Identification and genomic characterization of Shiga toxin subtype 2j-producing Escherichia coli isolated from an asymptomatic carrier in Japan.

Shiga toxin (Stx) is the primary virulence factor of Shiga toxin-producing Escherichia coli (STEC). Stx is categorized into Stx1 and Stx2 and further classified into several subtypes based on amino acid sequence variations. During routine surveillance of STEC isolates in Japan, we identified strain 2021H102 which harbored an uncommon stx subtype. Whole genome sequencing combined with matrix-assisted laser desorption/ionization-time of flight mass spectrometry analysis revealed that 2021H102 was a Stx2j-producing E. coli. Despite similarity among the sequences of Stx2j encoding prophages, phylogenetic analysis revealed that stx2j-positive E. coli genomes are diverse. 2021H102 clustered with genomes identified in the United States by core-genome single nucleotide variant-based phylogenetic analysis, implying that 2021H102 may have been an imported case. Several detection PCR primers failed to amplify stx2j, implying that stx2j-positive STEC might not be detected in some clinical laboratories. To our knowledge, this is the first report of Stx2j-producing E. coli isolated from outside of North American continent.