1336. Choice of Antibiotics for Initial Double-Coverage of Suspected Gram-Negative Bacteremia
Session: Poster Abstract Session: Clinical Trials
Saturday, October 5, 2013
Room: The Moscone Center: Poster Hall C
  • IDSA_Poster.png (1.6 MB)
  • Background:

    Patients with suspected sepsis from gram negative organisms are often initially treated with two antibiotics to decrease the chance of "missing" a resistant isolate. However, resistance frequencies for different antibiotics may not be statistically independent and associations may vary geographically and over time. Detailed analysis of recent rates of dual-resistance for all antibiotic pairs might help guide initial empiric therapy.


    This was a retrospective, single-center, cohort study that analyzed all antibiotic sensitivity data from blood cultures growing Gram-negative organisms for the years 2000 to 2012 at Mount Auburn Hospital in Cambridge, Massachusetts. Rates of dual-resistance for all pairwise combinations were examined to determine which pairs showed the lowest rates of dual-resistance and which second antibiotics gave the largest decrease in dual resistance when added to a given antibiotic. 


    In general, addition of aminoglycosides to a lactam antibiotic gave the lowest dual-resistance and the greatest added benefit, in particular superior to quinolones in most combinations. For example, combining ceftriaxone and gentamicin resulted in 22% reduction in resistance compared to ceftriaxone and ciprofloxacin which ended in 13% reduction. For Pseudomonas aeruginosa isolates, aztreonam and amikacin outperformed ceftazidime and ciprofloxacin (a reduction of 19% v 3%). For penicillin-allergic patients, combining levofloxacin with gentamicin gave a 15% reduction of resistance. We also examined uncommonly used combinations for cases where allergies and/or toxicities preclude more standard pairs.


    At our institution over the past twelve years, resistance patterns for antibiotics used against Gram-negative organisms showed significant statistical associations relevant to the choice of initial double-coverage of suspected Gram-negative sepsis. Aminoglycoside-containing combinations often gave the greatest additional benefit as a second drug. These data may influence risk-benefit decisions in choice of initial therapy, where the toxicities of the drugs must be balanced against minimizing the chance of ineffective initial therapy. Similar hospital-based analysis may help tune therapy to current local resistance patterns.

    Dooshanveer Nuckchady, MD, Mount Auburn Hospital, Cambridge, MA and Robin Colgrove, MD, Department of Microbiology and Molecular Genetics, Harvard Medical School, Cambridge, MA


    D. Nuckchady, None

    R. Colgrove, None

    See more of: Clinical Trials
    See more of: Poster Abstract Session

    Findings in the abstracts are embargoed until 12:01 a.m. PST, Oct. 2nd with the exception of research findings presented at the IDWeek press conferences.