Early emergence of OXA-181-producing Escherichia coli ST410 in China

The aim of this study was to investigate the prevalence and characterisation of OXA-48-like-producing Enterobacteriaceae in Henan Province, China.

A total of 339 carbapenem-non-susceptible clinical Enterobacteriaceae isolates [imipenem or meropenem minimum inhibitory concentration (MIC) of >1μg/mL] obtained between January 2013 and December 2016 were screened for the presence of the bla_OXA-48-like gene by PCR and sequencing. Antimicrobial susceptibility to various antimicrobials agents was examined by MIC testing. Multilocus sequence typing (MLST) was performed for bacterial genotyping. The plasmid pEC21-OXA-181 was transformed into Escherichia coli DH5α by electroporation and was sequenced using an Illumina MiSeq platform, followed by subsequent annotation and genetic analysis.

Among the 339 carbapenem-non-susceptible Enterobacteriaceae isolates, only one (0.3%) E. coli strain EC21, belonging to ST410, was positive for bla_OXA-181, a variant of bla_OXA-48. This OXA-181-producing E. coli, recovered from a patient without a history of foreign travel, was obtained earlier than the first reported bla_OXA-181-positive E. coli (WCHEC14828) in Sichuan Province, China. Plasmid analysis revealed that bla_OXA-181 together with the quinolone resistance gene qnrS1 was carried by an IS26-flanked composite transposon on a 51-kb IncX3-type plasmid.

These findings indicate the emergence of OXA-181-producing E. coli in China earlier than previously thought. The bla_OXA-181 gene is associated with the widely disseminated potentially endemic E. coli ST410 clone and is carried by an IncX3 plasmid, a common vehicle for spreading NDM-type carbapenemases, which might promote the further dissemination of bla_OXA-181 among the Enterobacteriaceae in China.