Antibiotic therapy attenuates colitis in interleukin 10 gene-deficient mice

Background & Aims: Interleukin (IL)-10 gene-deficient mice, raised under ge rmfree conditions, do not develop colitis, implying a role for bacteria. Th is study mapped the appearance of luminal colonic bacteria and, using antib iotic treatment, determined their association with colitis in IL-10 gene-de ficient mice, Methods: Mice were treated with ciprofloxacin or with neomyci n and metronidazole, The intestine was harvested for histological scoring a nd bacterial assessment. Results: At 2 weeks of age, before the development of colitis, IL-10 gene-deficient mice demonstrated an earlier appearance o f Streptococcus and Clostridium sp., and had a greater proportion (P < 0.01 ) of bacteria adherent to the colonic mucosa, This pattern of increased adh erent bacteria persisted for the 12 weeks of study. Treatment of mice befor e the onset of colonic inflammation, with either antibiotic regime, reduced mucosal adherent bacteria and prevented colitis (P < 0.01). In contrast, t reatment of established colitis with neomycin and metronidazole did not red uce adherent bacterial levels, yet was more efficacious (P < 0.05) in treat ing established colitis than ciprofloxacin, which did reduce adherent colon ic bacteria. Conclusions: In the IL-10 gene-deficient mouse model, the appe arance and number of mucosal adherent colonic bacteria are altered before t he onset of colitis. Antibiotics both prevent and treat the colitis through correction of this primary bacterial alteration.