Cultivation, LD50 determination and experimental model of Streptococcus suis serotype 2 strain HA9801

The effects of nutritional components and submerged culture conditions on colony-forming unit (CFU) counts by Streptococcus suis serotype 2 strain HA9801 in flask culture was investigated, and the optimal medium and cultivation conditions was confirmed by using a 50 l bioreactor. The LD50 values of HA9801 in pigs before and after fermentation were 1.8 × 107 CFU, which indicated that the virulence of HA9801 was very stable in the fermentation process. In addition, an experimental model that closely mimics naturally occurring disease in conventional pigs was established.