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

Abstract

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 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.

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. 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.

Conclusion: 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.