The frequency with which species of bacteria were cultured from mesenteric lymph nodes and other peripheral sites did not mirror the composition of the intestinal flora. Among the translocated bacteria, Staphylococcus may be especially hard to recognize and difficult for the host-defense systems to destroy. Breast-feeding inhibited systemic bacterial translocation in the suckling period of the rat.

The barrier function of the intestinal mucosa is immature in the newborn mammal, and is strengthened by breast milk. We investigated this effect of breast milk by comparing the susceptibility to infection assessed in terms of adherent bacterial colonization of the intestinal tissue (AdC) and bacterial translocation (BT) between breast-fed and formula-fed newborn rats. Threeday-old rat pups were assigned to one of three groups: motherreared (MR), pseudo-cannulated (sham), and artificially reared (AR). AR rats were infused with formula through an intragastric cannula, under the control of a computer-regulated pumping machine. MR and sham rat pups were reared with their respective dams and received breast milk until weaning in a specially designed cage. In 10-d-old rats, there was no significant difference in the fecal or cecal flora between the AR and MR groups, whereas the AdC and the BT to the liver were greater in the AR than MR group. Enterobacteriaceae, Streptococcus and/or Enterococcus, and Staphylococcus were dominantly detected as microorganisms in AdC flora and BT. The AdC flora did not directly reflect the bacterial colonization flora. These findings suggest that AR rat pups mature normally, although there is a greater colonization of Enterobacteriaceae and BT in AR than MR pups. Consequently, the intestinal barrier function of the pups reared by artificial feeding may become susceptible to BT, and AdC may be more indicative than bacterial colonization of the susceptibility to BT. Recent advances in the quality of infant formulas have increased their similarity to human breast milk. Moreover, there are no major differences in the physical appearance of breast-fed and formula-fed infants. However, breast-fed infants have a lower morbidity and mortality than formula-fed infants. Studies have demonstrated significant infant protection against diarrhea, respiratory tract infections, otitis media, bacteremia, bacterial meningitis, botulism, urinary tract infections, necrotizing enterocolitis, and other diseases while the infant is receiving breast milk (1-5). There is also good evidence of continued protection against these medical conditions for years after breast-feeding has terminated (1, 6 -11).We previously reported in a rat study that BT to the liver was greater in formula-fed AR rat pups than in breast-fed rat pups (12). It was suggested that the outcome is the result of a difference in the intestinal microflora and maturation of the intestinal mucosa.There are reports on the development of the intestinal microflora in newborn animals, and studies have compared the intestinal microflora of breast-fed and formula-fed newborns. However, few reports have examined the role of the intestinal microflora and adherent bacteria in relation to infectious risks to the newborn during the suckling and weaning periods. In aerobic fecal microflora in human milk-fed and formula-fed infants in the intensive care unit, Staphylococcus was most dominantly detected at greater than 60% (13). There have been many studies abo...

The secretory IgA (sIgA) antibody response to 20 environmental antigens, including microorganisms, toxins, food, and inhaled allergens, was evaluated in the breast milk from 107 Japanese mothers 1–10 days after delivery. Specific sIgA antibody responses were detected in most milk samples against almost all of the antigens tested, although there was a wide variation in the specific sIgA antibody profiles of each individual’s milk. With regard to twelve bacterial antigens, highly specific sIgA antibody responses were detected against Escherichia coli, Yersiniaenterocolitica, and Pseudomonasaeruginosa. With regard to eight nonbacterial antigens, highly specific sIgA antibody responses were detected against rotavirus, cholera, and pertussis toxins. Similar sIgA antibody profiles were obtained when the 107 milk specimens were divided into colostrum (milk 1–5 days after delivery, n = 36) and transitional milk (milk 6–10 days after delivery, n = 71). This study provides information on the possible protective role of human milk sIgA antibodies and will serve as a baseline for future studies.

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