Indole inhibits quorum sensing‐dependent phenotypes and virulence of acute hepatopancreatic necrosis disease‐causing Vibrio parahaemolyticus

Abstract

Acute hepatopancreatic necrosis syndrome (AHPND) caused by a unique Vibrio parahaemolyticus strain (VPAHPND) has emerged as a serious disease of cultured shrimps and is causing great economic losses worldwide. In this work, the effects of indole on quorum sensing‐dependent (QS) phenotypes of VPAHPND were assessed. In QS‐inhibitory bioassay using biomonitor strains, indole could interfere with N‐acyl homoserine lactones (AHL)‐mediated violacein pigment production of Chromobacterium violaceum, and autoinducer‐1 (AI‐1) and autoinducer‐2 (AI‐2)‐mediated QS response (bioluminescence) in V. campbellii. Further testing of indole with VPAHPND demonstrated significant decrease in the swimming and swarming motilities. In addition, VPAHPND grown in the presence of indole exhibited a reduction in biofilm formation, extracellular polymeric substances (EPSs) production and autoaggregation index. However, indole did not affect the ability of VPAHPND to use ferrous sulphate (FeSO4) as an iron source. Interestingly, indole reduced the expression of pirA (~2 fold), pirB (~2 fold), cpsA (~1.5 fold) and scrA (~1.7 fold) resulting in the reduction of toxin and capsule production. Lastly, indole‐treated VPAHPND exhibited lower virulence towards an infected model and its specific host, Galleria mellonella larvae and Litopenaeus vannamei respectively. These demonstrated the effects of indole in reducing multiple QS‐dependent phenotypes and virulence of VPAHPND. Thus, using indole, indole‐containing compounds, or indole‐producing organisms might be an attractive anti‐virulence strategy to control infections caused by VPAHPND.

Quorum‐quenching enzymes: Promising bioresources and their opportunities and challenges as alternative bacteriostatic agents in food industry

“…In addition, the virulence (toxic protease; cytotoxic factors; brown pigment and transporter) of A. salmonicida , Aliivibrio salmonicida , and Edwardsiella tarda against fish was significantly impaired after blocking the QS systems, as the survival rate of fish infected with QS‐deficient strains increased by 50%, with significantly prolonged mean day to death (Hansen et al., 2015; Santos et al., 2021; Schwenteit et al., 2011). The threat of AHL‐mediated QS to aquaculture has been documented in other typical aquatic products, including shrimp (Paopradit et al., 2022), shellfish (Zhao et al., 2019), and sea cucumber (Zhang & Li, 2021), where host mass mortality due to QS regulation of virulence factors (adhesins, extracellular proteases, hemolysins, and siderophores) has resulted in huge economic losses in the China, Philippines, Vietnam, Japan, and other Southeast Asian countries (Guzman et al., 2022). There are also significant risks for agriculture, because AHLs‐producing strains account for up to around 20% of the culturable bacteria in rhizospheric environments, with important contributions to plant health (Helman & Chernin, 2015).…”