Background/Aims: The mode of delivery (vaginal or cesarean section) and feeding type (breastfeeding or formula feeding) of neonates are considered the most influential factors in the development of gut microbiota. Objectives: This study investigated the effect of prebiotic-rich breast milk on overcoming gut microbiota dysbiosis. Method: Stool samples from 36 healthy Japanese neonates were obtained at 4 days and 1 month of age, and divided into 4 groups based on mode of delivery and feeding type. The gut microbiota composition and bacterial diversity were assessed using 16S rRNA sequencing. Results: At 4 days old, vaginally delivered neonates had a significantly higher diversity of bacteria than those born by cesarean section. Bacteroidales and Enterobacteriales were overrepresented in vaginally delivered neonates (p = 0.0031 and p = 0.011), while Bacillales and Lactobacillales were overrepresented in caesarean section delivered neonates (p = 0.012 and p = 0.0016). However, there was little difference in bacterial diversity and bacterial relative abundance at 1 month of age between groups. Conclusions: Cesarean section delivery appeared to reduce the diversity of neonate gut microbiota, resulting in dysbiosis, but this improved to the equivalent level seen in vaginally delivered infants by 1 month of age. Breastfeeding, even for short periods, may therefore improve neonate gut dysbiosis.

Butyric acid produced in the intestine by butyric acid-producing bacteria (BAPB) is known to suppress excessive inflammatory response and may prevent chronic disease development. We evaluated whether fiber-rich barley intake increases BAPB in the gut and concomitantly butyric acid in feces. Eighteen healthy adults received granola containing functional barley (BARLEYmax^®) once daily for four weeks. Fecal DNA before intake, after intake, and one month after intake was analyzed using 16S rRNA gene sequencing to assess microbial diversity, microbial composition at the order level, and the proportion of BAPB. Fecal butyric acid concentration was also measured. There were no significant differences in diversities and microbial composition between samples. The proportion of BAPB increased significantly after the intake (from 5.9% to 8.2%). However, one month after stopping the intake, the proportion of BAPB returned to the original value (5.4%). Fecal butyric acid concentration increased significantly from 0.99 mg/g feces before intake to 1.43 mg/g after intake (p = 0.028), which decreased significantly to 0.87 mg/g after stopping intake (p = 0.008). As BAPB produce butyric acid by degrading dietary fiber, functional barley may act as a prebiotic, increasing BAPB and consequently butyric acid in the intestine.

Neonatal jaundice, caused by excess serum bilirubin levels, is a common condition in neonates. Imbalance in the gut microbiota is believed to play a role in the development of neonatal jaundice. Thus, we aimed to reveal the gut microbiota characteristics in neonates with jaundice. 16S rRNA gene sequencing was performed on stool samples collected on day 4 from 26 neonates with jaundice (serum total bilirubin > 15.0 mg/dL) and 17 neonates without jaundice (total serum bilirubin < 10.0 mg/dL). All neonates were born full term, with normal weight, by vaginal delivery, and were breastfed. Neonates who were administered antibiotics, had serum direct bilirubin levels above 1 mg/dL, or had conditions possibly leading to hemolytic anemia were excluded. The median serum bilirubin was 16.0 mg/dL (interquartile range: 15.5–16.8) and 7.4 mg/dL (interquartile range: 6.8–8.3) for the jaundice and non-jaundice groups, respectively. There was no difference in the alpha diversity indices. Meanwhile, in the jaundice group, linear discriminant analysis effect size revealed that Bifidobacteriales were decreased at the order level, while Enterococcaceae were increased and Bifidobacteriaceae were decreased at the family level. Bifidobacteriaceae may act preventatively because of their suppressive effect on beta-glucuronidase, leading to accelerated deconjugation of conjugated bilirubin in the intestine. In summary, neonates with jaundice had dysbiosis characterized by a decreased abundance of Bifidobacteriales.

We previously reported that a decrease in butyrate-producing bacteria in the gut is a potential cause of regulatory T cell (Treg) abnormalities in children with idiopathic nephrotic syndrome (INS). Therefore, we hypothesized that administration of butyrate-producing bacteria might reduce INS relapse and the need for immunosuppressants in these patients. Twenty patients in remission from INS (median age 5.3 years, 15 boys) were enrolled in the study and assigned to receive either daily oral treatment with a preparation of 3 g Clostridium butyricum or no probiotic treatment. The number of relapses and requirement for immunosuppressive agents were compared between the two groups. In the probiotic treatment group, analyses of the gut microbiota and Treg measurements were also performed. Probiotic-treated patients experienced fewer INS relapses per year compared with non-probiotic-treated patients (p = 0.016). Further, administration of rituximab in the probiotic treatment group was significantly less frequent compared with the non-probiotic-treated group (p = 0.025). In the probiotic treatment group, analyses before and after probiotic treatment revealed the significant increases in the relative abundance of butyrate-producing bacteria (p = 0.017) and blood Treg counts (p = 0.0065). Thus, oral administration of butyrate-producing bacteria during INS remission may reduce the frequency of relapse and the need for immunosuppressive agents.