Card Set Information

2010-10-24 13:31:58

Show Answers:

  1. How are streptococcus classified?
    • by serotype (cell wall carbohydrates)
    • by hemolytic pattern
    • by biochemical properties
  2. Name some basic characteristics of streptococcus bacteria (gram characterictic, shape, cultures, oxygen requirement, motility)
    • Gm+
    • oval shaped
    • grow in pairs or chains
    • facultative anaerobes
    • non-motile
  3. Name the three (3) groups that streptococcus bacteria can be classified into
    • pyogenic steptococci
    • pneumococci
    • viridans and nonhemolytic streptococci
  4. This group of streptococcus contains cell-wall antigens(group A through T) and causes purulent infections in humans
    pyogenic streptococci
  5. This group of streptococcus contains a polysaccharide capsule and consists of only one species.
  6. This group of streptococcus is alpha-hemolytic, lacks group of carbohydrate antigens and capsular antigens, is a member of normal oral flora, and is almost never invasive.
    Viridans and non-hemolytic streptococcus
  7. Streptococcus pyogenes (Group A strep) can cause
    a variety of acute infections
  8. Streptococcus agalactiae (group B strep) can cause
    neonatal sepsis and meningeal infection
  9. Streptococcus pneumoniae (pneumococci) can cause
    bacterial pneumonia and purulent meningitis
  10. A high concentration of what sugar inhibits streptococcus growth?
  11. Steptococcus colonies can be characterized by
    small white colonies with large zones of Beta hemolysis
  12. Which group-specific and type-specific antigens are found in the cell walls of streptococcus?
    • Lancefield group A antigen
    • M protein: associated with virulent strains
    • C-terminus: highly conserved among group A strep
    • N-terminus: above surface, responsible for antigenic variability among serotypes
  13. Describe the significance of the hyaluronic acid capsule
    encapsulated strains are more likely to be responsible for severe systemic infections
  14. What factors contribute to the success of a bacterial infection?
    • Avoiding phagocytosis
    • Adhere to Cell surface
    • Invade Cells
    • Produce toxins and enzymes
  15. What immunity and pathogenic mechanisms does streptococcus exhibit?
    • To avoid phagocytosis, M proteins binds to a host serum factor H necessary for immune pathway regulation and phagocytosis. Also can form capsules
    • M protein interacts with cutaneous tissues in order to adhere to cell surface
  16. Name four types toxins or enzymes produced by streptococcus bacteria
    • streptococcal pyrogenic exotoxins (SPE)
    • Streptolysin S
    • Streptolysin O
    • Streptokinase (A&B)
  17. Describe qualities of streptococcal pyrogenic exotoxins
    • heat-liable toxins
    • act as superantigens
    • responsible for many clinical manifestations (necrotizing faciitis, strep TSS, scarlet fever)
    • only produced in strains that have been lysogenized by a bacteria containing toxin gene
  18. Describe qualities of streptolysin S
    • Oxygen stable
    • non immunogenic
    • cell-bound hemolysin
    • causes death of phagocytic cells by stimulating release of cell contents
    • Responsible for Beta hemolysis on BAP media
  19. Describe qualities of streptolysin O
    • oxygen liable hemolysin
    • antibodies readily formed against streptolysin O
    • Can cause beta hemolysis under anaerobic conditions
  20. Describe qualities of streptokinase (A & B)
    • can lyse blood clots and fibrin deposits
    • facilitates rapid spread of S. pyogenes in tissues
  21. S. Pyogenes Suppurative Clinical Diseases
    Describe characteristics of pharyngitis( strep throat)
    • develops 2-4 days after exposure
    • symptoms include sore throat, fever, malaise, headache
    • spread through contact with secretions or large droplets
    • may be followed by rheumatic fever
  22. S. Pyogene Suppurative Clinical Diseases
    Describe the characteristics of Scarlet fever
    • results from complication of streptococcal pharyngitis
    • occurs when infecting strain is lysogenized by bacteriophage that mediates production of pyrogenic exotoxin
    • yellowish-white coating covers the tongue, then is shed revealing red, raw surface
    • after pharyngitis symptoms diffuse, rash on upper chest and extremeties appears
    • rash is followed by desquamation
  23. S. Pyogene Suppurative Clinical Diseases:

    Describe the characteristics of pyoderma (impetigo)
    • affects exposed areas of the skin
    • begins after contact with infected skin or fomite; introduced through a break in the skin
    • pustules develop, rupture and then crust over
    • can spread through skin by scratching
    • primarily seen during moist, warm summer months in young children
  24. S. Pyogene Suppurative Clinical Diseases:

    Describe the characteristics of Erysipelas
    • acute skin infection
    • localized pain, inflammation, lymph node enlargement and systemic symptoms
    • infected skin becomes raised
    • usually preceded by infections of the respiratory tract or skin with S. Pyogenes.
  25. S. Pyogene Suppurative Clinical Disease

    Describe the characteristics of Cellulitis
    • involves skin and deeper subcutaneous tissue
    • distinction between infected and non-infected skin not clear
    • local inflammation and systemic symptoms
    • can be treated with antibiotics
  26. S. Pyogenes Suppurative Clinical Disease

    Describe the characteristics of Necrotizing Fasciitis (flesh easting disease)
    • streptococcal gangrene
    • infection deep in the subcutaneous layer that spreads
    • extensive destruction of muscle and fat tissue
    • introduced through break in skin
    • begins as cellulitis, and then bullae form and then gangrene and systemic symptoms develop
    • tissue destruction is associated with obstructed blood flow
    • treated with surgical removal of infected tissue
    • toxicity, multi-organ failure and death may result
  27. S. Pyogene Suppurative Clinical Diseases

    Describe the characteristics of streptococcal TSS
    • soft tissue imflammation at the infection site
    • pain, nonspecific symptoms: fever, chills, malaise, nausea, vomiting, and diarrhea
    • progresses to shock and organ failure
    • infection is bacteremic and death rate is higher (~30%) than that in staphylococcal TSS
  28. S. Pyogenes Suppurative Clinical Disease

    Describe the characteristic Bacteremia
    • rarely seen with pharyngitis, pyoderma and erysipelas
    • seen mostly with TSS and necrotizing fasciitis.
    • Mortality ~40%
  29. S. Pyogenes Nonsuppurative clinical disease

    Describe the characteristics of Rheumatic Fever
    • complication of pharyngitis
    • inflammatory disease involving heart, joints, blood vessel and subcutaneous tissues
    • causes vigorous antibody response
    • high fever, swollen joints, damage to heart valves
  30. S. Pyogenes Nonsuppurative clinical disease

    Describe the characteristics of acute glomerulonephitis
    • kidney infection
    • children usually show full recovery
    • adults progress to loss of kidney function and death
    • can follow with respiratory or cutaneous strep infection
  31. How can streptococcus pyogenes be diagnosed on a microscopic level?
    • gram stains of the affected tissue
    • is not apart of normal flora
    • is apart of normal respiratory flora
  32. How can antigens of streptococcus pyogenes be identified?
    • antibodies react with group-specific carbohydrate in cell wall
    • sensitivity to antigens is low
    • negative results must be confirmed by throat culture
    • nut used for cutaneous and non-suppurative disease
  33. How can cultures be used in the identification of streptococcus pyogenes?
    • tonsil culture
    • from impetigo, sample comes from purulent material under crusted top of lesion
    • tissue and blood cultures can be used for necrotizing fasciitis
    • antibiotics can be added to suppress normal flora, but s. pyogenes growth takes longer under these conditions
  34. Name the only species of streptococcus that carries the B antigen
    streptococcus agalactiae
  35. Which streptococcus causes childbed fever, septicemia, pneumonia, and meningitis in new borns?
    streptococcus agalactiae
  36. Characterize streptococcus agalactiea colonies
    • colonies are large with narrow zone of Beta Hemolysis
    • some strains are non-hemolytic
  37. Describe the pathogenesis and immunity characteristics of streptococcus agalactiea
    • Makes use of polysaccharide capsule that interferes with phagocytosis until patient develops protective, type-specific antibodies.
    • Some types have sialic acid on capsular polysaccharide, which inhibits activation of the immune system pathway necessary for phagocytosis.
  38. Where does S. agalactiea colonize?
    In the GI tract and genitourinary tract. There is some vaginal carriage
  39. What is the risk for of S. agalactiea colonization in pregnant women?
    • 60% of infants born to colonized mothers become colonized and the risk of premature birth increases
    • Pregnant women are at a greater risk of disease than men and non pregnant women
    • Commonly manifests as UTI and wound infections in pregnant women
    • Manifests as skin and soft-tissue infections, bacteremia, UTI and pneumonia in men and nonpregnant women.
  40. S. agalactiea: early-onset neonatal disease
    • acquired in utero or at birth and develops in the first week of life
    • manifests as bacteremia, pneumonia and meningitis
    • mortality is less than 5%
    • those who survive meningitis have neurological conditions (blindness, deafness, mental retardation)
  41. S. agalactiea: late-onset neonatal disease
    • acquired from an exogenous sources (mother or another infant); develops after 1wk-3months of age
    • manifests as bacteremia with meningitis
    • Mortality is ~3% but neurologic complications are common
  42. Who do S. agalactaie infections typically affect men and non-pregnant women?
    • generally occurs in older patients with underlying conditions
    • manifests as bacteremia, pneumonia, bone and joint infections, skin and soft tissue infections
    • higher risk of mortality
  43. How can one distinguish a sample of Strep agalactiea in a laboratory diagnosis?
    • Group B strep cultures readily grow in enriched media and large colonies generally appear after 24 hours.
    • S. Agalactiea is catalase negative and cAMP positive (CAMP factor enlarges zone of beta hemolysis forms by Staph Aureus.
  44. How can strep agalactiea be treated?
    • witth penicillin (intravenous for pregnant women)
    • requires 10x more penicillin than strep pyogenes
  45. Is a heterogenous group of alpha hemolytic and non hemolytic strep. (can have beta hemolytic strains though)
    Viridans streptococci
  46. Species of streptococci that generally colonize in the respiratory, GI tract and genitourinary tract and that lack specific antigens, toxins and virulence that other groups have
    Viridans streptococci
  47. Viridians streptococci growth on media can be described as ________ _______
    nutritionally fastidious
  48. Describe physiological and structural features of strep pneumoniae
    • encapsulated
    • colonies undergo autolysis with aging (causes a dimple in the center of the colony)
    • can be beta-hemolytic if grown anaerobically and alpha hemolytic if grown aerobically.
  49. If grown aerobically on a BAP, strep pneumoniae is ___-hemolytic due to the production of ____ that degrades hemoglobin.
    alpha; pneumolysin
  50. this species of strep colonizes in the respiratory tract, then spreads to the lungs, sinuses and middle ear. Can be transported in blood to distal sites (brain)
    strep pneumoniae
  51. this species of strep produces secretory IgG (sIgA) protease and pneumolysin to counteract envelopment
    strep pneumoniae
  52. Describe characteristics of enterococcus
    • Gm+ cocci
    • grows aerobically and anaerobically
    • had complex nutritional needs.
    • forms large colonies that can either be non-hemolytic or alpha-hemolytic
    • can grow in the presence of high concentrations of NaCl and bile salts
  53. name clinical diseases associated with enterococcus
    • Nosicomal infections (usually involving urinary tract, peritoneum and heart tissue)
    • can result in endocarditis
  54. Laboratory diagnosis of enterococcus
    • grows on nonselective media (BAP and chocolate agar)
    • is resistant to optochin
    • does not dissolve when exposed to salts (s. pneumoniae does)