high prevalence of ctxm15 type extendedspectrum betalactamase among clinical isolates of klebsiella pneumoniae

<strong>background:</strong> production of β–lactamases by enterobacteriacea, especially <em>klebsiella pneumoniae</em>, is one of the emerging health problems in the world. the purpose of this study was to assess the frequency of <em>bla</em>_ctxm15 gene in <em>k. pneumoniae</em> isolates and determine the molecular diversity of ctxm producing isolates.<strong>methods:</strong> in this descriptive crosssectional study, 100 <em>k. pneumoniae</em> strains were tested for susceptibility to cephalosporins category by using disk diffusion method and the prevalence of <em>bla</em>_ctxm1,<em>bla</em>_ctxm2,<em>bla</em>_ctxm9 and <em>bla</em>_ctxm15 genesin these isolates were determined by pcr method. eventually, a number of isolates were sequenced and typed using single locus sequence typing (slst) of <em>bla</em>_{ctxm group1} gene. the phylogenetic relatedness of all ctxm producing isolates was determined using enterobacterial repetitive intergenic consensuspcr (ericpcr).<strong>results:</strong>the rates of resistance to cephalosporins category were in the following order: cefepime(57%), ceftazidime (54%), cefotaxime (36%), cefoxitine (32%), and ceftriaxone (31%). of all 100 <em>k. pneumoniae</em> isolates, 31 were harboring ctxm genes, and the <em>bla</em>_ctxm15 (77.5%) was the most common of the genes investigated. the results of slst showed that all of the sequenced isolates were divided into two groups. ericpcr method represented ten different genotypes in ctxm positive isolates.<strong>conclusion:</strong> the results of this study showed that one of the most important reasons for resistance to cephalosporins is the presence of <em>bla</em>_ctxm genes. in addition, there was a high genetic variation among <em>bla</em>_ctx_m genes positive isolates.