Investigation of vanA and vanB Genes in Vancomycin-Susceptible Enterococcal Strains

Abstract

AIM: The study aimed to investigate vanA/vanB resistance genes and to determine the frequency of vancomycin-variable enterococci(VVE). BACKGROUND: Enterococci that are phenotypically-susceptible to vancomycin but harbor glycopeptide resistance genes are called VVE. These strains cannot be detected by phenotypic methods, but it is possible by molecular methods. METHODS: Enterococcal strains, sensitive to vancomycin, were included in the study. These isolates were analyzed for the vanA and vanB genes by both monoplex and multiplex conventional PCR. ''Enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR)'' method was used to investigate the clonal relationship of the isolates. RESULTS: The study included 158(62.94%) E.faecalis and 93(37.05%) E.faecium strains that were susceptible to vancomycin.According to the results of multiplex PCR using vanA primers and vanB primers together, the vanA gene was detected in one(0.39%) E.faecalis isolate; the vanB gene was detected in two E.faecium and 98 E.faecalis isolates (39.84%)(Figure 1).According to the results of monoplex PCR using vanA primers, the vanA gene was detected in one (0.39%) E.faecalis isolate (Figure 2); As a result of monoplex PCR performed with vanB primers, the vanB gene was not found in any sample (Figure 3).No dominant pattern was observed by ERIC-PCR(Figure 4). CONCLUSION: When vanA and vanB primers were investigated together with multiplex PCR, it was observed that the vanB primer caused false positivity in agarose gel electrophoresis because it formed a band close to the base pair.Although enterococci with vanA and vanB genes were detected at a very low prevalence as a result of our study, the detection of VVE isolates is essential to prevent antimicrobial resistance.

Keywords

• Enterococcus
• glycopeptide resistance
• vanA
• vanB