The bifidus factor might be lacto-N-biose I [LNB], which is a derivative of mucin sugars.  However, the exact structure and mechanism behind the bifidus factor remains unknown.
The bacteria would break down lactic acid and acetic acid. The environment of the intestine would become acidic, preventing the growth of any harmful pathogens.  The function of LBN is unknown and it is possible that oligosaccharides with terminals of Galβ1-3GlcNAc are the bifidus factors.
Bifidobacteria might suppress infections in infants and children.