Enterococcus: review of its physiology, pathogenesis, diseases and the challenges it poses for clinical microbiology

The genus Enterococcus is composed of 38 species, the most important of which are Enterococcus faecalis and Enterococcus faecium—both human intestinal colonizers. Hospitals within the United States and around the world commonly isolate these bacteria because they are a cause of bacteremia, urinary tract infections (UTIs), endocarditis, wound infections, meningitis, intraabdominal and pelvic infections, and nosocomial and iatrogenic infections. Given the ubiquity of enterococci within the human population, it is important for laboratories to be able to distinguish these agents within hospitalized patients from other bacterial genera and also differentiate different species within the Enterococcus genus as well as different strains within each species. Unfortunately, the enterococci are emerging as serious pathogens in both the developed world, where surveillance needs to be improved and speciation procedures are inadequate or cumbersome, and in developing nations, which lack the trained hospital personnel or funding to sufficiently identify enterococci to the genus or species level. This review explores the Enterococcus genus and highlights some of the concerns for national and international clinical microbiology laboratories.