophorum act synergistically as agents of ovine infective bulbar necrosis. A. pyogenes produces an extracellular pathogen that enhances the proliferation of F. necrophorum.
  89. Aerobic Gram-positive Bacilli

    Aerobic Genera:
    Genus Corynebacterium
    • -Pathogenic Corynebacterium species vary in their host ranges and are associated with different disease conditions.
    • -C. diphtheriae causes human diphtheria. Clinical signs are attributed to the action of diphtheria toxin, which is a holotoxin with molecular weight 62,000. The toxin inhibits protein synthesis in selected human eucaryotic cells.
    • -C. pseudotuberculosis causes ovine caseous lymphadenitis. The lymph node lesions have a distinctive caseous necrosis and often resemble the lesions of tuberculosis.
    • -C. renale causes bovine contagious pyelonephritis. This is an ascending urinary tract infection that localizes in the ureters and kidneys.
  90. Aerobic Gram-positive Bacilli

    Aerobic Genera:
    Genus Dermatophilus
    • -D. congolensis is the only pathogen of humans and domestic animals.
    • -D. congolensis causes dermatophilosis in humans and selected domestic animals (cattle, horse and sheep). The disease is an acute or chronic infection of the epidermis and is characterized by exudative epidermitis with scab formation.
    • -D. congolensis has been isolated only from the integument of humans and domestic animals.
    • -D. congolensis probably has a saprophytic existence in soil, but attempts to isolate the bacterium have been unsuccessful.
    • -D. congolensis can exist in a quiescent form until exacerbation occurs when climatic conditions are favorable for its infectivity.
    • -Dermatophilosis has a worldwide distribution
  91. Aerobic Gram-positive Bacilli

    Aerobic Genera:
    Genus Erysipelothrix
    • -E. rhusiopathiae is a pathogen of humans and selected domestic animals.
    • -E. rhusiopathiae causes erysipeloid in humans and erysipelas in pigs.
    • -Porcine erysipelas can be manifested as an acute septicemia with a high mortality rate and as a chronic polyarthritis.
  92. Aerobic Gram-positive Bacilli

    Aerobic Genera:
    Genus Listeria
    • -In the genus Listeria, L. monocytogenes is the predominant pathogen and other Listeria species are occasionally isolated from humans and animals.
    • -L. monocytogenes causes human foodborne listeriosis with a mortality rate estimated from 20 to 25% in clinically affected people.
    • -L. monocytogenes bovine listeriosis and is frequently acquired by ingestion of poor quality silage.
  93. Aerobic Gram-positive Bacilli

    Aerobic Genera:
    Genus Nocardia
    • -Nocardia species cause chronic infections with pyogranulomatous lesions in humans and domestic animals.
    • -N. asteroides is more commonly isolated than N. brasiliensis.
    • -N. asteroides causes pulmonary nocardiosis.
    • -Infections occasionally occur in humans and domestic animals.
  94. Aerobic Gram-positive Bacilli

    Aerobic Genera:
    Genus Rhodococcus
    • -In the genus Rhodococcus, R. equi is the only pathogen of humans and domestic animals.
    • -R. equi causes foal pneumonia.
    • -R. equi is commonly isolated from humans with acquired immunodeficiency syndrome.
  95. Aerobic Gram-positive Bacilli

    Cellular Characteristics
    • -A. pyogenes, Corynebacterium species, E. rhusiopathiae, Nocardia species and R. equi are gram-positive nonmotile bacilli.
    • -D. congolensis is a dimorphic bacterium with motile zoospores and nonmotile pleomorphic bacilli. Zoospores have peritrichous flagella.
    • -L. monocytogenes has a temperature-dependent motility and is motile with peritrichous flagella at 20C and nonmotile at 37C.
    • -Nocardia species are partial acid-fast bacilli and can be stained with Kinyoun stain.
  96. Aerobic Gram-positive Bacilli

    Cultural Characteristics
    • -A. pyogenes, Corynebacterium species, D. congolensis, E. rhusiopathiae and L. monocytogenes are facultative anaerobes and can be cultured on blood agar under aerobic conditions at 37C.
    • -Nocardia species and R. equi are obligate aerobes and can be cultured on blood agar under aerobic conditions at 37C.
  97. Aerobic Gram-positive Bacilli

    Biochemical Characteristics
    • -A. pyogenes and E. rhusiopathiae are catalase-negative and saccharolytic.
    • -Corynebacterium species, D. congolensis and L. monocytogenes are catalase-positive and saccharolytic.
    • -Nocardia species and R. equi are catalase-positive and asaccharolytic.
  98. Aerobic Gram-positive Bacilli
    Human Diphtheria

    General
    Children are immunized with the DPT vaccine, which is composed of diphtheria toxoid, pertussis bacterin and tetanus toxoid.
  99. Aerobic Gram-positive Bacilli
    Human Diphtheria

    Etiology
    General
    C. diphtheriae is gram-positive bacillus and a host-adapted human pathogen.
  100. Aerobic Gram-positive Bacilli
    Human Diphtheria

    Etiology
    Diphtheroid Morphology
    Diphtheroid describes the cellular morphology of C. diphtheriae. The bacteria have V, L and Y shapes with club-shaped swellings in the ends or middle and tapered ends.
  101. Aerobic Gram-positive Bacilli
    Human Diphtheria

    Etiology
    Babes-Ernst Granules
    C. diphtheriae has Babes-Ernst granules that are composed of inorganic phosphate (volutin). These granules aid in differentiating C. diphtheriae from other aerobic gram-positive bacilli. With Albert's stain, Babes-Ernst granules stain black.
  102. Aerobic Gram-positive Bacilli
    Human Diphtheria

    Transmission
    C. diphtheriae is acquired by inhalation from clinically affected individuals or asymptomatic carriers.
  103. Aerobic Gram-positive Bacilli
    Human Diphtheria

    Clinical Features
    • -Pharyngeal pathology and systemic manifestations are attributable to the lethal action of diphtheria toxin on eucaryotic cells.
    • -Humoral antibodies neutralize diphtheria toxin providing protective immunity.
  104. Aerobic Gram-positive Bacilli
    Human Diphtheria

    Pathogenesis
    • -C. diphtheriae is acquired by inhalation and colonizes the nasopharynx. At this primary focus of infection, the bacteria proliferate and excrete diphtheria toxin. The characteristic local pathology results from the interaction of diphtheria toxin with eucaryotic cells.
    •  -Diphtheria toxin is excreted as an inactive prototoxin with molecular weight 62.000. The prototoxin is activated by proteolytic cleavage to form a biologically active holotoxin with1 A subunit with molecular weight 24,000 and 1 B subunit with molecular weight 38,000. The B subunit binds to susceptible human eucaryotic cells and facilitates the entry of the A subunit into the cytoplasm of the cell. The A subunit inhibits protein synthesis via enzymatic depletion of an enzyme required for assembly of peptides on the mRNA template. Diphtheria toxin inhibits polypeptide chain elongation by catalyzing the inactivation of elongation factor 2, which is required for translocating polypeptide tRNA from the acceptor site to the donor site on the eucaryotic ribosome. Elongation factor 2 is inactivated by being coupled with ADP resulting from cleaving of nicotinamide adenosine diphosphate. Humans are the only mammalian species with receptors for the B subunit thus allowing the A subunit to gain access to the cell cytoplasm. Selected human eucaryotic cells are susceptible to diphtheria toxin.
    • -Capacity to elaborate diphtheria toxin comes from the tox gene, which is carried by beta-bacteriophage. Lysogenic bacterial cells are responsible for biosynthesis of the toxin.
  105. Aerobic Gram-positive Bacilli
    Human Diphtheria

    Pathology
    • -Localized pharyngeal lesions develop in 3 stages.
    • -In the first stage, there is death of cells at the affected area.
    • -In the second stage, an exudate forms on the surface of the nasal pharynx.
    • -In the third stage, a pseudomembrane is formed.
    • -Systemic effects of diphtheria toxin are manifested when the toxin is absorbed into the blood.
  106. Aerobic Gram-positive Bacilli
    Human Diphtheria

    Diagnosis
    • -Pharyngeal lesions are characteristic of diphtheria.
    • -C. diphtheriae can be cultured on blood agar under aerobic conditions at 37C.
    • -Blood agar with potassium tellurite (differential medium) is used for the isolation of C. diphtheriae from clinical specimens. The tellurite ion passes into the cytoplasm of C. diphtheriae and forms a precipitated that imparts a black color to the colonies.
    • -Elek agar with serum antibodies to diphtheria toxin is used for the presumptive identification of C. diphtheriae. When colonies develop on the agar surface, C. diphtheriae excretes diphtheria toxin producing a precipitation reaction in the agar.
    • -Schick test (in vivo toxin neutralization test) is used to determine the presence or absence of humoral antibodies to diphtheria toxin when inoculated into the skin. A susceptible individual without antibodies to diphtheria toxin develop a reaction at the inoculation site, whereas a resistant individual with antibodies against diphtheria toxin do not develop a reaction at the inoculation site. Schick test indicates protective immunity acquired from a previous infection or immunization with diphtheria toxoid.
  107. Aerobic Gram-positive Bacilli
    Ovine Dermatophilosis

    General
    Dermatophilus congolensis derives its name from first being described in the Belgium Congo. The bacterium is an obligate pathogen of the epidermis.
  108. Aerobic Gram-positive Bacilli
    Ovine Dermatophilosis

    Etiology
    D. congolensis is a gram-positive dimorphic bacterium with nonmotile pleomorphic bacilli and motile zoospores.
  109. Aerobic Gram-positive Bacilli
    Ovine Dermatophilosis

    Transmission
    • -Dermatophilosis is ubiquitous among domestic herbivores and infected animals serve as reservoirs of infection.
    • -During dormant periods in chronically affected animals, D. congolensis exists in a quiescent form in the integument until exacerbation occurs when climatic conditions are favorable for its infectivity.
    • -To establish an infection, the zoospores must overcome protective barriers of the skin. Factors such as prolonged wetting by rain, high humidity, high temperature and various ectoparasites that reduce or permeate the natural barriers of the integument influence the development, prevalence, seasonal incidence and transmission of dermatophilosis. Spread of infection can follow shearing, dipping or the introduction of infected animals into a flock.
    • -Primary modes of transmission are direct contact with infected animals and biting insects that serve as mechanical vectors for the zoospores. Insect vectors can play a significant role in the persistence and spread of infection.
  110. Aerobic Gram-positive Bacilli
    Ovine Dermatophilosis

    Clinical Features
    • -Dermatophilosis is an acute or chronic infection of the epidermis and is characterized by an exudative dermatitis with scab formation. The dermatitis on an individual animal can vary from acute to chronic and the lesions are seldom at the same stage of progression.
    • -The incidence in flocks varies due to husbandry practices, time of year and ectoparasite populations. Epidemics occur during wet periods when protective skin barriers are damaged or deficient.
    • -Dermatophilosis is called lumpy wool when wooled areas of the body are affected and strawberry footrot when the distal portions of the limbs are affected.
    • -Lumpy wool is characterized by the continuous production of scab material over a period of months or years. The scab material is bound by wool fibers and forms dense pyramid-shaped masses over the back, flanks, face and head.
    • -Strawberry footrot is a proliferative dermatitis that affects skin on the lower parts of the legs.
    • -Few affected sheep exhibit pruritis.
    • -Sheep with generalized infections often lose condition and have difficulty in movement and grasping food if the lips and muzzle are severely affected.
    • -Most affected sheep recover spontaneously during dry weather.
  111. Aerobic Gram-positive Bacilli
    Ovine Dermatophilosis

    Pathogenesis
    • -In acute infections, moisture facilitates release of zoospores from lesions and their subsequent penetration into the epidermis. Zoospores are most active in the first hours after their release from the pleomorphic bacilli. Water provides a transport medium for zoospores. The respiratory efflux of carbon dioxide from the skin attracts zoospores to susceptible areas on the skin surface.
    • -Zoospores adhere to the skin then germinate to produce nonmotile pleomorphic bacilli. Bacilli penetrate into the epidermis. Branching bacilli subsequently spread in all directions from the initial focus of infection. The invaded epidermis is eventually separated from its dermal matrix. The epithelium separates from the skin in the form of a scab. New layers of scab are added, which causes a gradual increase in the size of the scab. After 10 to 14 days, infected tissues separate as a crust or scab.
    • -In chronic infections, the initial processes of tissue invasion and host reaction are similar to the acute lesion. The infection persists because of the continued invasion of new epidermis.
    • -Infected animals do not develop a significant immunity to reinfection.
  112. Aerobic Gram-positive Bacilli
    Ovine Dermatophilosis

    Pathology
    • -Gross lesions are characterized by scab material bound by wool fibers that form dense pyramid- shaped masses.
    • -Branching pleomorphic bacilli with multidimensional septa, coccus-shaped cells and zoospores characterize the microscopic epidermal lesions.
  113. Aerobic Gram-positive Bacilli
    Ovine Dermatophilosis

    Diagnosis
    • -Presumptive diagnoses depend on the appearance of lesions in clinically diseased animals.
    • -D. congolensis can be cultured on blood agar under microaerophilic conditions at 37C and identified using morphologic and biochemical test criteria.
  114. Aerobic Gram-positive Bacilli
    Porcine Erysipelas

    General
    Erysipelas can be manifested as an acute septicemia, subacute form characterized by necrosis of the skin, chronic polyarthritis or vegetative endocarditis. More swine are immunized for erysipelas than for any other bacterial disease.
  115. Aerobic Gram-positive Bacilli
    Porcine Erysipelas

    Etiology
    • -Erysipelothrix rhusiopathiae is a gram-positive bacillus.
    • -E. rhusiopathiae serovars are based on their somatic antigens. These antigens are qualitatively homogenous but differ quantitatively.
    • -E. rhusiopathiae serovars 1 and 2 represent 80% of the isolates from erysipelas.
  116. Aerobic Gram-positive Bacilli
    Porcine Erysipelas

    Transmission
    • -Most infections are acquired from ingestion of E. rhusiopathiae contaminated feed, feces, soil and water.
    • -E. rhusiopathiae can survive in the tonsils, gall bladders and gastrointestinal tracts of immune swine, which excrete the organisms in their feces.
    • -Other animals can carry E. rhusiopathiae in their gastrointestinal tracts.
    • -E. rhusiopathiae can survive for several weeks in alkaline soils.
    • -Flies, particularly from cutaneous lesions, where the bacteria can persist for months, can mechanically transmit erysipelas.
    • -E. rhusiopathiae can be maintained for years in swine without clinical signs or with chronic arthritis. When stressed, a pig can have a recrudescence of infection and then spread the infection to other swine.
    • -E. rhusiopathiae has been isolated from the tonsils of over thirty percent of healthy swine. These pharyngeal carriers shed the bacteria in their feces, which contaminate the environment.
  117. Aerobic Gram-positive Bacilli
    Porcine Erysipelas

    Clinical Features
    • -Erysipelas occurs in pigs of all ages. Pigs from 2 months-of-age to 1year-of-age are the most susceptible to infection and clinical disease.
    • -Erysipelas can be manifested as an acute highly fatal septicemia, a milder subacute form characterized by necrosis of the skin, chronic polyarthritis or vegetative endocarditis.
    • -Infected pregnant sows can abort or give birth to stillborn pigs.
    • -In acute infections, affected swine with septicemias have a fever, depression, lameness and high mortality rates. Sudden deaths can occur before clinical signs are manifested.
    • -In subacute infections, the disease is less severe than acute erysipelas. Affected swine live for 3 or 4 days. Pathognomonic cutaneous lesions develop on the skin of the abdomen, ears and extremities. Skin lesions are raised and rhomboid-shaped with a reddish-purple color. In swine that survive for several weeks, lesions are necrotic and occasionally coalesce over large areas of the skin. This results in an extensive cutaneous necrosis.
    • -In chronic infections, bacteria localize in the joints and on the endocardium. These conditions generally occur as sequelae to an acute infection after which the animal survives or a mild or in apparent systemic infection. A polyarthritis can occur in both acute and chronic infections.
    • -Acute arthritis can occur in pigs as young as 3 weeks-of-age. The acute inflammatory response can persist for 20 weeks.
    • -Chronic arthritis occurs in pigs 10 weeks-of-age or older and can persist for several years. Hock and knee joints are most often involved, but carpal and tarsal joints also can be affected.
    • -Vegetative endocarditis primarily involves the mitral valves and occurs as sequela in chronic infections. Most swine with vegetative endocarditis are asymptomatic, but vegetative endocarditis can result in valvular insufficiency and eventually congestive heart failure.
    • -During epidemics, the acute septicemic form predominates. When infection is endemic in a herd, disease tends to be sporadic and all forms of the disease can be manifested simultaneously.
  118. Aerobic Gram-positive Bacilli
    Porcine Erysipelas

    Pathogenesis
    • -In acute infections, E. rhusiopathiae is ingested by susceptible swine, penetrate the mucosa of the gastrointestinal tract, invade the bloodstream and proliferate. The septicemia disseminates the organisms to the lymph nodes and viscera.
    • -Diamond-shaped skin lesions are due to suffusion and congestion of the dermal capillaries with thrombosis of the dermal arterioles. This results in the necrosis of the skin.
    • -In polyarthritis, the bacterium can persist for up to 2 years in chronically infected joints despite a specific antibody response to the infection. The production of specific antibodies is an important factor in the pathogenesis of chronic proliferative changes that takes place in the synovium of infected joints. Articular proliferative changes are predominant when antibody titers are high. Localized immune complexes, which are comprised of bacterial antigens, antibody and complement, largely determine the level of chemotactic activity for neutrophils.
    • -Pathology associated with arthritis results from accumulation of neutrophils, which subsequently release their enzymes that damage cartilage and other joint tissues.
    • -With vegetative endocarditis, E. rhusiopathiae colonizes the endocardium and/or heart valves and eventually masses of fibrin and bacteria form on the valves.
  119. Aerobic Gram-positive Bacilli
    Porcine Erysipelas

    Pathology
    • -In acute and subacute infections, generalized lesions of septicemia are ecchymotic and petechial hemorrhages on the epicardium, skeletal muscles and serosal surface of the stomach. The liver and spleen are enlarged and hyperemic. Congestion and infarction of the gastric mucosa are often present.
    • -Diamond-shaped skin lesions are pathognomonic. Synovitis occurs in subacute cases.
    • -Chronic arthritic lesions are characterized by erosion of articular cartilage, nonsuppurative exudate and proliferative of the connective tissue capsule.
    • -With vegetative endocarditis, masses of fibrin and bacteria form on the heart valves. Septic emboli from the vegetative endocarditis lesions produce randomly distributed abscesses and infarcts in the kidneys, particularly the cortex.
  120. Aerobic Gram-positive Bacilli
    Porcine Erysipelas

    Diagnosis
    • -Clinical diagnoses are based on clinical signs, history and pathognomonic skin lesions.
    • -Gross lesions induced during the acute septicemia cannot be distinguished from other infections with an acute septicemia, particularly Salmonella Choleraesuis infections.
    • -Erosive, nonsuppurative and proliferative arthritic lesions distinguishes erysipelas from arthritic lesions caused by pathogens in the genera Haemophilus, Mycoplasma, Staphylococcus and Streptococcus.
    • -On aerobic blood agar cultures, E. rhusiopathiae produces complete hemolysis. Smooth 42 colonies are pinpoint-sized, convex, circular and transparent with an entire edge, but rough colonies are flatter, larger and opaque. Smooth colonies are recovered from acute infections and rough colonies are recovered from chronic infections.
    • -In Kligler iron agar cultures, E. rhusiopathiae ferments glucose and lactose and produces H2S. These reactions are diagnostic.
  121. Aerobic Gram-positive Bacilli
    Genus Listeria

    General
    Listeria monocytogenes is the most commonly isolated Listeria species from clinical infections.
  122. Aerobic Gram-positive Bacilli
    Genus Listeria

    Pathogenic Listeria Species
    • -L. monocytogenes causes human foodborne listeriosis.
    • -L. monocytogenes causes listeriosis in selected domestic animals.
  123. Aerobic Gram-positive Bacilli
    Genus Listeria

    Habitat and Ecology
    • -L. monocytogenes is ubiquitous in nature and is found in soil, vegetation and feces.
    • -L. monocytogenes is transient enteric flora of humans, animals, birds and fish. Asymptomatic carriers serve as reservoirs for the bacterium.
    • -L. monocytogenes prefers decaying vegetable matter with a neutral or alkaline pH. Feeding poor quality silage is a common source of infection for cattle and sheep.
  124. Aerobic Gram-positive Bacilli
    Genus Listeria

    Cellular Characteristics
    • -L. monocytogenes is a gram-positive bacillus with a temperature-dependent motility.
    • -In nature, L. monocytogenes is nonmotile at body temperature (37C) and motile with peritrichous flagella at room temperature (20C) and below.
    • -In motility test medium, L. monocytogenes is nonmotile at 37C and motile at room temperature (20C).
  125. Aerobic Gram-positive Bacilli
    Genus Listeria

    Cultural Characteristics
    L. monocytogenes is a facultative anaerobe and can be cultured on blood agar under aerobic conditions at 37C.
  126. Aerobic Gram-positive Bacilli
    Genus Listeria

    Biochemical Characteristics
    L. monocytogenes is catalase-positive and saccharolytic.
  127. Aerobic Gram-positive Bacilli
    Genus Listeria

    Disease Overview
    Animal, Bird and Human Listeria monocytogenes Infections
    • -L. monocytogenes is a facultative intracellular pathogen with high infectivity but with a low pathogenicity. A high infective dose is required to produce clinical disease.
    • -L. monocytogenes can cause clinical infections in humans, animals and birds.
    • -Cattle and sheep are more susceptible to L. monocytogenes than other domestic animals.
  128. Aerobic Gram-positive Bacilli
    Genus Listeria

    Disease Overview
    Human Listeriosis
    Clinical human foodborne infections have a mortality rate estimated at 20 to 25%. These infections are acquired by ingestion of large numbers of L. monocytogenes from dairy products, fruits, meat and vegetables.
  129. Aerobic Gram-positive Bacilli
    Genus Listeria

    Disease Overview
    Bovine Infections
    • -In cattle, L. monocytogenes causes four clinical syndromes.
    • -Asymptomatic enteric infections commonly occur.
    • -Visceral infections with a septicemia occasionally occur in newborn calves, but rarely occur in adults. Clinical signs in neonatal animals include a septicemia with gastroenteritis and bilateral meningitis. Deaths are frequent.
    • -Abortions occur in the last trimester of pregnancy. This is a sporadic condition.
    • -Neural listeriosis is the most commonly diagnosed clinical infection. Meningoencephalitis can result if L. monocytogenes penetrates the oral mucosa and affects the trigeminal and facial nerves with unilateral localization and microabscess formation in the brainstem. Microabscesses are 43 pathognomonic. Clinical signs include unidirectional circling, unilateral facial paralysis, corneal opacity, prostration, coma and death.
  130. Aerobic Gram-positive Bacilli
    Human Foodborne Listeriosis

    General
    Epidemics of foodborne infections are associated with consumption of Listeria monocytogenes contaminated dairy products, meats, fruits and vegetables. Clinical cases with a bacterial septicemia have the highest mortality rate of any foodborne infection or intoxification.
  131. Aerobic Gram-positive Bacilli
    Human Foodborne Listeriosis

    Etiology
    L. monocytogenes is an aerobic gram-positive bacillus with a temperature-dependent motility. The bacterium is nonmotile at body temperature (37C) and motile with peritrichous flagella at room temperature (20C) and below.
  132. Aerobic Gram-positive Bacilli
    Human Foodborne Listeriosis

    Transmission
    • -Most infections are acquired by ingestion of large numbers of L. monocytogenes from dairy products, meat, fruits and vegetables.
    • -L. monocytogenes can proliferate at refrigeration temperatures to attain an infective dose level.
  133. Aerobic Gram-positive Bacilli
    Human Foodborne Listeriosis

    Clinical Features
    • -Most localized visceral infections are asymptomatic, but some patients exhibit fever and gastroenteritis.
    • -Humans with systemic infections exhibit clinical signs of a septicemia with or without meningitis. These patients have a mortality rate from 20 to 25%.
  134. Aerobic Gram-positive Bacilli
    Human Foodborne Listeriosis

    Pathogenesis
    • -After ingestion of an infective dose, the gastrointestinal intestinal tract is the primary site of infection. The bacteremia/septicemia with infection in other organs such as the liver and meninges are common sequelae.
    • -L. monocytogenes is a facultative intracellular pathogen of neutrophils.
  135. Aerobic Gram-positive Bacilli
    Human Foodborne Listeriosis

    Pathology
    Gastrointestinal lesions and those from a bacterial septicemia are observed.
  136. Aerobic Gram-positive Bacilli
    Human Foodborne Listeriosis

    Diagnosis
    • -Most diagnoses are based on patient history, clinical signs and confirmed with cultural isolation from the affected individual and food source.
    • -L. monocytogenes can be cultured on blood agar under aerobic conditions at 37C and identified using biochemical test criteria.
  137. Aerobic Gram-positive Bacilli
    Genus Rhodococcus

    General
    Clinical Rhodococcus equi infections occur most frequently in humans and foals.
  138. Aerobic Gram-positive Bacilli
    Genus Rhodococcus

    Pathogenic Rhodococcus Species
    R. equi is an opportunistic pathogen in humans and animals and causes foal pneumonia.
  139. Aerobic Gram-positive Bacilli
    Genus Rhodococcus

    Habitat and Ecology
    R. equi is a transient enteric flora of horses and can persist for long periods on contaminated pasture.
  140. Aerobic Gram-positive Bacilli
    Genus Rhodococcus

    Cellular Characteristics
    R. equi is a gram-positive bacillus.
  141. Aerobic Gram-positive Bacilli
    Genus Rhodococcus

    Cultural Characteristics
    R. equi is an obligate aerobe and can be cultured on blood agar under aerobic conditions at 37C.
  142. Aerobic Gram-positive Bacilli
    Genus Rhodococcus

    Biochemical Characteristics
    R. equi is catalase-positive and asaccharolytic.
  143. Aerobic Gram-positive Bacilli
    Genus Rhodococcus

    Disease Overview
    Animal and Human Rhodococcus equi Infections
    • -In humans, R. equi is an opportunistic pathogen, particularly in patients infected with acquired immunodeficiency virus.
    • -R. equi infections are commonly reported in horses, but are rarely reported in other animals.
  144. Aerobic Gram-positive Bacilli
    Genus Rhodococcus

    Disease Overview
    Equine Infections
    Foal pneumonia is acquired by ingestion and/or inhalation of R. equi. Most infections occur in foals from 1 to 6 months-of-age. The decline in colostral antibody, which occurs about 6 weeks-of-age, coincides with the peak age for disease. Infections are usually sporadic, but outbreaks have been reported on farms where the disease is endemic. Pulmonary lesions include pyogranulomatous bronchopneumonia with lung abscesses and intestinal lesions include ulcerative colitis with mesenteric lymphadenitis.
  145. Aerobic Gram-positive Acid-fast Bacilli

    General
    Mycobacterium species, which are gram-positive acid-fast bacilli, can be stained with Ziehl-Neelsen stain. They cannot be stained with the Gram stain.
  146. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Aerobic Genus:
    Mycobacterium
  147. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Pathogenic Mycobacterium Species and Subspecies
    • -M. avium subspecies avium serovars one to three cause tuberculosis in birds and pigs.
    • -Selected M. avium subspecies avium serovars causes mycobacteriosis in humans and cattle and pigs (serovars 4 and above). Mycobacteriosis is rarely reported in other animals.
    • -M. avium subspecies paratuberculosis causes paratuberculosis in cattle and sheep.
    • -M. bovis causes tuberculosis in humans and cattle.
    • -M. bovis causes tuberculosis in humans and cattle.
    • -M. leprae causes leprosy in humans.
    • -M. tuberculosis causes tuberculosis in humans and cattle.
  148. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Runyon Classification Schema
    • -Runyon groups I, II, III and IV are based on their pigment production and growth rate. This classification schema is used for presumptive identification of various Mycobacterium species and atypical mycobacteria.
    • -In the pigment production procedure, 2 slants of Lowenstein-Jensen medium are inoculated. One slant is exposed to light and 1 slant is wrapped in foil. When colonies have formed on the slants, foil is removed from the covered slant and presence or absence of pigment is noted. If the culture is nonchromogenic, it is exposed to light for 1 hour. After exposure, the slant is covered and re-incubated overnight. Presence or absence of pigment in a culture grown exposed to light, in darkness and exposed to light for a brief period determines its characterization as a photochromogen, scotochromogen or nonchromogen.
  149. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Runyon Classification Schema
    Runyon Groups
  150. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Habitat and Ecology
    • -Mycobacterium species have a high environmental resistance due to the high lipid content in their cell walls.
    • -Some mycobacteria are host-adapted to humans, birds and various animals, but other mycobacteria are soil saprophytes and opportunistic pathogens.
    • -M. avium subspecies avium serovars one to three are host-adapted pathogens of birds and pigs and are called the avian tubercle bacilli.
    • -M. avium subspecies avium serovars 4 and above are soil saprophytes.
    • -M. avium subspecies paratuberculosis is a host-adapted ruminant pathogen.
    • -M. bovis and M. tuberculosis are called the mammalian tubercle bacilli.
    • -Cattle are the primary host for M. bovis, but cattle are also susceptible to M. tuberculosis.
    • -Humans are the primary host for M. tuberculosis, but humans are also susceptible to M. bovis.
    • -M. leprae is a host-adapted pathogen of humans and armadillos.
  151. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Cellular Characteristics
    Mycobacterium species are gram-positive acid-fast bacilli and can be stained with Ziehl-Neelsen stain.
  152. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Cultural Characteristics
    • -Mycobacterium species are obligate aerobes with fastidious growth requirements.
    • -Mycobacterium species cannot be cultured on blood agar under aerobic conditions at 37C, but most pathogenic species can be cultured on Lowenstein-Jensen agar under aerobic conditions at 37C.
    • -Generation times for most pathogenic species range from 18 to 24 hours. Cultures are incubated for 4 to 12 weeks to obtain visible growth. Reference laboratories generally conduct culture and identification procedures.
    • -Runyon classification schema is used for the presumptive identification of the mycobacteria.
  153. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Biochemical Characteristics
    Biochemical test criteria are used for their definitive identification.
  154. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Disease Overview
    Human and Domestic Animal Infections
    • -Selected pathogens in Runyon groups I, II and IV cause various clinical infections in humans and selected domestic animals. These infections are infrequently reported.
    • -Selected pathogens in Runyon group III cause specific diseases in humans and selected domestic animals. These pathogens include members of the M. avium subspecies avium, M. avium subspecies paratuberculosis, M. bovis, M. leprae and M. tuberculosis.
  155. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Disease Overview
    Human Infections
    • -Selected M. avium subspecies avium serovars cause mycobacteriosis (serovars 4 and above).
    • -M. bovis and M. tuberculosis cause tuberculosis.
    • -M. leprae causes leprosy.
  156. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Disease Overview
    Bovine Infections
    • -Selected M. avium subspecies avium serovars cause mycobacteriosis (serovars 4 and above).
    • -M. avium subspecies paratuberculosis causes paratuberculosis.
    • -M. bovis and M. tuberculosis cause tuberculosis.
  157. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Disease Overview
    Ovine Infections
    • -M. avium subspecies paratuberculosis causes paratuberculosis.
    • -M. bovis and M. tuberculosis cause tuberculosis.
  158. Aerobic Gram-positive Acid-fast Bacilli
    Genus Mycobacterium

    Disease Overview
    Porcine Infections
    • -M. avium subspecies avium serovars 1 to 3, M. bovis and M. tuberculosis cause tuberculosis. Infections caused by these organisms are very similar and are very difficult to distinguish from one another.
    • -Selected M. avium subspecies avium serovars cause mycobacteriosis (serovars 4 and above).
  159. Aerobic Gram-positive Acid-fast Bacilli
    Mycobacterium avium subspecies avium Infections

    General
    Mycobacterium avium subspecies avium causes a variety of disease conditions in humans, birds and selected domestic animals.
  160. Aerobic Gram-positive Acid-fast Bacilli
    Mycobacterium avium subspecies avium Infections

    Etiology
    • -M. avium subspecies avium is an aerobic gram-positive acid-fast bacillus and is a member of Runyon group III.
    • -M. avium subspecies avium has over 20 serovars.
    • -M. avium subspecies avium serovars 1 to 3 are host-adapted pathogens of birds and swine.
    • -Natural habitat of M. avium subspecies avium serovars 4 and above is the soil.
    • -Tuberculosis in chickens, turkeys and pet birds is caused by M. avium subspecies avium serovars 1 to 3.
    • -Tuberculosis in swine is caused by M. avium subspecies avium serovars 1 to 3 as well as M. bovis and M. tuberculosis.
    • -In humans, cattle and swine, mycobacteriosis is caused by selected M. avium subspecies avium serovars (serovars 4 and above).
    • -M. avium subspecies avium is commonly isolated from humans infected with conditions that result in immunosuppression such as cancer and cancer chemotherapy.
  161. Aerobic Gram-positive Acid-fast Bacilli
    Mycobacterium avium subspecies avium Infections

    Transmission
    • -In avian tuberculosis, ingestion of M. avium subspecies avium serovars 1to 3 is the most common mode of transmission.
    • -Historically in porcine tuberculosis, swine have been infected with M. avium subspecies avium serovars 1 to 3 after contact with chickens that have tuberculosis or with an environment previously occupied by poultry with tuberculosis. Today, avian tuberculosis in poultry has been drastically reduced so swine are only infrequently infected with these avian-adapted serovars.
    • -In human, bovine and porcine mycobacteriosis, selected M. avium subspecies avium serovars are acquired from the soil by ingestion or inhalation. These agents are noncommunicable among humans, cattle and swine.
  162. Aerobic Gram-positive Acid-fast Bacilli
    Mycobacterium avium subspecies avium Infections

    Clinical Features
    • -In poultry, most M. avium subspecies avium infections are found during meat inspections.
    • -In bovine and porcine mycobacteriosis and porcine tuberculosis, M. avium subspecies avium infections are difficult to diagnose clinically because infected cattle and swine are virtually asymptomatic. Most infections are found during meat inspections.
    • -In human mycobacteriosis, most M. avium subspecies avium infections occur in the lungs of immunocompromised patients with acquired immunodeficiency or cancer. These infections are frequently diagnosed utilizing contemporary methods such as radiology and culture.
  163. Aerobic Gram-positive Acid-fast Bacilli
    Mycobacterium avium subspecies avium Infections

    Pathogenesis
    M. avium subspecies avium serovars are facultative intracellular pathogens and induce chronic granulomatous lesions (mycobacteriosis lesions and tubercles).
  164. Aerobic Gram-positive Acid-fast Bacilli
    Mycobacterium avium subspecies avium Infections

    Pathology
    • -In birds and pigs, tubercles are pathognomonic for tuberculosis.
    • -In humans, cattle and swine, mycobacteriosis produces granulomatous lesions.
  165. Aerobic Gram-positive Acid-fast Bacilli
    Mycobacterium avium subspecies avium Infections

    Diagnosis
    • -M. avium subspecies avium can be cultured on Lowenstein-Jensen agar under aerobic conditions at 37C. M. avium subspecies avium serovars are identified with serologic methods.
    • -Tuberculin tests are seldom used for antemortem diagnoses of tuberculosis in swine.
  166. Aerobic Gram-positive Acid-fast Bacilli
    Human Leprosy

    General
    Leprosy is a chronic disease that primarily affects peripheral nerves and skin. Clinical manifestations are largely dependent upon the patient's cell-mediated immune response. Leprosy was recognized as a distinct disease condition during biblical times.
  167. Aerobic Gram-positive Acid-fast Bacilli
    Human Leprosy

    Etiology
    Mycobacterium leprae is an aerobic gram-positive acid-fast bacillus and facultative intracellular pathogen.
  168. Aerobic Gram-positive Acid-fast Bacilli
    Human Leprosy

    Transmission
    • -Most human infections are transmitted by skin-to-skin contact.
    • -Armadillos can be infected with M. leprae and are a potential source of human infections.
  169. Aerobic Gram-positive Acid-fast Bacilli
    Human Leprosy

    Clinical Features
    • -Leprosy involves the skin and peripheral nerves. There is often a profound anesthesia of affected areas.
    • -The 2 primary forms are lepromatous and tuberculoid leprosy, which are based on the differences in the affected individual's cell-mediated immune response to infection.
    • -When an individual exhibits a weak cell-mediated response, lepromatous leprosy develops. Lepromatous leprosy results in marked deformities of the hands and feet.
    • -When an individual exhibits a strong cell-mediated response, tuberculoid leprosy develops. Tuberculoid leprosy is characterized by skin lesions, which tend to remain localized.
  170. Aerobic Gram-positive Acid-fast Bacilli
    Human Leprosy

    Pathogenesis
    Cell-mediated immune response of the affected individual largely determines the pathogenesis, pathology and prognosis of the infection.
  171. Aerobic Gram-positive Acid-fast Bacilli
    Human Leprosy

    Pathology
    Acid-fast bacilli are observed in impression smears and histopathology sections of affected tissues.
  172. Aerobic Gram-positive Acid-fast Bacilli
    Human Leprosy

    Diagnosis
    • -Leprosy is diagnosed based on clinical signs and histopathology.
    • -M. leprae can be stained with the Ziehl-Neelsen stain, but cannot be stained with Gram stain.
  173. Aerobic Gram-positive Acid-fast Bacilli
    Bovine Tuberculosis

    General
    Tuberculosis is caused by Mycobacterium bovis and M. tuberculosis. These acid-fast bacteria can be stained with Ziehl-Neelsen stain, but cannot be stained with Gram stain. These mammalian tubercle bacilli have a generation time from 18 to 24 hours and can be cultured on Lowenstein- Jensen agar under aerobic conditions at 37C.
  174. Aerobic Gram-positive Acid-fast Bacilli
    Bovine Tuberculosis

    Etiology
    • -M. bovis and M. tuberculosis are aerobic gram-positive acid-fast bacilli and facultative intracellular pathogens.
    • -Cattle are the primary host of M. bovis.
    • -Humans are the primary host of M. tuberculosis.
  175. Aerobic Gram-positive Acid-fast Bacilli
    Bovine Tuberculosis

    Transmission
    • -Inhalation of aerosols from infected animals and ingestion of contaminated feed and water are the most common modes of transmission.
    • -Lungs are the primary sites of infection when the mycobacteria are inhaled.
    • -Intestinal tract is the primary site of infection when the mycobacteria are ingested.
  176. Aerobic Gram-positive Acid-fast Bacilli
    Bovine Tuberculosis

    Clinical Features
    • -Tuberculosis is a chronic and often asymptomatic disease.
    • -Tuberculosis is a rarely diagnosed in the United States. This has resulted from successful efforts of a national eradication program. The federal program is based on tuberculin testing and slaughter of cattle with tuberculosis. Most infected cattle herds are identified by traceback of animals with lesions at slaughter to the herds of origin. Tubercles and lesions with a caseous necrosis are cultured to confirm the diagnosis. Animals in the herd of origin are tuberculin tested. Animals with tuberculin-positive reactions are slaughtered and the herd is depopulated if possible.
  177. Aerobic Gram-positive Acid-fast Bacilli
    Bovine Tuberculosis

    Pathogenesis
    • -Tubercles are pathognomonic for tuberculosis and caseous necrosis lesions are characteristic. 48 Lesions can form in any organ where reticuloendothelial tissue is present. When the bacteria initially enter the host's tissues, there is an acute suppurative inflammatory reaction in the immediate vicinity of the mycobacteria. After a few days, lymphocytes and macrophages infiltrate into the area of inflammation with subsequent proliferation of connective tissue. Some macrophages develop into multinucleated giant cells, which often become the predominant cell type in the exudate. Coagulation necrosis and eventually caseous necrosis occur in the center of the lesion. Necrotic core is gradually enclosed by granulation tissue. As the lesion becomes encapsulated, macrophages are the predominant leukocyte in the area adjacent to the necrotic tissue and granulation tissue of the capsule. In time, many tubercles calcify.
    • -Lungs are the primary foci of infection following inhalation of organisms. Tracheobronchial and pulmonary lymph nodes, which drain the lymphatics from the lungs, are common secondary foci of infection.
    • -Intestines and lymph nodes associated with the gastrointestinal tract are primary foci of infection following ingestion of the organisms.
    • -Miliary tuberculosis with lesions in multiple organs can result from the erosion of a primary lesion into a blood vessel with hematogenous spread throughout the body.
    • -Cell-mediated immunity is the primary mechanism of acquired resistance.
    • -Humoral antibodies do not play a role in immunity to tuberculosis.
  178. Aerobic Gram-positive Acid-fast Bacilli
    Bovine Tuberculosis

    Pathology
    • -Tubercles are pathognomonic for tuberculosis.
    • -Lesions with a caseous necrosis are characteristic for tuberculosis.
    • -Lesions occur most frequently in the lungs and regional lymph nodes, but occur less frequently in the liver, peritoneum, pleura and spleen.
    • -Calcification of the lesions can occur, particularly in lymph nodes.
  179. Aerobic Gram-positive Acid-fast Bacilli
    Bovine Tuberculosis

    Diagnosis
    • -Caudal fold and comparative cervical tests are employed for the antemortem diagnoses of tuberculosis. These tests measure the delayed hypersensitivity of cattle that are infected with the mammalian tubercle bacilli or have had prior exposure to mammalian tubercle bacilli. False- positive tuberculin responses are caused by a variety of other mycobacteria (M. avium subspecies avium and M. avium subspecies paratuberculosis). Cattle with terminal tuberculosis and anergy often have false-negative tuberculin reactions.
    • -Caudal fold test is used for routine screening of cattle. The test involves the intradermal injection of 0.1 ml of M. bovis purified protein derivative (PPD) in the caudal fold of the tail. After 66 to 78 hours, reactions are palpated and measured. Only federally accredited veterinarians administer the test.
    • -Comparative cervical test uses M. bovis PPD and M. avium subspecies avium PPD to distinguish between homologous and heterologous tuberculin responses. This test is more sensitive and definitive than the caudal fold test and is used to clarify the status of suspects. In cattle infected with or sensitized to the mammalian tubercle bacilli, reactions to M. bovis PPD are greater than reactions to M. avium subspecies avium PPD. In cattle infected with or sensitized to M. avium subspecies avium serovars, M. avium subspecies paratuberculosis or saprophytic mycobacteria, reactions to M. avium subspecies avium PPD are greater than reactions to M. bovis PPD. However, the test cannot distinguish cattle infected with M. bovis from those infected with M. tuberculosis.
    • -Comparative cervical test can be applied up to seven days following observation of caudal fold test. Avian PPD and mammalian PPD are inoculated intradermally at two sites in the middle third of the neck. After 66 to 78 hours, each injection site is palpated and measured. Only federally trained veterinarians administer the test.
  180. Aerobic Gram-positive Acid-fast Bacilli
    Bovine Tuberculosis

    Market Traceback Program
    Market traceback program is used to identify the herd of origin with positive tuberculin reactions. Postmortem lesions are cultured to confirm the diagnosis.
  181. Aerobic Gram-positive Acid-fast Bacilli
    Bovine Tuberculosis

    Runyon Group III
    M. bovis and M. tuberculosis are classified in Runyon group III.
  182. Aerobic Gram-positive Sporeforming Bacilli
    Genus Bacillus

    General
    Bacillus species form endospores under aerobic conditions.
  183. Aerobic Gram-positive Sporeforming Bacilli
    Genus Bacillus

    Pathogenic Bacillus Species
    • -B. anthracis causes anthrax in humans and animals.
    • -B. cereus causes human foodborne intoxification.
  184. Aerobic Gram-positive Sporeforming Bacilli
    Genus Bacillus

    Habitat and Ecology
    • -B. anthracis is associated with alkaline or calcareous soils where endospores can survive indefinitely.
    • -Bacillus species, other than B. anthracis, are found ubiquitously in soil and environment.
  185. Aerobic Gram-positive Sporeforming Bacilli
    Genus Bacillus

    Cellular Characteristics
    • -Bacillus species are gram-positive sporeforming bacilli.
    • -Endospores do not distend the vegetative cells.
  186. Aerobic Gram-positive Sporeforming Bacilli
    Genus Bacillus

    Cultural Characteristics
    Bacillus species are facultative anaerobes and can be cultured on blood agar under aerobic conditions at 37C.
  187. Aerobic Gram-positive Sporeforming Bacilli
    Genus Bacillus

    Biochemical Characteristics
    Bacillus species are catalase-positive and saccharolytic.
  188. Aerobic Gram-positive Sporeforming Bacilli
    Genus Bacillus

    Anthrax Overview
    Virulence Factors of B. anthracis
    • -Genes coding the capsule and exotoxin complex are carried on 2 different plasmids.
    • -Polypeptide capsule is antiphagocytic and exotoxin complex is composed of factors I, II and III.
    • -Factor I is the edema factor.
    • -Factor II is the protective factor with antiphagocytic activity.
    • -Factor III is the lethal factor.
    • -To express biological activity, factors I and III must be associated with factor II.
  189. Aerobic Gram-positive Sporeforming Bacilli
    Genus Bacillus

    Anthrax Overview
    Human Cutaneous Anthrax
    Cutaneous anthrax infections are generally acquired via direct contact with infected food producing animals or contaminated products from food-producing animals. These infections are seldom life threatening.
  190. Aerobic Gram-positive Sporeforming Bacilli
    Genus Bacillus

    Anthrax Overview
    Human Pulmonary Anthrax
    Pulmonary anthrax infections are acquired via inhalation of endospores from contaminated hides and wool. These infections are life-threatening with almost a 100% mortality rate.
  191. Aerobic Gram-positive Sporeforming Bacilli
    Genus Bacillus

    Anthrax Overview
    Ruminant Anthrax
    In cattle and sheep, peracute infections are the most common form of anthrax. Acute infections are occasionally observed. Chronic infections are rarely observed. With peracute septicemias, deaths occur within 1 to 2 hours after clinical signs are first observed. With acute septicemias, deaths occur in 2 to 3 days.
  192. Aerobic Gram-positive Sporeforming Bacilli
    Genus Bacillus

    Anthrax Overview
    Canine, Equine, Feline and Porcine Anthrax
    • -In horses and swine, an acute pharyngitis is the most common syndrome observed. Acute infections are occasionally observed.
    • -In cats and dogs, anthrax is rarely observed.
  193. Aerobic Gram-positive Sporeforming Bacilli
    Human Bacillus cereus Foodborne Intoxification

    General
    Human foodborne intoxifications can be caused by enterotoxin-producing strains of Clostridium perfringens and Staphylococcus aureus subspecies aureus.
  194. Aerobic Gram-positive Sporeforming Bacilli
    Human Bacillus cereus Foodborne Intoxification

    Etiology
    • -B. cereus is an aerobic gram-positive sporeforming bacillus.
    • -Only B. cereus strains with the plasmid-mediated heat-labile enterotoxin and/or emetic toxin cause foodborne intoxifications. Most strains produce both the enterotoxin and emetic toxin, but some strains produce only enterotoxin or emetic toxin.
    • -B. cereus foodborne intoxifications include a diarrheal form and an emetic form.
  195. Aerobic Gram-positive Sporeforming Bacilli
    Human Bacillus cereus Foodborne Intoxification

    Transmission
    B. cereus foodborne intoxifications result from ingestion of preformed enterotoxin and/or emetic toxin from contaminated foods.
  196. Aerobic Gram-positive Sporeforming Bacilli
    Human Bacillus cereus Foodborne Intoxification

    Clinical Features
    After ingestion of contaminated food, incubation period generally ranges from 4 to 6 hours with an abrupt onset of clinical signs that include diarrhea and/or vomiting. Symptoms persist for 18 to 24 hours.
  197. Aerobic Gram-positive Sporeforming Bacilli
    Human Bacillus cereus Foodborne Intoxification

    Pathogenesis
    • -Enterotoxin of B. cereus causes a watery diarrhea. This enterotoxin has a distinct mode of action from the enterotoxins produced by C. perfringens and S. aureus subspecies aureus.
    • -Emetic toxin of B. cereus causes vomiting.
  198. Aerobic Gram-positive Sporeforming Bacilli
    Human Bacillus cereus Foodborne Intoxification

    Pathology
    Diarrhea is watery and no blood is observed.
  199. Aerobic Gram-positive Sporeforming Bacilli
    Human Bacillus cereus Foodborne Intoxification

    Diagnosis
    • -B. cereus can be cultured from contaminated food on blood agar under aerobic conditions at 37C. The isolate must be tested for the presence of enterotoxin and/or emetic toxin.
    • -Contaminated food can be tested for the presence of enterotoxin and/or emetic toxin.
  200. Aerobic Gram-positive Sporeforming Bacilli
    Bovine Anthrax

    General
    Anthrax is endemic in selected areas of the United States where infections are associated with alkaline or calcareous soils.
  201. Aerobic Gram-positive Sporeforming Bacilli
    Bovine Anthrax

    Etiology
    • -Bacillus anthracis is an aerobic gram-positive sporeforming bacillus.
    • -B. anthracis forms endospores under aerobic conditions. Within the sporangium, endospores have an oval shape with a subterminal location.
  202. Aerobic Gram-positive Sporeforming Bacilli
    Bovine Anthrax

    Transmission
    • -Anthrax often results from ingestion of contaminated feed or soil. Infections are associated with alkaline or calcareous soils where endospores of B. anthracis can remain viable for years.
    • -In endemic areas, endospores are found in soil and pasture that are contaminated with vegetative cells from dead and dying animals.
    • -To reduce the level of environmental contamination, dead animals are burned or buried in quicklime.
    • -Epidemic outbreaks of anthrax are often associated with extreme changes in climatic conditions (warm and wet weather). These environmental changes are responsible for germination of endospores and proliferation of B. anthracis.
  203. Aerobic Gram-positive Sporeforming Bacilli
    Bovine Anthrax

    Clinical Features
    • -Calves are seldom affected with anthrax.
    • -Bulls are more susceptible to anthrax than cows.
    • -Anthrax can be manifested as peracute septicemia, acute septicemia or chronic infection.
    • -Peracute septicemia is the most common form of anthrax. Deaths usually occur within 2 hours after clinical signs are first observed. Sudden deaths in cattle that appeared normal a few hours earlier are common.
    • -Death with the acute septicemia form occurs within 2 to 4 days after clinical signs are first observed. An animal can survive this form of the disease, but this is a rare occurrence. Clinical signs include anorexia, fever, hematuria and blood tinged diarrhea. Pregnant animals can abort and milk production is abruptly decreased. Terminal signs include depression, respiratory distress and convulsions.
    • -In chronic infections, clinical signs are manifested for more than 6 days.
    • -The number of animals that contract anthrax during an epidemic is variable.
    • -Case fatality ratio is greater than 90%.
  204. Aerobic Gram-positive Sporeforming Bacilli
    Bovine Anthrax

    Pathogenesis
    • -Ingestion of B. anthracis contaminated forages is the primary mode of infection and the intestinal tract is the primary portal of entry.
    • -Capsule (D-glutamic acid polypeptide) and exotoxin complex (factors I, II and III) are encoded on 2 different plasmids (pX1 and pX2).
    • -Capsule is antiphagocytic and plays an important role in establishment of infection. Antibodies to capsular polypeptide act as opsonins and prevent establishment of infection.
    • -Exotoxin complex is composed of factors I, II and III and is responsible for clinical signs in the toxemia stage of the infection. The blood level of the exotoxin increases rapidly late in the course of the disease.
    • -Factor I is the edema factor.
    • -Factor II has antiphagocytic activity and is the protective antigen.
    • -Factor III is the lethal factor.
    • -Antibodies to factor II prevent the expression of factor I and factor III.
  205. Aerobic Gram-positive Sporeforming Bacilli
    Bovine Anthrax

    Pathology
    • -Carcasses of cattle putrefy rapidly and develop incomplete rigor mortis. Blood is dark, clots poorly and exudes from anus, mouth and nose and spleen is enlarged, dark and friable. Affected lymph nodes are edematous and hemorrhagic and ecchymotic hemorrhages on serosal surfaces of abdomen and thorax are common. Subcutaneous edematous swellings are often present on the ventral aspect of the neck.
    • -If anthrax is suspected, necropsy of affected animals should be avoided to reduce environmental contamination and health risks to veterinarians. Carcasses are often buried at the site.
  206. Aerobic Gram-positive Sporeforming Bacilli
    Bovine Anthrax

    Diagnosis
    • -Presumptive diagnoses are made based on clinical signs and gross pathology.
    • -In Gram stained blood smears, vegetative cells of B. anthracis are arranged in chains of bacilli with square ends.
    • -In Giemsa stained blood smears and impression smears from affected organs, capsule of B. anthracis can be demonstrated.
    • -Culture and biochemical identification of B. anthracis is used to confirm the diagnosis.
    • -On aerobic blood agar cultures, colonies are large, flat, gray and nonhemolytic. Each colony is composed of parallel chains of cells, which give the margin of the colony its characteristic ‘Medusa head’ appearance.
    • -Endospores with an oval shape and subterminal location are demonstrated in Gram stained smears prepared from the colonies.
    • -Capsules are not formed on aerobic blood agar cultures, but capsules are formed on capnophilic blood agar cultures.
  207. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    General
    • -Pathogenic Clostridium species produce a variety of toxins and extracellular enzymes.
    • -Anaerobic Genus: Clostridium
  208. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    Pathogenic Clostridium Species
    • -Over 25 Clostridium species have been isolated from clinical infections in humans, birds and domestic animals.
    • -C. botulinum causes botulism in humans, birds and selected domestic animals.
    • -C. chauvoei causes bovine blackleg.
    • -C. perfringens causes human foodborne intoxification, human gas gangrene and ovine enterotoxemia.
    • -C. tetani causes tetanus in humans and animals.
  209. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    Habitat and Ecology
    • -Intestinal tracts of animals and soil are habitats of the medically important Clostridium species.
    • -Clostridia isolated from soils become associated with disease by direct contamination of wounds or as transient flora of the gastrointestinal tract.
    • -In general, clostridia cause disease only as opportunistic infections that are secondary to some primary injury or management problem.
  210. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    Cellular Characteristics
    • -Clostridium species are gram-positive sporeforming bacilli and form endospores under anaerobic conditions.
    • -Endospores produced by the Clostridium species distend vegetative cells.
  211. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    Cultural Characteristics
    Clostridium species are obligate anaerobes and can be cultured on brain heart infusion blood agar under anaerobic conditions at 37C.
  212. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    Biochemical Characteristics
    Clostridium species can be asaccharolytic or saccharolytic.
  213. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    Fluorescent Antibody Tests
    • -Fluorescent dyes include fluorescein and rhodamine.
    • -Fluorescent antibody conjugates are used for identification of selected Clostridium species (C. chauvoei). When specimens are stained and viewed under ultraviolet light with a fluorescent microscope, antibody-dye labeled specimens have yellowish-green fluorescence with fluorescein and reddish-orange fluorescence with rhodamine.
  214. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    Clostridia Intoxifications
    Clostridial intoxifications result from ingestion of a preformed toxin or toxin production from a localized infection (botulism and tetanus).
  215. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    Clostridial Infections
    Clostridial infections result from an infection of host tissues with subsequent toxin production (blackleg).
  216. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    Clostridial Virulence Factors
    • -Pathogenic Clostridium species produce extracellular enzymes and toxins that are predominant mediators of pathological changes in the host. These extracellular enzymes and toxins are highly immunogenic
    • -Some toxins are bacteriophage-mediated (C. botulinum toxins C and D).
  217. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    Clostridial Extracellular Toxins
    Most clostridial toxins are extracellular toxins, which have biological activity when they are excreted or released from the bacterium.
  218. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    Clostridial Protoplasmic Toxins
    • -Protoplasmic toxins are released after cell lysis.
    • -Protoplasmic toxins are synthesized as prototoxin (no biological activity) and subsequently acted on by proteases to form a holotoxin (biological activity).
    • -Botulinum toxins (A to F) and tetanospasmin are holotoxins with 1 A subunit and 5 B subunits. The A subunits possess the biological activity of the toxins, and the B subunits bind to susceptible host cells, which determines the host range and tissue tropism of the toxin.
    • -The A subunits of botulinum toxins cause a flaccid paralysis.
    • -The A subunit of tetanospasmin causes tonic muscular contractions.
  219. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. botulinum and Botulinum Toxins
    Environment and Enteric Flora
    C. botulinum is ubiquitous in the environment and is found in soil, vegetation and occasionally in the intestinal contents of birds, fish and mammals. Vegetative cells proliferate in dead material under anaerobic conditions and produce botulinum toxin. The toxin is released when the cells are lysed.
  220. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. botulinum and Botulinum Toxins
    Intoxifications and Toxicoinfections
    • -An intoxification where a preformed botulinum toxin is ingested is the most common form of transmission.
    • -A toxicoinfection where C. botulinum causes an infection of the digestive tract or wound with subsequent absorption of botulinum toxin is a rare mode of transmission.
  221. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. botulinum and Botulinum Toxins
    Botulinum Toxins
    • -Botulinum toxins affect the autonomic nervous system, central nervous system and peripheral motor nerves. Botulinum toxins cause a flaccid paralysis with death due to asphyxiation. Botulinum toxins attach to the presynaptic terminal of cholinergic nerves where they block the release of acetylcholine. Toxin receptors in the presynaptic membrane contain gangliosides that bind the toxin. Once the toxin has become fixed to the nerve endings, botulinum antitoxins cannot neutralize the toxin.
    • -Botulinum toxin types A to F are immunologically distinct, but the mode of action of each toxin type is identical. Each toxin type is synthesized as a prototoxin with no biological activity. Prototoxin is cleaved by proteases to produce a holotoxin with 1 A subunit and 5 B subunits. Interchain disulfide linkages hold the A subunit and B subunits together. The A subunit is responsible for flaccid paralysis and the B subunits bind to susceptible neurons and determine host range.
    • -Clinical botulism does not induce demonstrable antibody because the amount of toxin sufficient to induce a humoral immune response would be lethal.
    • -Botulinum toxins are the most potent toxins on a gram for gram basis to produce intoxifications in humans and susceptible animals and birds.
  222. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. botulinum and Botulinum Toxins
    Genetics of Botulinum Toxin
    • -Genes for botulinum toxin types A, B, E and F are carried on the chromosome.
    • -Genes for botulinum toxin types C and D are carried by lysogenic bacteriophages. It is possible to cure C- and D-producing C. botulinum strains, which result in nontoxigenic strains. The reinfection of a nontoxigenic strain with a bacteriophage restores toxigenicity. If a cured strain is infected with a heterologous bacteriophage carrying a different toxin type, the strain will produce a different toxin type. Each C. botulinum strain produces only one botulinum toxin type.
  223. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. botulinum and Botulinum Toxins
    Physical Properties of Botulinum Toxins
    • -Botulinum toxins are heat-labile when treated at 100C for 10 minutes.
    • -Botulinum toxins are inactivated by the acidity of the gastric secretions.
  224. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. botulinum and Botulinum Toxins
    Human and Animal Susceptibility to Botulinum Toxins A to F
    • -Humans are susceptible to botulinum toxins A, B, E and F.
    • -Cattles are susceptible to botulinum toxins C and D.
    • -Horses are susceptible to botulinum toxin B.
    • -Cats, dogs and pigs are resistant to botulism.
  225. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. botulinum and Botulinum Toxins
    In Vivo Botulinum Toxin Neutralization Tests
    • -C. botulinum toxin types A to F are identified on the basis of their botulinum toxins, which cause flaccid paralysis and death in mice. Botulinum toxins are tested in mice for identification of toxin type in a culture of the suspect organism, animal's serum or food sample by specific antitoxin. Mice inoculated with the toxin but not with an appropriate antitoxin develop flaccid paralysis that results in asphyxia and death. Mice protected with type-specific antitoxin survive.
    • -For example, botulinum antitoxin A protects mice against botulinum toxin A, but botulinum antitoxin A does not protects mice against botulinum toxins B, C, D, E or F.
  226. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. botulinum and Botulinum Toxins
    Botulinum Antitoxins and Toxoids
    • -Commercial botulinum antitoxins are available. These type-specific antisera provide passive humoral immunity.
    • -Commercial botulinum toxoids are available. These type-specific toxoids provide active humoral immunity.
  227. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. tetani and Tetanus Toxin
    Environment and Enteric Flora
    C. tetani is found in soil and is a common inhabitant of intestinal tracts of animals (horses). Endospores of C. tetani are commonly found where manure is used as a fertilizer.
  228. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. tetani and Tetanus Toxin
    Intoxification and Toxicoinfection
    • -Tetanus is a toxicoinfection where an intoxification follows an infection.
    • -There are three modes of transmission (parental infections from wounds contaminated with endospores, puerperal infections acquired postpartum and newborn infections acquired via the umbilical cord).
    • -In a wound, endospores germinate and vegetative cells proliferate to form a focus of infection. On cell lysis, tetanospasmin is released as a prototoxin with no biological activity. Prototoxin is cleaved by proteases to produce a holotoxin with 1 A subunit and 5 B subunits. Interchain disulfide linkages hold the A subunit and B subunits together. The A subunit is responsible for tonic muscular contractions and the B subunits bind to susceptible neurons and determine host range.
  229. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. tetani and Tetanus Toxin
    Neural Toxin
    • -Tetanospasmin reaches the central nervous system by neural or vascular spread.
    • -With neural spread, tetanospasmin is transported along axons centripetally from peripheral nerve endings to the central nervous system. A localized ascending tetanus is produced.
    • -With vascular spread, blood transports tetanospasmin. A generalized descending tetanus is produced that begins with the head and progressively involves the body below the head.
    • -Tetanospasmin affects motor cells within the cerebrospinal axis and fixes to ganglioside and is avidly bound to gray matter. The main action of tetanospasmin is on anterior horn cells of the spinal cord and brainstem. The spasmogenic effect of tetanospasmin is due to its blocking action of spinal inhibitory synapses resulting in hyperflexia and spasms of skeletal muscle. Tetanospasmin blocks release of gamma-amino-butyric acid and glycine. Gamma-amino-butyric acid causes presynaptic inhibition and glycine causes postsynaptic inhibition.
    • -Tetanus is characterized by tonic muscular contractions (extremities, face, neck and other parts of the body). Muscular spasms are provoked by the slightest stimulation (movement, noise and touch). Spasms in response to stimuli are pathognomonic and painful with a sudden onset. There is violent rigidity and opisthotonus is extreme. Severe contractions can compromise respiration.
  230. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. tetani and Tetanus Toxin
    Human and Animal Susceptibility to Tetanus Toxin
    • -Tetanus occurs in humans and animals, but their susceptibility varies.
    • -Clinical tetanus does not induce demonstrable antibody because the amount of toxin sufficient to induce a humoral immune response would be lethal.
    • -Tetanospasmin is 1 of the most potent bacterial toxins on a gram for gram basis to produce intoxifications in humans and animals.
  231. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. tetani and Tetanus Toxin
    In Vivo Tetanus Toxin Neutralization Tests
    To test for C. tetani, culture filtrate of a suspected organism is injected into mice. Some mice have been protected by previous inoculation of tetanus antitoxin, which contains antibodies to tetanus toxin. In a positive test, mice without antitoxin have tonic muscular contractions that result in asphyxia and death. Mice protected with antitoxin survive.
  232. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. tetani and Tetanus Toxin
    Tetanus Antitoxin and Toxoid
    • -Commercial tetanus antitoxin is available. This antitoxin provides passive humoral immunity.
    • -Commercial tetanus toxoid is available. The toxoid provides active humoral immunity. C. perfringens
  233. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. perfringens
    Major Lethal Toxins and Diseases
    General
    C. perfringens types A, B, C, D and E are identified on the basis of their major lethal toxins and toxin neutralization tests for determining major lethal toxins are conducted using mice.
  234. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. perfringens Major Lethal Toxins and Diseases
    Major Lethal Toxins
    • -C. perfringens type A produces alpha toxin.
    • -C. perfringens type B produces alpha toxin, beta toxin and epsilon toxin.
    • -C. perfringens type C produces alpha toxin and beta toxin.
    • -C. perfringens type D produces alpha toxin and epsilon toxin.
    • -C. perfringens type E produces alpha toxin and iota toxin.
  235. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. perfringens Major Lethal Toxins and Diseases
    In Vivo Major Lethal Toxin Neutralization Tests
    • -In mice, type A antiserum protects against type A.
    • -In mice, type B antiserum protects against types A, B, C and D.
    • -In mice, type C antiserum protects against types A and C.
    • -In mice, type D antiserum protects against types A and D.
    • -In mice, type E antiserum protects against types A and E.
  236. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. perfringens Major Lethal Toxins and Diseases
    Human Foodborne Intoxification
    Enterotoxin producing C. perfringens strains cause human foodborne intoxifications. These are acquired by ingestion of preformed enterotoxin. After a 4 to 6 hour incubation period, affected individual exhibits diarrhea and vomiting for 18 to 24 hours.
  237. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. perfringens Major Lethal Toxins and Diseases
    Human and Animal Infections
    • -C. perfringens is the most common cause of extraintestinal infections in humans and animals.
    • -C. perfringens causes human gas gangrene.
  238. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    C. perfringens Major Lethal Toxins and Diseases
    Ovine Infections
    • -C. perfringens type A causes anemia, hemoglobinuria and icterus.
    • -C. perfringens type B causes an enterotoxemia with acute hemorrhagic enteritis in lambs less than 2 weeks-of-age.
    • -C. perfringens type C causes hemorrhagic enteritis with diarrhea in lambs and convulsions and sudden deaths in adults.
    • -C. perfringens type D causes an enterotoxemia with minimal intestinal lesions and brain lesions with liquefactive necrosis.
  239. Anaerobic Gram-positive Sporeforming Bacilli
    Genus Clostridium

    Clostridial Immunogens and Immunization
    • -Clostridial cells, extracellular enzymes and toxins are highly immunogenic.
    • -Anacultures, antitoxins, bacterins and toxoids are used to immunize humans and/or animals.
    • -Anacultures are comprised of bacterins and toxoids.
  240. Anaerobic Gram-positive Sporeforming Bacilli
    Human Botulism

    General
    Humans are susceptible to botulinum toxin types A, B, E and F.
  241. Anaerobic Gram-positive Sporeforming Bacilli
    Human Botulism

    Etiology
    Clostridium botulinum is an anaerobic gram-positive sporeforming bacillus.
  242. Anaerobic Gram-positive Sporeforming Bacilli
    Human Botulism

    Transmission
    • -C. botulinum is found in soil, vegetation and intestinal contents of animals, birds and fish. Vegetative cells proliferate in dead material under anaerobic conditions and produce botulinum toxin, which is released on autolysis of the cells.
    • -Intoxication where preformed botulinum toxin is ingested is the most common mode of infection.
    • -Toxicoinfection where C. botulinum causes an infection of the digestive tract or wound with subsequent toxin absorption is an infrequent mode of infection.
  243. Anaerobic Gram-positive Sporeforming Bacilli
    Human Botulism

    Clinical Features
    Botulism is characterized by flaccid paralysis with death due to asphyxiation.
  244. Anaerobic Gram-positive Sporeforming Bacilli
    Human Botulism

    Pathogenesis
    • -Botulinum toxins A, B, E and F attach to presynaptic terminal of cholinergic nerves and depress formation and/or release of acetylcholine at the myoneural junction.
    • -Botulinum toxins affect the autonomic nervous system, central nervous system and peripheral motor nerves.
    • -Each botulinum toxin is synthesized as an inactive prototoxin.
    • -Each holotoxin has 1 A subunit and 5 B subunits. The A subunit has the biological activity and causes the flaccid paralysis and the B subunits bind to receptors on neurons.
  245. Anaerobic Gram-positive Sporeforming Bacilli
    Human Botulism

    Pathology
    Botulism is a physiologic disease, and lesions are not produced.
  246. Anaerobic Gram-positive Sporeforming Bacilli
    Human Botulism

    Diagnosis
    • -Clinical diagnoses are based on clinical symptoms.
    • -Diagnoses are confirmed by demonstrating the presence of botulinum toxin in serum or feces.
    • -C. botulinum can be cultured from the environment, feces or food.
    • -C. botulinum can be cultured on brain heart infusion blood agar under anaerobic conditions at 37C.
  247. Anaerobic Gram-positive Sporeforming Bacilli
    Human Tetanus

    General
    Tonic muscular contractions are caused by tetanospasmin, which is the neurotoxin of Clostridium tetani.
  248. Anaerobic Gram-positive Sporeforming Bacilli
    Human Tetanus

    Etiology
    C. tetani is an anaerobic gram-positive sporeforming bacillus.
  249. Anaerobic Gram-positive Sporeforming Bacilli
    Human Tetanus

    Transmission
    • -C. tetani is found in soil and is a transient enteric flora of animals.
    • -Three modes of transmission are recognized.
    • -Parental tetanus infections occur when a wound is contaminated with endospores.
    • -Newborn tetanus infections are acquired when the umbilicus is contaminated with endospores.
    • -Puerperal tetanus infections result from a postpartum infection in a mother.
    • -Most infections result from endospore contamination of wounds.
  250. Anaerobic Gram-positive Sporeforming Bacilli
    Human Tetanus

    Clinical Features
    • -Tetanus is characterized by tonic muscular contractions.
    • -Muscular spasms are provoked by the slightest stimulation (noise, movement and touch). Clinical signs in response to stimuli are pathognomonic. Spasms are painful with a sudden onset. There is violent rigidity with opisthotonus. Severe contractions often compromise respiration.
    • -The term lockjaw is used to describe muscular contractions that rigidly close or lock the jaws together.
    • -Tetanus is a nonimmunizing disease because the amount of tetanospasmin needed to produce disease and cause death is too small to induce an immune response.
  251. Anaerobic Gram-positive Sporeforming Bacilli
    Human Tetanus

    Pathogenesis
    • -C. tetani produces tetanolysin (hemolysin) and tetanospasmin (neural toxin).
    • -Tetanospasmin is responsible for clinical manifestations of tetanus.
    • -After the period of active growth has ceased and the bacterial cells are lysed, tetanospasmin is released as a prototoxin. Proteolytic enzymes nick the prototoxin to form the holotoxin with 1A subunit and 5 B subunits. The B subunits bind to the membrane of neuronal cells and the A subunit is responsible for the toxicity. Tetanospasmin affects motor cells within the cerebrospinal axis. The toxin fixes to a specific ganglioside and is avidly bound to gray matter. The main action of tetanospasmin is on anterior horn cells of the spinal cord and brainstem. Spasmogenic effect is due to its blocking action of spinal inhibitory synapses. This results in hyperflexia and spasms of skeletal muscle. Tetanospasmin blocks release of gamma-amino-butyric acid and glycine. Gamma-amino-butyric acid mediates a presynaptic inhibition and glycine mediates a postsynaptic inhibition.
    • -Endospores contaminate a wound then germinate in the wound. On cell lysis, tetanospasmin is released and reaches the central nervous system by neural or vascular spread.
    • -Neural spread produces an ascending localized tetanus where tetanospasmin is transported by axoplasmic route from the peripheral nerve endings to central nervous system along the axons.
    • -Vascular spread by blood produces a descending generalized tetanus that begins with the head and progressively involves the body below the head. Descending tetanus occurs when more tetanospasmin is present at the infection site than can be absorbed by motor nerves. The excess toxin is taken into the circulatory and lymphatic systems. Spread of toxin occurs through neural pathways after it has been taken up by the nerve endings.
    • -Tetanospasmin cannot cross the blood-brain barrier.
  252. Anaerobic Gram-positive Sporeforming Bacilli
    Human Tetanus

    Pathology
    Tetanus is a physiological disease without gross or microscopic lesions.
  253. Anaerobic Gram-positive Sporeforming Bacilli
    Human Tetanus

    Diagnosis
    • -The initial diagnosis of tetanus is based on clinical symptoms with a history of a puncture wound contaminated with soil or feces.
    • -C. tetani can be cultured on brain heart infusion blood agar under anaerobic conditions at 37C. The isolation of C. tetani from infected humans is often difficult because the organism is not invasive and the amount of toxin needed to produce clinical tetanus is so small an infected wound site is not observed to culture.
  254. Anaerobic Gram-positive Sporeforming Bacilli
    Human Gas Gangrene

    General
    Clostridium perfringens type A is the most common cause of gas gangrene.
  255. Anaerobic Gram-positive Sporeforming Bacilli
    Human Gas Gangrene

    Etiology
    C. perfringens is an anaerobic gram-positive sporeforming bacillus.
  256. Anaerobic Gram-positive Sporeforming Bacilli
    Human Gas Gangrene

    Transmission
    • -Most cases of gas gangrene result from contamination of wounds with endospores or vegetative cells of C. perfringens type A.
    • -C. perfringens is a common inhabitant of the intestinal tracts of humans, birds and animals.
  257. Anaerobic Gram-positive Sporeforming Bacilli
    Human Gas Gangrene

    Clinical Features
    • -C. perfringens is generally introduced into tissue by trauma or surgery with incubation period of several days to a week.
    • -Gas gangrene is characterized by extensive muscle necrosis with gas formation in affected tissues. Patients often exhibit shock, renal failure and death within two days of initial onset of clinical disease.
  258. Anaerobic Gram-positive Sporeforming Bacilli
    Human Gas Gangrene

    Pathogenesis
    C. perfringens produces a variety of extracellular enzymes and toxins (alpha, delta, kappa, lambda, mu and theta toxins and neuraminidase) that play a role in the disease process.
  259. Anaerobic Gram-positive Sporeforming Bacilli
    Human Gas Gangrene

    Pathology
    Affected tissues exhibit a marked myonecrosis with gas accumulation.
  260. Anaerobic Gram-positive Sporeforming Bacilli
    Human Gas Gangrene

    Diagnosis
    • -Most cases of gas gangrene are diagnosed based on clinical signs and pathology.
    • -C. perfringens can be cultured on brain heart infusion blood agar under anaerobic condition at 37C. The bacterium produces double-zone hemolysis.
  261. Anaerobic Gram-positive Sporeforming Bacilli
    Bovine Blackleg

    General
    More cattle are immunized for blackleg with Clostridium chauvoei anacultures than for any other disease.
  262. Anaerobic Gram-positive Sporeforming Bacilli
    Bovine Blackleg

    Etiology
    C. chauvoei is an anaerobic gram-positive sporeforming bacillus.
  263. Anaerobic Gram-positive Sporeforming Bacilli
    Bovine Blackleg

    Transmission
    Endospores in soil and forages are ingested, penetrate the intestinal tract and eventually lodge in muscle tissues where they reside latently until the infections are activated.
  264. Anaerobic Gram-positive Sporeforming Bacilli
    Bovine Blackleg

    Clinical Features
    • -Most clinical infections occur in cattle from 6 months-of-age to 2 years-of-age. Calves less than 6 months-of-age are apparently resistant to clinical disease and cattle over 3 years-of-age are seldom involved. Blackleg occurs primarily in animals in good body condition that are kept on permanent pasture. The disease is frequently associated with particular farms or pastures.
    • -Blackleg is an acute febrile disease with lameness that is almost always associated with a characteristic swelling in heavily muscled areas of the back, hip, neck and shoulder.
    • -Cattle usually die within three days after symptoms appear.
    • -Cattle are frequently found dead without clinical signs having been observed.
  265. Anaerobic Gram-positive Sporeforming Bacilli
    Bovine Blackleg

    Pathogenesis
    • -Infections are acquired by ingestion of endospores.
    • -Endospores are transported across the alimentary mucosa in macrophages and then distributed in the muscles as well as other tissues.
    • -Endospores reside in the muscle as a latent infection until injured by bruising or other injuries that devitalize the tissue. Germination of the endospores and vegetative growth require an alkaline pH and low oxidation-reduction potential. Once vegetative cells become established in the initial focus of infection, extracellular enzymes and toxins produced by the bacteria provide a suitable and expanding environment for further bacterial growth. In the devitalized muscle, there is edema, necrosis and gas formation. There is evidence of infection with swelling in the heavy muscle areas within 24 hours of endospore germination. This necrosis results from extracellular enzymes and toxins produced by C. chauvoei.
    • -Incubation period ranges from one to five days and blackleg is usually fatal from one to three days after symptoms appear. Death results from a systemic intoxication.
  266. Anaerobic Gram-positive Sporeforming Bacilli
    Bovine Blackleg

    Pathology
    • -Carcasses of affected animals have swellings in musculature with stiff extension of the limbs. Depending on how long the animal has been dead and environmental temperature, the carcass can be distended with gas. Affected skeletal muscles are dark brown or dark red and streaked with black. Similar lesions are occasionally found in the tongue. Subcutaneous tissue in the area of infection has a blood-tinged exudate with large deposits of gas.
    • -Acute endocarditis lesions occur in 20 to 30% of the cattle that die of blackleg. The lesions generally involve the left atria.
  267. Anaerobic Gram-positive Sporeforming Bacilli
    Bovine Blackleg

    Diagnosis
    • -Swelling in the affected area, muscle lesions and stiff limbed posture of a carcass distended with gas are characteristic of blackleg.
    • -Fluorescent antibody conjugates specific for somatic antigens of C. chauvoei are used for laboratory confirmation.
    • -C. chauvoei can be cultured on brain heart infusion blood agar under anaerobic conditions at 37C.
  268. Anaerobic Gram-positive Bacilli

    General
    Clinical significances of extracellular pathogens in the genera Actinomyces, Bifidobacterium, Eubacterium and Propionibacterium are presented. Genus Actinomyces includes both facultative anaerobes and obligate anaerobes, but other genera are obligate anaerobes.
  269. Anaerobic Gram-positive Bacilli

    Anaerobic Genera:
    • -Actinomyces, Bifidobacterium, Eubacterium, Propionibacterium
    • -Note: Some Actinomyces species are facultative anaerobes.
  270. Anaerobic Gram-positive Bacilli

    Anaerobic Genera:
    Genus Actinomyces
    • -Actinomyces species cause chronic granulomatous or pyogranulomatous lesions.
    • -In cattle, A. bovis causes actinomycosis and is characterized by proliferative osteomyelitis of the mandible and/or maxilla and chronic granulomatous lesions in soft tissues of head and neck.
    • -In dogs, A. hordeovulneris infections are associated with foreign bodies, especially grass awns implanted into soft tissues.
    • -In humans, A. israelii causes actinomycosis.
    • -In dogs, A. viscosus causes pulmonary actinomycosis.
  271. Anaerobic Gram-positive Bacilli

    Anaerobic Genera:
    Genera Bifidobacterium, Eubacterium and Propionibacterium
    • -Bifidobacterium, Eubacterium and Propionibacterium species are enteric flora.
    • -Propionibacterium species are flora of mucous membranes.
    • -From suppurative lesions and abscesses, these opportunistic pathogens are isolated in mixed culture with obligate anaerobes and/or facultative anaerobes. From polymicrobial infections, two or more bacterial species are isolated.
  272. Anaerobic Gram-positive Bacilli

    Cellular Characteristics
    • -Actinomyces, Bifidobacterium, Eubacterium and Propionibacterium species are gram-positive bacilli.
    • -Actinomyces species are pleomorphic bacilli and occasionally exhibit branching in vivo.
    • -Bifidobacterium species are pleomorphic bacilli with distinctive club-shaped and branching forms.
  273. Anaerobic Gram-positive Bacilli

    Cultural Characteristics
    • -A. bovis and A. israelii are obligate anaerobes and can be cultured on brain heart infusion blood agar under anaerobic conditions at 37C.
    • -A. hordeovulneris and A. viscosus are microaerophilic bacteria and can be cultured on blood agar under microaerophilic conditions at 37C. Carbon dioxide concentrations from 3 to 8% are required for optimal growth of many Actinomyces species.
    • -Bifidobacterium, Eubacterium and Propionibacterium species are obligate anaerobes and can be cultured on brain heart infusion blood agar under anaerobic conditions at 37C.
    • -Brewer jar with a GasPak generator provides an anaerobic atmosphere.
  274. Anaerobic Gram-positive Bacilli

    Biochemical Characteristics
    Actinomyces, Bifidobacterium, Eubacterium and Propionibacterium species are saccharolytic with a fermentative metabolism.
  275. Anaerobic Gram-positive Bacilli
    Genus Actinomyces

    General
    Actinomyces species cause chronic granulomatous or pyogranulomatous tissue reactions.
  276. Anaerobic Gram-positive Bacilli
    Genus Actinomyces

    Pathogenic Actinomyces Species
    • -A. bovis causes bovine actinomycosis and equine fistulous withers.
    • -A. hordeovulneris causes canine opportunistic infections.
    • -A. israelii causes human actinomycosis.
    • -A. viscosus causes canine pulmonary actinomycosis.
  277. Anaerobic Gram-positive Bacilli
    Genus Actinomyces

    Habitat and Ecology
    • -Pathogenic Actinomyces species occur as commensals on mucous membranes of the genital tract and oral and nasal cavities.
    • -Soil is the natural habitat of many Actinomyces species.
  278. Anaerobic Gram-positive Bacilli
    Genus Actinomyces

    Cellular Characteristics
    • -Actinomyces species are gram-positive pleomorphic bacilli.
    • -Some Actinomyces species exhibit branching in vivo, but they seldom exhibit branching in vitro.
  279. Anaerobic Gram-positive Bacilli
    Genus Actinomyces

    Cultural Characteristics
    • -A. bovis and A. israelii are obligate anaerobes and can be cultured on brain heart infusion blood agar under anaerobic conditions at 37C.
    • -For optimal growth of most Actinomyces species, carbon dioxide concentrations from three to eight percent are required.
    • -A. hordeovulneris and A. viscosus are microaerophilic and can be cultured on blood agar under microaerophilic conditions at 37C.
  280. Anaerobic Gram-positive Bacilli
    Genus Actinomyces

    Biochemical Characteristics
    Actinomyces species are saccharolytic with a fermentative metabolism.
  281. Anaerobic Gram-positive Bacilli
    Genus Actinomyces

    Disease Overview
    Human and Domestic Animal Infections
    • -Selected Actinomyces species cause chronic granulomatous or pyogranulomatous tissue reactions in humans and animals.
    • -Most A. bovis infections occur in cattle, but rarely occur in humans or other animals.
    • -Most A. israelii infections occur in humans, but rarely occur in animals.
    • -Most A. viscosus infections occur in dogs, but rarely occur in humans or other animals.
  282. Anaerobic Gram-positive Bacilli
    Genus Actinomyces

    Disease Overview
    Human Infections
    Chronic granulomatous lesions with multiple draining tracts characterize A. israelii infections. Most infections are acquired from the endogenous oral flora. In affected soft tissues, colonies of A. israelii form granules with a yellowish-white color. These granules are called ‘sulfur granules’ due to their color.
  283. Anaerobic Gram-positive Bacilli
    Genus Actinomyces

    Disease Overview
    Bovine Infections
    A. bovis causes actinomycosis. The disease is characteristic by chronic proliferative osteomyelitis of the mandible and/or maxilla. Soft tissue granulomatous lesions with granules are also commonly observed. Granules with a yellowish-white color are composed of a bacterial colony in a hyaline matrix. These granules are called ‘sulfur granules’ due to their color.
  284. Anaerobic Gram-positive Bacilli
    Genus Actinomyces

    Disease Overview
    Canine Infections
    • -A. hordeovulneris infections are generally initiated when grass awns are implanted into tissues producing chronic pyogranulomatous lesions.
    • -A. viscosus is the primary agent of pulmonary actinomycosis (empyema and pleuritis) and can be isolated in pure or mixed culture with facultative anaerobes and/or obligate anaerobes. Pulmonary actinomycosis is often indistinguishable from pulmonary nocardiosis, which is caused by Nocardia asteroides.
  285. Anaerobic Gram-positive Bacilli
    Genus Actinomyces

    Disease Overview
    Equine Infections
    A. bovis, like Brucella abortus, causes fistulous withers with chronic draining lesions. In fistulous withers, bursa between the nuchal ligament and dorsal spines of the thoracic vertebrae are affected.
  286. Anaerobic Gram-positive Bacilli
    Bovine Actinomycosis

    General
    Actinomyces bovis produces encapsulated granulomatous lesions with granules in soft tissues of the head and neck. When the mandible and/or maxilla are affected, the condition is called lumpy jaw. These lesions are pathognomonic for actinomycosis. When the bones of the jaw are not affected and soft tissues are chronically infected, it is difficult to differentiate actinomycosis from actinobacillosis, which is caused by Actinobacillus lignieresii.
  287. Anaerobic Gram-positive Bacilli
    Bovine Actinomycosis

    Etiology
    A. bovis is an anaerobic gram-positive bacillus.
  288. Anaerobic Gram-positive Bacilli
    Bovine Actinomycosis

    Transmission
    • -A. bovis is a transient inhabitant of the bovine oral flora.
    • -A. bovis is implanted into soft tissues of the head and neck and the mandible and/or maxilla from the endogenous oral flora. Abrasions of oral mucous membranes allow the bacterium to establish an infection in the underlying soft tissues and/or bones of the jaw.
    • -A. bovis does not invade intact mucus membranes.
  289. Anaerobic Gram-positive Bacilli
    Bovine Actinomycosis

    Clinical Features
    • -Classical features of lumpy jaw are painless hard swellings on the mandible and/or maxilla, which result from proliferative osteomyelitis. When soft tissues are involved, granulomatous lesions are formed with draining tracts. These chronic infections can persist for months or years.
    • -Affected animals are afebrile and may be emaciated through interference with mastication, which is common if the mandible and/or maxilla are involved.
    • -The occurrence of actinomycosis is sporadic.
  290. Anaerobic Gram-positive Bacilli
    Bovine Actinomycosis

    Pathogenesis
    • -Virulence factors of the bacterium are poorly understood.
    • -When the mandible and/or maxilla are infected, the infection destroys the bone and stimulates new growth. This is called a proliferative osteomyelitis.
    • -When soft tissues are infected, encapsulated granulomatous lesions with granules are formed. Granules are two to three millimeters in diameter with a pale yellow color and are called ‘sulfur granules’ due to their color. Granule contains a bacterial colony surrounded by a protein precipitate.
    • -Infections frequently spread to regional lymph nodes.
    • -Acquired immunity to the infection is poorly understood.
  291. Anaerobic Gram-positive Bacilli
    Bovine Actinomycosis

    Pathology
    • -Proliferative osteomyelitis lesions of the mandible and/or maxilla are pathognomonic.
    • -Encapsulated granulomatous lesions in soft tissues of the head, neck and regional lymph nodes with granules are characteristic.
  292. Anaerobic Gram-positive Bacilli
    Bovine Actinomycosis

    Diagnosis
    • -Proliferative osteomyelitis lesions of the mandible and/or maxilla are pathognomonic.
    • -Encapsulated granulomatous lesions in soft tissues of the head and neck with granules in the exudate are characteristic. 
    • -Gram stained granules with a central mass of gram-positive pleomorphic bacilli are pathognomonic. Granules of A. bovis are larger and harder than granules of A. lignieresii.
    • -A. bovis can be cultured on brain heart infusion blood agar under anaerobic conditions at 37C.
    • -A. bovis can be identified to the genus level using gas-liquid chromatographic analyses of volatile and nonvolatile fatty acid products of glucose metabolism that are produced from anaerobic peptone-yeast extract-glucose cultures. The bacterium can be identified to the species level using biochemical test procedures for anaerobic bacteria.

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