The two-component regulatory system CpxA/R is required for the pathogenesis of Aeromonas hydrophila

Abstract

Aeromonas hydrophila is a causative pathogen of many infectious diseases in fish and human. The two-component regulatory system enables bacteria to response to a wide range of stimuli, growth conditions and environments. The two-component system CpxA/R is prevalent in microorganisms and involved in the pathogenesis of a number of pathogens. In this study, we generated a ΔcpxA/R mutant of A. hydrophila ZYAH72 to explore the biological functions mediated by the CpxA/R in this organism. Compared to the wild type strain, the knockout mutant strain ΔcpxA/R exhibited a significant impairment in adherence to human epithelial cells Caco-2 and resistance against host killing in fish blood. However, the mutant strain and the wild type strain showed no difference in the cytotoxicity assay revealed that the absent of CpxA/R did not influence the cytopathic effect of this pathogen in vitro. Furthermore, the virulence of ΔcpxA/R was attenuated in zebrafish (Danio rerio) and grass carp (Ctenopharyngodon idella) infections, with reduced mortality or delayed death time. These findings suggest that CpxA/R is required for the virulence of A. hydrophila.