| Enterotoxigenic Escherichia coli(ETEC)can cause diarrheal diseases,which can lead to the death of animals.At present,antibiotics are the main drugs to treat diarrhea caused by ETEC.However,the abuse of antibiotics will leave drugs in animals and lead to the emergence of drug-resistant strains,which pose a potential threat to human health.Many studies have shown that Bacillus subtilis has physiological functions such as promoting the absorption of nutrients,improving the body’s antioxidant capacity and improving the intestinal morphology and structure.It has been widely used in animal husbandry,but there is not enough research and attention on rabbits at present.Therefore,in this experiment,the newborn rabbits were taken as the experimental object,and the protective effect of Bacillus subtilis on intestinal function of ETEC-challenged newborn rabbits was explored by gavage,aiming to provide data support and reference for clinical application of Bacillus subtilis in veterinary medicine.In this experiment,20 1-month-old New Zealand rabbits were randomly divided into 4 groups:control group(group D,saline),model group(group M,attack+saline),antibiotic group(group K,attack+norfloxacin),and probiotic group(group Y,attack+Bacillus subtilis bacterial solution),with 5 replicates of each treatment group,and the experimental period was 15 d.Groups M,K and Y were treated with 0.5 m L of Bacillus subtilis by intraperitoneal injection.The E.coli disease model was constructed by intraperitoneal injection of 1×10~9 CFU/m L ETEC live bacterial solution into rabbits.The success of the rabbit E.coli model was verified by observing the diarrhea of the rabbits on the 3rd day after injection.1 g norfloxacin was administered orally to group K and 2 m L1×10~8 CFU/m L Bacillus subtilis bacterial solution was administered orally to group Y.2 m L saline was administered orally to groups D and M.All groups were administered at the same time and the frequency of administration was once a day.Blood,ileum,colon and colonic feces were collected from the litter on the 15th day after the attack.During the experimental period,we observed and recorded the defecation of the rabbits every day and scored them according to the diarrhea scoring scale;we tested the peripheral blood routine indexes of the rabbits using the automatic blood test,and recorded the changes of total leukocytes,lymphocytes and red blood cell pressure;we observed the changes of the length of the villi and the depth of the crypt in the ileum and colon under the microscope by HE staining method;we tested the serum inflammation indexes of the rabbits by the kit The changes of serum inflammatory indexes IL-1,IL-6,IL10,TNF-αand antioxidant indexes TAC,CAT and MDA contents in the rabbits;the changes of intestinal gut flora structure were analyzed by high-throughput sequencing.The feasibility of Bacillus subtilis application in clinical diarrhea treatment was finally evaluated.The results showed that:(1)Bacillus subtilis can significantly reduce the diarrhea score after ETEC infection and improve the diarrhea of newborn rabbits.(2)Bacillus subtilis can reduce the contents of IL-1,IL-6 and TNF-α,and alleviate the inflammatory reaction in newborn rabbits.(3)Bacillus subtilis has a tendency to increase the serum TAC of newborn rabbits,and can also significantly reduce the content of serum MDA,thus protecting the body from peroxide damage.(4)Bacillus subtilis can significantly increase VH and V/C in ileum,decrease CD in ileum and improve intestinal morphology and structure.(5)Bacillus subtilis can improve the intestinal flora structure to some extent,increase the abundance of Lactobacillus,reduce the abundance of Acinetobacter and Shigella,and play a role in protecting intestine.The results show that Bacillus subtilis can produce a good intestinal protection effect on young rabbits challenged with ETEC,and can meet the clinical needs.It can be used as a substitute for antibiotics to prevent or treat diarrhea,and has a good clinical application prospect. |
