In vitro activity of sulbactam/durlobactam against clinical isolates of Acinetobacter baumannii collected in China

Background: Durlobactam is a broad-spectrum inhibitor of class A, C and D beta-lactamases. Sulbactam is a generic beta-lactam most commonly used as a beta-lactamase inhibitor in combination with ampicillin; however, it has a unique property in that it has selective intrinsic activity against Acinetobacter baumannii. Currently, there is widespread resistance caused by multiple beta-lactamases including class A carbapenemases and class C and class D enzymes. The addition of durlobactam to sulbactam restores in vitro activity against MDR A. baumannii that possess multiple beta-lactamases. Objectives: Previously, susceptibility data for sulbactam/durlobactam were limited to isolates from patients in Western countries. This study was undertaken to determine the activity of sulbactam/durlobactam against A. baumannii isolated from patients in mainland China. Methods: Nine hundred and eighty-two recent A. baumannii clinical isolates were collected from 22 sites across mainland China during 2016-18. The isolates were collected from lower respiratory tract, intra-abdominal, urinary tract and skin and skin structure infections. The in vitro activities of sulbactam/durlobactam and comparators were determined by broth microdilution. Results: The addition of durlobactam restored the activity of sulbactam against the majority of the strains tested. The MIC90 of sulbactam/durlobactam was 2mg/L for all A. baumannii, compared with 64mg/L for sulbactam alone. The MIC90 of sulbactam/durlobactam of 2mg/L remained unchanged for 831 carbapenem-resistant isolates. Colistin was the only comparator with comparable activity (MIC90=1mg/L). Conclusions: This study demonstrated the potential utility of sulbactam/durlobactam for the treatment of infections caused by A. baumannii in China.