Relevance of class 1 integrons and extended-spectrum β-lactamases in drug-resistant Escherichia coli

Escherichia coli is a common cause of community- and hospital-acquired urinary tract infections, and class 1 integrons are the prior elements of gene transference in the capture and distribution of gene cassettes among clinical gram-negative bacillus. In the present study, the resistance of Escherichia coli to antimicrobial agents was investigated. A total of 97 isolates were found to be susceptible to 16 antimicrobial agents and were detected in the production of extended beta-lactamases (ESBLs), distribution of CTX-M-type beta-lactamases, presence and characterization of class 1 integrons and a variable region of integron-positive isolates. Escherichia coli isolates possessing CTX-M (31; 32%) were detected in 19 isolates (61.5%). The presence of ESBLs was associated with resistance to penicillins, third-generation cephalosporins, ciprofloxacin, aminoglycosides and monocyclic beta-lactam antibiotics. Escherichia coli isolates (69; 71.1%) possessed class 1 integrons associated with resistance to ciprofloxacin and numerous third-generation cephalosporins, penicillins, tobramycin and trimethoprim-sulfamethoxazole. The four gene cassette arrangements were as follows: dfrA17-aadA5, aadA1, aacC4-cmlA1 and dfr2d, and 8 carried two disparate class 1 integrons. Five isolates presented class 1 integrons containing no gene cassettes. The distribution of ESBLs and class 1 integrons in Escherichia coli were prevalent with drug resistance in Chengdu. In addition, the resistance range of Escherichia coli isolates that harboured ESBLs and carried class 1 integrons were similar. The current study demon-strated the presence of class 1 integrons and ESBLs, which jointly mediate the resistance of Escherichia coli isolates to a number of antibacterial agents.