[First steps in the bacterial colonization of the digestive tract of neonates (author's transl)].

Meconium samples obtained from 14 children aged 18 to 51 h were subjected to a quantitative differential analysis. The meconium of one of the children (47 h old) was sterile; in those of the 11 infants aged less than 47 h the dominant flora was composed of either enterobacteria, mainly Escherichia coli sensitive to usual antibiotics, or of streptococci. The genus Acinetobacter constituted the dominant flora in one case only. Staphylococcus, Corynebacterium, Clostridium (C. perfringens), Bacteroides, Peptococcus, when present in the meconium, represented a very small proportion of the total flora. In the two children aged 48 h and more, the flora was more complex and Bacteroides, Bifidobacterium, Veillonella, Peptostreptococcus, Clostridium and Staphylococcus were associated to streptococci and enterobacteria. A very small number of lactobacilli was found in one child only. No yeasts were detected. The sequence of establishment of the various bacteria was studied in a child (OG) by an analysis of 8 samples obtained between 0 and 74 h after its birth. E. coli and Streptococcus became established 24 h after parturition, Bifidobacterium and Bacteroides the 2nd and 3rd day, respectively. Lactobacillus and Peptococcus were only present in very low number in the first 2 meconium samples and did not become established in the child, although they were present in a rather large number in the vaginal and faecal samples from the mother. In addition, use of axenic mice inoculated with the 3rd meconium from the infant OG revealed the existence of certain genera of bacteria probably of faecal origin which had not been detected by the direct analysis of the meconium. These genera did not become established in the child. The hypothesis according to which the meconium chooses among the fortuitous contaminations before true colonization of the digestive tract is established, is discussed. It was also observed that the evolution of the ratio between the number of E. coli and Proteus morganii in the successive samples obtained from OG was very different from that observed in the mice inoculated with these samples.