Abstract

Xingjian Cao, Zhaoming cao, Guohua Tao, Wei Xie, Xiang Chen and Shuo Wang

The purpose of this study was to investigate the infectious pathways used by Streptococcus suis type 2 and enterohemorrhagic Escherchia coli O26 (EHEC O26) in mice. Six-week mice were intraperitoneally injected with mitomycin (0.2 mg/mouse) to decrease the protective immunity. The mice were then challenged with S. suis type 2 and EHEC O26 strains through wounded skin, stomach lavaging and intraperitoneal injection. Enterococcus faecalis ATCC 29212 and E. coli ATCC25922 were used as negative controls. Clinical and microbiological examinations were performed for all the infected mice routinely. The mortality rate of the mice infected with S. suis type 2 strain through wounded skin was 60% within 2 - 5 days. The mortality rate of the mice infected with S. suis type 2 strain through stomach lavaging was 60% within 7 - 10 days. S. suis type 2 can be isolated from the puncturing fluid of heart in the dead mice. Mortality was not observed in mice infected by S. suis type 2 and E. faecalis ATCC 29212 strains through intraperitoneal injection. However, intraperitoneal injection with EHEC O26 and E. coli ATCC25922 caused death of mice within 10 h. We demonstrated an important pathway used by S. suis type 2 strain in mouse infection model. Intraperitoneal injection with gram negative bacteria (E. coli ATCC25922 and EHEC O26) caused non-specific death in mice. These results provided fundamental bases for investigating the pathogenesis of S. suis type 2, designing vaccine and evaluating the efficiency of antimicrobial drugs.