Analysis of Bacillus spp. in the diet and feces of laboratory mice under barrier-housing and non-sterile conditions

M.V. Morozova1,2,
G.V. Kalmykova2,
N.I. Akulova2,
E. A. Litvinova1, 2

1Siberian Federal Scientific Centre of Agro-BioTechnologies of the Russian Academy of Sciences,
630501, Russian Federation, Novosibirsk region, Krasnoobsk, st. Central, Presidium
2Scientific Research Institute of Neurosciences and Medicine,
630117, Russian Federation, Novosibirsk, st. Timakova, 4
Е-mail: morozova.maryana@mail.ru

Abstract

Сurrently, the standard for housing laboratory animals is barrier vivariums, which ensure the sterility of conditions for environment and diet. These conditions are not physiological and can be harmful to animals, since they deprive them of the probiotic load of the cosmopolitan bacteria Bacillus spp.  These bacteria are not representatives of the natural microflora inhabiting the intestines, but get into it when they are accidentally eaten, since they are not rare in the environment. In absence of Bacillus spp. source, the intestines are naturally cleared of them, i.e. bacteria Bacillus spp., do not colonize the intestines of mammals. Currently, a number of data has been accumulated about positive action of Bacillus spp. representatives on digestion, resistance to bacterial and viral infections, reproductive health of animals and humans. Probiotic preparations for medicine and veterinary medicine have been developed based on Bacillus spp. The most common probiotic food supplements are B. subtilis and B. licheniformis. In this study, we examined non-autoclaved and autoclaved diet and bedding for the presence of Bacillus spp. bacteria, as a factor affecting the health of laboratory animals. It was found that non-autoclaved diet for rodents contains 103 spores/g, and the feces of animals eating non-autoclaved diet - 104 spores/g. Samples of bedding, autoclaved diet and feces of animals eating autoclaved diet, did not shown any vegetative forms or spores of Bacillus spp. PCR with primers to the 16S ribosomal RNA gene of bacteria showed the presence of bacteria in non-autoclaved diet and strong degradation of bacterial DNA in the autoclaved one. Thus, animals consuming non-autoclaved diet receive a probiotic load in the form of representatives of Bacillus spp., mainly in the spore form, while mice kept under sterile conditions are deprived of the positive effect of metabolites of the Bacillus spp. representatives. The activation of the immune system in these animals is also reduced due to the fragmentation of bacterial DNA.

This study can be useful for specialist to decide on the need to maintain the sterility of the keeping of laboratory animals and the need to introduce probiotic bacterial cultures into the diet.

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Acknowledgements

Project was supported by Russian Laboratory Animal Science Association research grant (# NI2 03/04/2021) and Budgetary funding for basic scientific research   # 0533-2019-0003.

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