Intestinal flora during the first months of life: new perspectives

Abstract

Increasing awareness that the human intestinal flora is a major factor in health and disease has led to different strategies to manipulate the flora to promote health. The complex microflora of the adult is difficult to change in the long term. There is greater impact of diet on the infant microflora. Manipulation of the flora particularly with probiotics has shown promising results in the prevention and treatment of diarrhoea and allergy. Before attempting to change the flora of the infant population in general, a greater understanding of the gut bacterial colonisation process is required. The critical stages of gut colonisation are after birth and during weaning. Lactic acid bacteria dominate the flora of the breast-fed infant. The formula-fed infant has a more diverse flora. The faeces of the breast-fed infant contain mainly acetic and lactic acid whereas the formula fed-infant has mainly acetic and propionic acid. Butyric acid is not a significant component in either group. The formula-fed infant also has higher faecal ammonia and other potentially harmful bacterial products. The composition of the microflora diversifies shortly before and particularly after weaning. The flora of the formula-fed infant develops more quickly than that of the breast-fed infant. Before embarking on any strategy to change the flora, the following questions should be considered: Should we retain a breast-fed style flora with limited ability to ferment complex carbohydrates? Can pro- and prebiotics achieve a flora with adult characteristics but with more lactic acid bacteria in weaned infants? Are there any health risks associated with such manipulations of the flora?

Development of Intestinal Microbiota in Mice and Its Possible Interaction with the Evolution of Luminal IgA in the Intestine

“…This nibbling at the solid food, a part of the weaning process, may have contributed to the increase in the intestinal microbiota diversity before 21 days old. The diversification promoted by the weaning diet is normally gradual and thus takes some time after the beginning of the ingestion to appear [6]. The rapid decrease in the level of defense molecules, the maternal IgA in this case, is another potential reason for the increase in the diversity of intestinal microbiota [16].…”

Innate mechanisms for Bifidobacterium lactis to activate transient pro‐inflammatory host responses in intestinal epithelial cells after the colonization of germ‐free rats

“…[8][9][10] Clinical and animal studies provide evidence that certain strains of Bifidobacterium animalis (lactis), B. longum, B. infantis and B. breve may be effective in the prevention and/or treatment of gastroenteritis, necrotizing enterocolitis and chronic intestinal inflammation. 11,12 The molecular mechanisms underlying these protective effects of probiotic bifidobacteria in the gut are completely unknown.…”

Honor thy symbionts

“…These considerations, together with reports that host development (4,11,12), host genotype (13), and environmental factors (14) influence the composition of the microbiota, emphasize how challenging it is to define and compare microbial community structures within and between specified intestinal niches of a given individual at a particular point in his or her life history, let alone to compare the microbiota among groups of individuals living in a particular geographic locale or among more broadly distributed populations.…”