Investigation of the Frequency of PER-1 Type Beta-Lactamase and Antimicrobial Resistance Rates in Nosocomial Isolates of Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa which is a common cause of nosocomial infections, usually leads to treatment difficulties due to multi-drug resistance. PER-1 type extended-spectrum beta-lactamase (ESBL) producing bacteria are shown to be common in Turkey. Since limited number of antibiotics such as antipseudomonal penicillins, cephalosporins, aminoglycosides, fluoroquinolones and carbapenems are available for the treatment of P.aeruginosa infections, it is essential to monitor and eventually control the spread of antibiotic resistance genes. The aims of this study were to investigate the presence of PER-1 type ESBLs in nosocomial P.aeruginosa isolates and to evaluate their resistance to some commonly used antibiotics. A total of 110 P.aeruginosa strains isolated from clinical samples [40 urine, 26 exudate, 20 blood, 24 others (sputum, tracheal aspirate, tissue biopsy, cerebrospinal fluid, pleural fluid, conjunctiva)] of the inpatients who were proven to have nosocomial infections in Ondokuz Mayis University Faculty of Medicine Hospital between May 2002-June 2003 were included in the study. Identification of the isolates was performed by ATB system ID 32 GN (bio-Merieux, France). Antibiotic susceptibilities were detected by standard disk diffusion method and PER-1 type ESBL was searched by polymerase chain reaction using PER-1 and PER-2 primers. PER-1 positivity was detected in 62 of 110 (56.4%) P.aeruginosa isolates and 51 of 65 (78.5%) ceftazidime-resistant strains. The highest susceptibility rate was detected for ciprofloxacin (76.4%), while the lowest susceptibility rate was for ticarcillin-clavulanic acid (22.7%). Rates of resistance to beta-lactam agents (excluding piperacillin/tazobactam), amikacin and gentamicin were statistically significantly higher for PER-1 positive strains than PER-1 negative ones. Resistance rates to ceftazidime, cefepime, aztreonam, piperacillin and ticarcillin-clavulanic acid in PER-1 positive isolates versus negative ones were as 82.3% vs. 29.2% (p < 0.01), 75.8% vs. 25% (p < 0.01), 83.9% vs. 30.4% (p < 0.01), 73.8% vs. 52.2% (p < 0.05), 85.5% vs. 66.7% (p < 0.05), respectively. Considering resistance rates to piperacillin-tazobactam and ciprofloxacin, PER-1 positive isolates versus negatives were 35.5% vs. 31.3%, and 19.4% vs. 29.2%, respectively, revealing no statistical significance (p > 0.05). As a result, PER-1 type ESBL frequency and beta-lactam and aminoglycoside resistance rates were found remarkably high in nosocomial P.aeruginosa strains isolated in our hospital. It was concluded that antibiotic resistance should be continously monitorized and necessary measures to prevent further increase in resistance should be promptly established.