In general, the infection that develops is dependent on the virulence of the particular strain, the inoculum size, and immune status of the host.
Staphylococcal infections are typically suppurative, producing abscesses filled with pus and damaged leukocytes surrounded by necrotic tissue. Skin infections range from superficial - boils, carbuncles and furuncles, to bullous impetigo; largely opportunistic infections that develop as a result of previous injury e.g., cuts, burns, surgical wounds - and scalded skin syndrome (extensive exfoliative dermatitis; also known as Ritter disease).
Other major infections include pneumonia, osteomyelitis (localized infection of bone), and septic arthritis.
S. aureus also causes food poisoning as a result of ingestion of food contaminated with an enterotoxin producing strain (enterotoxins A&D) and the potentially fatal toxic shock syndrome, a multisystem disease most often associated with the use of highly absorbent tampons. Toxic shock syndrome is attributed to another toxin (enterotoxin F – TSST1) released by certain strains of S. aureus.
Human staphylococcal infections usually remain localized by the normal host defenses. Foreign objects (fomites) such as sutures or intravenous (IV) lines - are readily colonized by S. aureus from skin and can allow the organism to spread systemically via the blood stream – bacteremia/septicemia - leading to more serious infections. Staphylococcal pneumonia is becoming a frequent complication of influenza.
Whatever the mode of entry, the invasive nature of S. aureus always poses the threat of more serious deeper tissue invasion and/or bacteremia and hematogenous spread.