Staphylococcus

Staphylococcus

1. Coagulase +

   • s. aureus
     • colonize anterior nares and skin
       • carriers are healthy, asymptomatic ppl
       • direct or indirect spread
         • fomites a problem
     • leading cause of nocosomial infections
     • Signs of Infection
       • hallmark of infection = abscess
         • heat, redness, swelling and pain
     • virulence factors
       • surface
         • expressed during exponential growth
           • coagulase
           • elastin binding protein
           • protein A
             • for immune evasion
               • binds Fc part of IgG
                 • prevents recognition by Fc receptor of phagocyte
           • fibronectin binding protein
           • collagen binding protein
       • secreted (aka exotoxins)
         • expressed during stationary phase
           • alpha toxin
             • hemolysins that kill WBC (and RBC)
           • super antigens
             • enterotoxin B
             • TSST 1
     • Diseases due to Direct Effect
       • skin lesions
         • impetigo
           • bullous
           • non bullous
         • stye
         • foruncle
         • carbuncle
       • deep abscesses
         • localized
         • may have constitutional symptoms
       • systemic infections
         • bacteremia/septicemia
         • pneumonia
         • osteomyelitis
         • endocarditis
           • infection of heart valves
     • Toxin Mediated Diseases
       • toxic shock syndrome (TSS)
         • menstrual toxic shock syndrome
           • caused by TSST 1
         • fever, hypotension, rash, multiorgan dysfunction
         • occurs in assoc. w/ flesh eating disease
         • non mentrual toxic shock syndrome
         • caused by superantigens
           • overactivate T cells to cause systemic inflammatory response
       • scaled skin syndrome
         • proteases
       • food poisoning
     • resistant forms
       • MRSA
         • has mec genes
           • has PBP2A

2. Coagulase -

   • s. epidermidis
     • known to cause catheter and prostheses problems
   • s. saprophyticus
   • important cause of biofilm assoc. infections

3. coccus shaped

4. Characteristics

   • gram +
   • extracellular pathogen