Risk factors for colonisation by colistin-resistant Klebsiella pneumoniae in critically ill patients

Abstract number: P620

Kontopidou F., Plachouras D., Koukos G., Papadomichelakis E., Galani I., Antoniadou A., Poulakou G., Armaganidis A., Giamarellou H.

Introduction: Emergence of colistin resistant Gram-negative bacteria, and especially strains of Klebsiella pneumoniae, in the ICU severely limits our treatment choices in critically ill patients. The aim of this study was to investigate the risk factors for colonisation by such strains.

Methods: The study was performed in a 12-bed University General ICU from November 2003 to December 2006. Empirical antimicrobial treatment was guided by weekly active surveillance of patients' floras. All specimens were cultured in MacConkey agar plates containing antibiotics in order to focus on resistant pathogen detection. Colistin resistance was defined by Etest according to BSAC breakpoints (>4 mg/L). Demographic and clinical data of the patients were recorded. Risk factors for colonisation by CRKP were assessed by univariate and logistic regression analysis.

Results: 150 patients (mean age 65.1 years) with mean APACHEIII score (SD) 18.7 (7.8) and mean days of hospitalisation (SD) 76.0 (54.0) were included in the study. 29 (19.3%) patients were colonised with CRKP. Among these patients seven (24%) developed an infection by CRKP with fatal outcome in six of them. The median number of hospitalisation days was 64.5 in the group colonised with colistin resistant isolates compared to 34 days in the non-colonised group (p 0.01). Mean APACHEIII score was 19.6 and 18.4 respectively (NS) in the two groups. Administration of colistin was significantly associated with colonisation by CRKP strains (p 0.001). The median duration of colistin treatment was 23.0 and 14.7 days among patients colonised and not colonised with CRKP respectively (p NS). Among the patients with CRKP 26 (89.7%) had previously received colistin. 15 (16.1%) of patients who had received piperacillin/tazobactam were colonised by CRKP compared to 14 (24.6%) of patients who had not received this combination (p NS). In the multivariate analysis model the only significant risk factors for colonisation with colRKP were administration of colistin (p 0.005, OR 6.7) and piperacillin/tazobactam (p 0.017, OR 0.32).

Conclusions: Colistin use is the only significant risk factor associated with the emergence of resistant Klebsiella pneumoniae strains, jeopardising treatment choices in the ICU. Unnecessary or prolonged administration of colistin should be avoided.