Halogenated Indoles Decrease the Virulence of Vibrio campbellii in a Gnotobiotic Brine Shrimp Model.

Area of Science:

• Microbiology
• Marine Biology
• Drug Discovery

Background:

• Antibiotic resistance in aquaculture necessitates novel antivirulence strategies.
• Indole signaling in Vibrio species is linked to virulence factor production.
• Vibrio campbellii causes significant disease (vibriosis) in shrimp aquaculture.

Purpose of the Study:

• To evaluate the antivirulence properties of indole analogues against Vibrio campbellii.
• To investigate the structure-activity relationship of halogenated indoles for virulence inhibition.
• To assess the efficacy of indoles in an in vivo shrimp model.

Main Methods:

• Screened 44 indole compounds for antimicrobial and antivirulence activity.
• Tested 17 selected halogenated indole analogues in brine shrimp challenged with V. campbellii.
• Assessed the impact of indoles on V. campbellii virulence factors: motility, biofilm, protease, and hemolytic activity.

Main Results:

• 17 halogenated indoles significantly enhanced brine shrimp survival against V. campbellii.
• 6-bromoindole, 7-bromoindole, 4-fluoroindole, 5-iodoindole, and 7-iodoindole provided >80% survival at 10 μM.
• Indoles reduced bacterial swimming motility and biofilm formation, with minor effects on protease and no effect on hemolytic activity.

Conclusions:

• Halogenated indole analogues represent a promising class of antivirulence compounds against V. campbellii.
• This study establishes a structure-activity relationship for indole-mediated virulence inhibition in an in vivo model.
• Indole analogues offer potential for protecting shrimp from vibriosis, supporting sustainable aquaculture practices.