The aim of this study was to determine the risk factors for
nosocomial infections of
imipenem-resistant Pseudomonas aeruginosa (IRPA). A prospective case-control study was performed at a tertiary care hospital in Ankara from January to December 2004. The patients with nosocomial P. aeruginosa
infection were included in the study. The features of the patients with IRPA
infections were compared to those with
imipenem-sensitive P. aeruginosa (ISPA)
infections. Only the first isolation of P. aeruginosa was considered.
Nosocomial infections were defined according to Center for Disease Control (CDC) criteria. IRPA was isolated from 75 (44.1%) patients, and ISPA was isolated from 95 (55.9%) patients during the study period. IRPA were most frequently isolated from endotracheal aspirate (19%) cultures (p=0.048), whereas ISPA were most frequently isolated from urine (28%) cultures (p=0.023). In multivariate analysis, a longer duration of
hospital stay until P. aeruginosa isolation (odds ratio [OR], 1.027; 95% confidence interval [CI], 1.002-1.054, p=0.034), arterial
catheter administration (OR, 2.508; 95% CI, 1.062-5.920, p=0.036),
vancomycin (OR, 2.882; 95% CI, 1.130-7.349, p=0.027),
piperacillin-tazobactam (OR, 6.425; 95% CI, 2.187-18.875, p=0.001), and
imipenem (OR, 3.580; 95% CI, 1.252-10.245, p=0.017) treatment within the 14 days before isolation of IRPA were independently associated with
imipenem resistance. It was concluded that treatment with
imipenem,
vancomycin and
piperacillin-tazobactam were major risk factors for IRPA
infections in hospitalized patients. The nosocomial occurrence of IRPA was also strongly related to the duration of
hospital stay, arterial
catheter administration.