347 - Preterm infants fed exclusive mother’s own milk exhibit decreased stool alpha diversity over time

An exclusive Mother’s own milk (MOM) diet in preterm infants has been shown to be the most significant factor affecting the diversity of the intestinal microbiome. MOM contains commensal bacteria and human milk oligosaccharides which can serve as substrates for beneficial bacteria and decoy receptors for pathogenic bacteria, potentially protecting against dysbiosis. We hypothesize that microbial diversity in the stool will change over time and will be affected by mode of delivery and antibiotic exposure at birth.

Objective:

1) Describe microbial diversity over the 1st 28 days in preterm infants who are exclusively fed MOM. 2) Assess for differences in microbial diversity associated with mode of delivery and exposure to antibiotics at birth.  

Design/Methods:

A convenience sample of preterm infants fed exclusive MOM (< 32 weeks and < 1500 grams) were included in this analysis. Each infant’s first stool and serial stools on days  7, 14, 21, and 28 were collected. The stool microbiome was characterized using 16S ribosomal DNA sequencing. Genus-level Shannon diversity index (representative of alpha diversity) and Bray-Curtis dissimilarity (representative of beta diversity) were calculated. Wilcoxon signed rank tests were used to test for differences in the distribution of alpha diversity and PERMANOVA was used to test for differences in beta diversity. A Bonferroni adjusted significance level of 0.0125 was used to adjust for multiple testing with a family-wise error rate of 0.05. 

Results:

14 infants who received 100% MOM for all stool samples (n = 54) were included in the analysis. A significant difference was observed between the distribution of alpha diversity in the first stool and the day 21 stool (p < 0.001). Differences were not significant after the Bonferroni adjustment between the first stool and stools collected on days  7, 14, and 28 (p = 0.049, 0.042, 0.016, respectively) (Figure 1). Mode of delivery and antibiotic exposure did not affect stool diversity. No significant differences in beta diversity were observed.

Conclusion(s):

This cohort of exclusively MOM-fed preterm infants shows that microbial diversity is different from the first stool compared with serial stools throughout the first 28 days. The finding that diversity decreases over time is in contrast to what has previously been reported in preterm infants. It is surprising that mode of delivery and antibiotic exposure did not affect diversity. It is possible this diet is protective against dysbiosis and further research with larger sample sizes is needed to investigate this further.