Results
A total of 281 neonates were enrolled in the study, consisting of 139 and 142 neonates in the vaginal delivery group (VG) and the cesarean section group (CS), respectively. Three cases from the VG group were excluded due to inability to provide a fecal sample within 48 hours, and two cases from the CS group were excluded due to preterm delivery, after a review of data. The mean fecal collection times were 18.6 (12.1) hours and 21.0 (14.8) hours in the VG and CS groups, respectively.
The sequencing successfully identified the microbial taxonomy of the gut in 89 (64.0%) samples of the VG group and 44 (31.43%) samples of the CS group. We used only these data for statistical analysis. The demographic data of the patients is presented in Table 1. Overall, the mean maternal age was 27.9 (5.1) years old. There were significantly higher levels of income, education status, and underlying maternal disease in the CS group. All mothers consumed all types of food except three cases in the CS group with seafood allergies.
The 16S rRNA sequencing results revealed higher total gut microbiome reads in the VG group (7,019,452) than in the CS group (3,359,444). Of those reads, 6,897,967 (98.27%) and 3,299,355 (98.21%) were classified as microbiomes in the VG and CS groups, respectively. The diversity of the neonates’ gut microbiomes was greater in those born via vaginal delivery than those born via cesarean delivery. Of the species identified in this study, 17 (51.5%) were found exclusively in the VG group, while nine (27.3%) were found exclusively in the CS group. Only seven species (21.2%) were found in both groups (Figure 3).
Bifidobacterium was the dominant genus in both the VG group and the CS group. The proportion of Bifidobacterium was significantly higher in the CS group (Table 2). Among all the Bifidobacterium species identified,Bifidobacterium breve was the most dominant, followed byBifidobacterium longum. In the 89 samples of the VG group, 24 bacteria species were found with a relative abundance percentage of more than 0.5%, and in the 44 samples of the CS group, 16 bacteria species were found with a relative abundance percentage of more than 0.5%. (Figure 4). A significantly higher abundance of Bifidobacterium, Enterobacter, and Enterococcus species was found in the CS group compared to the VG group (Table 2).
In the VG group, Clostridium (6.9%), Enterococcus (5.5%), Escherichia (4.5%), and Streptococcus (4.4%) were found to be the second most abundant genera in fecal specimens. Some, such as the genera Fusobacterium, Streptococcus, Bacteroides, Megamonas, and Escherichia, were found exclusively in the VG group. In the CS group, the most abundant genera after Bifidobacterium were Enterobacter (11.2%), Lactobacillus (7.8%), Enterococcus (7.2%), and Klebsiella (4.6%). However, opportunistic pathogens such as Enterococcus, Klebsiella, and Clostridium were found in both groups.
In the CS group, there was no significant difference in neonatal gut microbiome abundancy between those presenting with labor and those presenting without labor before cesarean delivery (Table 3).