A study to determine the frequency of van A and van B genes in vancomycin-resistant Enterococcus faecalis strains obtained from clinical specimens in northwestern Iran

One of the significant global challenges today is the increasing prevalence of vancomycin-resistant enterococci (VRE). This study aims to understand the antibiotic resistance patterns, investigate the prevalence of VRE-causing genes in clinical samples, and evaluate the prevalence of enterococcal strains. For this study, 200 urine and blood samples were collected from patients visiting healthcare centers in Tabriz. Antibiotic susceptibility was determined using the disk diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines, and the minimum inhibitory concentration (MIC) for vancomycin was assessed using the E-Test method. Additionally, polymerase chain reaction (PCR) techniques were employed for precise bacterial identification and to examine the presence of vancomycin resistance genes van A and van B. Molecular analysis revealed that 100 out of 200 samples (50%) belonged to Enterococcus faecalis (E. faecalis). The isolates exhibited the highest resistance to penicillin (83%), tetracycline (43%), and ciprofloxacin (41%), while they showed the greatest sensitivity to linezolid (87%), imipenem (85%), and teicoplanin (70%). A total of 31 samples were identified as resistant to vancomycin, with 18 strains (58.06%) containing the vanA genotype, 8 strains (25.81%) containing the vanB genotype, and 5 strains (16.13%) harboring both van A and van B genes. Given the high prevalence of VRE strains, it is essential to evaluate these organisms in all clinical samples.