1848. Activity of Antimicrobial Agents Recommended by IDSA/SIS for Empiric Therapy of Intra-abdominal Infections in Adults – SMART United States 2014-2015
Session: Poster Abstract Session: Antibacterial Susceptibility Surveillance
Saturday, October 29, 2016
Room: Poster Hall
  • Merck_P07_IAI IDSA guidelines US_IDWeek 2016_v1_final.pdf (832.6 kB)
  • Background: In 2010, the Infectious Diseases Society of America (IDSA) and the Surgical Infections Society updated recommendations for empiric therapy of hospital-associated (HA) and community-associated (CA) intra-abdominal infections (IAI). The Study for Monitoring Antimicrobial Resistance Trends (SMART) has tracked susceptibility of IAI aerobic gram-negative bacilli (GNB) globally since 2002.  This report reviews susceptibility of GNB from the United States to many of the drugs recommended in the guidelines.

    Methods: 22 US laboratories collected 2,866 GNB from adults with IAI in 2014-2015 (up to 100 consecutive isolates per year per lab; 1 isolate per species per patient). Susceptibility testing and determination of extended-spectrum-β-lactamase (ESBL) phenotype were done using CLSI broth microdilution methods and breakpoints. An IAI was defined as HA or CA if cultured ≥48 hours or <48 hours post-admission, respectively.

    Results: The proportion of P. aeruginosa resistant to ceftazidime (CAZ) was 22.9% and 11.6% for isolates from HA and CA IAI, respectively; the proportion of ESBL+ isolates among E. coli, K. oxytoca, K. pneumoniae, and P. mirabilis was 11.9% (HA) and 7.2% (CA).  Only ertapenem (ETP), imipenem (IPM), and amikacin (AMK) had susceptibility values >90% vs. HA and CA ESBL+ isolates, followed by piperacillin-tazobactam (TZP) with 69.7% (HA) and 73.8% (CA).

    Susceptibility (with 95% confidence limits) of all GNB combined is shown below, using breakpoints of each species and assuming 0% susceptible if no breakpoint exists for any drug/species.



    • Of the studied agents recommended for empiric therapy of HA IAI, IPM, cefepime (FEP), CAZ, TZP, and AMK were active against >80% of isolates in the US.
    • However, because cephalosporins are not recommended if >20% of P. aeruginosa are resistant to CAZ or if ESBL+ Enterobacteriaceae are suspected, cephalosporins may not be appropriate for empiric therapy of HA IAI in the US.
    • Furthermore, even though TZP is recommended for empiric therapy of HA IAI if ESBL+ isolates are suspected, it inhibited <70% of HA ESBL+ isolates in this study, making its empiric use questionable.
    • Among drugs suggested for CA IAI, ETP, IPM, FEP, CAZ, and TZP were active against >85% of CA isolates.
    Sibylle Lob, MD, MPH1, Robert Badal, BS1, Katherine Young, MS2, Mary Motyl, PhD3 and Dan Sahm, PhD1, (1)International Health Management Associates, Inc., Schaumburg, IL, (2)Merck & Co., Inc., Kenilworth, NJ, (3)Infectious Disease, Merck & Co., Inc., Kenilworth, NJ


    S. Lob, IHMA, Inc.: Independent Contractor , Research support

    R. Badal, IHMA, Inc.: Independent Contractor , Research support

    K. Young, Merck & Co., Inc.: Employee , Salary

    M. Motyl, Merck & Co., Inc.: Employee , Salary

    D. Sahm, IHMA, Inc.: Independent Contractor , Research support

    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.