Comparison of diarrheal and non-diarrheal stool. (A) Proportional abundance of genera in non-diarrheal controls and MSD cases in different age categories. Each color represents a different group. The order and color for each group is the same for controls (patients without MSD) and MSD cases. The eight groups most frequently found in controls (Prevotella, Bacteroides, Escherichia/Shigella, Veillonella, Streptococcus, Lactobacillus, Faecalibacterium, Megasphaera, plus unassigned and other) are depicted. (B) Shannon diversity index across ages and diarrheal status. Average Shannon diversity indices for the five different age strata as well as the corresponding 95% confidence intervals. Both cases and controls exhibited higher mean Shannon diversity index scores at higher age groups compared to lower age groups (P <0.001, one-way ANOVA). The diversity of healthy samples positively correlates with age in the first 2 years of life, as previously reported . The diversity index for cases is significantly less than that for controls within each country (P <0.02, Tukey’s t-test corrected for multiple comparisons). Also see Additional file 2: Table S2 and Additional file 3: Figure S1.