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

Mitsuru Matsumura,1 Seika Matsumura,1 Yuma Ito,1 Akane Ohshima,1 Suguru Hiramoto,2 Hajime Takikawa1 1Department of Clinical Laboratory Science, Faculty of Medical Technology, Teikyo University, Tokyo, Japan; 2Clinical Laboratory, Gunma University Hospital, Maebashi, Gunma, JapanCorrespondence: Mitsuru Matsumura, Email matumura@med.teikyo-u.ac.jpBackground: 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