aureus  epidermidis nonhem olytic usua lly epidermidis epidermidis

• major component skin flora major component skin flora • opportunistic infections opportunistic infections – less common than less common than S.aureus S.aureus • nosocomial infections nosocomial infections – heart valves heart valves • Identification Identification – Non-hemolytic Non-hemolytic sheep blood agar sheep blood agar – Does not ferment mannitol Does not ferment mannitol – Non-pigmented Non-pigmented – Coagulase-negative Coagulase-negative Staphylococcus saprophyticus Staphylococcus saprophyticus • urinary tract infections urinary tract infections • coagulase-negative coagulase-negative – not differentiated from not differentiated from S. epidermidis S. epidermidis The Streptococcus Streptococcus Morphology Identification • facultative anaerobe facultative anaerobe • Gram-positive Gram-positive • Chains Chains or pairs or pairs • Catalase Catalase negative negative staphylococci are catalase positive staphylococci are catalase positive Cell surface structure of S pyogenes and extracellular substances • Lancefield groups Lancefield groups one or more species per group one or more species per group surface antigens: M, T, R surface antigens: M, T, R groupable streptococci streptococci • A, B and D A, B and D – most important most important • C, G, F

C, G, F –

Rare Rare Non-groupable Non-groupable • S. pneumoniae S. pneumoniae – pneumonia pneumonia • viridans streptococci viridans streptococci – e.g. e.g. S. mutans S. mutans dental dental caries caries Lipoteichoic Acid and F-protein Lipoteichoic Acid and F-protein fibronectin fibronectin lipoteichoic acid lipoteichoic acid F-protein F-protein epithelial cells epithelial cells M protein M protein • major target major target – natural immunity natural immunity • strain variation strain variation – antigenicity antigenicity • re-infection re-infection – occurs with different strain occurs with different strain M protein M protein M protein M protein fibrinogen fibrinogen r r r peptidoglycan peptidoglycan r r r IgG IgG Complement Complement IMMUNE IMMUNE NON-IMMUNE NON-IMMUNE