364. Therapeutic Management of Bloodstream Infection Resulting from Pseudomonas aeruginosa that is Non-Susceptible to Carbapenems but Susceptible to Cephalosporins and/or to Penicillins
Session: Poster Abstract Session: HAI: Multi Drug Resistant Gram Negatives
Thursday, October 27, 2016
Room: Poster Hall
  • ID-Week poster - PA BSI - Carb-R b-Lactam-S 10-11-2016 1 dm.pdf (524.8 kB)
  • Background: In bloodstream infections (BSI) resulting from Pseudomonas aeruginosa(PA) which are non-susceptible to carbapenems, it is debatable whether other beta-lactams can be used, even if the isolate is supposedly susceptible.

    Methods: A retrospective cohort study was conducted at Assaf Harofeh Medical Center (AHMC) from 01/2010 to 08/2014. Adult patients with PA-BSI with minimal inhibitory concentration (MIC) > 2 to either meropenem or imipenem, but with MIC < 16 to ceftazidime, or <32 to piperacillin, or < 32/4 to piperacillin-tazobactam were enrolled. We compared the outcomes of patients who got (≥2 doses) an appropriate (per in-vitroreport) beta-lactam agent (“cases”) to those who got (≥2 doses) appropriate non-beta-lactam regimens (“controls”). Patients who received agents from both study arms were excluded. Whole genome sequencing for one representative blood isolate was executed, and mechanisms of carbapenem resistance and genotyping (MLST) were queried.

    Results: There were 26 patients with PA BSI who met the inclusion criteria: 18 were treated with a beta-lactam (7 cephalosporin, 5 penicillins with/out beta-lactamase inhibitor, and 6 combinations) and 8 were treated with a non-beta-lactam (4 fluoroquinolones, 2 colistin, 1 fluoroquinolone with aminoglycoside and 1 colistin with aminoglycoside). Patients’ characteristics were similar between groups (prediction score to control for biases associated with being a “case” in not presented due to model instability). All clinical outcomes were similar between groups: e.g., 1) 30-day mortality (57% among cases vs. 50% among controls, OR=1.2, p<0.99), 2) median length of stay from infection to discharge after excluding the dead (11 days among cases and controls, p=0.3). There were huge variations in phenotypic susceptibilities of strains. Detailed molecular investigation of a representative isolate revealed a strain that belonged to MLST-175 with OXA-28 and OXA-19 present.

    Conclusion: Even for invasive BSI, when the PA is non-susceptible to carbapenems, it is reasonable to choose another “appropriate” (per MIC breakpoints) non-carbapenem-beta-lactam agent. However, larger confirmatory studies are needed.

    Asaf Miller, MD1, Hadas Ofer-Friedman, MD1, Ronit Zaidenstein, M.D.2, Mor Dadon, BsC1 and Dror Marchaim, MD3, (1)Assaf Harofeh Medical Center, Beer Yaacov, Israel, (2)Medicine a, Assaf Harofeh Medical Center, Beer Yaacov, Israel, (3)Infectious Diseases, Assaf Harofeh Medical Research Fund, Zerifin, Israel


    A. Miller, None

    H. Ofer-Friedman, None

    R. Zaidenstein, None

    M. Dadon, None

    D. Marchaim, Merck: Grant Investigator and Speaker's Bureau , Research grant and Speaker honorarium
    Pfizer: Scientific Advisor , payment for participating in advisory board

    Findings in the abstracts are embargoed until 12:01 a.m. CDT, Wednesday Oct. 26th with the exception of research findings presented at the IDWeek press conferences.