Isolation And Identification Of Salmonella From The Indigenous Chicken Breeds And Study On The Control With Star Anise-Cinnamon Essential Oil

Salmonella is an important pathogen in the poultry industry,which can infect chickens and cause decreased performance,and even death,bring huge losses to the poultry industry.For the control Salmonella,the poultry industry has long been relied mainly on the use of antibiotics,which has led to the increasingly serious phenomenon of resistance and even antimicrobial multiresistance(AMR).Finding suitable antibiotic alternatives and clarifying the possible mechanisms are of great significance for the control of Salmonella infection.The purpose of this study is to investigate the contamination and antimicrobial resistance of Salmonella in the production chain of indigenous chicken breeding farms in Guangxi,and explore the effect and potential pharmacological mechanisms on controlling Salmonella infection with star anise-cinnamon essential oil(SCEO),one of the local famous and excellent specialties in Guangxi,in order to provide experimental data and application basis for its usage in the control of salmonellosis in the poultry industry.A total of 1 377 samples,from different tache in the production chain of six indigenous chicken breeding farms in Guangxi,were taken for the isolation and identification of Salmonella,and antimicrobial sensitivity test to 17 common used antibotics was then conducted on the Salmonella isolates.The results showed that the total positive detection rate of Salmonella was 6.75%(93/1377),farm DGGX12 had the highest detection rate(13.85%)among all the farms,and the dead embryos at the late hatching period had highest detection rate(13.33%)in all the tache of the production chain.All isolated Salmonella strains belong to Salmonella pullorum(SP);The results of antimicrobial sensitivity test showed that the isolates had the highest resistance rate to SIZ(95.69%),TMP(93.54%),and SXT(88.17%),while they were more sensitive to CRO(22.58%),CIP(22.58%),etc.;The AMR phenomenon of isolates is severe,with a high proportion of 97.85% of the isolates resistant to three or more antimicrobials.SCEO was used to conduct in vitro bacteriostatic tests and in vivo anti-infection experiments against the three common Salmonella serotypes found in the indigenous chicken breeding farms,namely SP,Salmonella give,(SG),and Salmonella kentucky,(SK).The results showed that the minimum inhibitory concentrations(MIC)of SCEO(containing 1-6 g/L of trans-cinnamaldehyde and 0.2-6 g/L of trans-anethole)against SP,SG,and SK were 125 μL/m L,500 μL/m L and 500 μL/m L,respectively;70 day-old Three-yellow chicks were randomly divided into group A(30 birds),served as the prevention/challenge group,group B(30 birds),served as the non-prevention/challenge group,and group C(10 birds)served as the non-prevention/non-challenge control.During the trial of 35 days,group A was fed a commercial diet(free of antibiotics)and was supplemented continually with SCEO(1.25 m L/L)in the drinking water,groups B and C were fed the same commercial diet as group A but without SCEO supplemented in the drinking water.At 7 days of age,birds in groups A and B were randomly divided into three subgroups in equal number birds,designated as subgroups A1,A2,A3 and B1,B2,B3.Subgroups A1 and B1 were infected orally with SP,subgroups A2 and B2 were infected orally with SG,subgroups A3 and B3 were infected orally with SK.At 35 days of age,all birds were dissected after weighing,gross pathological changes were observed and recorded,and the challenged Salmonella strains were isolated.The results showed that the average body weight(BW)of birds in the prevention/challenge(SP,SG,SK)groups were significantly higher than those in the non-prevention/challenge group(P<0.05),the recovery rate of the challenged strains in the prevention/challenge(SP,SG)groups were significantly lower than those in non-prevention/challenge group(P<0.05),and while that in the prevention/challenge(SK)group was lower than that in the non-prevention/challenge group(P>0.05).The possible action targets and signaling pathways of SCEO for against the infection of Salmonella were predicted by network pharmacology,and further validates its targets by molecular docking.The results showed that four core targets Prostaglandin G/H synthase 2(PTGS2),Aryl hydrocarbon receptor,(AHR),Estrogen receptor 1(ESR1)and V-Rel Reticuloendotheliosis Viral Oncogene Homolog A(RELA),and chemical carcinogenesis-DNA adducts,chemical carcinogenesis-receptor activation and other signal pathways were screened out.The results of this study demonstrated that SP is still the absolutely dominant serotype of Salmonella contaminated in the indigenous chicken breeding farms,and Salmonella isolates have very severe antimicrobial resistance and their AMR spectrum is complex and diverse;SCEO has good inhibitory activity against SP,SG,and SK,and can effectively reduce Salmonella infection in vivo and significantly improve the decrease in weight gain caused by the infection of Salmonella;SCEO may resist against the Salmonella infection by multiple targets and signal pathways.