Akademik Veri Yönetim Sistemi
Mikrobiyoloji Bulteni, cilt.59, sa.4, ss.425-436, 2025 (SCI-Expanded, Scopus, TRDizin)
Vancomycin-variable enterococci (VVE) are Enterococcus strains that appear phenotypically susceptible to vancomycin but harbor glycopeptide resistance genes, representing a significant diagnostic and therapeutic challenge and posing a risk for therapeutic failure. These strains are often undetectable by conventional susceptibility methods but can be identified by molecular techniques. This study aimed to investigate the prevalence of vanA and vanB resistance genes in vancomycin- and teicoplanin-susceptible Enterococcus faecalis and Enterococcus faecium clinical isolates using multiplex and monoplex polymerase chain reaction (PCR) techniques. A total of 251 clinical Enterococcus isolates phenotypically confirmed as susceptible to vancomycin by disc diffusion test, broth microdilution and gradient diffusion test (Etest®), were retrospectively analyzed. Multiplex PCR targeting vanA and vanB genes was performed on all isolates, followed by monoplex PCR for the confirmation of positive results. Among the 251 isolates screened, only one E.faecalis isolate (0.4%) from a urinary sample of a 91-year-old female patient detected as positive for the vanA gene in both multiplex and monoplex PCR. In contrast, vanB gene was detected as positive in 100 isolates (39.8%) by multiplex PCR, but none of these were confirmed by monoplex PCR. The detection of a vanA-positive E.faecalis isolate that was phenotypically susceptible to vancomycin highlights the risk of missing vancomycin-variable enterococci (VVE) when relying solely on conventional testing. The high rate of false-positive vanB results obtained by multiplex PCR demonstrates the limitations of this method and underscores the necessity of confirmatory testing within molecular workflows. Integrating gene-specific PCR assays into standard diagnostic protocols may facilitate more effective detection of VVE strains and the development of appropriate antimicrobial management strategies, particularly in settings with high glycopeptide use or unexplained treatment failures.