In general, the infection that develops depends on the virulence of the particular strain, the inoculum size, and the 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 (e.g., boils, carbuncles, and furuncles) to bullous impetigo; largely opportunistic infections that develop as a result of previous injury (e.g., cuts, burns, and 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 and 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 (TSST-1, formerly known as enterotoxin F) 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 the skin and can allow the organism to spread systemically via the bloodstream (i.e., 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 and deeper tissue invasion or bacteremia and hematogenous spread, or any combination thereof.
