P088 Restoration of gut microbiota and changes in inflammatory susceptibility by dextran sulfate sodium after antibiotic treatment in mice

Abstract Background It has been suggested that changes in gut microbiota have an important effect on the development of inflammatory bowel disease (IBD). In studies using germ-free mice, it has been reported that the absence of microbiota rarely causes dextran sulfate sodium (DSS)-colitis. This study was to investigate whether the changes in DSS-colonic inflammation in mice treated with antibiotics were comparable to the results in germ-free mice. Methods Ampicillin + enrofloxacin were treated in six 9-week-old C57BL/6 mice for initial 3 days and stools were sampled daily to measure the total amount of bacterial 16S rRNA. The time of loss and restoration of gut microbiota was investigated after repeated antibiotics. The severity of colitis and barrier damage were compared between the following groups: (i) control group, (ii) DSS group, and, and (iii) DSS + antibiotics group. The DSS group was allowed to drink 3% DSS from day 5 and maintained for 7 days, and colon tissues were obtained from all groups on day 12. The inflammatory markers (IL-1α, IL-6, IL-17, tumor necrosis factor (TNF)-α) and gut barrier markers (Zonular occludens (ZO)-1, occludin, claudin-1, claudin-4) in colon tissues were comparatively analyzed between groups. Results Bacterial 16S rRNA was not detected from day 4 after the antibiotics, and restoration started from day 11. After repeated antibiotics, microbial depletion was re-confirmed on day 14, but restoration appeared on day 18, confirming faster recovery. The expression levels of IL-1α, IL-17, and TNF-α in the DSS + antibiotics group did not differ from the control but were significantly lower than the DSS group (all p < 0.01). However, the expression of ZO-1 and claudin-4 was significantly lower in the DSS + antibiotics treatment group than in the control group (p < 0.05). Conclusion The antibiotic cocktail could dramatically reduce gut microbiota over a period, but the effect would decrease as it is repeated. Depletion of gut microbiota after antibiotics would dramatically reduce DSS-colonic inflammation but could damage the gut barrier or at least not prevent barrier dysfunction.