Bifidobacterium, Bacteroides, and Clostridium spp. in fecal samples from breast-fed and bottle-fed infants with and without iron supplement.

Bifidobacterium, Bacteroides, and Clostridium spp. isolated from the feces of 23 neonates during the first 3 months of life were identified. Of the 23 neonates, 10 were breast fed, 6 received an infant formula with iron supplement (5 mg/liter), and 7 received the formula without iron supplement (iron concentration, less than 0.5 mg/liter). The Bifidobacterium spp. most frequently isolated from the three groups of infants were B. longum, B. breve, B. adolescentis, and B. bifidum. The bacteroides spp. most frequently isolated were B. fragilis and B. vulgatus. The most common Clostridium sp. in the three groups of infants was C. perfringens. The type of milk did not select for species of Bifidobacterium, Bacteroides, or Clostridium, except for Clostridium butyricum, which was isolated significantly more often from bottle-fed infants with iron supplement than from the other groups, and Clostridium tertium, which was more often isolated from breast-fed infants. The species of the three anaerobic genera did not persist for a long period of time in the three groups of infants.

Effect of iron on neonatal gut flora during the first three months of life.

To study the effect of milk supplemented with iron on neonatal gut flora, faecal specimens of ten infants receiving breast milk, six receiving a cow-milk preparation supplemented with iron (5 mg/l) and seven receiving the same product without iron supplement (iron concentration less than 0.5 mg/l) were examined during the first 12 weeks of life. In breast-fed infants bifidobacteria was predominant, counts of Escherichia coli were low, and other bacteria were rarely present. Infants receiving fortified cow-milk preparation had high counts of Escherichia coli, counts and isolation frequency of bifidobacteria were low and other bacteria were frequently isolated. In those on unfortified cow-milk preparation isolation frequency of Escherichia coli, bifidobacteria and bacteroides was comparable with that in breast-fed infants; however, counts of Escherichia coli were high. It is concluded that the faecal flora of infants fed unfortified cow-milk preparation acquires characteristics of that found in breast-fed infants.

Effect of iron on neonatal gut flora during the first week of life.

Faecal specimens from 23 infants during the first week of life were compared. Ten infants received breast milk, six received cow-milk preparation supplemented with iron (+/- 5 mg/l) and seven unfortified cow-milk preparation (iron concentration less than 0.5 mg/l). Those on breast milk had low faecal pH, high counts of bifidobacteria and low counts of Enterobacteriaceae, bacteroides and clostridia. Infants receiving fortified cow-milk preparation had a high faecal pH and high counts of Enterobacteriaceae and putrefactive bacteria such as bacteroides and clostridia. Counts of bifidobacteria were also high. In those on unfortified cow-milk preparation a slow rise was observed in counts of Enterobacteriaceae followed by an increase in counts and isolation frequency of bifidobacteria: the latter was still rising on day 7. It is concluded that a low iron content in standard preparations of cow's milk enhances resistance of the neonatal gut to colonization.