2175. In vitro Potency of Ceftolozane/Tazobactam and Other Antipseudomonal β-lactams Against P. aeruginosa
Session: Poster Abstract Session: Healthcare Epidemiology: HAI Surveillance
Saturday, October 6, 2018
Room: S Poster Hall
  • IDWeek poster C-T AntiPSA BLs 9-17-18.pdf (432.0 kB)
  • Background: Challenges due to multidrug resistant Gram-negative bacterial pathogens such as P. aeruginosa (PSA) are increasing globally. Suboptimal antimicrobial therapy of infections caused by PSA is associated with increased morbidity and mortality. As a result, antimicrobial susceptibility (%S) studies are pivotal to identifying trends in antimicrobial resistance that inform decisions regarding choice of antimicrobial therapy. This study assessed the in vitro potency of 7 antipseudomonal agents including ceftolozane/tazobactam against PSA collected from numerous sites across the US.

    Methods: Multiple US hospitals provided non-duplicate respiratory and blood isolates of PSA for potency testing. MICs against PSA were determined using broth microdilution methods according to CLSI for 7 antimicrobials with antipseudomonal activity: aztreonam, cefepime, ceftazidime, ceftolozane/tazobactam, imipenem, meropenem and piperacillin/tazobactam. Susceptibility (%S) was defined per CLSI or FDA breakpoint criteria.

    Results: Fourteen hospitals geographically spread across the US provided total of 560 PSA isolates. Of the antibiotics assessed, %S to C/T was the highest at 95% with an MIC50 of 1µg/ml and MIC90 of 2µg/ml. In comparison, other %S (MIC50 / MIC90) were as follows: ceftazidime 76% (4 / 64); cefepime 75% (4 / 32); piperacillin/tazobactam 73% (8 / 128), meropenem 72% (0.5 / 16); aztreonam 65% (8 / 32) and imipenem 65% (2 / 16).

    Conclusion: For this geographically diverse PSA population, ceftolozane/tazobactam demonstrated the highest overall susceptibility (95%). Other antipseudomonal agents inclusive of the carbapenems displayed susceptibilities of 65-76%. In the era of escalating PSA resistance to the β-lactams, the potency of ceftolozane/tazobactam may represent an important clinical option.

    Safa Almarzoky Abuhussain, PharmD1,2, Christina Sutherland, BS3 and David P. Nicolau, PharmD, FCCP, FIDSA2, (1)Department of Pharmacy, Um-alQura university, Makkah, Saudi Arabia, (2)Center for Anti-Infective Research and Development, Hartford Hospital, Hartford, CT, (3)Center Anti-Infective Research and Development, Hartford Hospital, Hartford, CT


    S. Almarzoky Abuhussain, None

    C. Sutherland, None

    D. P. Nicolau, Merck: Consultant , Grant Investigator and Speaker's Bureau , Consulting fee , Research grant and Speaker honorarium .

    Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 3rd with the exception of research findings presented at the IDWeek press conferences.