Composition and dynamics of intestinal fungi during the postnatal 2 months of very low birth weight infants.

Unlabelled: It has been found that intestinal fungi play a role in the composition of the intestinal microecology and in the formation and development of the immunity during childhood. We investigated the gut fungi composition of preterm infants to analysis composition and dynamics of intestinal fungi during the postnatal 2 months of very low birth weight infants. We collected feces from 34 very low birth weight infants (VLBWI) and 28 preterm infants with birth weight >1500 g. We extracted total fungal DNA from feces and analyzed the composition of gut fungus through ITS sequencing. The fungal detectable rate in the experimental group peaked on day 3 (85.19%), then gradually decreased and started to show an increasing trend again by day 28. There were significant differences in the alpha diversity of intestinal fungus between VLBWI and controls, and the VLBWI had its own characteristics at different time points in richness and diversity. A total of 10 phylums and 342 genera were identified in all VLBWI samples. The dominant fungal phylum of the VLBWI group is Ascomycota (50.3%)and Basidiomycota (48.8%). The functional metabolic activity of the experimental group was lower than that of the control group.

Conclusion: The composition and abundance of VLBWI intestinal fungal showed several alterations during the first 2 months of life. The prediction of gut microbiota function suggests that intestinal metabolic function may be altered in VLBWI.

What Is Known: • A limited number of studies has been found that symbiont fungi may be able to calibrate host immunological responses, promote development of peripheral lymphoid organs, promote T cell responses, and even may be associated with the development of certain diseases, such as inflammatory bowel disease (IBD), NEC, and allergic diseases. However, previous studies on intestinal microecology have mainly focused on adults while neglecting the role of fungi in the gut of children due to the much lower abundance of intestinal fungi than bacteria, limitations of techniques for detecting fungi, the difficulty of obtaining samples, and the absence of largescale reference databases.

What Is New: • In recent years, the discovery and development of fungal detection technologies such as 18s rDNA sequencing technology, Internal Transcribed Spacer(ITS), and DNA fingerprinting technology have further broadened the perspective on the impact of intestinal fungal exposure in early life.