Characterization Of Fecal Microbiota,Short-chain Fatty Acids Concentrations In Children With Cow Milk Protein Allergy

Cow milk protein allergy(CMPA)is one of the most common allergies in infants and children.In general,the majority of CMPA children can recover spontaneously by the age of 5 years,but 10% of CMPA children continued allergic symptoms more than 5 years old.The intestinal microbiota,as the largest "microbial organ" of the human body,is closely related to health.Under normal conditions,the intestinal flora is in a state of dynamic equilibrium.When the balance is destroyed,it may cause diseases such as allergies.Short-chain fatty acids(SCFAs)are the major end products of microbial metabolism in the gut and participate in immune regulation and development.At present,most studies focus on the changes of intestinal microflora structure and SCFAs of infants with CMPA.There are few studies on the intestinal microbiota and SCFAs of 5-10 years old children with CMPA.Therefore,we investigated the changes of intestinal microbiota and fecal SCFAs and lactic acids in children aged 5-8 years with CMPA.In this study,6 children aged 5-8 years with CMPA diagnosed by Harbin Children's Hospital from June 2016 to December 2016 were selected.At the same time,8 healthy children of the same age group in Harbin were selected as controls.All children's feces samples were collected for analyzing.The study is mainly divided into two parts.The first part analyzes all fecal samples by 16 S rDNA amplicon sequencing to study the diversity and difference of the intestinal microbiota in children with CMPA and healthy children.In the second part,the levels of SCFAs and lactic acid in the feces of two groups were determined by high-performance liquid chromatography technique(HPLC),and the correlations between SCFAs and intestinal flora were analyzed.The results of this study indicated that there were significant differences in the structural composition of the intestinal microbiota between the two groups of samples.At the phylum level,the abundance of the Firmicutes in the intestinal flora of CMPA children was significantly higher than that of healthy children,but the abundance of Proteobacteria was significantly decreased.At the class level,the abundance of Clostridia was significantly increased in CMPA children.At the family level,there were also differences between the two groups.Compared with healthy children,the abundance of Ruminococcaceae in the intestinal flora of children with CMPA increased significantly.At the genus level,there was no significant difference in the dominant genus(abundance > 2%)between the two groups,but this study found that non-dominant genus Pseudomonas was significantly reduced in the allergic group,while Halomonas and Eubacterium was significantly increased in the CMPA group.In addition,LEfSe(LDA Effect Size)analysis revealed a total of 45 enriched taxa in the two groups.There were 40 enriched taxa(LDA value > 2)in the CMPA group.The most important group(LDA value > 4)was Firmicutes,Ruminococcaceae,Subdoligranulum,and in the control group,there were only 5 higher abundance bacteria,Family_XI,Gemella,Lachnospiraceae_NK4B4_group,Ruminococcaceae_V9D2013_group and Lactobacillus_gasseri.In addition,there was no statistically significant difference in alpha diversity indixes of two groups.Through the analysis of SCFAs,the study found that the total SCFAs in the feces of CMPA children significantly decreased,but the difference in the content of lactic acid and each short-chain fatty acid in the feces of the two groups was not statistically difference.Spearman analysis found that SCFAs and lactic acids were associated with intestinal microbiota.The main results were that acetic acid and total SCFAs were positively correlated with the abundance of intestinal microbiota,and lactic acids was significantly negatively correlated with Bacteroides.Conclutions: There are significant differences in the compositional structure of the intestinal microbiota and the levels of SCFAs of CMPA children and healthy children.Alterations in the composition of fecal microbiota and SCFAs in the 5-8-year-old children with CMPA may reduce immune function and potentially promote this allergy.