Antimicrobial Activities of Aztreonam-Avibactam and Comparator Agents against Contemporary (2016) Clinical Enterobacteriaceae Isolates

ABSTRACT A total of 10,451 contemporary (2016) Enterobacteriaceae isolates from 84 U.S. medical centers and 116 metallo-β-lactamase- and/or OXA-48-like-producing Enterobacteriaceae isolates from other countries were tested against aztreonam-avibactam and comparators. All U.S. isolates were inhibited at aztreonam-avibactam MICs of ≤8 μg/ml (MIC 50 , ≤0.03 μg/ml; MIC 90 , 0.12 μg/ml), including Klebsiella pneumoniae carbapenemase-producing isolates ( n = 102; MIC 50 , 0.25 μg/ml; MIC 90 , 0.5 μg/ml), multidrug-resistant isolates ( n = 876; MIC 50 , 0.06 μg/ml; MIC 90 , 0.25 μg/ml), and extensively drug-resistant isolates ( n = 111; MIC 50 , 0.12 μg/ml; MIC 90 , 0.5 μg/ml). The highest aztreonam-avibactam MIC value among ex-U.S. isolates was 4 μg/ml.