Investigation of Effect of the Colistin Loading Dosage on the clinical, Microbiological, and Laboratory Results in Acinetobacter baumannii Ventilator-Associated Pneumonia /Pneumonia

Abstract

Introduction and Objectives. The comparative efficacy of colistin with a loading dose (LD) and without LD remains unknown. We aimed at assessing the efficacy and safety of colistin with LD in patients with multidrug resistance (MDR) Acinetobacter baumannii ventilator-associated pneumonia (VAP) or pneumonia, compared with colistin without LD. Materials and Methods. Adult patients administered colistin with and without LD for MDR Acinetobacter baumannii VAP/pneumonia in intensive care units (ICUs) in a tertiary teaching hospital between 1 January 2018 and 31 December 2019 were included in this retrospective cohort study. The primary endpoint was an assessment of clinical and microbiological success between treatment groups. Secondary endpoints included 14- and 30-day mortality and development of nephrotoxicity. Results. A total of 101 patients were included (colistin with LD, n = 57; colistin without LD, n = 44). No significant difference in clinical success was observed between groups (73.7% versus 77.3%; $p=0.670$ ). In patients receiving colistin with LD, the microbiological success rate increased from 65.9% to 71.9%, but there was no statistically significantly difference ( $p=0.510$ ). In terms of using combination therapies with carbapeneme and/or tigecycline, there was no significant difference between treatment groups ( $p=0.30$ ). The rates of 14- and 30-day mortality were similar between groups. The colistin with LD group had a higher rate of nephrotoxicity compared to the other group (52.6% versus 20.5% $p=0.001$ ). The clinical and microbiological response times were found significantly higher in the colistin with LD group ( $p=0.001$ ; $p=0.017$ ). Conclusion. Colistin with LD was associated with a higher risk of nephrotoxicity and was not related to clinical success, microbiological success, and prolonged survival. Randomized comparative studies are needed to confirm the efficacy of LD colistin regimen on MDR Acinetobacter infection.