The Study of Antibiotic Resistance Pattern and the Frequency of Extended-Spectrum Beta-Lactamases (ESBL) in Pseudomonas aeruginosa Strains Isolated from Medical Centers in Arak City, Iran

Pseudomonas aeruginosa is one of important causes of nosocomial infections that is an important medical problem in developed and developing countries. Resistance of this gram-negative organism towards various antibiotics, particularly beta-lactam and carbapenem has been reported increasingly. This study was done aiming at determining antibiotic resistance pattern and the frequency of extended-spectrum beta-lactamase in clinically isolated P. aeruginosa strains.

In this cross-sectional study, 108 P. aeruginosa strains were collected from medical centers of Arak city. Antibiotic susceptibility of the isolated strains to antibiotics, such as, ceftazidime, imipenem, meropenem, ciprofloxacin, amikacin, and gentamicin was determined using disk diffusion method (Kirby-Bauer). Identification of ESBL producing strains was performed by combined disk method. Also, MIC test was done on 36 isolates with four antibiotics including imipenem, ceftazidime, cefipime, and ciprofloxacin.

Among the 108 isolates of P. aeruginosa, resistances to ceftazidime (33.3%), imipenem (22.2%), meropenem (24%), amikacin (20.3%), ciprofloxacin (15.7%) and gentamicin (19.4%) were obtained. In the MIC test, the rates of resistance to antibiotic were respectively reported 15, 20, 10, and 15%. Thirty-two strains out of 36 ceftazidime resistant strains (88.8%), were detected ESBL-positive.

The results of this study are indicative of a high level resistance against different antibiotics of among P. aeruginosa isolates. Therefore, it is necessary to use a more appropriate treatment protocols.