Mortality attributable to different Klebsiella susceptibility patterns and to the coverage of empirical antibiotic therapy: a cohort study on patients admitted to the ICU with infection.

Purpose: To evaluate the prognostic importance of different Klebsiella spp. sensitivity patterns: multi-susceptible Klebsiella (MS-K), extended-spectrum cephalosporin-resistant, but carbapenem-susceptible Klebsiella (ESCR-CS-K), and carbapenem-resistant Klebsiella (CR-K).

Methods: We developed a prognostic model to predict hospital mortality in patients with infection on admission to the intensive care units (ICUs), and assessed its calibration in the subgroups of interest: patients with infections due to MS-K, ESCR-CS-K, CR-K. We assessed the calibration of the model also in ESCR-CS-K treated empirically with carbapenems and with piperacillin-tazobactam.

Results: A total of 13,292 adults with an ongoing infection were admitted to 137 Italian ICUs in 2012-2013. Of 801 Klebsiella spp. infected patients, 451 had MS-K, 116 ESCR-CS-K, and 234 CR-K. The prognostic model calibrated well for the MS-K and ESCR-CS-K subgroups. In the CR-K subgroup there were more deaths than predicted (standardized mortality ratio 1.20; 95% CI 1.08-1.31), indicating a negative prognostic role of the infection, mainly in the medium and high risk-of-death patients. When infection was caused by ESCR-CS-K, treatment with piperacillin-tazobactam increased adjusted mortality among the most severe patients (similarly to CR-K), while treatment with carbapenems did not (similarly to MS-K).

Conclusions: In low risk-of-death patients admitted to the ICU with a Klebsiella spp. infection, the appropriateness of empirical antibiotic therapy seemed uninfluential to eventual mortality, while it appeared to be crucial in high-risk ones. The use of piperacillin-tazobactam may be inappropriate in severe patients with ESCR-CS-K infection. CR-K is associated to a significant 20% increase of adjusted mortality, only for patients at higher risk of death.