Antimicrobial susceptibility pattern of clinical isolates of Pseudomonas aeruginosa in a tertiary care hospital

BACKGROUND AND PURPOSE: Pseudomonas aeruginosa is an important cause of morbidity and mortality in hospitalized, critically ill patients and patients with underlying medical conditions such as cystic fibrosis, neutropenia, and iatrogenic immunosuppression. The prevalence of multiresistant P. aeruginosa isolates has been increasing. The aim of this study was to determine the antimicrobial susceptibility patterns in P. aeruginosa strains isolated at a university teaching hospital in Kuala Lumpur, Malaysia.
METHODS: The Laboratory Information System of the microbiology department was retrospectively reviewed to determine the susceptibility patterns of P. aeruginosa isolates to anti-pseudomonal antibiotics, from January to June 2005. Disk diffusion methods were employed and results were interpreted according to National Committee for Clinical Laboratory Standards guidelines.
RESULTS: 505 clinical isolates of P. aeruginosa were tested. Major sources of these isolates included respiratory tract, wound, urine and blood. The rates of antimicrobial resistance of isolates were 6.73% to amikacin, 12.9% to gentamicin, 10.1% to netilmicin, 10.9% to ceftazidime, 11.3% to ciprofloxacin, 9.9% to imipenem, 10.8% to piperacillin, 9.4% to piperacillin-tazobactam and 0% to polymyxin B. Of the 505 isolates, 29 (5.74%) were found to be multidrug-resistant; these were most commonly isolated from respiratory tract specimens of patients in surgical units, followed by respiratory tract specimens in patients in medical units.
CONCLUSIONS: The data in this study showed low rates of antibiotic resistance among P. aeruginosa isolates. Combinations of aminoglycosides plus beta-lactams or quinolones should be the appropriate choice for empirical therapy in P. aeruginosa infections. Active antibiotic susceptibility testing and surveillance should be continued in order to curtail the problem of antibiotic resistance.