Significance of broad-spectrum racemases for the viability and pathogenicity of Aeromonas hydrophila

Aim: To investigate the function of broad-spectrum racemases in Aeromonas hydrophila (BsrA). Results: The A. hydrophila gene encoding BsrA (bsr) mutants (AH Delta bsr) exhibited a significant decrease in growth, motility, extracellular protease production and biofilm formation compared with the wild-type. Furthermore, bsr gene knockout instigated cell wall damage compared with the wild-type strains. The survival rate and replication capability in the blood and organs of the AH Delta bsr-infected mice were significantly decreased. The degree of tissue injury in the AH Delta bsr-infected group was lower than that of the wild-type-infected group. Moreover, there was a significant decrease in the expression of 12 AH Delta bsr virulence genes. Conclusion: The bsr gene is essential for the viability and virulence of A. hydrophila.