In vitro susceptibility and distribution of beta-lactamases in Enterobacteriaceae causing intra-abdominal infections in North America 2010-2011.

Abstract The Study for Monitoring Antimicrobial Resistance Trends has been monitoring the activity of antimicrobials indicated for the treatment of intra-abdominal infections since 2004. This report documents the in vitro activity of several recommended antimicrobials against 3449 gram-negative bacilli isolated from the 30 and 25 participating sites in North America in 2010–2011, respectively, and characterizes the extended-spectrum beta-lactamases (ESBL) identified in ESBL-positive and ertapenem-non-susceptible isolates of Enterobacteriaceae. Escherichia coli , Klebsiella pneumoniae , Enterobacter cloacae , Proteus mirabilis , Klebsiella oxytoca , Citrobacter freundii , Enterobacter aerogenes , Serratia marcescens , and Morganella morgannii were the most common species isolated. The incidence of beta-lactamase production was 8.8% and 8.9% for E. coli and K. pneumoniae , respectively. Overall the most active antimicrobials were amikacin, piperacillin-tazobactam, imipenem, and ertapenem, although beta-lactamase production reduced the activity of most agents. Characterization of beta-lactamase genes determined that bla SHV , bla CTX-M , bla AmpC , and bla KPC were commonly found in most beta-lactamase–positive isolates.