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Mol Med Rep. 2013 Oct;8(4):1251-5. doi: 10.3892/mmr.2013.1626. Epub 2013 Aug 12.

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

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  • 1Department of Pharmacology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chengdu, Sichuan 610041, P.R. China.


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 β‑lactamases (ESBLs), distribution of CTX‑M‑type β‑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 β‑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 demonstrated the presence of class 1 integrons and ESBLs, which jointly mediate the resistance of Escherichia coli isolates to a number of antibacterial agents.

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