Risk factors for nosocomial infections due to Pseudomonas aeruginosa producing metallo- -lactamase in two tertiary-care teaching hospitals

OBJECTIVES: To assess risk factors for nosocomial infections due to Pseudomonas aeruginosa producing metallo-beta-lactamase (MBL-PA) in two teaching hospitals where horizontal dissemination has been demonstrated. METHODS: A case-control study was performed in both hospitals (assigned as hospital 1 and 2). Cases were patients with MBL-PA infections and controls were those with non-MBL-PA infections. Multivariate analysis was performed to identify independent risk factors. RESULTS: A total of 86 cases and 212 controls were included in the study. A logistic regression model showed that exposure to beta-lactams [odds ratio (OR) 3.21; 95% confidence interval (CI) 1.74-5.93] or fluoroquinolones (OR 3.50; 95% CI 1.46-8.37) was associated with MBL-PA infections. Other independent risk factors were neurological disease (OR 3.00; 95% CI 1.61-5.58), urinary tract infection (OR 2.48; 95% CI 1.21-5.09) and renal failure (OR 2.29; 95% CI 1.13-4.65). Admission to hospital 1 (OR 5.97; 95% CI 3.45-14.09) and intensive care unit stay (OR 2.07; 95% CI 1.46-3.96) were also associated with increased risk for MBL-PA infections. CONCLUSIONS: beta-Lactam exposure is an important risk factor for MBL-PA infections even in a setting where patient-to-patient transmission plays a major role in the spread of the isolates. Other risk factors deserve further investigation, particularly exposure to fluoroquinolones.