Isolation, identification, serotyping and pathogenicity of Salmonella from Yaks in Tibet

Abstract:

The purpose of this study was to understand the prevalence, distribution and serotypes of Salmonella from yak sources in Tibet. By collecting yak diarrhea feces in seven districts of Tibet, the bacteria in the samples were isolated and identified by using bacterial culture, biochemical characteristics, and molecular biology methods, and then the isolated strains were serotyped according to serum specific agglutination, and finally, animal infection and HE staining of animal tissue were used to understand the pathogenicity of strains. The results showed that a total of 50 Salmonella strains were isolated from the whole region of Tibet, with a detection rate of 25.13% (50/199). Among them, the separation rate of Lhasa, Qamdo, and Shannan was higher than the other four, and the Ngari area is the lowest; the serotyping results show that 4 serogroups including B group, C1 group, C2 group and D group were isolated. The serogroup includes 18 serotypes including Salmonella Dublin, Salmonella Typhi, and Salmonella Aboni. According to serogroup statistics, among the 4 serogroups, group D accounts for the most serogroups and is a common serogroup; 50 Salmonella strains were dominated by Salmonella, accounting for 20.00% (10/50 ) of all strains; The typing results of Salmonella in various regions show that the number of serogroups and serotypes in each region are different. The results of the pathogenicity test showed that the LD50 of KM mice infected with yak-derived S.dublin was 0.368×108CFU/mL, which was a highly lethal strain. The results of tissue HE staining showed that yak-derived S.dublin could cause systemic damage to the host. Among them, the spleen, lung, intestine and stomach have more severe lesions. The results of this experiment suggest that Salmonella does exist in Tibetan Yak sources, and has a certain trend of prevalence. At the same time, the common serogroups, dominant serotypes and dominant serotypes of Salmonella dublin from yak sources in Tibet have been identified, and the pathogenicity of the dominant serotype was also identified.