Distribution of ESBLs, AmpC β-lactamases and carbapenemases among Enterobacteriaceae isolates causing intra-abdominal and urinary tract infections in the Asia-Pacific region during 2008-14: results from the Study for Monitoring Antimicrobial Resistance Trends (SMART)

Objectives: To investigate the antimicrobial resistance and assess the molecular characteristics of β-lactamases (ESBLs, AmpC β-lactamases and carbapenemases) among Enterobacteriaceae isolates that caused intra-abdominal infections (IAIs) in patients hospitalized in the Asia-Pacific region during 2008-14.

Methods: Multiplex PCR was used to detect the specific types of β-lactamase in 2893 isolates with MICs of ertapenem >0.5 mg/L. In-hospital acquisition times for most isolates were also delineated.

Results: Among 2728 (94.3%) isolates proven with β-lactamase production, the rates of non-susceptibility to imipenem were low (average = 7.9%) among IAI Enterobacteriaceae isolates from all Asia-Pacific countries except Vietnam (17.7%) and the Philippines (10.2%). A stepwise and significant increase in annual rates of carbapenemase production among these isolates was noted. CTX-M-15 and CTX-M-14 were the dominant ESBL variants in most IAI Enterobacteriaceae species. The most abundant AmpC β-lactamase variants were bla_CMY-2 among isolates of Escherichia coli and bla_DHA-1 among isolates of Klebsiella pneumoniae. In addition, the IAI Enterobacteriaceae isolates harbouring a bla_CMY-2 or bla_DHA-1 allele were associated with high community-acquired rates (38.0% and 42.6%, respectively). AmpC ACT and MIR variants were mostly detected in Enterobacter species. The bla_NDM-1,4,5,7-harbouring isolates of E. coli, K. pneumoniae and Enterobacter cloacae were most commonly identified among IAI isolates from Vietnam and the Philippines. Also of note, bla_OXA-48-harbouring IAI Enterobacteriaceae isolates were detected exclusively in Vietnam.

Conclusions: The high resistance burden in Vietnam and the Philippines warrants aggressive control policies to combat the worsening trend in antimicrobial resistance among Enterobacteriaceae species causing IAIs.