Activity of Antimicrobial Agents Recommended by IDSA/SIS for Empiric Therapy of Intra-abdominal Infections in Adults—SMART United States 2014–2015

Abstract

Background. In 2010, the Infectious Diseases Society of America (IDSA) and the Surgical Infections Society updated recommendations for empiric therapy of hospitalassociated (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. Twenty-two US laboratories collected 2866 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% versus HA and CA ESBL+ isolates, followed by piperacillintazobactam (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. Conclusion. • 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 United States. • 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 United States. • 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. (Table Presented) .