The arcA gene contributes to the serum resistance and virulence of Haemophilus parasuis serovar 13 clinical strain EP3

•An arcA gene deletion mutant of a Haemophilus parasuis serovar 13 clinical strain EP3 was first constructed by a natural transformation system.•The arcA gene associates with growth under anaerobic condition, sensitivity to serum, biofilm formation and virulence in Haemophilus parasuis.•The arcA gene is involved in pathogenesis in Haemophilus parasuis.

As a global transcriptional factor, ArcA regulates the expression of hundreds of genes involved in aerobic and anaerobic metabolism. Here we deleted arcA gene and investigated the biological characteristics of arcA deletion mutant (ΔarcA) in Haemophilus parasuis (H. parasuis) serovar 13 clinical strain EP3. Results indicated that deletion of arcA impaired growth of EP3 strain under anaerobic condition, and reduced virulence of EP3 strain in mice. Additionally, the ΔarcA strain showed greater sensitivity in porcine serum and produced less biofilm mass than the EP3 strain. Taken together, these findings suggested that the arcA gene may be involved in pathogenesis in Haemophilus parasuis.