Relationship between the digestive microflora of the newborn and maternal microflora in rodents as evidenced by a transit marker.

The cutaneous and digestive microflora of the dam, constitute the main sources of bacteria likely to colonize the digestive tract of the newborn. Our objective was to study the conditions (delay, level) in relation to the maternal microflora. Spores of Bacillus stearothermophilus were used as a tracer. They were spread on the mother's udder or given per os to the mother. In our study, we used holoxenic rats and axenic mice. The tracer was then followed in newborn rats and newborn mice. Transfer of the spore from the dam to the digestive tract of the newborn were generally observed very shortly after the contact between the dam and the newborn (2 or 3 h). This transfer requires a minimal concentrations of spores 1.5 x 10(6) spores/g feces and 3 x 10(6) spores/udder for the rat; 10(6) spores/g feces and 1.5 x 10(6) spores/udder for the mouse). Transfer of spores in the digestive tract of neonates is proportional to the level of spores on the udder. But only a hundredth or less of the initial inoculum is transferred. The transfer of spores via the udder or via the maternal feces led to very similar levels of implantation of spores in the digestive tract of neonates. These results emphasize the important role of the maternal fecal and mammary microflora in the colonization of the digestive tract of the newborn.