Prevalence of virulence factors and antibiotic resistance in vancomycin-resistant Enterococcus faecium isolated from sewage and clinical samples in Iran

Purpose: The purpose of the present study was to perform a molecular epidemiological survey by investigating the antibiotic resistance and the presence of known virulence factors in Enterococcus faecium isolates in Iran. The data collected from this study would allow us to control the spread and develop strategies for treatment of the enterococcal infections. Materials and Methods: In this study, 156 vancomycin-sensitive E. faecium (VSEF; 58) and vancomycin-resistant E. faecium (VREF; 98) samples were isolated from clinical specimen and sewage treatment plants (STPs). These isolates were screened for the presence of genes encoding for aggregation substance (asa1), cytolysin (cyl), enterococcal surface protein (esp), gelatinase (gelE) and hyaluronidase (hyl) by polymerase chain reaction (PCR). Results: Although significantly different, the results showed the presence of hyl and esp genes in both clinical (41 and 75%, respectively) and sewage (3.2 and 41%, respectively) isolates. Sensitivity of all isolates to seven antibiotics was examined. The results of the clinical isolates showed that the majority of esp positive isolates were also resistant to vancomycin, ciprofloxacin and erythromycin. Furthermore, cyl, gelE and asa1 were not found in either clinical or STP isolates. Finally, we determined the distinct types of isolates using Pulse Field Gel Electrophoresis (PFGE), which confirmed that most of the isolates were clonally unrelated. Conclusion: Our results demonstrated that higher number of the clinical E. faecium isolates carried virulence genes than the isolates from STP. Finally, the lack of the genes in clinical and STP isolates confirmed that these genes do not transfer horizontally