Microbiology Lecture Test 3

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Microbiology Lecture Test 3
2014-04-08 12:33:48

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  1. The Main Genera of Gram Positive Cocci
    • 1. Family Streptococcaceae
    • 2. Family Micrococcaceae
  2. Family Streptococcaceae
    • Family Streptococcaceae
    • 1. genus Enterococcus
    • 2. genus Streptococcus
  3. 2. Family Micrococcaceae
    • Family Micrococcaceae:
    • 1. genus Staphylococcus
    • 2. genus Micrococcus
  4. Catalase Test
    differentiates between 1. Micrococcae and 2. Streptococcacea

    • 1. Micrococcaceae= catalase (+)
    • 2. Streptococcacea= catalase (-)

    • Staphylococci contain the enzyme catalase which converts H2O2 (hydrogen peroxide) into water and oxygen.
    • The test is performed by emulsifying a colony of staphylococcus in H2O2 and observing a bubbling reaction as O is liberated.
  5. Hemolysis types
    • 1. Gamma (y) hemolysis- no hemolysis
    • 2. Alpha hemolysis -zone  of green - partial lysis of RBC's
    • 3. Beta hemolyisis- clear zone of hemolysis - complete lysis of RBC's
  6. Staphylococcus General Characteristics
    • Gram (+)
    • cocci
    • clusters

    • mainly inhabitants of the skin, skin glands, and mucous membranes
    • generally opportunistic pathogens that enter through skin ruptures
    • 31-40 diff species
    • 6-7 are clinically significant, the rest are found mainly in animals
  7. Staphylococcus (most commonly isolated species)
    • 1. Staphylococcus aureus (most serious pathogen)
    • The Coagulase (-)
    • 2. Staphylococcus epidermidis
    • 3. Staphylococcus capitis
    • 4. Staphylococcus hominis
    • 5. Staphylococcus saprophyticus
  8. Staphylococcus aureus
    Growth and Physiological Characteristics
    • Size: M-L
    • Color: buttery white to creamy to golden
    • w/some strains being B-hemolytic
    • facultative anaerobes
    • extremely resistant to adverse environmental conditions: pH, temp, drying, and many disinfectants
    • Virulent Factors Enzymes and toxins:
    • 1. Coagulases (triggers clotting of plasma)
    • 2. Staphylokinase (fibrinolysin) - dissolves fibrin clots
    • 3. Lipases
    • 4. Hyaluronidases
    • 5. Deoxyribonucleases
    • Toxins:
    • 1. Cytolytic toxins (1. Hemolysins 2. Leukocidins)
    • 2. Enterotoxins -A, B, C, C2, D, E, and F
    • 3. Exfoliative toxin (epidermolytic toxin) and Toxic Shock Syndrome toxin (TSST)
    • Staphylococcus aureus is present in most environments, colonization of some infants begins hrs after birth
    • carriage rate in normal healthy adults ranges from 20%-60% mostly in the anterior nares (will be present in the on the skin and mucous membranes)
    • main predisposing factors include: tissue injury, preexisting primary infections, diabetes mellitus, poor hygiene
    • Methicillin Resistant (MRSA)
    • emerged in mid 80's as 1 of the so called "superbugs"
    • multi-resistant organism that poses an epidemiological problem in the hospital setting (nosocomial infections)
    • 10-15% of population are carries
    • 95% of strains of S. aureus have acquired genes for penicillinase
    • Strains of MRSA carry multiple resistance to antimicrobials including methicillin, gentamicacin, cephalosporins, tetracycline, erythromycin, and even quinolones
    • few strains have acquired resistance to all major drug groups except Vancomyosins
    • Scope of clinical Staphylococcal disease:
    • 1. Localized cutaneous infections (superficial skin infections)
    • a.Boils or furuncles
    • b. Carbuncles
    • 2. Post-operative wound infections
    • 3. UTI's
    • 4. Bacteremia, meningitis, osteomyelitis
    • Staphylococcal infections
    • inhabit nasopharynx, they can be aspirated into the lungs and cause a pneumonia involving multiple abcesses and symptoms of fever, pain, and bloody sputum
    • circulating bacteria can be transported to the liver, kidney and spleen and form abscesses
    • Toxigenic Staphylococcal disease
    • 1. Food Poisoning- caused by strains that produce enterotoxins A, B, and D in improperly refrigerated food (mayonnaise. processed meats, sauces, ham, chicken)
    • 2. Scalded Skin Syndrome (SSS) or Ritter's disease- caused by strains that produce the exofoliative or epidermolytic toxin
    • 3. Toxic Shock Syndrome (TSS)
    • associated w/high fever, rash, vomiting, and sometimes death
    • caused by strains that producce the toxin TSST-1 also known as enterotoxin F
    • originally associated w/tampon use
    • (sunburn-like rash, fascitis necroticans- extreme infection of skin and deeper parts, influenza-like rash, signs of soft tissue infection, coma, multiogan failure,

  9. Osteomyelitis
    • established in the metaphysis of a variety of bones (femur, tibia, ankle, wrist)
    • abcess formation in the infected area result in a tender lump causing bone breakage
    • symptoms: fever, pain, chills, and muscle spasms
  10. TSS Prevention
    • read manufacture's instructions about the use of tampons
    • compare absorbency from brand to brand
    • be familiar with the terms "junior", "regular", "super", and "super plus"
    • wear only during the day
    • replace 4-6hrs
    • wash hands before inserting
  11. Coagulase
    • Coagulase is a plasma clotting enzyme secreted by Staphylococcus aureus- allows for clot formation
    • 1. (+) Staphylococcus aureus
    • 2. (-) Staphylococcus epidermis or S. saprophyticus
  12. Staphylococcus epidermidis
    • generally part of the normal flora of the skin and mucous membranes
    • mainly associated w/nosocomial infections such as catheter site infections, shunts, incision site infections, and nosocomial UTI"s
    • associated w/ UTI's in elderly
    • Characteristics of S. epidermidis:
    • resembles S. aureus in microscopic and colonial morphology
    • Coagulase (-)
    • Novobiocin- sensitive

  13. Staphylococcus saprophyticus
    • generally produces white to extremely white colonies
    • microscopic morphology resembles S. aureus
    • it is mainly part of the normal skin flora
    • Clinical Significance:
    • mainly associated w/UTI's that involve the bladder and (or) the kidneys in young sexually active women or in adolescent girls
    • Coagulase (-)
    • key biochem test is that it is resistant to Novobiocin disc
  14. Treatment of Staphylococcal infections
    • penicillin susceptible strains (about 5%) are treated w/penicillin
    • majority strain of S. aureus lactamase which allows them to breakdown penicillin
    • susceptibility studies are recommended due to the variability in susceptibility patterns of penicillin resistant strains
    • Drainage of abscesses should be performed for successful therapy
    • 40% of nosocomial S. aureus infections are caused by MRSA
    • new threat is an increasing number of Vancomycin resistant S. aureus
  15. Family Streptococcaceae
    • 1. Streptococcus
    • 2. Enterococcus
  16. Family Streptococcaceae
    • 1. Streptococcus 2. Enterococcus
    • gram (+)
    • generally arranged in chains
    • catalase (-)
    • divided into categories based in the type of hemolysis they produce
    • Classification and naming of Streptococci
    • streptococci are classified and named following two systems:
    • 1. Hemolytic pattern in conjunction with the Lancefield grouping
    • 2. Scientific name from taxonomic organization
    • Beta Hemolytic Streptococcus
    • 1. Streptococcus pyogenes
    • S. pyogenes is a strict parasite generally involved in upper respiratory tract infections
    • Taxonomy-Beta Hemolytic
    • these organisms can be further divided into a number of immunologic groups known as the Lancefield Groups (given alphabetic designations)
    • Groups A, B, C, F, and G are commonly associated w/human infections
    • Group A: Streptococci= S. pyogenes
    • Group B Streptococci= S. agalactiae
    • Virulence factors and toxins:
    • 1. C carbohydrates- can also be teichoic acids found on surface of cell wall-protect from host cell's lysozyme defense
    • 2. M-protein- resists phagocytosis and increases adherence
    • 3. Capsule- chemically indistinguishable from HA capsules of host
    • 4. Streptolysins- hemolysin that destroys that injures WBCS, liver, and heart tissue
    • 5. Erythrogenic toxin- contributes to red rash and fever of scarlet fever
    • 6. Streptokinase
    • 7. Hyalyronidase
    • Epidemiology and Pathogeneis:
    • humans are the only significant reservoirs of S. pyogenes
    • 5-15% of population are carriers
    • outbreaks are seasonal, main pop. group affected is children 5-15yrs
    • Main infections associated with S. pyogenes:
    • skin infections: 1. Empetigo (associated w/poor hygiene, insect bites, and crowded living conditions)
    • 2. Erysipelas
    • 3. Cellulitis
    • 4. Wound infections
  17. Strept Throat
    • redness, edema, and swelling of pharyngeal membranes which results in difficulty in swallowing
    • other fever, headache, nausea, and abdominal pain
    • purulent discharge exudate may form over the tonsils and swollen lymph nodes
    • tonsils may be white patch and contain white abscesses as well as pus
  18. Upper respiratory tract infections
    • 1. Pharyngitis- tonsillitis (strep throat)- often diagnosed by symptoms and direct antigen testing
    • 2. Scarlet fever- caused by a strain capable of producing the pyrogenic toxin
    • similar symptoms as in pharyngitis w/ addition of a skin rash and yellow to white coloration of tongue
  19. Long term complications and conditions associated w/ S. pyogenes
    • 1. Rheumatic fever (inflammatory condition of the joints, heart, and subcutaneous tissues)
    • 2. Acute glomerulonephritis (AGN) (affects filtration of blood)
    • 3. Streptococcal toxic shock syndrome
    • 4. Streptococcal gangrene (necrotizing fascitis) also known as "flesh eating disease)
    • note: necrotixing (dead) fascitis- connective tissue sheath around muscles and other organs
  20. Complications
    • Rheumatic fever (begin between 6 weeks after a strep infection)
    • return fever after strep infection has finished
    • pain, swelling and redness in joints
    • shortness of breath
    • unusual skin rashes
    • unusually fast heart beat or heart damage
  21. Glomerulonephritis
    • develops between 3-6 weeks after the initial strep infection
    • puffiness of face
    • swelling of ankles
    • headaches
    • high blood pressure
  22. Necrotizing Fascitis
    • streptococcus are introduced into small abrasions or cuts, where they grow rapidly
    • their enzymes digest connective tissue in skin, while their toxins poison the epidermal and dermal tissue
    • rare, but potential for harm is high
    • most aggressive infections have come from the Rocky Mountains and East
    • Epidemiologists believe that these new strains are probably mutants that have acquired toxin genes from infecting viruses
    • high incidence in 80's
    • note that even the most virilant strains are not antibiotic resistant
  23. Other infections include:
    • 1. Ear infections
    • 2. Bacteremia and septicemia
    • 3. Endocarditis
    • 4. Meningitis
  24. Identification of Streptococcus pyogenes
    • size: Pinpoint-Small
    • large zone of hemolysis
    • key biochem reaction- sensitive (+) to bacitracin (A) disc
    • Latex agglutination
  25. Antibiotic identification discs:
    • 1."A" disc- Bacitracin disc
    • 2."P" disc- Optochin disc
  26. 1. "a" disc
    • 1. Bacitracin discs ("A" disc)
    • distinguishes Streptococcus pyogenes from Streptococcus agalactiae
    • Streptococus agalactiae is resistant to it
  27. 2. Streptococcus agalactiae
    • B-hemolytic Streptococcus group B
    • normal flora in: GI tract, vaginal canal
    • size: Pinpoint-Small convex
    • very small zone of hemolysis
    • key biochem reaction- positive CAMP test
  28. Main infections associated w/ Streptococcus agalactiae
    • In adults:
    • UTI's, skin infections, bacteremia, endocarditis, osteomyelitis, post-partum infections (septicemia), urogenital (reproductive and urinary) infections in females
    • In neonates:
    • #1 agent implicated in pneumonia, bacteremia, meningitis
  29. 3. B-helolytic Streptococcus groups C, F, and G (found in animals)
    • may be involved in the same types of infections as groups A and B but with less frequency and generally in a milder form of the disease (NP infections, pneumonia, abscesses, meningitis)
    • are not identified with one single biochemical test;
    • identified by a Latex agglutination test 
  30. Alpha hemolytic Streptococcus
    • 1. Streptococcus viridans group
    • 2. Streptococcus pneumoniae
  31. Other Viridans strains
    • Streptococcus oralis
    • Streptococcus mutans
    • produce slime layers that are made of glucose polymers that adhere to tooth surfaces
    • these sticky polysaccharides are the basis for plaque, the adhesive white material that comes from coinfected with other bacteria and fosters dental disease
  32. Streptococcus viridans group
    • alpha hemolytic
    • group of at least 5 species of gram(+) cocci that are Alpha-hemolytic resembling Streptococcus pneumoniae (Streptococcus mitans, S. mutans, S. Milleri, S. salivarius, S sanguis)
    • part of normal flora of the oral cavity (gingiva, cheeks, tongue, saliva) as well as teh nasopharyx, genital tract, and skin
    • occasionally involved in subacute endocarditis
    • differential from Streptococcus pneumoniae by a negative (resistant) optochin "P" disc
  33. Endocarditis (Symptoms)
    range from fever, heart murmur, emboli, weight loss, anemia
  34. 1. Streptococcus pneumoniae
    • Alpha-hemolysis
    • gram (+)
    • lancet shaped
    • Pinpoint
    • "checker" appearance
    • "P" disc-Optochin
    • Most common infections caused:
    • 1. Lobar Pneumonia, mainly caused by the encapsulated strain
    • 2. Nasopharyngeal infections
    • 3. Eye and ear infections
    • 4. Occasionally meningitis on newborns or infants
    • Symptoms of Pneumonia:
    • chills, shaking, rapid breathing, fever
    • severe pain in the chest wall, cyanosis, a cough that produces rusty colored blood sputum
    • In children, can spread to the meninges and cause meningitis
  35. 2. "P" disc
    • "P" disc- Optochin disc
    • identifies Streptococcus pneumoniae as it is sensitive to it
  36. chart Streptococcus Species
  37. Genus Enterococcus
    • Non-hemolytic
    • gram (+)
    • cocci
    • catalase (-)
    • part of normal flora of GI tract and skin
    • Opportunistic pathogens- mainly involved in UTI's and superficial skin infections and surgical wound infections
  38. Main species in the genus Enterococcus:
    • 1. Enterococcus faecalis
    • (in elderly patients undergoin surgery and affect the urinary tract, endocardium, wounds, blood, appendix, and other intestinal structures)
    • is isolated w/much more frequency
    • "superbug" VRE

    • 2. Enterococcus faecium
    • (large intestine)
    • 3. Enterococcus durans
    • (large intestine)
    • ALL species are involved in the same infections, but E. faecalis is isolated w/much more frequency
    • identified to species level by automated methods (Vitek, Microscan)
    • Key biochem test: PYR (+)
  39. Non-hemolytic (gamma)
    Hemolytic Streptococcus
    • generally part of normal flora of skin, mucous membranes, or oral cavity
    • generally non-pathogenic
    • need to be differentiated from Enterococcus by PYR test
    • Ex: S. bovis, S. equinus, and others
    • source-animals
  40. Gram (+) Antibiotic Resistance
    • 5 most significant strains in nosocomial infections are:
    • 1. Methicillin resistant Staphylococcus aureus (MRSA)
    • 2. Vancomycin resistant enterococcus (VRE)
    • 3. Multidrug resistant Streptococcus pneumonia (MDRSP)
    • 4. Vancomycin resistant Staphylococcus aureus (VRSA)
    • 5. Methicillin resistant Staphylococcus epidermsi (MRSE)
  41. Genus Neisseria
    • General Characteristics:
    • gram (-)
    • diplococci
    • adjacent side flattened (coffee or kidney bean shape)
    • capnophilic- requiring a CO2 concentration between 3-10% 
    • fastidious
    • cold labile
    • oxidase (+)
    • fimbriae

  42. Gonorrhea
    • caused by Neisseria Gonorrhoeae
    • symptoms:
    • symptomatic, mild, severe
    • appears: 2-5 days, moths, year
    • Transmission: vaginal intercourse, anal intercourse, anal intercourse, oral sex, mother to child
    • symptoms in men:
    • prostatitis, periurethral abscesses, epididymitis, sterility
    • Other complications: gonococcal conjunctivits, newborn and adylt: eye inflammation, discharge
    • gonococcal pharyngitis, sore throat, fever, chills
    • top 5 sexually transmitted diseases
    • oropharyngeal and anorectal infections
    • Specimen collection and processing:
    • plated and incubated ASAP 
    • collected on MTM based media that provide CO2 environment such as JEMBEC plates
    • Meningococcus
    • found in nasopharynx of 3-15% asymptomatic individuals
    • main strains associated with disease are: A, B, C, Y and W-135; with B being the most prevalent in the U.S. 
    • main virulent factors include the capsule, fimbriae and endotoxin production
  43. Meningitis
    • inflammation of the meninges
    • infections of the CSF
    • infections and conditions associated w./Neisseria meningitis infects the mucous membranes of the nose and throat (nasopharyngeal), causing a sore throat
    • Bacterial meningitis
    • caused by 1of3 types of bacteria
    • 1. Streptococcus pneumoniae (Pneumococcal)
    • 2. Heaemophilus influenza (Hib meningitis)
    • 3. Neisseria Meningitidis (Meningococcal)
    • Neisseria Meningitidis
    • come in 3 main or common strain called A, B, and C, and two rarer strains called Y and W-135
    • each group can be recognized by molecules present in the capsule
    • gram (-)
    • diplococcus
    • Infections and conditions associated w/ Neisseria meningitidis
    • can cause meningitis can if the bacteria enters blood and cerebral spinal fluid where it can infect the protective covering (meninges) of the brain and spinal cord.
    • Incubated: Chocolate Agar
    • Marked by: fever, sore throat, headache, stiff neck, convulsions, and vomiting
    • Symptoms:
    • early symptoms are similar to flu
    • In adults and children, the 1st are fever, vomiting, and drowsiness
    • In infants:
    • high-pitched moaning cry fever, perhaps cold hand and feet, difficult to wake up, dislike of being handled, vomiting, arching back
    • Spread: sharing utensil, drinking containers, lipstick, cigarettes, kissing
    • Aftereffects: balance problems, brain damage, deafness, epilepsy, recurring headaches, violent temper tantrums, amputations
    • Prevention: vaccination, chemoprophilaxis, drinking containers, spoon, forks, knives, covering of mouth when sneezing or coughing, good hygiene
  44. 4. Meningococcus and subcutaneous hemorrhages
    when pathogen spreads endotoxin into the generalized circulation, which is a potent white blood cells. Damage to the blood vessels caused by cytokines leads to vascular collapse, hemorrhage, and crops of legions called pertechiae
  45. Meningococcemia
    • 5. Meningoccemia can become a disease that has a sudden onset, marked by high fever, chills, delirium, and severe widespread ecchymoses
    • 6. Generalized intravascular clotting, cardiac failure, damage to the adrenal glands, and death can occur within a few hours.
    • Who is at risk?: newborns, children, young adults, elderly, AIDS patients, college students, and soldiers