Intestinal microbiota and secretory immunoglobulin A in feces of exclusively breast‐fed infants with blood‐streaked stools

Episodes of blood- streakedstools are not uncommon in exclusivelybreast-fed infants under 6 months of age. Such bleeding is thought to be associated with food protein-induced proctocolitis, however the pathomechanism remains unclear. The aim of this study was to investigate intestinal microbiota and secretory immunoglobulin A in the fecesof exclusivelybreast-fed infants with blood- streakedstools. Fecal specimens from 15 full-term infants with blood- streakedstools and 15 breast-fed healthy infants were studied and the results compared. All infants had been delivered vaginally and exclusivelybreast-fed. The fecal microbiota were investigated by phylogenetic analysis combined with culture methods for some bacterial species, and feceswere assessed for the presence of fecal secretory immunoglobulin A by enzyme-linked immunosorbent assay. Phylogenetic cluster analysis revealed four major clusters of fecal bacteria, cluster A being found only in healthy infants. The Bacteroides fragilisgroup was observed more frequently in controls than in patients (P < 0.05). In the controls, the predominant species belonging to the Enterobacteriaceae group was Escherichia coli, whereas in the patients it was Klebsiella (P < 0.05). Concentrations of secretory immunoglobulin A were high in one third of the healthy controls. In conclusion, the pathomechanism of rectal bleeding in exclusivelybreast-fed infants may be related to differences in the composition of their intestinal flora.