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.
Hospital Infections Program, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. ncc1@cdc.gov
N C
NC
Clark
L M
LM
Teixeira
R R
RR
Facklam
F C
FC
Tenover
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