Abstract
In this study, we aimed to assess the geographic distribution and molecular characteristics of β-lactamases among Enterobacterales isolates causing intra-abdominal infections (IAIs) from 2015 to 2018 in the Asia-Pacific region. Isolates were investigated for extended-spectrum β-lactamases (ESBLs), AmpC β-lactamases, and carbapenemases using multiplex PCR assays and full-gene DNA sequencing. A total of 832 Enterobacterales isolates from 8 different countries with β-lactamase genes were analysed. Plasmid-mediated ESBLs and AmpC β-lactamases were encoded in 598 (71.9%) and 314 (37.7%) isolates, respectively. In 710 (85.3%) carbapenemase-negative isolates, positivity for both AmpC β-lactamases and ESBLs was identified in 51 (8.5%) Escherichia coli and 24 (3.4%) Klebsiella pneumoniae isolates. The most prevalent countries were Taiwan and Vietnam, and the co-occurrence of CMY/CTX-M in E. coli and DHA-1/ESBLs in K. pneumoniae was predominant. All isolates showed high susceptibility to colistin, but susceptibility to carbapenems varied among different resistance mechanism combinations. Among 122 (14.7%) isolates encoding carbapenemase, NDM (n=67, including 64.2% NDM-1) was the most common, followed by the OXA-48-type (n=49), KPC (n=24) and IMP (n=4). The most prevalent country was Thailand (n=44), followed by Vietnam (n=35) and the Philippines (n=21). Twenty-two isolates were found to encode multiple carbapenemases, 16 of which were collected from Thailand and harbored NDM-1, OXA-232 and CTX-M-15. Despite high susceptibility to amikacin, susceptibility to colistin was only 56%. The emergence of carbapenem-non-susceptible AmpC/ESBL co-occurring Enterobacterales and colistin non-susceptible carbapenemases co-occurring K. pneumoniae highlights potential therapeutic challenges in the Asia-Pacific region.
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