Potential use of Lactobacillus cell density in feces as a non-invasive bio-indicator for evaluating environmental stress during mouse breeding.

From the viewpoint of the quality assurance of laboratory animals, it is important to guarantee that they have not accidentally been exposed to any stress during breeding. In this study, we investigated non-invasive indicators of the exposure of mice to stress. The stress of horizontal shaking and no-bedding was applied to mice and the intestinal bacterial flora in their feces was analyzed. The cell density of total lactic acid bacteria was influenced by the shaking stress but not affected by the no-bedding stress. In contrast, the cell density of Lactobacillus, a member of lactic acid bacteria, decreased significantly to 1/10 at 48 h under both types of stress. Therefore, the cell density of Lactobacillus in feces may be used as a non-invasive bio-indicator of the stress exposure of mice.