1.School of Medicine, Southeast University, Nanjing 210009, China; 2. College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
Abstract：The eha gene is an important transcriptive regulating gene in E. tarda virulence strain ET-13. We explored the gene for regulation of the virulence of ET-13. By comparing the differences between LD50 of the wild strain and that of the Δeha strain to mice, the LD50 of Δeha was 2.5 times more than that of the wild, which indicated that the virulence of the Δeha was decreased. The numbers of the Δeha strains was significantly lower than those of the wild in a liver, a spleen and a kidney of mice post infection, which indicated that the survival viability of Δeha strains in host in vivo decreased obviously. In order to compare the host pathological damages caused by the two kinds of strains, these tissues changes infected with the wild and the Δeha were microscopically analyzed. Results showed that the liver cells edema and neutrophil infiltration, spleen cells necrosis and edema of the renal tubules lesions occurred after the mice were infected by the wild, which indicated that the wild was toxic effects to the liver, spleen and kidney, while the Δeha wasn’t. Results by RT-PCR showed that the transcriptional levels of T3SS secretion protein gene C (eseC) and OMP gene (pagC) in the Δeha were significantly lower than those in the wild. Results showed that as the lower virulence factors were expressed in the Δeha, the bacterial virulence and host pathological changes were decreased significantly. Therefore, eha gene is a positive regulating gene of the virulence of E. tarda.
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2015, Vol. 31 
