Emergence of multidrug-resistant E. coli ST8346 isolates carrying three distinct plasmids with NDM-5, KPC-2, and OXA-181.

BACKGROUND

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 blaNDM-5, blaKPC-2, and/or blaOXA-181. This study aimed to characterize the genetic and plasmid structures of these isolates to understand their transmission and resistance mechanisms.

METHODS

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.

RESULTS

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

CONCLUSION

This study is the first to identify and characterize the coexistence of blaNDM-5, blaKPC-2, and blaOXA-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.