Bacillus subtilis-Mediated Protection from Citrobacter rodentium-Associated Enteric Disease RequiresespHand Functional Flagella

Abstract

ABSTRACTCommensals limit disease caused by invading pathogens; however, the mechanisms and genes utilized by beneficial microbes to inhibit pathogenesis are poorly understood. The attaching and effacing mouse pathogenCitrobacter rodentiumassociates intimately with the intestinal epithelium, and infections result in acute colitis.C. rodentiumis used to model the human pathogens enterohemorrhagicEscherichia coliand enteropathogenicE. coli. To confirm thatBacillus subtilis, a spore-forming bacterium found in the gut of mammals, could reduceC. rodentium-associated disease, mice received wild-typeB. subtilisspores and 24 h later were infected by oral gavage with pathogenicC. rodentium. Disease was assessed by determining the extent of colonic epithelial hyperplasia, goblet cell loss, diarrhea, and pathogen colonization. Mice that received wild-typeB. subtilisprior to enteric infection were protected from disease even thoughC. rodentiumcolonization was not inhibited. In contrast,espHandhagmutants, defective in exopolysaccharides and flagellum production, respectively, did not protect mice fromC. rodentium-associated disease. AmotABmutant also failed to protect mice from disease, suggesting thatB. subtilis-mediated protection requires functional flagella. By expanding our current mechanistic knowledge of bacterial protection, we can better utilize beneficial microbes to prevent intestinal disease caused by pathogenic bacteria, ultimately reducing human disease. Our data demonstrate that wild-typeB. subtilisreduced disease caused byC. rodentiuminfection through a mechanism that requiredespHand functional flagella.