Background: Pseudomonas aeruginosa is among the most important nosocomial bacterial infections with innate resistance to many antibiotics. This study was designed to evaluate the frequency of extended-spectrum beta-lactamase (ESBL) multidrug-resistance produced by P. aeruginosa isolated from clinical and environmental specimens in Kashan Shahid Beheshti hospital.

Materials and Methods: This descriptive study was conducted on clinical isolates (n=76) of P. aeruginosa from Kashan Shahid Beheshti hospital during 2010-11. Antibiotic susceptibility testing for eight antimicrobial agents was carried out according to the clinical and laboratory standards institute (CLSI) guidelines and ESBL-producing strains were confirmed using double-disk diffusion test. MDR-isolates were defined as those resistant to three or more classes of antibiotics.

Results: Among all P. aeruginosa isolates, the highest resistance was seen for piperacillin, imipenem, cefotaxime, ceftriaxone, gentamicin, ceftazidime, aztreonam and ciprofloxacin, respectively. Seven strains (9.2%) were ESBL-positive. Twenty-seven percent of the isolates were resistant to at least three classes of antibiotics 8 out of 14 tracheal discharges 4 out of 9 wound and 2 out of 3 blood samples were MDR.

Conclusion: The study emphasizes the high frequency of MDR-P. aeruginosa in clinical and environmental specimens isolated from this hospital. Imipenem resistance in MDR-P. aeruginosa isolates is also high in this study. This calls for strict infection control measures to prevent further microbial spread.