In Vitro Activities of Ceftazidime-Avibactam and Aztreonam-Avibactam against 372 Gram-Negative Bacilli Collected in 2011 and 2012 from 11 Teaching Hospitals in China

Ceftazidime-avibactam, aztreonam-avibactam, and comparators were tested by reference broth microdilution against 372 non-repetitive Gram-negative bacilli (346 unselected plus 26 selected meropenem-nonsusceptible Enterobacteriaceae isolates) collected from 11 teaching hospitals in China in 2011 and 2012. Meropenem-nonsusceptible isolates produced extended-spectrum beta-lactamases (ESBLs; e. g., CTX-M-14/3), AmpCs (e. g., CMY-2), and/or carbapenemases (e. g., KPC-2 and NDM-1). Avibactam potentiated the activity of ceftazidime against organisms with combinations of ESBLs, AmpCs, and KPC-2. Aztreonam-avibactam was active against all beta-lactamase producers (including producers of NDM-1 and IMP-4/8) except bla(OXA)-containing Acinetobacter baumannii and some Pseudomonas aeruginosa isolates.