Sader HS, et al. - Researchers consecutively collected 18,656 Enterobacteriaceae and 4,175 Pseudomonas aeruginosa from 85 US hospitals and tested them for susceptibility by broth microdilution methods in a central monitoring laboratory (JMI Laboratories). They identified ceftazidime-avibactam to be active against 99.9-100.0% of Enterobacteriaceae. Among Enterobacteriaceae from pneumonia, lower β-lactam susceptibility rates were observed. Activity of ceftazidime-avibactam against 97.0% to 99.4% of P. aeruginosa was noted. Among isolates from pneumonia, the frequencies of multidrug-resistant/extensively drug-resistant P. aeruginosa were highest.