关键词: 贵州矮马; 鼠伤寒沙门氏菌; 侵袭蛋白A基因; 致病力

Abstract:

To investigate the reason of the diarrhea in Guizhou pony,we used the feces of pony as experimental material to isolate and detect pathogenic bacteria.S6 strain was isolated from SS and XLD medium,and identified using Gram staining,biochemical tests and molecular phylogeny methods.The results showed that S6 strain could growth on SS and XLD medium,and the Gram staining was negative.Biochemical test suggested that its phenotype features were accordance with Salmonella.The 16S rRNA gene sequence of S6 strain was determined in a nucleotide sequence identity of 99% with Salmonella typhimurium ATCC 13311 (NR_119108).Based on the morphological and molecular phylogenetic results,the strain was identified as Salmonella typhimurium S6 strain.It was virulent to mice with the median lethal dose (LD₅₀) of 4.71×10² CFU.Then,we amplified the invasion protein A (invA) gene by PCR method.The invA gene isolated from S6 strain contained 6 to 8 bp different from the known gene,which resulted in only one amino acid substitution.The mutant sites of invA gene might attribute to the pathogenicity of S6 strain.The detection rate of Salmonella was 57% in Guizhou pony population.It was inferred that the diarrhea in Guizhou pony might be caused by virulent Salmonella typhimurium.

Key words: Guizhou pony; Salmonella; invasive protein A gene; pathogenicity