Pathogenic characteristics of Streptococcus suis type 2 and type 9 isolated from Guangdong province

Two strains of pathogenic bacteria were isolated from 9 dead pigs in Guangdong Province between summer and autumn in 2005.The morphological and culture characteristics indicated that the isolates belonged to the genus Streptococcus.The biochemical characteristics was similar between the 2 isolates,and the isolates were not able to be agglutinated by the Lancefield group A-G latex diagnostic kit.Serotype-specific PCR revealed that one of the isolates represented Streptococcus suis type 2 and the other represented S.suis serotype 9.Moreover,genetype sly+epf+mrp+ was detected in the isolate of type 2,and the isolate was low in virulence and was able to infect mice(2/10) on day 6-15 post-inoculation.Genetype sly-epf-mrp-was detected in the isolate of serotype 9,but the isolate was highly virulent to mice(9/10) and its LD50 was 1.70×106CFU.The results demonstrated that S.suis type 2 and 9 were able to cause swine streptococcosis in Guangdong province.