Lec 5 (Staphylococci)- summary.docx

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Department
Microbiology and Immunology
Course
Microbiology and Immunology 2500A/B
Professor
John Mc Cormick
Semester
Fall

Description
Staphylococci - G+, staphyle = bunch of grapes - Facultative anaerobe (can use O but doesn’t need it) - 2 types- coagulase test- “snowflake” like clots - Coagulase +: S. aureus ONLY aureus=gold - Coagulase -: S. epidermidis, S. saprophticus, many others S. aureus: - efficient colonizer, no problems - likes the nose (mucous memb.) & skin (resistant to high salt) - carriers- greater risk of infection, BUT better prognosis (baseline immunity) - spread by direct or indirect contact- Fomites (towels, razors etc) - uses adhesins- to bind host tissue (fibronectin, collagen, EBP).., imp. in endocarditis Stats - Leading cause of nosocomial infections - >10mill skin/soft tissue infections/yr - 94000 invasive infetions - 19000 deaths Infections/symptoms - extracellular pathogen - pyogenic (pus- producing) infections Pus= dead nuetrophils - Hallmark = abscess (heat, red, swollen, pus) - abcess- mostly on skin, can spread to any organ - DO NOT heal themselves… rewuire Drainage, anitbiotics Causes MANY infections of diff organs/systems - because MANY VF’s – all of them regulated expression (surface or secreted when needed) - Surface VF- during exponential growth- for colonization Happy to grow in abscess, run out of - Secreted VF- during stationary phase- for invasion/spread food, then will spread VF’s- Immune invasion mechanisms 1. Protein A: on surface, binds FC region of IgG.. that the neutrophil FC receptor is supposed to bind 2. Toxins kill leukocytes: cytolytic, actual targets are WBC, but can lyse RBC, so are called Hemolysins - e.g. α toxins, leukocidins Diseases from DIRECT effect of ORGANISM – (not toxins) 1. SKIN LESIONS a) Impetigo- superficial skin infection i) Non-bullous: pimple-like w/ pus - ALSO caused by S. pyogenes ii) Bullous: painless, fluid filled blisters - ONLY caused by S. aureus b) Stye- eye’s sebaceous glands infected, drains itself, warm compress c) Furuncle (boil)- hair follicle infected, warm compress d) Carbuncle- several infected hair follicles merged 2. DEEP ABSCESSES - not superficial, still localized - wounds, surgery - constitutional symptoms - can become systemic 3. SYSTEMIC INFECTIONS - no single focus
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