Development of a genetic manipulation system for Haemophilus parasuis.

Haemophilus parasuis is a member of the family Pasteurellaceae and an important respiratory-tract pathogen of swine, which is the etiological agent of Glasser's disease. Because no genetic manipulation system is available for H. parasuis so far, in vivo studies about the role of its genes involved in virulence are unfeasible. Here we demonstrate that H. parasuis has a cyclic AMP (cAMP)-dependent natural transformation system that enables the uptake of DNA in which the ACCGAACTC sequence signal must be present. After improving DNA transformation parameters, such as cAMP and DNA concentration and exposition time of the exogenous DNA, a knockout mutant of H. parasuis defective in the thy gene, encoding the thymidylate synthase enzyme, has been constructed. Data presented in this work open the possibility for the functional analysis of genes involved in the infectious process of this animal pathogen.