Genetic and Molecular Epidemiological Characterization of ESBL-Producing Escherichia coli Isolated from University Students in Japan

Background: Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli are major contributors to global antimicrobial resistance. Colonization in healthy individuals represents a silent reservoir that links community and healthcare settings. Determining the prevalence and molecular characteristics of ESBL-producing strains in community populations is essential for effective infection control. Methods: We enrolled 96 healthy third-year students and collected perianal swabs to detect ESBL-producing E. coli . Antimicrobial susceptibility testing, ESBL genotyping, phylogrouping, and POT-based molecular epidemiological typing were performed to characterize the isolates and identify ST131 and its H30 subclone. Results: ESBL-producing E. coli were detected in 7.3% of students (7/96; 95% CI: 3.0– 14.4%). All isolates harbored CTX-M–type ESBL genes, and the high-risk clone ST131/H30 was frequently identified. POT-based molecular typing revealed distinct patterns for all isolates, indicating independent acquisition rather than clonal transmission within the cohort. Conclusion: The detection of multidrug-resistant ST131-H30 in healthy young adults highlights the potential role of community carriers in introducing high-risk clones into healthcare settings. Strengthened surveillance and integrated One Health–based approaches are needed to curb the spread of antimicrobial resistance. Keywords: ESBL-producing Escherichia coli , CTX-M, phylogroup, ST131/H30 subclone, POT typing, antimicrobial resistance