characterization of ctx-m-type extend-spectrum β-lactamase producing klebsiella spp. in kashan, iran

Context: the ctx-m family consists of more than 50 β-lactamases, which are grouped on the basis of sequences into five subtypes including ctx-m-1, ctx-m-2, ctx-m-8, ctx-m-9 and ctx-m-25.objectives: the current study aimed to detect subtypes of ctx-m extended-spectrum β-lactamases (esbls) among esbl positive klebsiella isolates from patients in kashan, iran.materials and methods: a total of 100 clinical isolates of klebsiella were collected and the isolates, which showed resistance or reduced susceptibility to cefotaxime, ceftazidime and/or aztreonam by the disk diffusion method were selected. these isolates were identified as esbl-producing isolates by double disk synergy tests using clavulanic acid, cefotaxime, ceftazidime and aztreonam. the blactx-m type determinants were identified by the polymerase chain reaction (pcr) method followed by dna sequencing.results: of the 100 klebsiella isolates, 41 (41%) demonstrated resistance or reduced susceptibility to ceftazidime and/or aztreonam and 35% (n = 35) were esbl-producers. twenty-eight (8o%) of the esbl-producing isolates carried the blactx-m type genes. based on pcr assays and sequencing of blactx-m genes, ctx-m-1, ctx-m-2 and ctx-m-9 were identified in 21 (60%), 15 (42%) and nine (34%) of these isolates, respectively (genbank accession numbers kj803828-kj803829).conclusions: our study showed that the frequency of blactx-m genes among klebsiella isolates in our region is at an alarming rate. also, we found a high prevalence of blactx-m-1 β-lactamase in klebsiella isolates in kashan.