Allergic diseases, which are closely related to the composition and metabolism of maternal and infant flora, are prevalent in infants worldwide. The mother’s breast milk, intestinal, and vaginal flora directly or indirectly influence the development of the infant’s immune system from pregnancy to lactation, and the compositional and functional alterations of maternal flora are associated with allergic diseases in infants. Meanwhile, the infant’s own flora, represented by the intestinal flora, indicates and regulates the occurrence of allergic diseases and is altered with the intervention of allergic diseases. By searching and selecting relevant literature in PubMed from 2010 to 2023, the mechanisms of allergy development in infants and the links between maternal and infant flora and infant allergic diseases are reviewed, including the effects of flora composition and its consequences on infant metabolism. The critical role of maternal and infant flora in allergic diseases has provided a window for probiotics as a microbial therapy. Therefore, the uses and mechanisms by which probiotics, such as lactic acid bacteria, can help to improve the homeostasis of both the mother and the infant, and thereby treat allergies, are also described.

Bifidobacteria capable of metabolizing human milk oligosaccharides (HMOs) regulate microbial balance and enhance immune defenses, yet their adhesive properties and pathogen-inhibitory capacity remain understudied. We examined auto-aggregation, surface hydrophobicity, adhesion, and pathogen antagonism in 12 HMO-metabolizing bifidobacterial strains isolated from infant feces, using Bifidobacterium longum subsp. infantis ATCC 15697 (BI_15697) and M63 (BI_M63) as reference strains. Bifidobacterium bifidum BB_Y10 and BB_Y22 exhibited the highest auto-aggregation, hydrophobicity, and adhesion. Adhesion assays using Caco-2 cells and mucin, combined with scanning electron microscopy (SEM) for qualitative morphological observation, revealed distinct surface characteristics among the strains. These morphological differences may be associated with, but do not directly establish, the observed variability in adhesion capacity. Surface-associated molecules, including surface layer proteins (SLPs), extracellular polysaccharides (EPS), and lipoteichoic acid (LTA), differentially contributed to adhesion across the strains. BB_Y10 and BB_Y22 demonstrated strong adhesive capacity and enhanced pathogen antagonism in competitive, exclusion, and displacement assays in vitro, suggesting their potential to inhibit pathogen colonization in future in vivo studies and identifying them as promising probiotic candidates for further development.