Breast milk and defence against infection in the newborn.

The value of breast milk in defense against infection in the newborn infant is examined. Following birth the gastrointestinal tract is colonized by several bacterial species: Esch. coli Costridium welchii steptococci bacteroides and lactobacilli. This colonization appears to proceed according to a uniform schedule in different mammals including humans. Thus far it is unknown whether the common colonization of the newborn with Candida albicans is related to bottle feeding or not. It has been shown that unsaturated lactoferrin of breast milk inhibits growth of Candida albicans (Kirkpatrick et al. 1971). Although the difference in incidence of enteric infections in breast-fed and bottle-fed infants is well known it is difficult to determine whether this difference is because of a beneficial effect of breast milk or an increased contamination during bottle feeding. Several observations suggest a protective role of breast milk against enteric infections. For example an epidemic among newborns of enterocolitis caused by Esch. coli 0 111-BR remained uncontrolled for 6 months despite the use of classical epidemiological measures. Administration of unprocessed breast milk was accompanied by a rapid cessation of the epidemic. Breast milk contains immunoglobulins with antibody activity against several micro-organisms (Hanson and Johansson 1970). The assumption that these antibodies were of minor importance since they were not absorbed by the gut of the human infant became challenged when it was learned that IgA was the predominant immunoglobulin in milk in contrast to serum and that the milk IgA was antigenically different from serum. The antimicrobial activity of breast milk also contains lymphoid cells which produce IgA and mediate cellular immunity as well as neutrophils and macrophages with phagocytic activity. Human milk contains many components which may promote a normal bacterial colonization of the gastrointestinal tract and may suppress the invasiveness of certain pathogenic micro-organisms.