Aztreonam-Avibactam Susceptibility Testing Program for Metallo-beta-lactamase-producing Enterobacterales in the Antibiotic Resistance Laboratory Network, March 2019-December 2020.

Aztreonam-avibactam is a drug combination pending phase 3 clinical trials and is suggested for treatment of severe infections caused by metallo-beta-lactamase (MBL)-producing Enterobacterales by combining ceftazidime-avibactam and aztreonam. Beginning in 2019, four Antibiotic Resistance Laboratory Network regional laboratories offered aztreonam-avibactam susceptibility testing by broth microdilution. For 64 clinical isolates tested, the MIC50 and MIC90 values of aztreonam-avibactam were 0.5/4 μg/ml and 8/4 μg/ml, respectively. Aztreonam-avibactam displayed potent in vitro activity against the MBL-producing Enterobacterales tested.