The Normal Fecal Flora of Infants between Two Weeks and One Year of Age: I. Serial Studies

Abstract

Periodic culture of the feces of 22 normal infants under 1 yr. of age showed only a few spp. of many isolated aa members of the normal fecal flora even with 25% incidence as a minimum figure. The following spp. were included: Escherichia coli, 93.4%; Streptococcus fecalis, 78.5%; Clostridium welchii, 68.7%; Cl. tertium, 51.6%; Bacteroides, Group I, 47%; Bacterium aerogenes, 44%; Str. mitis, 29.7%; Micrococcus epidermidis, 26.4%; Lactobacillus bifidus, 24.2%. The figure for L. bifidus, found in all the stools from nurslings, was greatly influenced by preponderance of stools from weaned babies. Except for the action of mothers'' milk on the presence of L. bifidus, the effect of apparently normal diets on the remainder of the fecal flora of normal infants is obscure. The expectancy of finding any bacterial species, except possibly the streptococci, would depend not so much on the child as the diet. Bact. aerogenes, Bact. coli-mutabile, sporulating anaerobes, the tiny gram-negative non-sporu-lating anaerobes of the genus Bacteroides and other spp. were much more frequently isolated after weaning. Sta-phylococci were found more often in breast and supplemented breast-fed babies than in weaned infants.