Antibacterial effects of cinnamaldehyde and hesperitin on resistant Glaesserella parasuis by suppressing QseBC two-component system.

BACKGROUND: Glaesserella parasuis (G. parasuis) is one of the most important porcine pathogens causing Glässer's disease, and QseBC two-component system (TCS) is associated with various behaviors of G. parasuis. Our preliminary tests confirmed that plant-derived compounds cinnamaldehyde (CAL) and hesperitin (HES) exhibited promising antimicrobial activity against G. parasuis. Here, we further investigate the antimicrobial effects of CAL and HES on G. parasuis and the underlying mechanisms. RESULTS: We observed that CAL and HES affected the morphology and physiology of G. parasuis based on the biofilm biomass, confocal laser scanning microscope (CLSM) assay, scanning electron microscope (SEM) assay, and conductivity determination as well as intracellular iron level measurement either used alone or in combination. Moreover, CAL and HES can inhibit QseBC TCS of G. parasuis by down-regulating the QseBC related genes and quenching the QseC protein based on quantitative reverse transcription polymerase chain reaction (qRT-PCR) and molecular docking and fluorescence quenching assay. In vivo study further evident that CAL and HES exhibited significant antimicrobial and anti-inflammatory activity on G. parasuis-infected mice. CONCLUSIONS: These findings suggested that CAL and HES can exert antibacterial activity on resistant G. parasuis by targeting QseBC, and they may serve as the promising antimicrobial agents for the treatment of G. parasuis infection.