[Development of intestinal flora in neonates].
The development of faecal bacterial flora was studied using quantitative anaerobic and aerobic culture methods to determine the differences between various types of feeding. Enterobacteria first colonized predominantly in neonatal intestine, and their viable counts on the first day of life were between 10(8)-10(10) per gram faeces. In the breast-fed group, enterobacteria decreased gradually and their level on the 6th day of life was about 10(6) per gram faeces. Bifidobacteria began to increase after 2 or 3 days of life and outnumbered other bacteria, amounting to about 10(10) per gram faeces on the 6th day. In the bottle-fed group, enterobacteria maintained their high counts despite the increase of bifidobacteria, and their counts (10(9.3 +/- 1.1)/g) on the 6th day still exceeded those of bifidobacteria (10(8.4 +/- 1.6)/g). At 1 and 3 months of age, bifidobacteria were the most prevalent organisms in all feeding groups. However, the numbers of other bacteria such as enterobacteria were significantly greater in the bottle-fed infants than in the breast-fed infants. In the breast-fed formula supplemented group, bacterial colonization of the intestine was in the middle range between the breast-fed group and the bottle-fed group. In addition to the microbiological study, physicochemical properties of faeces and milk (i.e. pH and buffering capacity) were examined to explore their effects on the faecal bacterial flora. Faeces from breast-fed infants had a lower pH and lower buffering capacity than those from bottle-fed infants. The buffering capacity of formula was almost twice as much as that of human milk. It is postulated therefore, that low buffering capacity of human milk seems to produce an acidic environment in the intestine, which is favourable for the growth of bifidobacteria and unfavourable for the growth of potential pathogenic bacteria such as enterobacteria. These results suggest that breast feeding is beneficial for protection against intestinal and/or systemic infection.
Iseki
K
K
Department of Pediatrics, Fukagawa General Hospital.
D001644:Bifidobacterium / Q000302:isolation & purification; D001942:Breast Feeding; D002021:Buffers; D005243:Feces / Q000382:microbiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007225:Infant Food; D007231:Infant, Newborn / Q000382:microbiology*; D007422:Intestines / Q000382:microbiology*
D002021:Buffers