Enterococci: Key points in the literatures

§  Enterococci (Enterococcus spp.) are common Gram-positive cocci that colonize the gastrointestinal tract of man and many other animals. All humans and many animals carry enterococci in normal intestinal microbiota. Enterococci are only pathogenic to humans in specific circumstances.

§  Although enterococci as such are not particularly virulent, they are becoming more important as nosocomial pathogens. This is related to their resistance to several antimicrobial agents, and this resistance can be intrinsic (low-level resistance to penicillin, cephalosporins, and aminoglycosides), as well as acquired (glycopeptides, high concentrations of aminoglycosides).

§  Glycopeptide antibiotics, vancomycin and teicoplanin, are used in the treatment of serious infections due to enterococci in cases of resistance or allergy to β-lactams.

§  Despite more than 40 years of clinical use of vancomycin, glycopeptide resistance in enterococci has rarely been detected. However, resistant strains responsible for colonization or infection have been isolated with an increasing frequency from patients in the presence or absence of glycopeptide therapy.

§  Enterococci were well established as a cause of endocarditis and urinary tract infections by the early 1900s, and members of the species E.  faecalis were known to be a common cause of nosocomial infections by the early 1980s.

§  People who get VRE usually have other medical conditions which make them prone to infection. Such medical conditions include: critically ill patients in intensive care units; patients with severe underlying disease or problems with their immune systems; patients in hospital who have had major surgery; patients with urinary catheters; and patients who have received many antibiotics. Healthy people are unlikely to get VRE. If healthy people do get VRE, they usually have it only for a short time and rarely become ill.

§  The emergence of enterococci with resistance to vancomycin, seen predominantly in the species E. faecium, has been followed by an increase in the frequency with which this species is recovered. Of all enterococcal species, E. faecium, because it is often resistant to both vancomycin and ampicillin, is the most difficult to treat.

§  Current studies have demonstrated the existence of major differences in the epidemiology of the spread of vancomycin resistance between the United States and Europe. Whereas VRE in the USA seems to be a nosocomial problem, probably attributable to the extensive use of vancomycin and other broad-spectrum antibiotics, VRE in Europe are present among hospitalized patients as well as in the community possibly caused by the former use of avoparcin as growth promoters in agriculture and the consequent transmission of VRE via the food chain.

§  VRE are now the second most common cause of hospital-acquired infections. Since the vanA and vanB vancomycin resistance determinants are transferable, glycopeptide resistance might be passed on to other pathogens such as methicillin-resistant Staphylococcus aureus (MRSA), thus creating a highly dangerous pathogen difficult to treat with currently available antibiotics.