Abstract
Introduction: Pseudomonas aeruginosa isolates are among the most common pathogens causing nosocomial
infections. They are intrinsically resistant to most of antibiotics such as novel β-lactams and therefore, can
develop resistance during treatment, culminating in failure in remedy.
Objectives: The aim of this study was to detect the genes encoding class A extended-spectrum betalactamases
(ESBLs) such as PER-1, VEB-1 and PSE-1 among P. aeruginosa isolates from intensive care unit
(ICU) patients.
Materials and Methods: A total of 65 isolates were collected from ICU in three hospitals of Tehran in 2016.
The antibiotic susceptibility test was conducted according to Clinical and Laboratory Standards Institute
(CLSI) guideline. MIC of ceftazidime was done with agar dilution method. The combine disk test was
performed for detection of isolates producing ESBLs. Polymerase chain reaction (PCR) was performed to
detect the PER-1, VEB-1 and PSE-1 genes using specific primers.
Results: Fifty-four percent (n=38) of patients were male and 46% (n=27) were female. The majority of ICU
isolates were resistant to augmentin (93.8%, n=61) and cefpodoxime (84.8%, n=56). Fifty (77%) isolates
were ESBL positive, among which 94% (n=47) harbored PER-1 gene followed by 52% (n=26) VEB-1 and
16% (n=8) PSE-1 genes.
Conclusion: Concomitance presence of blaPER1 and blaVEB1 was observed among 10 isolates, and 7 amplified
all these three genes. A high number of ICU P. aeruginosa isolates were ESBL producers. The frequency
of blaVEB1 and blaPER1 were relatively high, while blaPSE1 was detected among a low number of isolates.
Moreover, resistance to carbapenems was low. It is necessary to follow up ICU centers because of drugresistant
P. aeruginosa isolates.