Distribution of TEM, SHV and CTX-M Genes among ESBL-producing Enterobacteriaceae isolates in Iran

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Antibiotic resistant especially to Extended Spectrum Beta-Lactamases (ESBLs) producing bacteria has been known as a healthy problem in treatment of patients with infection. The aim of this study is to determine the antimicrobial resistance patterns ofEnterobacteriaceae isolated from clinical samples and also detect the phenotypic and genotypic ESBLs producing organisms. In this study, 420 Enterobacteriaceae strains isolated from 8000 clinical specimens were identified by biochemical standard tests. Their primary antimicrobial susceptibility was determined to seven antibiotic and ESBLs producing strains were also detected by a combined disk method (CDM). Finally, presence of blaTEM, blaSHV and blaCTX_M genes was evaluated by Multiplex PCR Method.Escherichia coli and Klebsiella pneumoniae were the most common among ofEnterobacteriaceae isolates. Drug resistance frequency of these strains to cefotaxime, ceftriaxone, ceftazidim, cefepim, cefepirom was 44, 44, 42, 39.5 and 39%, respectively. 128 of 420 strains (30.5 %) produced ESBLs by CDM. 73 of 128 (57%) ESBL-producing strains were positive for TEM and/or SHV by Multiplex PCR. The prevalence of blaTEM andblaSHV were 65.5 and 15%, respectively. 14 isolates (19%) had both blaTEM and blaSHVgenes, but blaCTX-M was not detected in ESBL-producing strains. The results of this study showed noticeable prevalence of ESBLs and multiple antibiotic resistant among ofEnterobacteriaceae isolates, especially E. coli and K. pneumoniae. So, we suggest that beta-lactam antibiotics and beta-lactamase inhibitors or carbapenems to be limited only to patients with serious infections. Key words: ESBLs, TEM, SHV, Enterobacteriaceae and multiplex PCR.