Detection and differentiation of vanC-1, vanC-2, and vanC-3 glycopeptide resistance genes in enterococci.
The VanC phenotype, as found in Enterococcus gallinarum, E. casseliflavus, and E. flavescens, is characterized by intrinsic low-level resistance to vancomycin. The nucleotide sequences of the vanC-1 gene in E. gallinarum, the vanC-2 gene in E. casseliflavus, and the vanC-3 gene in E. flavescens have been reported, although there is some disagreement as to whether E. flavescens is a legitimate enterococcal species. Previous attempts to differentiate the vanC-2 and vanC-3 genes by PCR analysis have been unsuccessful. The purpose of the present study was to detect and differentiate the three vanC determinants and examine the distribution of these genes in a collection of both typical and atypical enterococci. The 796-bp vanC-1 PCR product was amplified only from E. gallinarum isolates. As expected, due to the extensive homology in the vanC-2 and vanC-3 gene sequences, all of the E. casseliflavus and E. casseliflavus/flavescens isolates produced the 484-bp vanC-2 PCR product, although the E. gallinarum isolates were negative. Only the E. casseliflavus/flavescens isolates produced the 224-bp vanC-3 product. Using the three sets of primers, we were able to detect and distinguish the vanC-1, vanC-2, and vanC-3 genes from both typical and atypical enterococci strains. Antimicrobial susceptibility tests and analysis of genomic DNA by pulsed-field gel electrophoresis were also performed, but the results indicated that they were not able to distinguish among strains possessing the three vanC genotypes.
Clark
N C
NC
Hospital Infections Program, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. ncc1@cdc.gov
Teixeira
L M
LM
Facklam
R R
RR
Tenover
F C
FC
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000145:classification / Q000235:genetics*; D004352:Drug Resistance, Microbial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D016983:Enterococcus / Q000145:classification / Q000187:drug effects* / Q000235:genetics*; D005798:Genes, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods; D014640:Vancomycin / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C079914:VanC protein, Bacteria; D014640:Vancomycin