Prevalence of biofilm formation and vancomycin-resistant genes among Enterococcus faecium isolated from clinical and environmental specimens in Lorestan hospitals

Background and Objectives: The antibiotic resistance among Enterococcus faecium strains has increased worldwide. Additionally, biofilm-forming isolates of E. faecium play an important role in human infections. This study was conducted to investigate the prevalence of virulence and antibiotic resistance genes between biofilm-producing and non-biofilm-producing E. faecium strains. Materials and Methods: In this study, 228 E. faecium isolates from clinical and environmental specimens were obtained from different wards of hospitals in Lorestan province (Iran). Then, the pattern of antibiotic resistance and minimum inhibitory concentration (MIC) against β-lactams, glycopeptides, aminoglycosides and other common antibiotics was investigated using disk diffusion and agar dilution methods. Biofilm formation was investigated using polystyrene microtiter plates. PCR assay was conducted for antibiotic resistance and biofilm related genes. Pulse field gel electrophoresis (PFGE) was used to determine the clonal spread of isolates. Results: Most of isolates (78%) were resistant to penicillin, but all were susceptible to linezolid and tigecycline. The biofilm- producing isolates were more resistant to β-lactams, glycopeptides and aminoglycosides compared to non-biofilm-producing strains. In biofilm-producing isolates, pilA, pilB, efaAfm and esp were the dominant virulence genes and vanA and pbp5 genes were the dominant resistant genes. PFGE analysis exhibited a similar pattern between the clinical and environmental isolates, suggesting the presence of a common origin of the infection by E. faecium. Conclusion: The results of the antibiotic resistance, biofilm assay, and PFGE analysis suggest that there is a common clone of persistent and biofilm-producing strains of E. faecium, which could rapidly disseminate in patients and the environment.