Autoclaved Diet with Inactivated Spores of Bacillus spp. Decreased Reproductive Performance of Muc2(−/−) and Muc2(+/−) Mice

SIMPLE SUMMARY: Within barrier facilities for the housing of laboratory animals, the sterilization of feed, bedding, and cages is used to reduce contact with bacteria. However, in nature, animals come into contact with a lot of bacteria. We investigated the effect of an autoclaved diet on the reproductive performance of Muc2(−/−) mice. Muc2(−/−) mice develop intestinal barrier defects and are sensitive to changes of the gut microbiota. We have shown that the autoclaved diet negatively affects the reproductive performance of Muc2(−/−) females and their healthy Muc2(+/−) siblings. Thus, the autoclaved diet led to earlier rectal prolapse of Muc2(−/−) females combined with intestinal inflammation, compared to mice fed with the non-autoclaved diet. We hypothesize that this effect is due to the reduction of the diet nutritional value and inactivation of Bacillus spp. spores in the autoclaved diet. ABSTRACT: Within barrier facilities, autoclaved diet and bedding are used for husbandry of laboratory rodents. Bacillus spp. are ubiquitous in nature and some of them are known as probiotics. Inactivation of the Bacillus spores and reduction of the diet nutritional value due to autoclavation could be especially critical for immunodeficient mice. We studied the effect of the autoclaved and non-autoclaved diets on the reproductive performance and the age of prolapse manifestation in Muc2(−/−) mice with impaired gut barrier function and, therefore, sensitive to change of microbiota. We found that the non-autoclaved diet led to enhancement of the fertility index of Muc2(−/−) and Muc2(+/−) female mice. The non-autoclaved diet affected the prolapse of Muc2(−/−) mice that occurred later in comparison with females eating the autoclaved diet. We showed that Bacillus spp. was present in the non-autoclaved diet and feces of mice on the non-autoclaved diet. Bacterial strains of the non-autoclaved diet and feces belonged to B. amyloliquefaciens, B. thuringiensis, B. subtilis, Lysinibacillus macrolides, B. cereus, and other representatives of Bacillus spp. Moreover, autoclavation of the diet affected on the percent of the blood and spleen immune cells, the bacterial composition of the intestine, and increased the level of methionine in the thigh muscle of mice. Enhanced reproductive performance and delayed prolapse manifestation in Muc2(−/−) mice could be due to improved digestion, as Bacillus spp. from diet and feces had enzymatic activity.