Distribution of blaTEM, blaSHV, and blaCTX-M genes among ESBL-producing P. aeruginosa isolated from Qazvin and Tehran hospitals, Iran.

INTRODUCTION: Pseudomonas aeruginosa is as an important opportunistic human pathogen, which is associated with several clinical infections that are usually difficult to treat because of resistance to multiple antimicrobials. The production of extendedspectrum ß-lactamases (ESBLs) is an important mechanism of ß-lactam resistance. The aims of this study were to determine the prevalence of ESBLs, antimicrobial susceptibility, and to detect the blaTEM, blaSHV, and blaCTX-M genes.

METHODS: In this study, carried out from March 2013 to December 2014, 266 P. aeruginosa isolates were collected from patients admitted to teaching hospitals of Qazvin and Tehran, Iran. All isolates were initially screened for ESBL production by disk diffusion method and were further confirmed using a combined disk method. Antimicrobial susceptibility of ESBL-producing isolates was determined by standard disk diffusion method. Polymerase Chain Reaction (PCR) and sequencing techniques were employed for detection of blaTEM, blaSHV, and blaCTX-M genes.

RESULTS: In total, 262 (98.5%) P. aeruginosa isolates were nonsusceptible to the used extended spectrum cephalosporins, and, among these, 75 (28.6%) isolates were ESBL producers. Fifty-nine (78.7%) of ESBL-producing isolates showed multidrug-resistance pattern. Of 75 ESBL-positive isolates, the blaTEM-1 (26.7%) was the most common gene, followed by blaCTX-M-15 (17.3%), blaSHV-1 (6.7%), and blaSHV-12 (4%), either alone or in combination.

CONCLUSIONS: The results of this study showed the notable prevalence of ESBLs among the clinical isolates of P. aeruginosa in Iran, indicating the urgency for the implementation of appropriate follow-up measures for infection control and proper administration of antimicrobial agents in our medical settings.