LAUSR

BACKGROUND Guidelines for treatment of resistant Gram-negative infections do not include Acinetobacter baumannii (AB), leaving a knowledge gap in best practices for treatment. This study described treatments and outcomes of extensively-drug resistant (XDR) AB. METHODS Retrospective cohort study including patients with XDRAB (non-susceptible to at least 1 agent in all but 2 or fewer classes) and antibiotic treatment between 2012-2018 at Veterans Affairs Medical Centers. Descriptive statistics summarized antibiotics; propensity score adjusted regression models were fit to compare outcomes. RESULTS 276 patients with 439 XDRAB cultures and Gram-negative targeted antibiotic treatment were included. 118 (43%) patients received monotherapy while 158 (57%) received combination therapy, most commonly including a carbapenem (n=106, 67%) and polymyxin (n=66, 42%). 184 (67%) patients received inadequate treatment. In adjusted models, combination therapy did not decrease the odds of in-hospital (aOR 1.24, 95%CI 0.60-2.59) or 30-day (aOR 1.43, 95%CI 0.86-2.38) mortality, or median post-culture length of stay (aIRR 1.11, 95%CI 0.86-1.43). Likewise, receipt of inadequate treatment was not associated with poorer outcomes. CONCLUSIONS In this national cohort of patients with XDRAB, neither combination therapy nor receipt of adequate treatment improved outcomes. Further research is needed on optimal management of this difficult-to-treat pathogen with few effective antibiotic options.