Abstract：Capsular polysaccharide of Haemophilus parasuis (HPs) is known as one of crucial virulence factors in pathogenicity. Wza gene plays a vital role in transporting the capsular polysaccharide from inside to the surface of the cell. In this study, an Wza-deficient mutant of HPs (ZJ1208-ΔWza) was successfully screened from Kan-TSA following natural transformation of Haemophilus parasuis with pUC18-LR-Kan. According to preliminary research on biological characteristics, ZJ1208-ΔWza mutant and ZJ1208 wild strain had no visual difference in colonial morphology and capsular after 12 h culture in vitro. ZJ1208-ΔWza mutant reached the maximum OD600 at 1.246, while wild strain reached 2.196, nearly 0.95 higher than ZJ1208-ΔWza mutant. The logarithm of viable count was 9.7634 for ZJ1208 wild strain after 8 h culturing, and 9.322 2 for ZJ1208-ΔWza mutant. With regard to mycelial morphology, the long-chain or long rod of ZJ1208-ΔWza could be observed in 6 h culture in vitro, whereas wild strain formed shorter cells. Moreover, ZJ1208-ΔWza mutant had higher ratio of sedimentation, and was more sensitive to porcine alveolar macrophage (PAM) phagocytosis, and was less virulent in mice toxicity assay than ZJ1208 wild strain. This study showed that Wza deficiency had a multiple affects on biological characteristic of haemophilus parasuis and also lay a foundation for furtherly researching the roles of Wza gene in formation of capsular polysacchaaride around HPs.
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