Enterococcus faecium Overview
Originally classified in the 1930s as Group D Streptococci, Enterococci were officially given genus status in 1984 after hybridization studies showed a more distant relationship to Streptococci. Enterococci are gram-positive, spherical bacteria that colonize in groups or chains. They are naturally found as part of the digestive tract flora in many organisms, including humans. They are robust microbes able to tolerate relatively high salt and acid concentrations. They also seem to be able to withstand low levels of detergents, explaining why inadequate cleaning procedures can promote Enterococcus infections.
What is now recognized as pathogenic Enterococcus was studied as early as the late 1900s. Currently, Enterococcus infections account for 12% of all nosocomial infections, second only to E. coli. An Enterococcus infection can cause complicated abdominal infections, skin and skin structure infections, urinary tract infections and infections of the blood stream. These infections can be difficult to treat, particularly in cases where the strain involved has developed resistance to several antibiotics. Infection can be life threatening in such instances, especially if the patient is already immunodeficient.
There are two species of Enterococci which cause the symptoms described above, E. faecalis, which accounts for the majority of infections (79%), and E. faecium. In a study conducted between 1995 and 1997, data were collected from over 15,000 Enterococcus isolates. Of those, less than 2% of E. faecalis were found to be resistant to ampicillin and vancomycin, whereas 83% of the E. faecium isolates were resistant to ampicillin and 52% were resistant to vancomycin.
E. faecium is known to have a resistance to several types of antibiotics including quinolones and aminoglycosides. Resistance to penicillin was first observed in E. faecium in 1983, and in 1988 the first cases of resistance to the "antibiotic of last resort", vancomycin, were detected in Europe. Vancomycin-resistant strains of E. faecium were reported in the US in 1989. Resistance to several antibiotics and tolerance for adverse conditions makes E. faecium a major concern for the medical community, which has dubbed this microbe a "supergerm".
For more information on E. faecium and antibiotic resistance please see Related Links.
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Joint Genome Institute