Pseudomonas aeruginosa isolates are intrinsically resistant to many antibiotics such as novel β-lactam antibiotics and therefore, can develop resistance during treatment, culminating in high morbidity and mortality. The aim of this study was to detect the genes encoding class A ESBLs of bla PER-1, bla- VEB-1 and bla- PSE-1 among clinical isolates of P. aeruginosa among ICU patients. In this study, a total of 65 clinical isolates of P. aeruginosa were collected from intensive care unit (ICU) patients in several hospitals. The antibiotic susceptibility test was conducted according to Clinical and Laboratory Standards Institute (CLSI) guidelines. The combined disk test was performed to detect the isolates producing Extended Spectrum B- Lactamases (ESBLs). PCR was performed to detect the class A carbapenemase genes including per-1, veb-1 and pse-1 with specific primers. The study revealed that the majority of the isolates were resistant to augmentin (93.8%, n=61) and cefpodoxime (84.8%, n=56). Ten (15.3%) isolates of P. aeruginosa were ESBL positive, of which 40% (n=4) belonged to male and 60% (n=6) were collected from female patients. Of the ten ESBL -positive isolates, 20% (n=2) harbored per-1. The veb-1 and pse-1 were also detected in 10% (n=1) and 0% (n=0) of the isolates, respectively. The prevalence of ESBL production and the related bla veb-1, bla per-1 and bla pse-1 was not high among ICU patients studied in several hospitals of the country. Moreover, resistance to carbapenems was low. Understanding resistance mechanisms and follow up the patterns and strains relationship is helpful for better treatment of infections.

Keywords: P. aeruginosa, ICU patients, ESBLs, Carbapenems