Distribution of antibiotic resistance and the presence of vancomycin-resistance genes (vanA and vanB) in Enterobacteriaceae isolated from the Sea of Marmara, the Canakkale Strait and the Istanbul Strait, Turkey

We investigated the frequency of antibiotic resistance of Enterobacteriaceae and the presence of vancomycin-resistance genes in samples taken from the Sea of Marmara, and the Istanbul and Canakkale Straits, Turkey. Different colony-forming bacteria were isolated and identified with the VITEK 2 Compact 30 system. The antibiotic resistance of the isolates was determined by the disc diffusion method. The isolates were tested against amoxicillin, ampicillin, aztreonam, ceftazidime, cefotaxime, cefuroxime, ofloxacin, vancomycin, tetracycline, kanamycin and gentamycin. The presence of vancomycin-resistance genes (vanA and vanB) was also investigated. The level of Enterobacteriaceae species was higher in the Sea of Marmara than in the Istanbul Strait and the Canakkale Strait. Isolates showing resistance to the greatest number of antibiotics were identified from E. coli isolates. The resistance of the selected bacterial isolates were as follows: kanamycin (82%), vancomycin (78%) and ampicillin (60%). Some intermediately vancomycin-resistant Enterobacteriaceae isolates had the vanA gene. This study provides evidence of widespread bacterial resistance to clinically relevant antibiotics in marine environments. It also contributes to the knowledge on the distribution of antibiotic resistance among Enterobacteriaceae and indicates the importance of control measures in domestic water treatment.