| Diarrhea in weaned piglets is a common disease and one of the imp ortant causes of piglet death,which brings huge economic losses every year.At present,the pathogenesis of diarrhea in weaned piglets is not clear.How to prevent and control the disease has become an important scientific issue.It is a positive progress to adjust the ecological balance of piglet intestines by using probiotics to prevent diarrhea in weaned piglets.However,the effects of probiotic lactic acid bacteria in different individuals and different farms vary greatly.According to the research progress in recent years,catecholamine hormones in piglets will be significantly increased during weaning stress.The effects of these hormones on probiotic lactic acid bacteria have not been reported.This study intends to use norepinephrine as a represent ative of catecholamine hormones to explore the effect of stress hormones on the growth,bacteriostasis and anti-infection ability of Lactobacillus,providing a theoretical basis for the analysis of the problem of unstable clinical application of lactic acid bacteria.In this experiment,serum-SAPI medium was used to simulate the in vivo environment to investigate the effect of norepinephrine on the growth,viable bacterial count,bacteriostatic ability,acid production capacity and hydrogen peroxide production capacity of probiotic Lactobacillus.Then,we established BALB/c mouse infection model caused by enterotoxigenic Escherichia coli(ETEC)strain CVCC230,explored the effect of norepinephrine on the probiotic Lactobacillus against ETEC infection,and detected the bacterial loadin mouse organs,intestinal pathology Changes,duodenal oxidative damage,expression of duodenal inflammatory factors and intestinal mucosal barrier-related factors,and intestinal flora of mice.The main results are as follows:(1)The measurement of the growth curve shows that norepinephrine will promote the growth of most(70%)Lactobacillus strains.After 24 h,norepinephrine has a more obvious promotion effect on Lactobacillus.For some(20%)Lactobacillus Growth has little effe ct and will also inhibit the growth of a small number(10%)of Lactobacillus.(2)The test for the determination of the number of viable cells showed that the promotion effect was more obvious within 24 hours,and the viable cell count of all Lactobacillus strains showed an increasing trend.(3)Norepinephrine significantly reduced the bacteriostatic ability of Lactobacillus against ETEC,Staphylococcus aureus and Pseudomonas aeruginosa.(4)Under the co-culture conditions of lactic acid bacteria and E.coli,norepinephrine significantly increased the number of viable bacteria in E.coli.(5)Norepinephrine enhances the acid-producing ability of most strains of Lactobacillus.(6)By establishing a mouse model of ETEC standard strain CVCC230 infection,the following results were obtained:a The observation of the tissue load showed that norepinephrine significantly attenuated the inhibitory effect of Lactobacillus 23017 on the colonization of ETEC.b Observation of intestinal pathological sections revealed tha t norepinephrine significantly weakened the protective effect of Lactobacillus 23017 on duodenal lesions caused by ETEC infection.c The measurement results of the duodenal oxidative damage index found that under the action of norepinephrine,the activities of SOD,GSH-PX and T-AOC in the 23017+CVCC230 group decreased,the activity of MDA increased,and norepinephrine it significantly reduce the protective effect of Lactobacillus 23017 on oxidative damage caused by ETEC.d The test results of the intestinal flora of mice found that norepinephrine increased the relative abundance of pathogens such as Pasteurella and Helicobacter pylori in the intestines of mice in group 23017 + CVCC230,while reducing probiotics such as lactic acid The relative abundance of bacillus and bifidobacteria suggests that norepinephrine reduces the ability of lactobacillus to inhibit pathogenic bacteria in the intestine.The above results show that norepinephrine can promote the growth of most probiotic Lactobacillus and enhance the acid production capacity of most of Lactobacillus strains,but it reduces the ability to inhibit ETEC,Staphylococcus aureus and Pseudomonas aeruginosa,weakening lactic acid The ability of Bacillus 23017 to resist ETEC infection weakens the protective effect of Lactobacillus on the body.The results of this study can provide new data references and theoretical support for the prevention and treatment of diarrhea in weaned piglets,and provide new ideas for better application of lactic acid bacteria. |
