Enterococcis: pathogens of the 90s.

The genus Enterococcus consists of at least 12 species, two of which account for over 95% of the clinically important strains, E faecalis (85%-90%) and E faecium (5%-10%). Despite their ubiquity and frequent isolation, they have not been thought to cause serious disease because they lack common virulence factors. Now, however, enterococci are regarded as true pathogens and are the second leading cause of nosocomial infections. This change results from their increasing antimicrobial resistance and the extensive use of antimicrobial drugs (for example-cephalosporins) that are not active against them. Serious infections should usually be treated with a beta-lactam and an aminoglycoside, but glycopeptides have been increasingly used during the last decade. Two novel resistance patterns of particular concern recently are high level aminoglycoside resistance (HLAR) and vancomycin resistance. The prevalence of HLAR is between 15% and 55%, and glycopeptide resistance has become widespread in various geographical areas. This poses a serious problem, as such resistance may spread to other Gram-positive organisms and is often associated with resistance to other antimicrobial drugs. This may theoretically result in groups of organisms for which there will be no effective antimicrobial treatment.