Assay for Integrons and Pattern of Antibiotic Resistance in Clinical Escherichia coli Strains by PCR-RFLP in Southern Iran

The purpose of this study was to determine the prevalence of multidrug-resistant Escherichia coli in clinical specimens. In addition, the existence of integrons in resistant isolates was assessed by amplification of intergase genes. Susceptibility of 200 isolates from five Shiraz hospitals and health centers to 13 antibiotics was determined by the Kirby-Bauer disk diffusion method. The majority of the bacteria were isolated from urine (70.5%) and stool (25.5%) specimens. Antibiotic resistance patterns were observed as follows: amoxicillin 63%, tetracycline 57.5%, co-trimoxazole 48%, cephalotin 40%, nalidixic acid 36%, ciprofloxacin 21%, nitrofurantoin 25%, norfloxacin 20.5%, gentamicin 18%, chloramphenicol 18%, ceftazidime 14%, amikacin 8.5% and imipenem 2%. Of 200 isolates tested, 165 (82.5%) were multidrug resistant. The frequency of multidrug resistance to more than 5 antibiotics was 24.2%. The existence of integrons was confirmed in 44.8% of isolates. Significant association between resistance to gentamicin, amikacin, cephalotin, nalidixic acid, ciprofloxacin, norfloxacin and co-trimoxazole with the existence of integrons was obtained by the PCR-RFLP method. These results showed that integrons may be partly responsible for multidrug resistance. Imipenem, amikacin and ceftazidime were the most effective antibiotics in vitro; however, the clinical efficacy of these antibiotics remains to be assessed.