Genetic properties of bla(CTX-M) and bla(PER) β-lactamase genes in clinical isolates of Enterobacteriaceae by polymerase chain reaction

OBJECTIVE(S): bla(CTX-M) and bla(PER) are two genes that encode class A extended-spectrum β-lactamases (ESBLs) and can be responsible for therapeutic problems. This study was carried out to evaluate the molecular properties of these genes in clinical isolates of Enterobacteriaceae by polymerase chain reaction (PCR), restriction digestion and sequencing. MATERIALS AND METHODS: During six months, starting from January 2012, one hundred clinical isolates of Enterobacteriaceae were collected from urinary samples. The ESBL-producing isolates were detected by phenotypic confirmation test. After plasmid extraction, bla(PER) and bla(CTX-M) genes were detected using PCR by specific primers. The bla(CTX-M) PCR products were digested with Taq1, and two of the bla(CTX-M) genes were sequenced. RESULTS: Phenotypic tests showed that 27 (27%) isolates were ESBL producers with the highest frequency for Klebsiella pneumoniae (47.4%) and Escherichia coli (17.9%). Twenty six (26%) of Enterobacteriaceae isolates harbored the bla(CTX-M) gene, and none of them had bla(PER). The restriction analysis of PCR products showed that all bla(CTX-M) amplified products had the same patterns. Both sequenced bacteria were CTX-M-15 type ESBL carriers. CONCLUSION: The results of this study showed the bla(CTX-M-15) gene in Enterobacteriaceae isolates for the first time in Mashhad, Iran. High degrees of associated resistance to co-trimoxazole and gentamicin were found in ESBL producers. Therefore, an integrated and regular management of antibiotic prescription need to be trained in our society.