Gram-Positive Cocci Flashcards
Staphylococcus: Genus Characteristics
- Gram-positive cocci
- Grape-like clusters
- Catalase positive
Staphylococcus Aureus : Species Characteristics
Coagulase positive • Golden colonies on blood agar • β - hemolytic • Ferments mannitol on mannitol salt agar
Staphylococcus Aureus: Reservoir
Normal flora, nose and skin
Staphylococcus Aureus : Transmission
• Hands • Sneezing • Surgical wounds • Contaminated food
Staphylococcus Aureus: Predisposing Factors
• Breaks in skin • Foreign body • Neutropenia • Intravenous drug abuse • Chronic granulomatous disease • Cystic fibrosis
Staphylococcus Aureus : Pathogenic Features
• Coagulase: Converts fibrinogen to fibrin • Alpha Toxin : Pore-forming, cytolytic toxin • Protein A: Inhibits IgG opsonization by binding Fc component • Enterotoxins: Fast acting, heat stable • Toxic Shock Syndrome Toxin-1 (TSST-1): Acts as superantigen • Exfoliatins: Proteases specific for cadherin desmoglein 1, promote epidermal blistering of scalded skin syndrome and bullous impetigo
Clinical Syndromes of S. aureus: Food poisoning
3-6 hours onset, salty foods, picnics (ham, canned meats, custard pastries, potato salad) Pathogenesis: Enterotoxlns A·E, preformed In food, heat stable
Clinical Syndromes of S. aureus: Infective endocarditis
Acute onset, fever. malaise, leukocytosis, heart murmur Pathogenesis: Coagulase, cytolytic toxins
Clinical Syndromes of S. aureus: Pneumonia
Typical pneumonia, salmon·colored sputum, nosocomial, ventilator. postinfluenza, high fatality Pathogenesis: Coagulase, cytolytic toxins
Clinical Syndromes of S. aureus: Osteomyelitis (No. 1 cause overall)
Bone Pain, fever, swelling, redness, lytic lesions on imaging Pathogenesis: Coagulase, cytolytic toxins
Clinical Syndromes of S. aureus: Surgical Infections
Fever. cellulitis, abscess Pathogenesis: Coagulase, oxfollaUns. TSST
Clinical Syndromes of S. aureus: Mastitis
Subcutaneous tenderness, heat, redness Pathogenesis: Coagulase cytolyslns
Clinical Syndromes of S. aureus: lmpetigo
Erythematous papules and bullae
Pathogenesis: Coagulase, exfollatlns
Clinical Syndromes of S. aureus: Scalded skin syndrome
Dlffuse epidermal peeling
Pathogenesis: Coagulase, exfollatlns
Clinical Syndromes of S. aureus: Toxic shock syndrome
Scarlatiniform: rash desquamates, involves palms and soles, fever, hypotension, multi-organ failure Pathogenesis: TSST-1 (superantigen)