Bifidobacterium species are known to fulfill important functions within the human colon. Thus, stimulating the activity of bifidobacteria is important to maintain host health. We revealed that culture supernatants of Bacillus subtilis C-3102 (referred to as C-3102) stimulated the growth of Bifidobacterium species. In this study, we isolated and identified six bifidogenic growth factors, which were cyclo (D-Val-D-Ile), cyclo (L-Val-D-Ile), cyclo (D-Val-L-Ile), cyclo (L-Val-L-Ile), cyclo (D-Val-L-Leu) and cyclo (L-Val-L-Leu). These six cyclic dipeptides increased the growth of Bifidobacterium species and had no effect on potentially harmful gut organisms. Moreover, supplementation with a mixture of these six cyclic dipeptides significantly increased the abundance of microorganisms related to the genus Bifidobacterium in a human colonic microbiota model culture system, although supplementation with a single type of dipeptide had no effect. These results show that cyclic dipeptides containing Val-Leu and Val-Ile produced by C-3102 could serve as bifidogenic growth factors in the gut microbial community. In the past few decades, the human gut microbiota has been reported to play an important role in the promotion of health, and several illnesses are known to be influenced by imbalances of gut microbiota 1. Therefore, manipulation of the gut microbiota is a clinical target for the treatment of gut microbiota-related diseases 2. Bifidobacterial populations belonging to the phylum Actinobacteria are the most dominant microbial group present in the healthy infant gut 3. The population of Bifidobacterium in the human gut decreases gradually from infancy to childhood, then remains relatively stable during an adult's life, and ultimately decreases in old age 4. Numerous health-promoting effects have been ascribed to certain strains of the genus Bifidobacterium, which are widely used as probiotics 5. For instance, one Japanese study reported that allergic children had less bifidobacteria compared to non-allergic children at an early stage, 4 months of age, and prenatal supplementation of bifidobacteria to mothers and postnatal supplementation to infants reduced the risk of allergies 6. It has also been reported that ingestion of Bifidobacterium breve has an anti-obesity effect in mice fed a high-fat diet 7 , and ingestion of Bifidobacterium infantis was effective in relieving symptom of irritable bowel syndrome in women 8,9. These findings suggest an important role for bifiodobacteria in regulating intestinal homeostasis. Some Bacillus subtilis strains are safe, survive passage through the human gastrointestinal tract, and do not induce any undesirable physiological effects in human subjects 10,11. One reported probiotic effect of B. subtilis was associated with inhibiting the growth of pathogenic bacteria such as Salmonella enterica to improve the growth of beneficial bacteria such as lactobacilli 12. In our previous study, B. subtilis C-3102 (hereinafter, referred to as C-3102) was tested using the TNO Gastro-Intestinal Mod...

The intestinal microbiome changes dynamically in early infancy. Colonisation by Bifidobacterium and Bacteroides and development of intestinal immunity is interconnected. We performed a prospective observational cohort study to determine the influence of antibiotics taken by the mother immediately before delivery on the intestinal microbiome of 130 healthy Japanese infants. Faecal samples (383) were collected at 1, 3, and 6 months and analysed using next-generation sequencing. Cefazolin was administered before caesarean sections, whereas ampicillin was administered in cases with premature rupture of the membranes and in Group B Streptococcus-positive cases. Bifidobacterium and Bacteroides were dominant (60–70% mean combined occupancy) at all ages. A low abundance of Bifidobacterium was observed in infants exposed to antibiotics at delivery and at 1 and 3 months, with no difference between delivery methods. A lower abundance of Bacteroides was observed after caesarean section than vaginal delivery, irrespective of antibiotic exposure. Additionally, occupancy by Bifidobacterium at 1 and 3 months and by Bacteroides at 3 months differed between infants with and without siblings. All these differences disappeared at 6 months. Infants exposed to intrapartum antibiotics displayed altered Bifidobacterium abundance, whereas abundance of Bacteroides was largely associated with the delivery method. Existence of siblings also significantly influenced the microbiota composition of infants.

Abstract Background Intestinal flora changes dynamically in early infancy. Association between colonisation of Bifidobacterium and Bacteroides, the dominant bacterial genera in the intestinal flora 6 months after birth, and development of intestinal immunity has been suggested. Antibiotic administration to the mother is an important factor in this colonisation, but few studies have considered antibiotics taken immediately before delivery, including before Caesarean section. The association of the gut flora with the delivery method is also uncertain. Here, we performed a cohort study to determine the influence of antibiotics taken immediately before delivery on the intestinal flora in early infancy, with a focus on Bifidobacterium and Bacteroides, in 130 healthy Japanese infants. Results Faecal samples were collected from infants at 1, 3, and 6 months after birth (383 samples) in a hospital in Japan. The samples were analysed using a next-generation sequencer. Two β-lactam antibiotics were administered to mothers immediately before delivery: Cefazolin was used before Caesarean sections and ampicillin was used for cases with premature rupture of the membranes and in Group B Streptococcus positive cases. At all ages, Bifidobacterium and Bacteroides were dominant, and the mean combined occupancy was 60–70%. Bifidobacterium was the most dominant at all ages but its abundance was significantly lower in infants who were exposed to antibiotics at delivery, and 1 and 3 months after birth, whereas no difference was found between the delivery methods. Bacteroides were the second or third dominant bacteria at all ages but their abundance was significantly lower after Caesarean section compared with that after vaginal delivery, whereas there was no difference due to antibiotic exposure. These effects were confirmed in a linear mixed-effect model. In addition, occupancy by Bifidobacterium at 1 and 3 months and by Bacteroides at 3 months differed between infants with and without siblings. Conclusions Exposure to antibiotics at delivery has an important effect on Bifidobacterium, the dominant bacterial genus of the intestinal flora, at an early age in Japanese infants, whereas Bacteroides is more associated with the delivery method. The influence of siblings is also significant. The clinical significance of these results in later life requires further exploration.