Enterococcal-type glycopeptide resistance genes in non-enterococcal organisms.

Although the emergence of vancomycin-resistant enterococci can be attributed, in part, to the increasing use of vancomycin in clinical practice, and glycopeptide use in animal husbandry, the origins of the enterococcal vancomycin resistance genes are not clear. The vancomycin resistance-associated genes in Enterococcus gallinarum, Enterococcus casseliflavus/flavescens, Lactobacillus spp., Leuconostoc spp., Pediococcus spp., and Erysipelothrix rhusiopathiae, are not the source of the high-level vancomycin resistance-associated genes in enterococci. There are, however, environmental organisms which have been found to have gene clusters homologous to the enterococcal vanA, vanB and vanC gene clusters; these include the biopesticide Paenibacillus popilliae, and, to a lesser extent, the glycopeptide-producing organisms Amycolatopsis orientalis and Streptomyces toyocaensis. Still, the exact sources of the enterococcal vancomycin resistance genes remain a mystery.