| The abuse of livestock and poultry antibiotics on livestock and poultry products leads to drug residues and resistant strains of pollution and other issues,seriously endangering the quality and safety of animal food so that results in serious social public health and food safety.The animal microecological preparation,is one of green alternatives to antibiotics,has extensive application value,Lactic acid bacteria is the typical strains for investigating animal microecological preparation.It can regulate the stability of micro ecological environment in animal gut and prevent host intestinal disease,which has far-reaching significance to ensure the safety of animal food.Salmonella pullorum is one of the intestinal bacterias that endangers poultry industry and freshly hatched broilers,which is important for public health and food safety.Prevention Salmonella pullorum infection of chickens and reduction its colonization in the broiler intestines are of great significance on the livestock and poultry meat processing safety and human health.In lactic acid bacteria genera,lactic acid bacteria is the main type,which include Lactobacillus casei,Lactobacillus fermentum,Lactobacillus acidophilus,Lactobacillus acidophilus and so on.L.fermentum,naturally existing in the gut,has the advantage in strong gastrointestinal environment.The reports related to prevention and treatment of Salmonella pullorum CVCC533 infection are seldom.Therefore,in this study,we screened lactic acid strains which can inhibit the growth of Salmonella pullorumCVCC533,and studied the anti-infection of Salmonella pullorum in vivo,so the protective effect of lactic acid bacteria on the infection of chicken against pathogenic bacteria can be discussed further.The specific research content and results as follows:1.Comparison properties of different lactic acid bacteria and the activity of bacteriostasisBased on the screening of lactobacillus bacteria in the laboratory,we choose 4 Lactic acid bacterias(L.casei1.2435?L.fermentum1.2133?L.acidophilus1.1854? S.thermophillus 1.2471)to analyze and compare the bacteriostatic properties.Comparison the properties of Lactic acid bacteria through acid resistance and bile salt resistance experiment,cell adhesion experiment,hydrophobic experiment,antibacterial experiment.The results showed that the survival rate of L.fermentum 1.2133 was 68%,which was significantly higher than that of the other three strains,after 2 hours of culture of lactic acid bacteria in ph medium of 2.5.The survival rate of L.f-ermentum1.2133 was more than 60% after 2 h incubation in medium with bile salt concentration of 0.3%.The results of lactic acid surface hydrophobicity experiment showed that the difference was significant among lactic acid strains,and the L.fermentum 1.2133 had high surface hydrophobicity;Each strain on the target strains have a certain adhesion ability,the L.fermentum 1.2133 self-polymerization ability was the most strong.The results of antibacterial test showed that four strains of Lactobacillus had certain bacteriostatic ability to E.coli AE17,E.coli O78 and S.Pullorum CVCC533,and the strain was different.L.fermentus1.2133 had strong antibacterial activity against S.pullorum CVCC533,and the antibacterial activity of L.acidophilus 1.1854 was significant for E.coli AE17,and the activity of E.coli O78 was stronger.The S.thermophillus1.2471 antibacterial activity is weak.2.Observation in vitro effect of L.fermentum1.2133 on bacteriostasis S.pullorum CVCC533The viability of bacteria in S.pullorum CVCC533 biofilm was observed by fluorescence microscopy on L.fermentum1.2133 fermentation supernatant.After incubation with L.fermentum1.2133 fermentation supernatant with S.pullorum CVCC533 for 24 h,In the microscope,the S.pullorum CVCC533 cells in the biofilm of S.pullorum CVCC533 in the experimental group were mostly red fluorescence and had only a small amount of green fluorescence.The control group was basically green fluorescence,only a small amount of red fluorescence.The results of competitive co-cultivation of L.fermentum 1.2133 and S.pullorum CVCC533 in vitro showed that,At 0-18 h,L.fermentum1.2133 increased the growth inhibition of S.Pullorum CVCC533 with the passage of time,and the number of S.Pullorum CVCC53 decreased gradually,and became stable after 18 h.L.fermentum1.2133 had antagonistic effect on the growth of S.pullorum CVCC533,and the competitive effect of different initial bacterial concentration was different.The competitive concentration of bacteria was 10: 1.3.Observation histopathological and L.fermentum 1.2133 infection intestinal flora of S.pullorum CVCC533A total of 120 1-day-old Roman broilers were randomly divided into four groups: control group(group I),being fed L.fermentum1.2133(2.5×108 cfu / chick)at 1-day-old as group II,being fed L.fermentum1.2133 at 1-day-old to the 14 th day of counteracting toxic substances S.pullorum CVCC533(5×108cfu / chick)as pretreatment group(Group III),and to the 14 th day direct infection S.pullorum CVCC533 as group IV,respectively,for intestinal bacterial count and pathological sections were observed,the results showed that the number of lactic acid bacteria in group II was significantly higher than that in group III and group IV,and the number of Salmonella decreased significantly and the total number of aerobic bacteria increased.The chickens of duodenum,jejunum and ileum were normal in group II,and the intestine was complete and the pathological changes were more complete than that of group I chickens.The second group of chickens showed that mild enteritis sexual cell infiltration;jejunum villus central axis of some red blood cells,cecal villi performance of local injury.Group IV duodenal villi rupture,villous self-evident phenomenon,jejunum villus central axis erythrocyte accumulation,ileal intestinal villus epithelium of the goblet cells were dissolved,villous self-contained phenomenon is obvious,the third group compared with the fourth group,Chicken small intestine of the intestinal inflammation and bleeding points and other symptoms 4.Effects of L.fermentum1.2133 on the expression of AvBD2 mRNA in L.fermentum1.2133 infection S.pullorum CVCC533In this study,we used RT-PCR to study the regulation of L.fermentum1.2133 on chicken intestinal infection,and determined the transcription level of L.fermentum1.2133 on intestinal AvBD2 mRNA in S.pullorum CVCC533.The chicks were harvested within 72 h(0 h,12 h,24 h,36,48 h and 72 h).The results showed that AvBD2 was expressed in the small intestine.The transcription level of AvBD2 mRNA in group III and group IV was significantly different from that in group II.The transcription level of AvBD2 mRNA in group II was stable at the same time.In group III,the transcriptional level of AvBD2 mRNA was decreased in the fourth group,and decreased significantly in group IV,which was significantly lower than that in group I.The experimental results showed that L.fermentum1.2133 had significant effect on chicken.The expression of defensin AvBD2 has a regulatory effect.The results showed that L.fermentum1.2133 had a good tolerance to the intestinal environment of chicken,and its fermentation supernatant had an inhibitory effect on the formation of S.pullorum CVCC533 biofilm and had significant bacteriostatic effect on S.pullorum CVCC533.the chicken intestinal flora has a regulatory role,but also promote the small intestine ?-defensin 2 expression in the anti-S.pullorum infection process. |
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