Introduction: The Study for Monitoring Antimicrobial Resistance Trends (SMART) is a global longitudinal surveillance program that tracks antimicrobial susceptibility of aerobic gram-negative pathogens from intra-abdominal infections (IAI) to ertapenem, imipenem, amikacin, ampicillin-sulbactam, cefepime, cefotaxime, cefoxitin, ceftazidime, ceftriaxone, ciprofloxacin, levofloxacin, and piperacillin-tazobactam. Data from this program can help in development and updating of therapy guidelines as bacterial resistance to many drugs increases. This report compares incidence of extended-spectrum beta-lactamase (ESBL) producing isolates and the susceptibility of IAI pathogens recovered from surgical ICUs (SICU) to those of isolates from medical ICUs (MICU).

Methods: 120 hospitals in 35 countries collected 1,596 isolates representing 34 species from patients in SICU (713) or MICU (883) in 2008-2009. All isolates were sent to a central lab in the US for identification, confirmation of ESBL production, and susceptibility testing using CLSI methods. Only the 9 species with >10 isolates recovered from both SICU and MICU were included in this analysis. Fisher’s Exact Test was used to determine statistical significance.

Results: In 21 drug/species combinations a difference of >10% susceptibility between MICU and SICU was seen: Proteus mirabilis had 7, Enterobacter aerogenes 5, Citrobacter freundii 4, Acinetobacter baumannii and Pseudomonas aeruginosa 2 each, and E. cloacae 1. SICU %S values were generally lower for A. baumannii, E. aerogenes, and E. cloacae, while MICU %S values were usually lower for C. freundii, P. mirabilis, and P. aeruginosa; however, in only 3 cases were the differences significant (P<.05), and only one of those, P. mirabilis vs. ciprofloxacin, had potential clinical significance. ESBL rates (%) in MICU/SICU for Escherichia coli, Klebsiella pneumoniae, K. oxytoca, and P. mirabilis were 24/28, 38/35, 12/9, and 21/4, respectively; however none of the differences in ESBL rates between MICU and SICU were significant (P>.05). Only ertapenem, imipenem, and amikacin maintained %S values >85 in both MICU and SICU for all species except A. baumannii and P. aeruginosa, while amikacin did so for all species except A. baumannii and C. freundii. No other drug did so in more than 3 species.

Conclusions: Although there were some differences observed between MICU and SICU regarding drug susceptibilities and ESBL incidence, most were not statistically significant. Among the agents included in SMART, ertapenem, imipenem, and amikacin had the most in vitro activity against IAI pathogens in both MICU and SICU.