Fig. 3

Impact of gestation and postnatal ages on developmental trajectories in antibiotic-naïve preterm infant gut microbiome. Infants were assigned to gestational age cohorts in 2-week intervals. PCA was applied to generalized log2 transformed microbiome composition data from antibiotic-naïve infants at week 1 and week 3. Samples were then colored by group membership and an ellipse was drawn at the 95% confidence interval around the group centroid. Arrows were drawn between the centroids to indicate the magnitude and direction of microbiome change in the first two dimensions. PCA calculation and graphing on the first two dimensions is the same for A and B. A MRPP was used to assess the significance of difference in microbiome composition between groups. Mean Bray-Curtis distance was computed for all pairwise comparisons between group members. At both week 1 and week 3, there was stepwise progression in microbiome composition across the 4 gestation age cohorts; however, none of the differences in composition between gestation cohorts attained statistical significance. Mean Bray-Curtis distances are indicated (BC). B Microbiome composition demonstrated progression from week 1 to week 3 in a similar trajectory in the first two dimensions at all gestational ages. Differences in composition were statistically significant at the earliest two gestational ages. Mean Bray-Curtis distances between the two groups are indicated (BC) (week 1: 28 to 30 weeks GA, n=25; 30⁺¹ to 32 weeks GA, n=15; 32⁺¹ to 34 weeks GA, n=20; 34⁺¹ to 36 weeks GA, n=3. Week 3: 28 to 30 weeks GA, n=25; 30⁺¹ to 32 weeks GA, n=15; 32⁺¹ to 34 weeks GA, n=18; 34⁺¹ to 36 weeks GA, n=2)