Prevalence of class 1 integrons and extended spectrum beta lactamases among multi-drug resistant Escherichia coli isolates from north of Iran

ABSTRACT

Extended spectrum beta lactamases [ESBLs] are an important cause of transferable multidrug resistance [MDR] in gram-negative bacteria. The most described ESBL genes are generally found within integron like structures as mobile genetic elements. The aim of this study was to identify the accompanying of class 1 integrons and ESBLs in the MDR E. coli isolates. Susceptibility to antimicrobial agents was determined for 33 E. coli strains by the disk diffusion method. Double-disk synergy test was applied for screening ESBL. To identify the strains carrying integrons, the conserved regions of integron-encoded integrase gene intI1 were amplified. For detection of gene cassettes, 5'CS and 3'CS primers were used. All E. coli isolates were identified as multi-drug resistant. More than 50% of the isolates were resistant to tetracycline, cephalothin, cefuroxime, amoxicillin-clavulanic acid, and third generation cephalosporines. Nearly all of the isolates displayed sensitivity to piperacillin. There was a significant correlation between production of ESBL and resistance to all antibiotics except for ciprofloxacin and piperacillin [P < 0.01]. Thirty two MDR strains [97%] included class 1 integron, and some isolates that included integrons were similar in the size of gene cassettes. The isolates were different in the resistance profiles; however, some others had similar resistance profiles. Of eight ESBL positive isolates, seven [87.5%] carried class 1 integrons. Class 1 integrons were frequent in MDR and also ESBL-producing E. coli isolates. High prevalence of class 1 integrons confirms that integron-mediated antimicrobial gene cassettes are important in E. coli resistance profile