CHARACTERIZATION OF ESCHERICHIA COLI STRAINS ISOLATED FROM WELL WATERS: MOLECULAR TYPING BY PULSED-FIELD GEL ELECTROPHORESIS, ANTIBIOTIC RESISTANCE PATTERNS AND PLASMID PROFILES

A number of previous studies have shown that characterization and determination of genetic relationships of the microorganisms in case of possible outbreak are of vital importance. In this study, the genetic relations and genetic diversities, susceptibility to antibiotics and plasmid profiles of 43 Escherichia coli isolates recovered from well water samples were investigated. The pulsed-field gel electrophoresis (PFGE) method was used to identify the genetic relations and diversities of E. coli isolates. PFGE revealed 30 pulsotypes represented by 6 subtypes among the strains according to evaluation of restriction profiles. Antibiotic susceptibility tests were conducted against 15 antibiotics by using a disc diffusion method. The isolates exhibited four different types of resistance profiles. The strains showed the greatest resistance to ampicillin (97.67%), followed by ticarcillin-clavulanic acid (9.3%) and cefuroxime and ceftazidime (6.97%). Plasmid isolation studies of the strains conducted by the method of alkaline lysis revealed that 19 (44.18%) of 40 E. coli strains contain 19 different plasmid bands ranging between 78.2 and 2.6 kb. Based on the results obtained from tests, PFGE analysis revealed very high genetic diversity among the strains. Antibiotic resistance ratios increased in E. coli isolates when compared with data obtained from previous studies. Plasmids of E. coli strains demonstrated random distribution, and any significant correlation between antibiotic resistance patterns and plasmids has not been found. E. coli strains leaked to the well water sources were not closely related. Studies and surveillances should be conducted periodically to see resistance of environmental strains.