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26 Cards in this Set
- Front
- Back
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Staphylococcus Aureus |
-ID by colonial and gram stain morphology -Coagulase Positive -Inhabits anterior nares, throat, and skin -gets all over us when we groom ourselves |
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Staphylococcus Aureus: Virulence Factors |
Cell Wall V. Factors: Protein A - binds to the Fc portion on IgG to inhibit phagocytosis Fibronectin-binding protein (FnBP) - bodies mucosal defence Ab's. Fn causes our upper RT to be gram positive b/c it competes with Gram negative rods. FnBP causes it to be gram negative, which allows S. aureus to bind Membrane damaging exotoxins: alpha, beta, delta, omega?, and leukocidin (kills white cells) |
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S. Aureus Virulence Factors cont'd |
Superantigen exotoxins: - high affinity for the MHC2 complex - generate a broad range of T cells and create a cytokine storm (high fever, hypotension, etc.) - exfoliation (causes scalded skin syndrome) - enterotoxins A, B, C, D, E, G cause food poisoning b/c they develop heat resistant toxins - Toxic shock syndrome toxin |
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S. Aureus: 4 Major Diseases |
1) Localized Abscess 2) Sepsis and acute endocarditis (infection of lining of the heart) 3) Hospital-acquired and post-influenzal pneumonia 4) Toxin-associated syndromes |
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Folliculitis/ Furunculosis |
hair follicle infections rarely any eruptions on palms or soles due to no hair follicles on thick skin in that area presents as little red spots/bumps everywhere |
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Toxin-Associated Syndromes |
Food Poisoning: - enterotoxins A-E, G Scalded Skin Syndrome: - Ritters disease, Staph "scarlet fever", bullous impetigo (like blisters) Toxic Shock Syndrome |
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Toxic Shock Syndrome |
- high fever - hypotension - diffuse erythema (resembles a sunburn) - hyperemia of mucous membranes - vomiting and diarrhea - sometimes progress to multi-system organ failure and death - late superficial desquamation Vagina is normally anaerobic, but air filled tampons increase toxin proudction. Ca++ and Zinc neutralize toxins - compressed foam rubber depleted zinc and caused microfisuring of vaginal wall, so the toxin entered circulation and caused toxic shock syndrome - need to remove tampons immediately from pt.s |
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Toxic Shock Syndrome Rx |
- remove source of intoxication (drain abscesses, remove tampon) - aggressive IV fluid - IV immunoglobulin - Ab's mainly serve to prevent recurrences |
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Ab S. Aureus susceptibility |
1950s - B lactamase 1980s - MRSA/EMRSA in hospital Mid 1990s - CAMRSA Late 1990s - VISA Mid 2000s - CAMRSA explosion S. aureus is getting more resistant |
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CAMRSA |
- not related to hospital MRSA - large soft tissue abscesses which tend to relapse - may cause sepsis |
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Staphylococcus Epidermis |
- coagulase negative - skin commensal, opportunistic-infections - produces slime, has affinity for prosthetic devices - loves to get on plastic - Ab resistant, needs Vancomycin |
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Staphylococcus Saprophyticus |
- coagulase negative - novobiocin resistant (for lab ID) - 2nd most common cause of UTIs in young women (1st is E. coli) - Ab susceptible |
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Streptococci |
- gram positive, spherical - do not utilize O2, but are not anaerobes (aerotolerant) - usually stain in chains (conga line) - complex nutritional requirements - distinguished from staph by colonial morphology (small, translucent colonies often hemolytic) and they lack catalase enzyme |
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Strep Classification |
- hemolytic reaction - Lancefield grouping: serotyping of C carbohydrate from cell wall --> A, B, C... - phenotypic characteristics (biochemical tests) |
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Streptococcus Pyogenes |
- B-hemolytic - Lancefield Group A - Penicillin Susceptible |
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Streptococcus Pyogenes Virulence Factors |
-capsule: hyaluronic acid -Fimbriae: M protein -Protein F (FnBP) -Exotoxins: pyrogenic exotoxins streptokinase streptodornases (DNAse) Hyaluronidase - high concentration Streptolysins O and S C5a peptidase |
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Strep pyogenes Diseases |
- acute suppurative (pus forming) infections - toxin-mediated syndromes - post-streptococcal disease |
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Acute Suppurative Infections |
Pharyngitis Skin and Soft Tissue Infections i) impetigo - amber crusts ii) Cellulitis - rapidly spreading iii) Erysipelas iv) necrotizing fascitis, non gas forming (flesh eating disease) Sepsis |
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S. Pyogenes Toxin-mediated Syndromes |
- scarlet fever: strawberry tongue and pastia's lines - strep toxic shock syndrome |
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Post-strep disease - activation of our own immune system |
- Acute Glomerulonephritis .hematuria, hypertension, edema - Rheumatic Fever .after pharyngitis only |
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Streptococcus Pneumoniae |
- lancet-shaped diplococci - alpha hemolytic, no Lancefield antigen - two colonial morphologic variants: rough and smooth --> enscapsulated and more virulent - normal throat flora, carried by up to half the population. - about 20% of strains in Canada are resistant to penicillin |
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S. Pneumoniae Diseases |
- lower RT infections - community-acquired - most common casue of pediatric otitis media and sinusitis, up to 50% - Bacterial meningitis - one of the most common - Sepsis |
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S. Pneumoniae Vaccines |
- pneumovax, a polysaccharide vaccine against 23 sterotypes for the elderly - prevnar, a heptavalent conjugate vaccine for children |
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Streptococcus agalactiae (Group B) |
- cause of nenonatal pneumonia, sepsis and meningitis - carried in the vagina by 25% of normal women, also common in throats of M&W - infants can be colonized during birth, all stereotypes - 2% of colonized infants develop pneumonia/sepsis in first postpartum week, mortality 55% -2nd week infections are meningitis |
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Group C |
- S. equi, ssp. equi and zooepidemicus - S. dysgalacgtiae, ssp. - Group C occassionally cause human sepsis associate with horses |
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Viridians |
- alpha hemolytic strep species which do not possess Lancefield antigens, not referring to S. pneumoniae - normal oral flora - the most common causes of subacuate bacterial endocarditis - S. mutans associated with caries |
