Study of the pattern of plasmid and antibiotic resistance of Escherichia coli isolated from outpatients with urinary tract infection

Escherichia coli is the most common organism found in urinary tract infection (UTI) and the incidence of UTI caused by E. coli isolates resistant to antibiotics is on the rise. Many antibiotic resistant genes are encoded by plasmids. In this study, we investigated the plasmid profile of E. coli isolated from the patients with urinary tract infection. A total of 200 E. coli were isolated from the urine of the outpatients with UTI by using culture and biochemical tests. Antibiotic susceptibility was determined by disk diffusion, and ESBL production was determined using the double disc method. Using plasmid kits, plasmids were extracted and then were digested by using HindIII and BamH1 enzymes and the size and patterns of plasmids were determined by electrophoresis and DNA markers. All E. coli isolates were susceptible to imipenem whereas 80.7% of them were resistant to ampicillin. Resistance rates to co-trimoxazole, ciprofloxacin, tobramycin, and aztreonam were 57.49, 36.99, 23.35 and 22.5%, respectively. A total of 166 isolates (83%) contained plasmids mostly with the sizes of 15 to 24 kb. The results of this study indicated that E. coli isolates had a high rate of antibiotic resistance. A strong relationship was observed between plasmid and ESBL which was indicative of the role of plasmid in the development of antibiotic resistance to various antibiotic groups, in particular cephalosporins. The similarity of plasmid patterns of isolates explains transmission and dissemination of antibiotic resistance.