Detection of ESBLs and MDR in Pseudomonas aeruginosa in a tertiary-care teaching hospital

Background: Pseudomonas aeruginosa is characterized as an important nosocomial pathogen with increasing antimicrobial resistance. The multidrug-resistant (MDR) phenotype in P. aeruginosa is increasing worldwide. The purpose of this study was to evaluate the prevalence of antibiotic susceptibility, ESBLs (Extended spectrum beta lactamases) producing and multidrug resistant (MDR) P. aeruginosa, isolated from clinical specimens of patients and environment of hospital. Patients and methods: This descriptive study was carried out on 76 isolates of P. aeruginosa from a 500-bed tertiarycare general teaching hospital in Kashan, Iran in 2010. Susceptibility testing according to the CLSI (Clinical Laboratory Standards Institute) recommended to eight antipseudomonal agents was performed. ESBLs producing strains were confirmed by double disk diffusion method. Multidrug-resistant isolates were defined as those resistant to three or more classes of antipseudomonal agents. Results: The highest resistance rates from the isolated P. aeruginosa were shown against piperacillin, imipenem, cefotaxime, ceftriaxone, gentamicin, ceftazidime, aztreonam, and ciprofloxacin, respectively. Seven isolates (9.2%) were ESBL producers. More than 30% of the isolates were resistant to at least three classes of antibiotics, and 13% of MDR strains were resistant to all eight tested classes of antimicrobials. Among the total isolates, 6.6% were susceptibleto all studied agents, and 9.2% were resistant to a single agent. The isolated bacteria from the tracheal samples showedthe highest MDR rate. Conclusion: Prevalence of P. aeruginosa producing ESBL and MDR strains from our clinical samples and environment is still low.