The bacterial colonization of the large bowel of pre-term low birth weight neonates.

The bacterial colonization of the large bowel of 11 pre-term, low birth weight neonates who were nourished by expressed breast milk was examined by culturing serial faecal samples and compared to that observed in eight breast-fed and seven formula-fed full-term neonates. Pre-term neonates were colonized by high counts of facultatively anaerobic bacteria from the first days of life while bifidobacteria colonized only six babies during the first week and appeared in only one baby before day 5. Bacteroides spp. and clostridia were isolated from seven and six pre-term babies respectively during week 1 and were first observed on day 2. The intestinal colonization of pre-term infants differed from that in full-term breast-fed infants in the high counts of facultatively anaerobic bacteria and late appearance of bifidobacteria, and from both groups of full-term infants in the early stable colonization by Bacteroides spp. It is postulated that the composition of the normal intestinal microflora of pre-term low birth weight babies contributes to their predisposition to neonatal necrotizing enterocolitis. Results are discussed in relation to the effect of infant feeding regimens on intestinal microbial populations.