Vancomycin-resistant Enterococcus faecalis from a wastewater treatment plant in Tabriz, Iran.

The aim of this study was to determine the resistance pattern and the type of resistance genes of vancomycin-resistant Enterococcus faecalis from Gharamalek wastewater treatment plant in Tabriz, Iran. Following filtering of sewage samples, approximately 300 colonies grew on specific media, of which 53 were randomly selected and purified using 0.45 microm membranes. The membranes were placed on culture media containing antibiotics to isolate the vancomycin-resistant Enterococcus. Biochemical tests, antibiogram and determining minimum inhibitory concentration of antibiotics with E-test including vancomycin were performed. Polymerase Chain Reaction (PCR) was carried out to determine the type of resistance genes. All tested samples were found to be E. faecalis. Antimicrobial susceptibility tests indicated multidrug resistance in the samples, with 98% of them highly resistant to vancomycin. The highest frequency was of vanA (96%), followed by vanB (4%); vanC was not seen among the tested samples. The results confirmed that the risk of exposure to antibiotic-resistant pathogens from the evaluated urban wastewater is considerable.