Clinical Significance in Humans
Mathias Herrmann and Mark S. Smeltzer
from: Staphylococcus: Genetics and Physiology (Edited by: Greg A. Somerville). Caister Academic Press, U.K. (2016) Pages: 23-44.
This chapter is intended to provide a broad overview of the staphylococci as a cause of human infections. Several key points must be made in this regard beginning with the observation that all staphylococcal species are generally adapted to live on humans and/or other animal species as commensals. However, all also exhibit some capacity to cause infection, and therefore can all be considered opportunistic pathogens. Nevertheless, the single most prominent pathogen in the context of human infections is Staphylococcus aureus, which has the capacity to cause a remarkably diverse array of infections ranging from superficial skin and soft tissue abscesses to life-threatening infections including bacteremia, endocarditis, and osteomyelitis. The prominence of S. aureus as a human pathogen is clearly linked to two factors, the first being that it is a commensal inhabitant of 30-50% of the population and is therefore available to cause disease when given the opportunity, and the second being its ability to produce a diverse array of virulence factors when called upon under selective pressure from the host to do so. The staphylococci are also highly adaptable at a genetic and phenotypic level, a primary manifestation of the first being the recent emergence of methicillin-resistant strains even among isolates associated with community-acquired infections, and a primary manifestation of the second being that these isolates exhibit phenotype characteristics that threaten the definition of S. aureus as an opportunistic pathogen. This brings up the additional key point that the epidemiology and pathogenesis of S. aureus infections has changed significantly in recent years. This is reflected in reports that now distinguish between classic healthcare-associated strains and those associated with community-acquired infections, with resistance to methicillin and its derivatives (e.g. oxacillin) being a common and troubling characteristic of both groups. However, the goal here is not to detail this diversity but rather to provide a broad overview of the staphylococci, with a specific emphasis on S. aureus, as both a commensal inhabitant of humans and as a human pathogen read more ...