Integrated genomic and phenotypic characterization of antimicrobial resistance in Shiga toxin-producing Escherichia coli from asymptomatic carriers in Japan

This study shows that asymptomatic carriers of Shiga toxin-producing Escherichia coli (STEC) represent a relevant reservoir for community transmission, but overall antimicrobial resistance (AMR) levels in these strains are relatively modest. Among 495 isolates from Japan, ~17% carried resistance genes, most commonly against older antibiotics (e.g. ampicillin, tetracycline), while resistance to critical drugs such as fluoroquinolones, fosfomycin, and amikacin was rare or absent. The AMR profiles resembled those of human commensal E. coli and were lower than in cattle-derived strains. The findings suggest that several key antibiotics remain effective against STEC, but highlight the need for continued genomic surveillance to monitor emerging resistance in this largely hidden carrier population.