Enterococcus (Enterococci)

Enterococci are a widespread bacterial genus  normally found in the intestines of humans and other animals. They are non-motile, catalase-negative, and characterized by group antigen D. They are able to proliferate at 45 °C, in the presence of 6.5% NaCl and at pH 9, qualities that differentiate them from streptococci. As classic opportunists, enterococci show only low levels of pathogenicity. However, they are frequently isolated as components of a mixed flora in nosocomial infections . Ninety percent of such isolates are identified as E. faecalis, 5-10% as E. faecium. Among the most dangerous enterococcal infections is endocarditis, which must be treated with a combination of an aminopenicillin and streptomycin or gentamicin. Therapeutic success depends on the bactericidal efficacy of the combination used. The efficacy level will be insufficient in the presence of high levels of resistance to either streptomycin (MIC >1000 mg/l) or gentamicin (MIC >500 mg/l) or resistance to the aminopenicillin. Enterococci frequently develop resistance to antibiotics. Strains manifesting multiple resistance are found mainly in hospitals, in keeping with the classic opportunistic character of these pathogens. Recently observed epidemics on intensive care wards involved strains that were resistant to all standard anti-infective agents including the glycopeptides vancomycin and teicoplanin.