PhD defence Jiyang Chan

Keywords: Gut microbiota, Antimicrobial resistance, Intercontinental travel, Irritable bowel syndrome

"Chronicles of the Travelling Gut: How Travel Influences Long-Term Microbiota-Associated Health and Antimicrobial Resistance Dynamics"

This thesis investigated how intercontinental travel affects the gut microbiome, antimicrobial resistance (AMR) gene acquisition, and the development of post-infection irritable bowel syndrome (PI-IBS). Using prospective cohort studies and longitudinal analyses, the research demonstrated that travel is associated with transient disruptions in gut microbial diversity and increased acquisition of AMR genes. Among travellers with travellers’ diarrhoea, approximately one in ten later developed PI-IBS, with risk factors including antibiotic use, dietary habits, and chronic illness. Distinct bacteria and reduced microbial diversity were associated with increased susceptibility to PI-IBS, and machine learning models successfully predicted PI-IBS risk. Travel-related AMR acquisition was influenced by travel destination, antibiotic use, chronic disease, and dietary exposures. High-frequency sampling further revealed rapid shifts in specific bacteria and AMR gene acquisition during the first days of travel. Overall, this thesis highlights the role of international travel in shaping gut microbiome dynamics, AMR dissemination, and long-term gastrointestinal health outcomes.

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