Screening Of Camelid Bacillus And Evaluation Of Its Preventive Effect On Colibacillosis In Mice

Bacillus,part of the natural gut microbiota,has been receiving great attention due to its wide-ranging biological roles.Camels are a special species in desert areas and have excellent adaptability to extreme environments.However,due to long-term lack of adequate nutrition,it is easy to cause intestinal flora and metabolic disorders and suffer from various diseases.Studies have shown that probiotics have great advantages in controlling pathogenic bacterial infections and enhancing immunity.However,the probiotics isolated from the original animal can better adapt to the gastrointestinal tract of the native animal,and there is no report on the Bacillus isolated from the camel intestine at home and abroad.This study intends to isolate the probiotic Bacillus bacteria from healthy camel feces that can inhibit E.coli to replace antibiotics and achieve the purpose of healthy breeding.The results of the study are as follows:1.Using the fresh feces of adult camels without antibiotics added during the feeding process as the bacterial source,through morphological identification,biochemical identification and 16S r RNA sequencing,to obtain a Bacillus subtilis and a Bacillus tequilensis,They are named LTF 6 and LTF 7respectively.The two strains have different degrees of tolerance to various adverse environments.Can inhibit the growth of E.coli,Staphylococcus aureus and Salmonella,Sensitive to 8 commonly used clinical antibiotics such as ampicillin,No hemolytic activity,And it can quickly enter the logarithmic growth phase after 2 h.2.A strain of Bacillus LTF7 with good stress resistance and strong inhibitory effect on E.coli was selected for in vivo safety testing.24 SPF male Kunming mice,weighing about 20±2 g,Randomly divided into control group and experimental group(LTF7),Aseptic PBS solution and 0.2 m L OF 1×10~8CFU/m L LTF7 bacterial suspension were intragastrically administered for 14 days.There was no difference in body weight between mice and control group(P>0.05).After necropsy,there were no obvious ocular pathological changes in abdominal organs of all mice.There was no difference in organ index between the experimental group and the control group,and the numbers of white blood cells,lymphocytes and neutrophils in the experimental group were significantly lower than those in the control group(P<0.05).but still within the normal range,Serum ALT,TP and BUN were not different(P>0.05).3.About 20 g of SPF male Kunming mice were randomly divided into three groups:A,B,and C.Group A was given 0.2 m L of sterile PBS every day.B and C two groups of Bacillus LTF7(1×10~8CFU/m L)for 14 consecutive days;Groups B and C were injected intraperitoneally with 80%of the minimum lethal dose of E.coli to induce diarrhea on the 13th day,and the mice were sacrificed 14 days later.Compared with group B,pretreatment in group C could reduce the death of mice and effectively increase the spleen coefficient(P<0.05).It also alleviated intestinal damage caused by E.coli,such as dissolution and rupture of intestinal mucosa,and decreased the concentrations of IL-6(P<0.05)and CRP and SAA.In summary,a strain of Bacillus LTF7 with the best probiotic effect was isolated from the fresh feces of healthy camels,and it was proved to be safe orally by mouse animal experiments,and it was found that it has a good preventive effect on mouse diarrhea caused by E.coli..