Staphylococci and Enterococci

  1. What is the general characteristics of streptococci and enterococci (G(-/+), oxygen requirement, catalase, oxidase, non-motile)
    • G (+) cocci in chains or diplococci
    • facultative anaerobes
    • requires enriched media with blood or serum
    • catalase (-)
    • oxidase (-)
    • non motile
  2. streptococcus antigen (lancefield groupings)
    • applies only to B hemolytic strep
    • strep antigens are grouped in A, B, C, F, and G
    • enterococci share D group with D group strep but are non hemolytic
  3. what are a hemolytic strep also called
  4. what are the viridian's group
    • anginosus
    • mitis
    • mutans
    • salivarius
    • bovis
  5. what are examples of B hemolytic streptococci (2)
    • s. progenies: group A
    • S. agalactiae: group B
    • S.anginosus
    • S. dysgalactiae
  6. what are some examples of viridans streptococci
    • s. pneumoniae: encapsulated
    • anginosus, minis, mutans, salivarius, bovis groups
  7. what are some examples of enterococcus (2)
    • e. faecalis
    • e. faecium
  8. aerococcus is similar to what group of strep and why
    • viridans
    • is catalase (-)
  9. what is the blood growth of streptococcus pyogenes
    • optimal growth on blood agar
    • small colonies with large B hemolytic zones
  10. what is the antigenic determinants on the cell surface of streptococcus pyogenes
    • Group A antigen
    • M protein: differs between strains
    • lipoteichoic acid and F protein: facilitate binding to host cells.
  11. what are the virulence factors of S. pyogenes (3)
    • hyaluronic acid capsule: imitates hyaluronic acid in connective tissue and masks the bacteria from immune system
    • M proteins: interfere with phagocytosis
    • C5a peptidase: protects bacteria from early clearance from infected tissues
  12. what are the molecules involved with attachment and invasion of host cells for S. pyogenes
    • lipoteichoic acid: binds to fibronectin and epic cells
    • M proteins and F protein: adhesions binding to specific host cell receptors
  13. what kind of antigens are streptococcal pyrogenic exotoxins (SpeA, SpeB, SpeC, SpeF)
  14. what are the toxins and enzymes released by s. pyogenes
    • streptolysin S
    • streptolysin O
    • streptokinase A and B
    • DNAses A to D
  15. what is the function of streptolysin S and where is it produced
    • oxygen stable, nonimmunogenic, hemolysin
    • stimulates release of lysosomal contents after engulfment, causing death of phagocyte
    • produced in presence of serum (hence "S")
  16. what is the function of streptolysin O
    • oxygen sensitive hemolysin
    • lyses RBC, leukocytes, platelets
  17. what inhibits streptolysin O
    cholesterol in skin lipids, prevents ASO antibodies do not form in skin infections
  18. what antibody is used to detect streptolysin O
    antistreptolysin O (ASO) antibodies
  19. what is the function of streptokinase A and B
    • destroys blood clots and fibrin deposits.
    • spreading factor for s. pyogenes
  20. function of DNAse A to D
    cleave DNa in pus
  21. what group is s. pyogenes
    Group A strep
  22. where is group A strep found in the body
    • oropharynx by transient colonization
    • not considered part of a healthy, stable microbiome
  23. what are the noninvasive diseases caused by s. pyogenes and how are they caused
    • pharyngitis: "strep throat"pyoderma: skin infection
    • infections caused before immune system produces antibodies or before normal microbiome organisms out compete them through respiratory droplets/ skin
  24. what are diseases caused by s. pyogenes that affects the throat
    • pharyngitis: strep throat
    • scarlet fever: complication of pharyngitis
  25. how does scarlet fever present itself
    • occurs when infecting s. pyogenes train is lysogenized by bacteriophage that mediates production of a pyrogenic (fever inducing) exotoxin
    • rash
    • strawberry tongue: yellow white coat on tongue
  26. what are the skin infections caused by s. pyogenes
    • pyoderma
    • impetigo
    • erysipelas
    • cellulitis
  27. what is pyoderma
    • any pyogenic (pus producing) skin disease
    • pyoderma=impetigo
  28. what is impetigo
    • confined infection of the superficial layer of skin, with papules that can get crusty
    • rarely leads to systemic infection
  29. what is erysipelas
    • infection of epidermis and involves the lymphatic system
    • bright red, salmon colored skin
    • includes pain, inflammation, and lymph node enlargement
  30. what is cellulitis
    • skin infection involving subcutaneous layers of skin and produces systemic symptoms of fever, chills, malaise
    • can develop into necrotizing fasciitis
  31. what is necrotizing fasciitis
    • infection of deep layers of skin including fascia (connective tissue).
    • includes late stage infections that spreads into fat, fascia, and muscle tissue
  32. what are the hallmarks of necrotizing fasciitis
    • toxicity
    • multi organ failure
    • death
  33. what is the treatment to necrotizing fasciitis
    extensive surgical intervention, cutting dead infected tissue
  34. what is the difference between streptococcal TSS from staphylococcal TSS
    streptococcal TSS has bacteremia and necrotizing fasciitis
  35. what is the difference between strains of s. pyogenes that cause TSS and pharyngitis
    strains that cause TSS have mucopolysaccharide acid capsules and pyrogenic exotics (SpeA and SpeC)
  36. what kind of fever is a complication of pharyngitis
    • rheumatic fever: involving inflammation of heart, joints, blood vessels.
    • affects mainly adults>children
  37. what are some clinical diseases associated with s. pyogenes
    • streptococcal toxic shock syndrome
    • rheumatic fever
    • acute glomerulonephritis
  38. what are the lab tests used to ID s. pyogenes
    • immunoassays: from throat swabs
    • nucleic acid amplification: sensitive, test of choice
    • antibody detection: ASO
    • physiological test: bacitracin susceptibility
  39. what is the effectiveness of gram stains for detecting s. pyogenes
    • gram stains are useful for s. pyogenes soft tissue infections
    • not useful for throat specific because there are too many various strains of streptococci in the normal throat microbiome
  40. what is the antibiotic treatment of s. pyogenes
    • penicillin/ amoxicillin
    • cephalosporin/ macroslide for ppl with penicillin allergies
  41. what type of group strep are not normally found in healthy microbiomes
    group A
  42. what is the treatment for s. pyogenes
    • antibiotics
    • surgical removal
    • intravenous antibiotics
  43. what group is streptococcus agalactiae
    group B antigen
  44. what are the identifying serological markers
    • group specific cell wall polysaccharide B antigen
    • specific capsular polysaccharides
    • surface proteins (most common is c antigen)
  45. what is the virulence factor of s. alagactiae and how does it commonly infect the type of people
    • contains polysaccharide capsule
    • neonates take longer to develop antibodies so they are most affected by S. Agalactiae infections
    • genital colonization has been associated with increased risk of premature delivery
  46. describe s. agalactiae induced early onset neonatal disease
    • acquired in utero/first week in life
    • bacteremia, pneumonia, meningitis
    • mortality rate <5%
    • <30% of infants who survive meningitis have severe neurological disorders: blindness, deafness, mental retardation
  47. what is the required test for suspected s. agalactiae early onset neonatal disease
    examination of CSF (cerebral spinal fluid) for suspected meningitis
  48. describe late onset neonatal disease induced by s. agalactiae
    • develops between 1 week and 3 months of age
    • bacteremia with meningitis
    • low mortality rate <3%
    • neurological complications common 25-50%
  49. what is the treatment of S. Agalactiae
    • GBS susceptible to penicillin
    • pregnant women are screen for colonization at 35-37 wks gestation
    • prophylactic antibiotics are administered to colonized pregnant women
  50. what are the general characteristics of streptococcus pneumoniae
    • polysaccharide capsules
    • G(+) cocci, in pairs or chains
    • a- hemolytic
    • colonies are mucoid, large and green
    • phosphorylcholine: unique to S. Pneumoniae cell walls and plays a role inc ell wall hydrolysis
  51. what are the enzymes S. Pneuomoniae release pathogenesis
    • secretory IgA protease and Pneumolysin: similar to streptolysin O, prevents envelopment and clearing
    • amidase, peptidolygcan, teichoic acids, pneumolysin: attract inflammatory immune cells to site of pneumococcal infection
  52. what are the virulence factors of S. Pneumoniae
    • surface protein adhesins
    • secretary IgA protease
    • pneumolysin
    • amidase
    • phosphorylcholine
    • H2O2
    • capsules
  53. what is phosphorylcholine
    molecule in cell wall that binds to receptors on host cells which allows pneumococci to enter cells and protects from opsonization
  54. what part of the body is pneumococci in the normal flora
    nasopharynx and throat
  55. what are the common clinical disease pneumococci can cause
    • sinusitis
    • otitis: ear infection
    • meningitis
    • pneumonia
    • bacteremia
  56. how can s. pneumoniae be  tested
    • gram stain of sputum
    • immunoassays: for C polysaccharide
    • soluble in bile
    • difficult to culture
    • optochin sensitivity: to ID s. pneumoniae from other G(+) cocci
  57. what antibiotics are S. Pneumoniae resistant to
    • penicillin
    • vancomycin
  58. what are the general characteristics of virdans streptococci
    • majority are non hemolytic and a-hemolytic
    • G (+)
    • highly antibiotic resistant

    • rarely found on skin surface
    • need 5-10% CO2 for growth
  59. what are the five sub groups of virdans
    • anginosus
    • mitis
    • salivarius
    • mutans
    • bovis
  60. enterococcus general characteristics
    • initially Group D strep
    • G(+) cocci in pairs/ chains
    • non hemolytic
    • grow aerobically and anerobically
    • wide pH range (4.6-9.9)
    • grows in high salt and bile concentrations
    • highly antibiotic resistant
    • infections are nosocomial
  61. what part of the body are enterococcus a part of the normal microbiome
    gut and genitourinary tract
  62. what are the virulence factors for enterococcus
    • not many virulence factors
    • surface proteins
    • membrane glycolipids
    • gelatinase
    • pili
  63. what are clinical diseases caused by enterococcus
    • UTI
    • peritoneal infections: caused by trauma or other disease
    • bacteremia
    • endocarditis
  64. what are some of the tests used to differentiate enterococcus
    nucleic acid test
Card Set
Staphylococci and Enterococci
characteristics of staphylococci and enterococci