An antibiotic-treated mouse model reveals the progression of intestinal botulism

Intestinal botulism, including infant botulism and adult intestinal toxemia botulism, is a life-threatening disease caused by intestinal infection with Clostridium botulinum ( Cb ) spores. Infants are particularly susceptible to Cb infection because of their immature gut microbiota, whereas healthy adults are generally protected by gut microbiota-mediated colonization resistance. Thus, immature gut microbiota or gut dysbiosis is thought to permit Cb colonization. However, the mechanisms underlying colonization resistance and disease progression remain poorly characterized. Here, using adult mice with antibiotic-induced dysbiosis, we established a model for studying Cb infection and characterized intestinal colonization, bacterial expansion, botulinum neurotoxin (BoNT) accumulation, and disease progression during intestinal botulism. Intestinal botulism developed in antibiotic-treated mice after intragastric administration of strain 62A spores, whereas untreated adult mice showed no symptoms. In antibiotic-treated mice, Cb expanded over time in fecal samples, followed by accumulation of serotype A BoNT (BoNT/A), which correlated with the progression of botulism symptoms. Cb growth and BoNT/A accumulation occurred mainly in the cecum and colon, but not in the small intestine. Furthermore, this mouse model was applicable to the analysis of intestinal botulism caused by other Cb strains, including 7I03-H, Okra, and Osaka05. Taken together, our findings clarify key aspects of intestinal botulism pathogenesis. This mouse model may provide a useful platform for elucidating the mechanisms underlying intestinal botulism, including infant botulism, and for developing novel therapeutic strategies. IMPORTANCE Botulism is a life-threatening disease caused by botulinum neurotoxin, one of the most powerful toxins known. In intestinal botulism, Clostridium botulinum spores enter the intestine, grow there, and release toxin inside the body. However, the detailed process by which intestinal botulism develops remains poorly understood. In this study, we established a mouse model that allows the progression of intestinal botulism to be examined over time. Using this model, we showed that bacterial growth in the intestine, accumulation of biologically active toxins, and worsening of symptoms are closely linked. We also identified the cecum and colon as the main sites of bacterial colonization and toxin accumulation. This model can be used to analyze multiple C. botulinum strains with different characteristics and provides a useful tool for understanding how intestinal botulism develops and for guiding future preventive and therapeutic strategies.