Risk factors for carbapenem-resistant Klebsiella pneumoniae infection/colonization: a case-case-control study

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is increasingly reported worldwide. The aim of the present study was to identify risk factors associated with the development of CRKP infections. A retrospective, case-case-control study was performed at the University Hospital of Heraklion, Greece. The study population included 83 patients from whom CRKP was isolated, 79 from whom carbapenem-sensitive K. pneumoniae (CSKP) was isolated and 161 (control group) from whom K. pneumoniae was not isolated. The median age of CRKP and CSKP patients was 79 (28-101) and 80 (39-97) years, respectively, while that of the controls was 75 (18-100) years. K. pneumoniae was isolated predominantly from urine in both case groups, followed by blood. Independent risk factors for CRKP infection/colonization were admission to ICU (p = 0.004), prior surgical procedure (p = 0.036) and presence of renal disease (p = 0.037), while for CSKP were neurological disease (p = 0.007), and older age (p = 0.011). No association between CRKP and prior antimicrobial exposure was found. Of the entire cohort 40 patients (12%) died; 22 (27%) in the CRKP, 12 (15%) in the CSKP and 6 (4%) in the control group. Isolation of any K. pneumoniae strain was associated with higher mortality compared to the control group (21% vs. 4%; p < 0.005). Mortality was not statistically different between those infected/colonized/with a CRKP or a CSKP strain (p = 0.084). According to these results prior ICU stay, prior surgical procedure and renal disease were independent risk factors for the development of a CRKP infection/colonization.