Acquisition of carbapenem-resistant Gram-negative bacilli in intensive care unit: predictors and molecular epidemiology.

Objectives: We had for aim to determine the risk factors for acquiring carbapenem-intermediate or -resistant Gram-negative bacilli (CR-GNB) in an intensive care unit (ICU) and to identify the resistance mechanisms involved.

Patients And Methods: We conducted an observational prospective cohort study during 6 months in medical and surgical ICUs of the Besançon Teaching Hospital. Patients with acquired CR-GNB were patients whose cultures (screening or diagnosis) became positive more than 48h after admission to the ICU. The risk factors for ICU-acquired CR-GNB were determined by multivariate logistic regression. CR-GNB isolates were typed by pulsed-field gel electrophoresis (PFGE) and screened for resistance mechanisms with phenotypic and genotypic tests.

Results: Twenty-three of the 347 included patients had acquired a CR-GNB. The multivariate analysis revealed significant associations between this acquisition and the duration of previous treatments with piperacillin-tazobactam (adjusted odds ratio [aOR], 1.13, P=0.02) and aminoglycosides (aOR, 1.62; P=0.005), but not with carbapenems. The CR-GNB strains were identified as Pseudomonas aeruginosa (n=10), Stenotrophomonas maltophilia (n=7), and Enterobacter cloacae (n=6). No acquired carbapenemase-producing strain was identified. PFGE typing identified 1 multiple clone among P. aeruginosa isolates (4 patients), whereas for the other bacteria, all the strains were different.

Conclusion: Our study results suggest that the strategy to prevent the emergence and spread of CR-GNB should not be limited to the sole restriction of carbapenem use in ICU settings.