Enterococci and vancomycin resistance.

The frequency of infections with multiply antibiotic-resistant gram-positive bacteria is increasing, and in some cases these organisms remain susceptible only to the glycopeptides vancomycin and teicoplanin. The appearance of transferable high-level glycopeptide resistance in enterococci--producing some strains that are now resistant to all available antibiotics--is thus a cause for concern. The enterococci readily colonize the bowel, spread rapidly among hospital patients, and transfer their antibiotic resistances widely among themselves and other gram-positive species. Glycopeptide resistance has not yet transferred in vivo to other significant pathogens, but experimental transfer to Staphylococcus aureus has been achieved in vitro. The emergence of glycopeptide-resistant enterococci has been encouraged by the increasing use of aminoglycosides, cephalosporins, and quinolones for the treatment of infections due to gram-negative bacteria and glycopeptides for infections due to staphylococci and clostridium difficile. In Europe this antibiotic pressure has been aggravated by the use of the glycopeptide avoparcin in animal feeds. The enterococci may now be poised to disseminate glycopeptide resistance among other more pathogenic gram-positive bacteria.