Emergence and Transmission of the High-Risk ST78 Clone of OXA-48-Producing Enterobacter hormaechei in a Single Hospital in Taiwan

Abstract

Carbapenem-resistant Enterobacter cloacae complex is a significant global healthcare threat, particularly carbapenemase-producing Enterobacter hormaechei (CPEH). From January 2017 to January 2021, twenty-two CPEH isolates from a regional teaching hospital in central Taiwan were identified with the carriage of carbapenemase genes bla KPC-2, bla IMP-8, and predominantly bla OXA-48. Over 80% of these CPEH strains clustered into the high-risk ST78 lineage, carrying a bla OXA-48 IncL plasmid (pOXA48-CREH), nearly identical to the endemic plasmid pOXA48-KP in ST11 Klebsiella pneumoniae. This OXA-48-producing ST78 lineage disseminated clonally from 2018 to 2021 and transferred pOXA48-CREH to ST66 and ST90 E. hormaechei. An IMP-8-producing ST78 strain harboring a bla IMP-8-carrying pIncHI2 plasmid appeared in 2018, and by late 2020, a KPC-2-producing ST78 strain was identified after acquiring a novel bla KPC-2-carrying IncFII plasmid. These findings suggest that the high-risk ST78 lineage of E. hormaechei has emerged as the primary driver behind the transmission of CPEH. ST78 has not only acquired various carbapenemase-gene-carrying plasmids but has also facilitated the transfer of pOXA48-CREH to other lineages. Continuous genomic surveillance and targeted interventions are urgently needed to control the spread of emerging CPEH clones in hospital settings.