The Expression of VanA Gene in Enterococcus faecium and Enterococcus faecalis Under Influence of Vancomycin

Background and Aim: Enterococci are increasingly recognized as important pathogens in clinical settings due to their intrinsic and acquired antibiotic resistance.The aim of this study was to investigate the prevalence of Enterococcus (E.) faecalis and E. faecium in clinical samples, their antibiotic resistance patterns, and the correlation between vancomycin resistance and the presence of the vanA gene in both species. Materials and Methods:A total of 120 isolates were identified from clinical samples.Phenotypic specification was confirmed by targeting D-alanine-D-alanine ligases specific for E. faecalis and E. faecium using PCR analysis.Antibiotic resistance was determined by antimicrobial susceptibility testing using disk diffusion method.The presence of van genes was investigated by multiplex PCR analysis.Real-time RT-PCR was used to determine the expression of vanA gene among vancomycinresistant isolates. Results:In this study, 82 E. faecalis (68.3%) and 38 E. faecium (31.6%) isolates from a total of 120 clinical samples were identified.Antimicrobial susceptibility testing revealed increased resistance rates among E. faecium, with resistance to ampicillin at 89.5% and penicillin at 84.2%, while E. faecalis showed lower rates of resistance at 5.8% and 7.2%, respectively.Multiplex PCR analysis confirmed that 54.1% of E. faecalis and 69.2% of E. faecium resistant isolates contained vanA gene.Notably, vancomycin-treated isolates exhibited 8.6-fold increase in vanA gene expression compared to untreated E. faecalis, while E. faecium showed 2.6-fold increase. Conclusion:This study found a high prevalence of vancomycin-resistant Enterococcus (VRE) isolates, with majority carrying vanA gene.Resistance rates to multiple antibiotics were significantly higher in E. faecium compared to E. faecalis.Furthermore, vanA gene expression was notably increased in VRE isolates treated with vancomycin.The research highlights the genetic and environmental factors driving VRE emergence and proposes potential treatment strategies to combat this public health concern.