Development of Intestinal Microflora in Humans and Animals

Abstract

The succession of bacterial populations in the large bowel of healthy infants was examined during the first week of life. The predominant fecal organisms by theend of the first week were bifidobacteria, bacteroides, clostridia, enterobacteria, and streptococci. The bacteria isolated from the feces of breast-fed and bottle-fed infants, aged about one month, were identified. The composition of the fecal bacteria varied according to the infant's diet. The organism that showed the highest count and the highest frequency of occurrence in both groups was Bifidobacterium breve. The counts and incidences of Clostridium paraputrificum, C. perfringens, and Bacillus subtilis, the counts of C. clostridiiforme, Bacteroides vulgatus, Veillonella parvula, Lactobacillus gasseri, Escherichia coli, Streptococcus bovis, Enterococcus faecalis, and E. faecium and the incidences of C. difficile, C. tertium, and Pseudomonas aeruginosa in the bottle-fed infants were significantly higher than those in the breast-fed infants. A comparison of the fecal bacteria in healthy adults and aged persons was also made. The numbers of B. distasonis, B. vulgatus, B. adolescentis, and B. longum in the healthy adults were significantly higher than those in the aged persons. A significantly increasednumber of Clostridium paraputrificum was found in the feces of senile subjects. Subsequent studies on development of intestinal microflora in pigs, dogs, rats, and chickens were also described. These dramatic changes in the development of gut colonization were probably brought about by bacterial interactions, as well as changes in food.