2176. Single β-lactams v. Combination Regimens: Assessing the Probability that an Active Agent Would be Selected When Considering Empiric Therapy for P. aeruginosa
Session: Poster Abstract Session: Healthcare Epidemiology: HAI Surveillance
Saturday, October 6, 2018
Room: S Poster Hall
Posters
  • IDWeek poster C-T + combo 9-14-18.pdf (402.3 kB)
  • Background: While the value of a combination versus monotherapy in the management of P. aeruginosa (PSA) infection continues to be a topic of debate, the rising antimicrobial resistance observed for this pathogen has made it increasingly difficult to select appropriate [i.e., susceptible] empiric regimens. Herein, we evaluated the probability of the β-lactams to provide a susceptible result for PSA when using the agents as either monotherapy or as part of a combination regimen.

    Methods: Contemporary non-duplicate PSA isolates derived from blood or the respiratory tract of patients hospitalized in the US were utilized. MICs were determined using broth microdilution methods for amikacin (AMK), cefepime (FEP), ceftazidime (CAZ), ceftolozane/tazobactam (C/T), ciprofloxacin (CIP), fosfomycin (FOF), meropenem (MEM), piperacillin/tazobactam (TZP) and tobramycin (TOB). Overall susceptibility (%S) of the regimen was derived from the monotherapy value plus the cumulative susceptibility of the additional agent for each isolate.

    Results: Total of 560 unique PSA were studied. When assessing β-lactam monotherapy, only ceftolozane/tazobactam exceeded 90% susceptibility, while cefepime, ceftazidime, meropenem and piperacillin/tazobactam ranged from 72-76% (Table). When considering combination therapy, the addition of the 2nd agent amikacin > tobramycin > ciprofloxacin > fosfomycin enhanced the achievable %S for cefepime, ceftazidime, meropenem and piperacillin/tazobactam, whereas very little change was noted for ceftolozane/tazobactam due to the intrinsic potency of this compound as a single agent (Table).

    Conclusion: While the addition of amikacin, tobramycin, ciprofloxacin or fosfomycin increased the probability that an active agent would be selected when considering empirical with cefepime, ceftazidime, meropenem and piperacillin/tazobactam, ceftolozane/tazobactam achieves a similar activity profile using a monotherapy approach.

    AMK

    C/T

    FEP

    CAZ

    CIP

    FOF

    MEM

    TZP

    TOB

    %S

    93

    95

    75

    76

    76

    46

    72

    73

    91

    %S + AMK

    -

    98

    96

    96

    -

    -

    96

    97

    -

    %S + CIP

    -

    97

    88

    90

    -

    -

    88

    89

    -

    %S + FOF

    -

    97

    86

    87

    -

    -

    85

    89

    -

    %S + TOB

    -

    97

    94

    94

    -

    -

    94

    95

    -

    Christina Sutherland, BS1, Safa Almarzoky Abuhussain, PharmD2,3 and David P. Nicolau, PharmD, FCCP, FIDSA3, (1)Center Anti-Infective Research and Development, Hartford Hospital, Hartford, CT, (2)Department of Pharmacy, Um-alQura university, Makkah, Saudi Arabia, (3)Center for Anti-Infective Research and Development, Hartford Hospital, Hartford, CT

    Disclosures:

    C. Sutherland, None

    S. Almarzoky Abuhussain, 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.