Resistance Rates of Intra-Abdominal Isolates from Intensive Care Units and Non-Intensive Care Units in the United States: The Study for Monitoring Antimicrobial Resistance Trends 2010-2012

Background: Enterobacteriaceae (3,235 isolates), Pseudomonas aeruginosa (476 isolates), and Acinetobacter baumannii (106 isolates) from inpatient intra-abdominal infections (IAIs) were collected for the 2010-2012 Study for Monitoring Antimicrobial Resistance Trends (SMART) program in the United States. This report evaluates the in vitro activity of several antimicrobial agents recommended for treatment of IAIs and compares profiles of isolates from intensive care units (ICUs) and non-intensive care units (non-ICUs). Methods: Gram-negative bacilli from hospitalized patients with IAIs were obtained each year from 2010-2012 from hospitals in the United States and tested for susceptibility to 12 antibiotics according to 2012 Clinical and Laboratory Standards Institute (CLSI) guidelines. Results: The most active agents against members of the Enterobacteriaceae family from both ICUs and non-ICUs were amikacin, ertapenem, and imipenem-cilastatin, whereas the least active agent was ampicillin-sulbactam. Amikacin was the only agent with good activity against P. aeruginosa, whereas none of the agents tested exhibited substantial activity against A. baumannii. Amikacin, ceftazidime, ceftriaxone, ciprofloxacin, levofloxacin, and imipenem-cilastatin were significantly less active against Enterobacteriaceae from ICU patients, whereas cefepime and ceftazidime were significantly less active against P. aeruginosa from ICU patients. Intensive care unit isolates were more likely to be multi-drug-resistant than non-ICU isolates, although there was no difference in extended-spectrum -lactamase (ESBL) production rates between the two patient groups. Conclusions: Despite increasing resistance trends, in this study amikacin, ertapenem, and imipenem-cilastatin were shown to have good in vitro activity against the most frequently isolated gram-negative bacilli from IAIs in ICU and non-ICU settings.