Impact of revised CLSI breakpoints for susceptibility to third-generation cephalosporins and carbapenems among Enterobacteriaceae isolates in the Asia-Pacific region: results from the Study for Monitoring Antimicrobial Resistance Trends (SMART), 2002–2010

Abstract

This study examined the rates of susceptibility to third-generation cephalosporins and carbapenems among Enterobacteriaceae isolates that had been obtained from patients with intraabdominal infections in the Asia-Pacific region as part of the Study for Monitoring Antimicrobial Resistance Trends (SMART). Susceptibility profiles obtained using 2009 Clinical and Laboratory Standards Institute (CLSI) breakpoints were compared with those obtained using the 2011 CLSI breakpoints. From 2002 to 2010, Escherichia coli and Klebsiella pneumoniae together accounted for more than 60% of the 13714 Enterobacteriaceae isolates analyzed during the study period. Extended-spectrum β-lactamase (ESBL) producers comprised 28.2% of E. coli isolates and 22.1% of K. pneumoniae isolates in the Asia-Pacific region, with China (55.6% and 33.7%, respectively) and Thailand (43.1% and 40.7%, respectively) having the highest proportions of ESBL producers. Based on the 2011 CLSI criteria, 77.2% of the Enterobacteriaceae isolates, 40.4% of ESBL-producing E. coli, and 25.2% of ESBL-producing K. pneumoniae isolates were susceptible to ceftazidime. Carbapenems showed in vitro activity against >90% of Enterobacteriaceae isolates in all participating countries, except for ertapenem in South Korea (susceptibility rate 82.2%). Marked differences (>5%) in susceptibility of ESBL-producing E. coli and K. pneumoniae isolates to carbapenems were noted between the profiles obtained using the 2009 CLSI criteria and those using the 2011 CLSI criteria. Continuous monitoring of antimicrobial resistance is necessary in the Asia-Pacific region.