Emergence of multidrug-resistant E. coli ST8346 isolates carrying three distinct plasmids with NDM-5, KPC-2, and...

E. coli ST8346 is a unique strain associated with the potential carriage of multiple carbapenemases. Three unique E. coli ST8346 isolates were identified, each concurrently harboring multiple carbapenemases, including bla_NDM-5, bla_KPC-2, and/or bla_OXA-181. This study aimed to characterize the genetic and plasmid structures of these isolates to understand their transmission and resistance mechanisms.

Antibiotic resistance profiles, genetic relatedness, and plasmid structures were determined using antibiotic susceptibility testing, multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), S1 nuclease PFGE, and long-read sequencing.

All the strains were carbapenem resistant. PFGE revealed close genetic relationships among the isolates, despite the lack of geographical or epidemiological connections. bla_NDM-5, bla_KPC-2, and bla_OXA-181 were located on separate plasmids. Plasmids harboring bla_NDM-5 showed genetic similarities to bla_NDM-5-bearing IncF plasmids in the United Kingdom. The IncA/C plasmids harboring bla_KPC-2 had identical sequences resembling a plasmid from a K. pneumoniae strain in Taiwan, except for the bla_KPC-2 region, which matched a strain from China, indicating a hybrid plasmid.

This study is the first to identify and characterize the coexistence of bla_NDM-5, bla_KPC-2, and bla_OXA-181 in E. coli ST8346 isolates. The spread appears to be due to independent acquisition events. We identified the putative origins of these plasmids and detected a possible recombination event in a novel IncA/C plasmid. These findings emphasize the importance of ongoing surveillance and further investigations.