Comparative Analysis of Virulent Genes and Drug Resistance of Salmonella Isolated from Different Sources

Song Xue;Zhao Ge;Liu Wenhua;Sun Tingting;Wang Juan;Zhao Jianmei;Hong Jun;Li Yuehua;Huang Xiumei;Liu Na;Zhang Linbo;Wang Junwei;College of Life Science,Jilin Agricultural University;Laboratory of Quality and Safety Risk Assessment for Livestock and Poultry products(Qingdao)of Ministry of Agriculture,China Animal Health and Epidemiology Center;Tancheng Animal Husbandry Bureau;

diseased animal;;healthy animal;;Salmonella;;virulence;;drug resistance

[Objective] In order to recognize the carrying situation of Salmonella in different livestock and poultry and analyze the virulence and drug resistance,so as to provide data and basis for its epidemiological analysis and prevention and control. [Methods] Samples collected from Shandong,Jilin,Jiangxi,Xinjiang,Yunnan were conducted Salmonella isolation and identification by the national method. Then these isolated strains were detected serotypes and virulent genes using related kits and PCR method respectively. Finally,drug resistance analysis was made through broth microdilution method(MIC). [Results] The isolation rate of Salmonella from healthy animals was 21.63%(141/652),while that in diseased animals was 13.64%(45/330). There were 4 dominant serotypes consisting of S.derby(42.6%),S.indian(26.2%),S.enteritidis(17.7%),and S.thompson(17%). Virulent gene analysis was conducted by detecting the 5 core protein genes of SPI-1~SPI-5,as well as the virulent plasmid genes of spv A、B、C、D and R. Results showed the carrying of virulent genes existing in Salmonella pathogenicity island was basically identical between the healthy and diseased animals,while the virulent genes carried by plasmids were significantly higher in diseased animals. According to the drug resistance test,a higher resistance rate was observed in diseased animals than in the healthy animals,except against Doxycycline and Gentamicin. Beside,Salmonella strains isolated from chicken and swine showed obviously differences in drug resistance against Gentamicin,Cefurofen,Ofloxacin and Colchicine. As for other antimicrobial agents,little difference was got. Most of the strains isolated from healthy livestock and poultry were resistant to 1~2 antibiotics,accounting for 55.32% of the total strains. On the other side,Salmonella strains derived from diseased animals which revealed resistance to more than 10 antibiotics took up a proportion of 44.44%. [Conclusion] The isolation rate of Salmonella in diseased animals was lower than that in healthy ones,however the virulent genes carried by plasmids in diseased animals was higher,showing severe and multiple drug resistance. This study would offer a basis for Salmonella risk assessment and the establishment of corresponding prevention and control measures.