Determination of Vancomycin Resistant Enterococcus faecium Diversity in Tehran Sewage Using Plasmid Profile, Biochemical Fingerprinting and Antibiotic Resistance

BACKGROUND Sewage treatment plants are considered to be the hotspots for antibiotic resistance transfer among bacterial species. Many fecal bacteria including Enterococci circulate and are exposed to antibiotic residues in this environment. Being as one of the most common cause of nosocomial infections, special concerns have risen worldwide about the rate and characteristics of Enterococci (especially, isolates with high resistance against glycopeptides) which are available in raw sewages. OBJECTIVES Study on the vancomycin Resistant E. faecium diversity in Tehran sewage by plasmid profile, biochemical fingerprinting and antibiotic resistance. MATERIALS AND METHODS Forty isolates recovered from an urban sewage treatment plant were studied during 2009- 2010. The antibiotic resistance of isolates against 7 antibiotics was examined by disk diffusion method. Extraction of plasmid DNA was performed and identification of van genotype (vanA and vanB) was done by PCR. Biochemical fingerprinting was done by the use of Phene-Plate system (PhP). RESULTS All isolates were found to be resistant to erythromycin, ampicillin and ciprofloxacin. The PCR analyses showed that all E. faecium isolates harbored vanA gene and 5 (13%) isolates harbored vanA and vanB concomitantly. By plasmid profiling the VRE isolates differentiated into 11 types. PhP showed that VRE isolates were grouped into 23 biochemical types. CONCLUSIONS The combination of plasmid profiling and PhP techniques revealed the presence of diverse population of VRE in sewage treatment plant in Tehran. Furthermore, the results showed that the PhP technique is a reliable method in determining the VRE clonal diversity.