Staphylococcus aureus*

Synonyms

Staph aureus

Classification

facultative anaerobic, gram+ bacteria, cocci, irregular clusters

Diseases

Sites and Sources

Diagnostic Factors

Virulence Factors

Treatment and Prevention

Commentary

This ubiquitous and hardy organism can produce, as attested to by the long (and probably not complete) list of diseases above, suppurative lesions of virtually any organ in the body. It is particularly prevalent in the hospital environment as a cause of nosocomial infection. The typical lesion is an abscess, but other presentations are common and toxin-producing strains can cause a number of systemic problems, notably toxic shock and scalded skin syndromes. The organism is also a common cause of pneumonia and is the most common cause of food poisoning. Virlulence factors include its coagulase, leukocidins, protein A (an FC binding protein), hemolysin, hyaluronidase, lipase, and a variety of toxins. The toxic shock toxin is a "superantigen" that stimulates release of interferon and IL-2, causing symptoms mimicking endotoxic shock. It is thought that this same toxin is responsible for the food poisoning. Virtually 100% of S. aureus strains are resistant to penicillin G by virtue of a plasmid encoded beta lactamase. Multiply resistant S. aureus (MSRA) is becoming more and more common with some strains even developing resistance to the antibiotic of last resort, vancomycin.