To investigate the distribution characteristics of the gut microbiome in infants with different delivery mode and feeding pattern at six weeks of life.

A total of 60 infants delivered between June and September in 2017 at Peking University First Hospital were recruited. According to delivery modes and feeding patterns, they were respectively divided into two groups, which were vaginal delivery (n=42) and cesarean delivery (n=18) groups, and exclusively breastfeeding (n=40) and mixed-feeding (n=20) groups. Stool samples of all subjects were collected at six weeks after birth. The V3-V4 region of 16s rRNA gene was sequenced on Illumina Hiseq 2500 platform, and the results were analyzed with SILVA database and QIIME software. Independent samples t-test or Mann-Whitney U test was used for statistical analysis.

(1) Eight bacterial phyla and 146 genera were identified in the 60 stool samples. Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes were four dominant phyla, and Bifidobacterium, Clostridium, Klebsiella, Bacteroides, Streptococcus, Escherichia-Shigella, Veillonella and Faecalibacterium were the top eight most abundant genera. (2) At the phyla level, the vaginal delivery group was characterized with reduced Firmicutes (0.56±0.10 vs 0.42±0.20, t=2.94, P<0.05) and increased Actinobacteria and Bacteroidetes [0.04 (0.01-0.11) vs 0.20 (0.05-0.36), U=223, P<0.05; 0.05 (0.01-0.23) vs 0.09 (0.02-0.29), U=315, P<0.05] as compared with the cesarean delivery group. However, there was no significant difference in the four dominant phyla between exclusively breastfeeding and mixed-feeding groups (all P>0.05). At the genus level, the relative abundance of Bifidobacterium was higher in the vaginal delivery group than in the cesarean delivery group [0.19 (0.02-0.36) vs 0.01 (0.00-0.07), U=210, P<0.01]. Similarly, there was no significant difference in the eight dominant genus between exclusively breastfeeding and mixed-feeding groups(all P>0.05). (3) The vaginal delivery group showed significantly lower Shannon and Simpson indexes than the cesarean delivery group [4.26 (3.61-5.52) vs 5.48±1.19, U=227, P<0.05; 0.86±0.08 vs 0.94 (0.92-0.97), U=194, P<0.05], while no significance was found in operational taxonomic unit (OTU) number and Chao1 index (all P>0.05). However, there was no significant difference in OTU number, Chao1, Shannon or Simpson index between the exclusively breastfeeding and the mixed-feeding groups (all P>0.05).

The early infancy is a critical period for the establishment of gut microbiome. Significant differences in the composition and diversity of gut microbiota are found between infants born vaginally and abdominally, but not in infants with different feeding patterns.

Infant; Gastrointestinal microbiome; Delivery, obstetric; Feeding behavior