Amelioration of the effects of Citrobacter rodentium infection in mice by pretreatment with probiotics

Background. Citrobacter rodentium is a naturally occurring murine pathogen that causes colonic epithelial-cell hyperplasia, disrupts the colonic mucosa, and elicits a predominantly T helper 1 cellular immune response; it thereby serves as a model for the study of mechanisms of disease induced by human attaching-effacing pathogens. We sought to determine whether pretreatment of mice with a mixture of Lactobacillus rhamnosus and L. acidophilus probiotics would attenuate C. rodentium-induced colonic disease in mice. Methods. Mice were administered sterile drinking water, probiotics (10(9) cfu/mL) in sterile drinking water, maltodextrin in sterile drinking water, orogastric C. rodentium (10(7) cfu in 0.1 mL), or maltodextrin in sterile drinking water for 1 week before C. rodentium infection, or they were pretreated with probiotics (10(9) cfu/ mL) for 1 week before challenge with C. rodentium. Results. Mice that received viable probiotics remained healthy. C. rodentium infection elicited mucosal inflammation, epithelial-cell hyperplasia, apoptosis in the colon, and interferon (IFN)-gamma production by splenocytes. Pretreatment with probiotics decreased levels of all but IFN-gamma production. Conclusions. Pretreatment with probiotics attenuates the effects of C. rodentium infection in mice. Understanding the mechanism of these beneficial effects will aid in determining the efficacy of probiotics in preventing infection with related attaching-effacing enteric pathogens in humans.