Effect Of Pathogenic E.coli O1 On Intestinal Mucosal Immune Barrier And Intestinal Flora In Calves

This experiment led to the study of diarrhea induced by E.coli O1 in calves,and to study the effect of diarrhea induced by E.coli O1 on intestinal mucosal immune barrier and intestinal flora in calves,and to provide reference for healthy breeding of calves and prevention of pathogenic diarrhea caused by E.coli O1.Experiment 1:56 male calves with a body weight between 40 and 43 kg were selected and randomly divided into a test group and a control group,with 28 animals in each group.The control group was not inoculated and routinely breastfed,on the basis of the same lactation,the test group established an animal diarrhea model by oral administration of 100 mL of a virulent E.coli O1 suspension with a viable count of 2.5 x 1011 CFU/mL.The test period was 10 days.The indexes of intestinal mucosal function in calves serum and tissues were detected by ELISA.The results showed that diarrhea induced by Pathogenic E.coli O1 could significantly increase the levels of DAO and ET(P＜0.05),and decrease the levels of Occludin,Claudin-1 and ZO-1(P＜0.05);the levels of TNF-α,IL-6,IL-1 β,IL-1 and 1L-2 were significantly increased(P<0.05),and the levels of IL-10,IL-4 and TGF-β were decreased(P＜0.05);the levels of IgA and IgM were significantly decreased(P＜0.05),IgG level decreased but not significantly(P＞ 0.05).The level of ITF decreased significantly(P＜0.05).Therefore,pathogenicity E.coli O1 can increase the intestinal mucosal permeability of calves,which means to destroy the balance between Thl cells and Th2 cells,inhibit the secretion of anti-inflammatory factors by Th2 cells,reduce the humoral immunity to foreign pathogens,destroy the local mucosal immune barrier and humoral immune function of calves,and further destroy the Intestinal mucosal immune barrier of calves.Experiment 2:16S rDNA method was used to detect the microbial community structure of ileum and colon mucosa of calves,the results show that:pathogenicity E.coli 01 significantly increased the abundance of Acinetobacter,Pseudomonas,lelliottia,Enterobacteriaceae and Burkholderia(P＜0.05),the abundance of Ruminococcaceae,Lachnospiraceae,Coriobacteriaceae and Enterococcaceae in colonic mucosa decreased(P＜0.05).Spearman correlation analysis showed that there was a negative correlation between IgA content and Proteobacteria abundance,and a positive correlation between IgA content and Lactobacillus abundance.There was a positive correlation between IL-6 content and Ralstonia.It can be seen that the pathogenic E.coli O1 affects the intestinal mucosa by stimulating intestinal mucosal immunity to destroy the intestinal mucosal barrier and immune function,promotes inflammatory reactions and destroys the internal environment of the intestinal mucosal microorganism.Experiment 3:high throughput sequencing technology was used to detect and identify the microbial structure of calves rectum,the results show that:at the level of the phylum,the dominant phylums of calves are Firmicutes,Proteobacteria,and Actinobacteria.Pathogenicity E.coli O1 decreased the diversity and richness of rectal microorganisms,and reduced the abundance of Pachybacteria,Lactobacillus,and Butycoccus.Spearman correlation analysis showed that there was a positive correlation between the abundance of Lactobacillus and the content of IgA,a negative correlation between the abundance of Proteobacteria and the content of IgA,a positive correlation with the content of IL-6,and a negative correlation between the abundance of Butycoccus and the content of TNF-α.It can be concluded that diarrhea induced by Pathogenic E.coli O1 in calves results in the decrease of intestinal microbial diversity,and the inhibition and disruption of intestinal microbial dynamic balance.