1831. Antimicrobial Activity of Ceftazidime-Avibactam Tested Against Pseudomonas aeruginosa Isolates from USA Hospitals Stratified by Site of Infection: Results from the INFORM Surveillance Program, 2013-2015
Session: Poster Abstract Session: Antibacterial Susceptibility Surveillance
Saturday, October 29, 2016
Room: Poster Hall
  • IDWeek16 CAZ-AVI PSA 1831.pdf (350.1 kB)
  • Background: Ceftazidime (CAZ)-avibactam (AVI) was approved by the United States (US) Food and Drug Administration (FDA) for treatment of complicated intra-abdominal and urinary tract infections in 2015 and is under clinical development for treatment of hospital-acquired pneumonia.

    Methods: 5,486 P. aeruginosa (PSA) isolates (one per patient) were consecutively collected in 2013-2015 from 77 USA medical centers (37 states from all 9 census regions) by the INFORM Surveillance Program. CAZ-AVI (AVI at fixed 4 µg/mL) and comparators were tested for susceptibility (S) by CLSI broth microdilution methods and results were stratified by infection type.

    Results: Isolates were mostly from pneumonia (n=2,903; 52.9%), skin/soft tissue (SSSI; 1,286; 23.4%), bloodstream (BSI; 436; 7.9%), urinary tract (UTI; 417; 7.6%) and intra-abdominal infections (IAI; 199; 3.6%). Overall, CAZ-AVI was active against 97.0% of isolates at the US-FDA S breakpoint of ≤8 µg/mL, while S rates for meropenem (MEM), piperacillin-tazobactam (PT) and amikacin (AMK) were 82.0%, 81.3% and 96.8%, respectively (Table). When stratified by infection type, CAZ-AVI S rates varied from 95.6% (BSI) to 98.2% (SSSI), whereas S rates for MEM varied from 78.9% (pneumonia) to 87.1% (SSSI). The occurrences of multidrug-resistance (MDR) and extensively drug-resistance (XDR) were highest among isolates from pneumonia (18.2 and 10.7%, respectively) and UTI (14.9 and 9.6%, respectively), and CAZ-AVI was active against 81.9 and 74.6% of MDR and XDR isolates, respectively. In contrast, S rates for MEM and PT were only 20.5 and 17.8% among MDR and 7.0 and 6.4% among XDR isolates, respectively. High rates of cross-resistance were observed among MEM, PT and CAZ; while CAZ-AVI retained good in vitro activity against PSA isolates that were not S to MEM, PT and CAZ, inhibiting 69.9% at 8 µg/mL.

    Conclusion: CAZ-AVI exhibited potent in vitro activity and spectrum when tested against a large collection (n=5,486) of recent PSA clinical isolates. CAZ-AVI was consistently active against PSA isolates from all infection types and retained activity against isolates not S to other anti-PSA β-lactams, as well as MDR and XDR strains.


    Helio S. Sader, MD, PhD, Mariana Castanheira, PhD, Michael D. Huband, BS and Robert K. Flamm, Ph.D., JMI Laboratories, Inc., North Liberty, IA


    H. S. Sader, Allergan: Research Contractor , Research grant

    M. Castanheira, Allergan: Research Contractor , Research grant

    M. D. Huband, Allergan: Research Contractor , Research grant

    R. K. Flamm, Allergan: Research Contractor , Research grant

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