Antimicrobial Activity of Ceftazidime-Avibactam and Comparator Agents Tested against Enterobacteriaceae and Pseudomonas aeruginosa from United States (US) Medical Centers Stratified by Infection Type (2015–2016)

BACKGROUND: We evaluated and compared the in vitro activities of ceftazidime-avibactam (CAZ-AVI) and comparators against of Enterobacteriaceae (ENT) and P. aeruginosa (PSA) from various infection types. METHODS: 23,440 isolates composed of 19,249 ENT and 4,191 PSA were consecutively collected from 85 US hospitals and tested for susceptibility (S) by broth microdilution methods in a central monitoring laboratory (JMI Laboratories). The antimicrobial S and frequency of key resistance (R) phenotypes, such as multidrug-R (MDR) and extensively drug-R (XDR) among others, were assessed and stratified by these infection types: bloodstream (BSI; 3,434 isolates; 14.7%), pneumonia (6,439; 27.5%), skin/skin structure (SSSI; 4,134; 17.6%), intra-abdominal (IAI; 951; 4.1%), urinary tract (UTI; 7,873; 33.6%), and others combined (609; 2.6%). RESULTS: CAZ-AVI was active against 99.9% to 100.0% of ENT and 97.0% (pneumonia) to 99.4% (UTI) of PSA isolates. S rates were consistently lower among ENT from pneumonia compared with other infection types for β-lactams such as CAZ (82.3% vs. 87.1–90.8%), piperacillin-tazobactam (P-T; 87.5% vs. 90.2–95.6%) and meropenem (MEM; 96.8% vs. 98.4–99.4%). S to gentamicin (GEN) was also generally lower among isolates from pneumonia, whereas S to levofloxacin (LEV) and colistin (COL) were lowest among BSI and SSSI isolates, respectively. The occurrence of MDR, XDR, and carbapenem-resistant ENT (CRE) phenotypes were markedly higher among isolates from patients with pneumonia compared with other infection types (Table). Among PSA, S rates for CAZ, P-T, and GEN were lowest among isolates from pneumonia, whereas S to MEM was similar among isolates from BSI, pneumonia, and IAI (77.3–77.9%), and S to LEV was markedly lower among UTI isolates (67.1%). The frequency of PSA isolates with MDR and XDR phenotypes, as well as non-S to CAZ, MER, and P-T, were also highest among isolates from patients with pneumonia (Table). CONCLUSION: Antimicrobial S rates were generally lower among ENT and PSA isolates from patients with pneumonia compared with other infections. CAZ-AVI was highly active against a large collection of contemporary ENT and PSA isolates from US hospitals (2015–2016), including MDR and XDR organisms, regardless of the infection type. DISCLOSURES: H. S. Sader, Allergan: Research Contractor, Research grant; M. Castanheira, Allergan: Research Contractor, Research grant; L. R. Duncan, Allergan: Research Contractor, Research grant; R. K. Flamm, Allergan: Research Contractor, Research grant