The intestinal microbiota represents an important factor affecting human health, exhibiting evolutionarily conserved roles in host metabolism, immunity, development, and behavior [13, 14]. It has been reported that the fecal microbiota of babies born by caesarean section is rich in Enterobacter, Streptococcus australis, and Veillonella, which are mainly derived from the skin, oral cavity, and the surrounding environment during birth. The intestinal microbiota of neonates born by vaginal delivery is rich in Escherichia-Shigella, Bacteroides, and Bifidobacterium, with Escherichia-Shigella being the most abundant genus . It has been reported that enrichment of genes involved in vitamin K2 synthesis in newborns is associated with a high abundance of Escherichia-Shigella, an organism with the ability to synthesize vitamin K2 [15, 16].
Streptococcus and Veillonella often coexist in the intestinal ecosystem [17, 18], and might cooperate in the metabolic process, so their combined immunoregulatory properties have also been investigated . Since the source of these bacteria in newborns is maternal, it can be implied that they play a role in clinical recovery and immune development of ileostomy patients after surgery. Data suggest that microorganisms in the small intestine are mainly involved in simple carbohydrate metabolism, a task predominantly performed by specific species including Streptococcus and Veillonella. Our results are consistent with findings of previous studies; that is, enterobacteria always include Streptococcus and Veillonella spp. in the ecosystem, and these are the most active members of the ileal microbiota . Functions of Streptococcus and Veillonella are often complementary, however, in our study we found a lower abundance of Veillonella in patients. Streptococci can metabolize a variety of carbohydrates, while Veillonella can utilize lactic acid as a carbon and energy source, and are proposed to metabolize lactic acid produced by Streptococcus [19, 20]. Metatranscriptomic analysis of ileostomy fluid also revealed that the presence of Streptococcus in the small intestine could be related to the transportation and metabolism of carbohydrate substrates . Escherichia or other microbes can substitute for this role when the abundance of Streptococcus is insufficient . Further studies identifying underlying mechanisms are needed to explain the contribution of Streptococcus and Veillonella to immunity and homeostasis in pediatric patients after ileostomy, and this could help guide future clinical practice. Faecalibacterium, a prominent member of the Firmicutes phylum, has been reported to possess immunoregulatory and anti-inflammatory properties . For example, Faecalibacterium prausnitzii produces anti-inflammatory proteins, and Crohn's disease (CD), a disorder associated with disrupted microbial ecology, is characterized by decreased abundance of F. prausnitzii. Moreover, the decrease in F. prausnitzii is associated with an increased risk of symptom recurrence after ileal CD surgery [21, 22]. A limitation of our study is that the sample size is too small to link specific bacterial populations to the 3 primary diseases. In addition, many of the clinical parameters we described could have influenced the dataset, including duration of antibiotic removal, breastfeeding, PN duration, and residual intestine length.
Nutritional factors have a significant influence on the composition of the intestinal microbiota. Breast milk is an optimal source of nutrition for infants, providing proteins, carbohydrates, lipids, fats, and some micronutrients essential for infant growth. Breast milk also contains several biologically active components that include immunoglobulins and oligosaccharides, and resulting microbiota plays a critical role in infant intestinal homeostasis and immune development . Our study found a trend of increased growth rate of body mass and decreased prevalence of colitis and sepsis in breastfeeding patients compared to non-breastfeeding patients. Thus, breastfeeding is likely to play a crucial role in maintaining the intestinal function and improving postoperative recovery of such patients.
Excessive Klebsiella and Escherichia-Shigella, and low abundance of Streptococcus, Veillonella, and Faecalibacterium, indicated that the small intestinal microbiota of our donors was in an unhealthy state. It has been reported that the relative abundance of Enterobacter or Klebsiella is significantly higher in breast milk of mothers of infants infected with rotavirus as well as in the intestine of the infected neonates, whereas the abundance of Streptococcus and Staphylococcus was significantly lower . Our data suggests a correlation between the presence of Klebsiella/Enterobacter and neonatal gastrointestinal disease, as well as a potential protective effect of Staphylococcus or Streptococcus. A frequent occurrence of Klebsiella species has also been reported in pathogenic genera identified in SBS II patients . Therefore, it would be beneficial to study further the effects of Klebsiella/Enterobacter in ileostomy and its prognosis, in order to provide novel hypotheses that guides future clinical practice.