Effectiveness of garden burnet, Sanguisorba officinalic L., in controlling acute hepatopancreatic necrosis disease caused by infection of Vibrio parahaemolyticus in shrimp farming

Abstract

Vibrio parahaemolyticus (VP) is a major pathogen that causes acute hepatopancreatic necrosis disease (AHPND) in shrimp. Among the multiple pathogenic factors, the type VI secretion system (T6SS) plays an important role in pathogenesis caused by VP. In the present study, we examined the effective bactericidal concentrations of ethanol-extracts and water-extracts of Sanguisorba officinalic L. (S. officinalic) on VPAHPND, a causative agent of AHPND. Moreover, we also investigated the dose-dependent effects of these extracts on the growth of VPAHPND and the expression levels of seven T6SS-related genes, including VP1388, VP1393, VP1400, VP1409, VPA1027, VPA1043 and VPA104. The results showed that although both extracts could inhibit the growth of VPAHPND, the ethanol-extract possessed the stronger antibiotic effect and could kill VPAHPND at 6.4 mg/mL within 10 h. Analysis of the expression levels of T6SS-related genes indicated that ethanol-extract at higher dosages could up-regulate the expression of the T6SS1 gene within a short period of time, although such effect was attenuated with time. In addition, the ethanol-extract could significantly inhibit the expression of T6SS2 at the mRNA level in a dose-dependent manner. Based on the function of each gene, we speculated that the ethanol-extract could weaken the adhesion of VPAHPND, reduce its infectivity to the host, and block the activation of other T6SS-related virulence factors through inhibiting the initiation of T6SS, leading to the attenuated pathogenicity of VPAHPND to the host. The results of a clinical trial confirmed that dried garden burnet had a strong inhibitory effect on Vibrio proliferation in shrimp. Taken together, our results confirmed that S. officinalic could be used as a potentially effective agent for controlling and even preventing VPAHPND infection.