Treatment of extensively-drug resistant (XDR) Acinetobacter and impact on clinical outcomes in U.S. veterans affairs (VA) medical centers.

Background: Guidelines for treatment of resistant Acinetobacter baumannii (AB) are limited, 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 and 2018 at Veterans Affairs Medical Centers. Descriptive statistics summarized antibiotics; propensity score adjusted regression models were fit to compare outcomes.

Results: Two hundred and seventy-six patients with 439 XDRAB cultures and Gram-negative targeted antibiotic treatment were included. One hundred and eighteen (43%) patients received monotherapy while 158 (57%) received combination therapy, most commonly including a carbapenem (n = 106, 67%) and polymyxin (n = 66, 42%). One hundred and eighty-four (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 postculture 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.