Staphylococcus aureus: biology, mechanisms of virulence, epidemiology.

The prominence of Staphylococcus aureus as a cause of serious human infection has prompted extensive studies of the microbiology, pathogenesis, and epidemiology of staphylococci and staphylococcal infections. Staphylococci are of the family Micrococcaceae, although there are diverse genetic and phenotypic differences between them and other members of this family. Of the more than 20 species of staphylococci, only three are clinically significant: S. aureus, S. epidermidis, and S. saprophyticus. These species can be distinguished by coagulase production and novobiocin resistance. Staphylococci produce a variety of structural, enzymatic, and toxic products, which are associated with adherence, invasion, toxicity, and avoidance of host defense mechanisms. In addition, a variety of host characteristics increase susceptibility to staphylococcal infection. Staphylococci are an important cause of infection in hospitals and the community. Following the introduction of antimicrobials, staphylococci rapidly developed resistance. A penicillin-resistant specific phage type, designated 80/81, caused severe outbreaks of nosocomial disease in the 1950s and 1960s. Staphylococci recently acquired resistance to methicillin and other antimicrobials, and persist as important nosocomial pathogens. Although S. aureus is one of the earliest recognized and most studied human pathogens, it is a perplexing, ever-changing, recurring public health problem.