Identification and Analysis of the hhdB-A Gene of Haemophilus parasuis

The research aimed to know the virulence-associated factors in pathogenic strains of Haemophilus parasuis.Nine strains(H1～H9)of bacteria were isolated from unsound swine of epidemic farms in different regions in Guangdong province,then the hhdB-A genes of the isolated strains were identified and analyzed.The results showed that the isolated strains belonged to Haemophilus parasuis by morphological observation,biochemical characterization and PCR identify,and had satellite phenomena and nonhemolytic characteristics.The nucleotide sequence similarities of hhdA genes between the isolated strains,Haemophilus parasuis SH0165,HPS59 were 99.0%～99.9% and 98%～100% respectively,and the nucleotide sequence similarities of hhdB genes between the isolated strains,Haemophilus parasuis SH0165 were 97.5%～99.8% and 99% respectively.The amino acid sequence of isolated strains hhdB-A gene and the bacterial hemolysin activation protein of Actinobacillus minor NM305 and Haemophilus ducreyi 35000HP were similar.RT-PCR indicated that the hhdB gene was expressed in all of the isolated strains.This study would be helpful for the identification of virulence gene and pathogenic mechanism study of Haemophilus parasuis.