Isolation, Identification And Epidemiologic Studies Of Salmonella From Yak

Yak is endemic to the Tibetan plateau, which is very important for local herdsmen’s lifeand production. Salmonellosis in yak is prevalent in pastoral areas for a long time, and causeyak serious diarrheal illnesses and deaths. Update compared with other numerous reportsabout salmonella in other animals, reports on salmonella in Yak is few. As the stool is themajor source of salmonella, it’s important for public hygienics to monitor pollution bysalmonella in fecal. The aim of the present study is to compare the method of isolation andidentification of salmonella and research on epidemiology in Yak.The following results:First, based on standard of ISO6579:2002(Annex D), NMKL71, DIN EN12824:1998and GB4789.42010, fecal sample which collected from26clinic healthy yak were used toassess the effection of isolating salmonella from yak stool. Three selective broths (TTB, SCand MSRV) and medias (XLD, SS and CAS) were used in this study. Result showed that9isolation methods presented difference in isolation rate. The highest positive rate was obtainedfrom TTB combination SS(8/26). In all, thirteen yaks carried salmonella have been poved. Bycompared, selective broth (TTB and MSRV) unit selective media(CAS and SS) has morehigher positive rate(12/26).According to literature reports at home and abroad, five PCR methods respectivetargeted invA、invE、stn、16S、bidui gene were used to evaluate influence for rapid detectionof salmonella from yak. The result showed all of5method could detect48salmonella stainsfrom yak. These results indicated that all the methods are suitable to rapidly identifySalmonella from yak. In accordance with Liu B’s report about detecting serogroup ofsalmonella by PCR, in48salmonella stains from yak there are9strains belonging toserogroup B,1strains belonging to serogroup C1,37strains belonging to serogroup D. Itdemonstrated this method apply to fast serogroup epidemiology investigation.Second, serotype and molecular epidemiology were been researched. Our researchdetected8serotypes in31strains. The dominant serotypes respectivly are S.Dublin (32.26%),S.Enterica (29.03%) and S.Typhimurium (12.90%). Other serotypes are S.Blegdam，S.Onarimon，S.Stanely，S. Orion，S.Newport. Interestingly, S. Orion and S. Onarimon are rare in literature report. In31isolates from yak, all strains have SPI-1to SPI-5indicating that nomutation havs happened on these gene. Five of8serotypes posses virulence plasmid. Itillustrated higher carrying rate of virulence plasmid in salmonella stains from yak, whichmake salmonella more virulence in yak. Apart from this, it is the first report S.blegdam and S.Onarimon carrying virulence plasmid.Third, pathogenicity of salmonella from Yak on mice was surveyed. Seven strains(including3S.Dublin,2S.enterica,1S.Typhimurium,1S.Stanely) were used in this study.Theresult showed that all of7strains were recovered from heart, liver, spleen, lung, intestine andkidney of infected mice by culturing. All the strains have capabled to lethal mice, indicatingthat salmonella from healthy yak by orally has strong virulence. Therefore, this result providevaluable information for further research on pathogenicity of salmonella from yak.