[Antimicrobial susceptibility of phenotypically extended spectrum beta-lactamase producing Pseudomonas aeruginosa and...

The aim of this study was to investigate the antimicrobial susceptibilities of Pseudomonas aeruginosa and Acinetobacter baumannii strains that were identified as producers of extended spectrum beta-lactamases (ESBL) phenotypically. Fifty three P. aeruginosa and 53 A. baumannii strains that were isolated from patients with hospital infections followed-up by Infectious Diseases Unit of Hacettepe University Adult Hospital in 2002-2004, were included in the study. The susceptibilities of the isolates to ceftazidime, cefotaxime, cefepime, tobramycin, ciprofloxacin, piperacillin-tazobactam, imipenem and meropenem were determined by Etest (AB Biodisk, Solna, Sweden) method. The susceptibility rates of A. baumannii isolates against tobramycin and carbapenem group were 54.7% and 49.1%, respectively; whereas for the rest of the antimicrobial agents tested, these rates were lower than 25 percent. The susceptibility rates of P. aeruginosa isolates against ciprofloxacin, carbapenem group, piperacillin-tazobactam and tobramycin differed between 35-38 percent. Of the P. aeruginosa isolates, 37.5%, and of the A. baumannii isolates 37.7% were resistant against imipenem/meropenem, piperacillin-tazobactam, ciprofloxacin and tobramycin simultaneously. As a result, phenotypically ESBL producing P. aeruginosa and A. baumannii isolates were found highly resistant not only against the third and fourth generation cephalosporins, but also to the antibiotics currently used in the therapy including carbapenemes.