Characterization of novel sequence type 12531 and O8:H7 serotype carbapenem-resistant <i>Escherichia coli</i> with strong swimming and intestinal epithelial cell barrier migration abilities

Carbapenem-resistant <i>Enterobacteriaceae</i> have become widely prevalent globally because of antibiotic misuse and the spread of drug-resistant plasmids, where carbapenem-resistant <i>Escherichia coli</i> (CREC) is one of the most common and prevalent pathogens. Furthermore, <i>E. coli</i> has been identified as a member of normal gut flora and does not cause disease under normal circumstances. However, certain strains of <i>E. coli</i>, due to the expression of virulence genes, can cause severe intestinal and extra-intestinal infections. Therefore, clinically, drug resistance and pathogenic <i>E. coli</i> strains are significantly challenging to treat. In this study, a novel CREC strain DC8855 was isolated from the ascites of a patient with intestinal perforation, identified as a novel sequence type 12531 (ST12531) and an unreported serotype O8:H7. It was revealed that the resistance of ST12531 CREC was predominantly conferred by an IncFII(K) plasmid carrying <i>bla</i>_NDM-4. Furthermore, phylogenetic analysis indicated that this is the first discovery of such plasmids in China and the first identification in <i>E. coli</i>. Moreover, regarding virulence, the swimming assays, qRT-PCR, and <i>in vitro</i> intestinal barrier model indicated that DC8855 had significantly higher motility, flagella gene expression, and intestinal epithelial cell barrier migration ability than the other sequence types CREC strains (ST167 and ST410). In conclusion, this study identified novel CREC which was multidrug resistant as well as enteropathogenic and therefore requires continuous monitoring.