A history of repeated antibiotic usage leads to microbiota-dependent mucus defects

Recent evidence indicates that repeated antibiotic usage lowers microbial diversity and lastingly changes the gut microbiota community. However, the physiological effects of repeated - but not recent - antibiotic usage on microbiota-mediated mucosal barrier function are largely unknown. By selecting human individuals from the deeply-phenotyped Estonian Microbiome Cohort (EstMB) we here utilised human-to-mouse faecal microbiota transplantation to explore long-term impacts of repeated antibiotic use on intestinal mucus function. While a healthy mucus layer protects the intestinal epithelium against infection and inflammation, using ex-vivo mucus function analyses of viable colonic tissue explants, we show that microbiota from humans with a history of repeated antibiotic use causes reduced mucus growth rate and increased mucus penetrability compared to healthy controls in the transplanted mice. Moreover, shotgun metagenomic sequencing identified a significantly altered microbiota composition in the antibiotic-shaped microbial community, with known mucus-utilising bacteria, including Akkermansia muciniphila and Bacteroides fragilis, dominating in the gut. The altered microbiota composition was further characterised by a distinct metabolite profile, which may be caused by differential mucus degradation capacity. Consequently, our findings suggest that long-term antibiotic use in humans results in an altered microbial community that has reduced capacity to maintain proper mucus function in the gut. ### Competing Interest Statement The authors have declared no competing interest.