Program Schedule

Antimicrobial Susceptibility of Obligate Anaerobes Isolated from Military Trauma Patients

Session: Poster Abstract Session: Diagnostic Microbiology: Bacterial Infections
Saturday, October 11, 2014
Room: The Pennsylvania Convention Center: IDExpo Hall BC
  • Poster susceptibility IDSA submitted.pdf (61.2 kB)
  • Background: Despite reports of high levels of antimicrobial (abx) resistance among obligate anaerobic bacteria, susceptibility testing is not routinely utilized to direct clinical care. This study clarifies distribution of obligate anaerobe susceptibility patterns in a combat-related trauma population.

    Methods: We utilized all initial unique isolates of obligate anaerobes collected as part of the Trauma Infectious Disease Outcome Study (9/09-5/13).  Susceptibility testing was performed using CLSI agar dilution method.  Tested abx included beta-lactam/beta-lactamase inhibitors (amp/sulb, pip/tazo ), cephalosporin (cefoxitin), carbapenems (ertapenem, imipenem, meropenem), clindamycin, metronidazole, moxifloxacin, tigecycline, and linezolid. Resistance was defined by CLSI criteria except for tige which utilized FDA criteria and no criteria exists for linezolid.


    48 patients with 63 unique anaerobic isolates were included ( 15 (24%) B. fragilis, 16 (25%) B. non-fragilis, 11 (17%) Clostridium spp., 12 (19%) Finegoldia and Peptostreptococus spp., and 9 (14%) P. acnes). For Bacteroides spp,  the 4 most active agents were metro (90% susceptible),  pip/tazo (93%), imipenem (95%) and tigecycline (95%) with an MIC50/90 of 4/8 mcg/ml for linezolid. 100% of Clostridium spp isolates were susceptible to amp/sulb, pip/tazo, ertapenem, meropenem, metro, and tige with a MIC50/90 of 4/16 mcg/ml for linezolid. 100% of Finegoldia, Peptostrepcoccus and P. acnes isolates were susceptible to amp/sulb, pip/tazo, cefoxitin, ertapenem, imipinem, meropenem, and tige with a linezolid MIC90 of 0.5 for P. acnes  and 2 for the other isolates. 6(10%) of the isolates were resistant to 3 or more classes(excluding tige and linezolid) of abx and (of those 6 isolates, 5 were Bacteroides spp.), 3 (5%) isolates to 4 or more classes (all Bacteroides spp.). One B. fragilis isolate was resistant to all abx tested except for tige. Of the 45 isolates that had prior exposure to 82 abx with anaerobic activity, 19 (23%) combinations of drug and bacteria demonstrated resistance.

    Conclusion: This study reveals high levels of resistance among some obligate anaerobes. Further studies are warranted to evaluate risk factors for resistance and to determine if in vitro susceptibilities correlate with clinical outcomes.

    Brian White, DO1, Katrin Mende, PhD2, Amy Weintrob, MD3, Miriam Beckius, MPH4, Wendy Zera, BS5, Dan Lu, MS6, William P. Bradley, MS6, David Tribble, MD, DrPH6, Clinton K. Murray, MD7 and Elizabeth Rini, MD8, (1)Infectious Disease Service, San Antonio Military Medical Center, JBSA San Antonio, TX, (2)Infectious Disease Clinical Research Program, Uniformed Services University, Bethesda, MD, (3)Infectious Disease Clinical Research Program, Washington DC, DC, (4)San Antonio Military Medical Center, JBSA Fort Sam Houston, TX, (5)Infectious Disease Clinical Research Program, Fort Sam Houston, TX, (6)Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, MD, (7)Brooke Army Medical Center, Ft. Sam Houston, TX, (8)Landstuhl Regional Medical Center, APO, AE


    B. White, None

    K. Mende, None

    A. Weintrob, None

    M. Beckius, None

    W. Zera, None

    D. Lu, None

    W. P. Bradley, None

    D. Tribble, None

    C. K. Murray, None

    E. Rini, None

    Findings in the abstracts are embargoed until 12:01 a.m. EDT, Oct. 8th with the exception of research findings presented at the IDWeek press conferences.

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