High Prevalence of bla CTX-M-1 Group Extended-Spectrum B-lactamase Genes in Escherichia coli Isolates From Tehran

Background: the emerge of extended-spectrum b-lactamases (esbls)-producing escherichia coli caused problems in antibiotic treatments. the more than 50 variants of ctx-m type esbls enzymes are available worldwide. rapid and discriminative typing methods are essential for epidemiological analysis of clinical ctx-m-producing isolates.objectives: to assess the frequency and genetic diversity of extended-spectrum ctx-m b -lactamases in e.coli isolates from tehran.materials and methods: during 2009 - 2010, 200 non-duplicate clinical isolates of e. coli were collected from five hospitals in tehran. antibacterial susceptibility was determined using disk diffusion and mic methods. esbl production was confirmed by combined disk and mic. ctx-m encoding genes were identified by pcr, and blactx-m -carrying isolates were genotyped by rep-pcr.results: a total of 140(70%) non-duplicate esbl positive e. coli were determined. imipenem and amikacin were effective against 100% and 85% of all tested isolates respectively. co-resistance of esbl positive isolates to erythromycin, tetracycline, co-trimoxazole and ciprofloxacin were found in 93%, 75%, 63% and 43% of the strains, respectively. the rate of cefotaxime and ceftazidime resistant isolates dramatically decreased from 72% to 8.5% and 39% to 4.5% respectively, in the presence of clavulanic acid. eighty nine (44.5%) e. coli isolates carried the blactx-m-1 group alleles. the levels of similarity of the rep-pcr fingerprints of blactx-m-1 isolates ranged from 40 to 90%.conclusions: the rapid dissemination of non clonal multi-resistant ctx-m-1 producing e. coli isolates approved the need for further studies in our medical centers.