CTX-M-15 Type β-lactamases From Clinical Isolates of Escherichia coli by Polymerase Chain Reaction and DNA Sequencing

Background: E. coli is a common cause of urinary tract infection and bacteremia in humans. That is frequently resistant to β-lactam antibiotics. Objectives: The aim of this study was to determine the antibiotic resistance and CTX-M extended-spectrum β-lactamases (ESBL) carrying E. coli isolated in hospitals from two different areas in Iran. Methods: In this descriptive cross-sectional study, 93 clinical isolates of E. coli were collected from urine culture of inpatients in Mashhad and Qom hospitals from August 2013 to February 2014. Bacteria were re-confirmed by Microgen kit. Antimicrobial and ESBL tests were performed using by standard disc diffusion method. Polymerase chain reaction (PCR) was used for detection of plasmid mediated CTX-M-1 and CTX-M-2 ESBLs. Four of the blaCTX -M genes were sequenced. Statistical analysis carried out using SPSS (version 16) software and Chi-square test. Results: High prevalent isolates were resistant to ampicillin, cephalothin, nalidixic acid and cotrimoxazole, but sensitive to imipenem, nitrofurantoin and amikacin. The ESBL phenotype was detected in 48 (51.6%) isolates, 42 of which were carrying blaCTX -M gene. There was no significant difference between the β-lactamase-producing bacteria from the two studied cities. 81% and 85% of blaCTX -M carriers from hospitals in Qom and Mashhad were respectively found to have CTX-M-1 ESBL, whereas none of them showed CTX-M-2 ESBL cluster. BlaCTX-M-15 was found in four selected bacteria by sequencing. Conclusions: This study showed a high rate of CTX-M-1 cluster and also presence of CTX-M-15 ESBL in two different areas of Iran, which emphasize the need for employing an excellent management program in antibiotic therapy.