Staphylococcus aureus
Gram-positive cocci in clusters, Catalase and Coagulase +ve, nonmotile, non–spore-forming.
Virulence factor
Protein A, binds Fc-IgG, inhibiting complement activation and phagocytosis.
Protein A, binds Fc-IgG, inhibiting complement activation and phagocytosis.
Causes
Inflammatory disease—skin infections organ abscesses, pneumonia (often after influenza virus infection), endocarditis, septic arthritis, and osteomyelitis.
Inflammatory disease—skin infections organ abscesses, pneumonia (often after influenza virus infection), endocarditis, septic arthritis, and osteomyelitis.
Toxic shock syndrome (TSST-1)
TSST is a superantigen that binds to MHC II and T-cell receptor, resulting in polyclonal T-cell activation. Staphylococcal toxic shock syndrome (TSS) presents as fever, vomiting, rash, desquamation, shock, end-organ failure. Associated with prolonged use of vaginal tampons or nasal packing.
TSST is a superantigen that binds to MHC II and T-cell receptor, resulting in polyclonal T-cell activation. Staphylococcal toxic shock syndrome (TSS) presents as fever, vomiting, rash, desquamation, shock, end-organ failure. Associated with prolonged use of vaginal tampons or nasal packing.
Food poisoning (enterotoxins)
Nonbloody diarrhea and emesis due to preformed toxins (heat stable). Short incubation period (2–6 hr).
Nonbloody diarrhea and emesis due to preformed toxins (heat stable). Short incubation period (2–6 hr).
Scalded skin syndrome (exfoliative toxin)
Most commonly in infants and children under the age of 5.
Symptoms
Blisters
Fever
Large areas of skin peel or fall away (exfoliation or desquamation)
Painful skin
Redness of the skin (erythema), which spreads to cover most of the body
Skin slips off with gentle pressure, leaving wet red areas (Nikolsky's sign)
Most commonly in infants and children under the age of 5.
Symptoms
Blisters
Fever
Large areas of skin peel or fall away (exfoliation or desquamation)
Painful skin
Redness of the skin (erythema), which spreads to cover most of the body
Skin slips off with gentle pressure, leaving wet red areas (Nikolsky's sign)
MRSA (methicillin-resistant S. aureus)
important cause of serious nosocomial and community-acquired infections; resistant to methicillin and nafcillin because of altered penicillin binding protein.
important cause of serious nosocomial and community-acquired infections; resistant to methicillin and nafcillin because of altered penicillin binding protein.
Staphylococcus epidermidis
Catalase +ve, Coagulase -ve and sensitive to Novobiocin. Component of normal skin flora. Infects prosthetic devices (e.g., hip implant, heart valve) and intravenous catheters by producing adherent biofilms.
Staphylococcus saprophyticus
Catalase +ve, Coagulase -ve and resistant to Novobiocin. Second most common cause of uncomplicated UTI in young women (first is E. coli).
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