Abstract
Despite extensive research on the gut bacteriome during infancy and its correlation with various chronic diseases, the influence of diet on gut mycobiome development in infants remains unexplored. To address this significant research gap, we conducted a study on 70 healthy Hong Kong Chinese infants who were either directly breastfed, expressed milk-fed, or formula-fed. Our analysis revealed that formula-fed infants had higher fungal diversity and composition in their gut mycobiome compared to those in breastfed and expressed milk-fed infants. The formula-fed group exhibited higher fungal richness, with a median of 58.5, compared to a median of 34 in the breastfed group (p = 0.04) and 28.5 in the expressed milk-fed group (p = 0.02). However, the breastfed and expressed milk-fed groups showed no significant differences. In terms of fungal compositions, formula-fed infants had a significant increase in the relative abundance of Pochonia (0 % in breastmilk vs 0.5 % in formula milk, false discovery rate (FDR)-corrected p = 0.05), Saccharomyces (0.95 % in breastmilk vs 2.7 % in formula milk, FDR corrected p = 0.03), and Tetrapisispora (0.6 % in breastmilk vs 3.0 % in formula milk, FDR corrected p = 0.002), whereas direct breastfed infants exhibited an increased abundance of Malassezia (breastmilk vs. formula milk = 1.4 % vs. 0.4 %, FDR-corrected p = 0.01). Overall, our results indicate that the composition of breastmilk and formula milk can have varying impacts on the gut mycobiome of infants, providing new insights into the diet-gut mycobiome dynamic in early life. Given the small sample size of the expressed milk group, the findings of this group should be considered preliminary or exploratory. Further studies are thus necessary to explore the potential health implications of these findings.