The antibiotic resistance of enterobacteriacae knows a worldwide worrying evolution with an increase of the extended-spectrum β-lactamases. The present study was to determine the prevalence and molecular typing of extended-spectrum β-lactamases (ESBLs) in clinical isolates of Escherichia coli, Enterobacter cloacae, and Citrobacter freundii, isolated between January 2010 and December 2012, at the Laghouat "Ahemida Ben Adjila" hospital, Algeria. Antimicrobial susceptibility testing was determined by disk diffusion on Mueller Hinton agar. Genetic transfers were performed by conjugation and plasmid DNA was extracted by the alcalin-lysis method. The characterization of ESBL genes were examined using PCR amplification and DNA sequencing and the clonal relatedness was investigated by ERIC-PCR. During the study period, twenty-one (8.23%) isolates were found to produce ESBLs, distributed as follows: 13 isolates of E. coli (61.9%), 6 isolates of E. cloacae (28.57%) and 2 isolates of C. freundii with 9.52 %. The CTX-M-15 ESBL were predominant (95.24%), followed by TEM-4 (14.28%) and SHV-12 (4.76%). ERIC-PCR analysis showed that the isolates are genetically unrelated and conjugation experiments showed that blaCTX-M-15 gene was transferred on a conjugative plasmid of high molecular weight (≈130 kb). This study indicated a high prevalence of CTX-M-15 enzymes among E. coli, E. cloacae and C. freundii in Laghouat hospital, Algeria.
Key words: Multiresistant bacteria, extended spectrum β-lactamase, CTX-M-15, genotyping, Algeria.
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