In vitro Evaluation of Capsaicin Inhibitory Effects on Vibrio choleraeToxin Production

Background: The acute secretory diarrhoea caused by Vibrio choleraeismostly due to cholera toxin (CT) and zonulaoccludens toxin (Zot) production. Isolates of V. cholerae have acquired resistance elements during the past decade.One of the most promising ways to treat resistant strains is to use antivirulence agents instead of killing the causative agent with conventional antibiotics.In this study, we examined whether different concentrations of capsaicin -the pungent fraction of red chili- can act as an antivirulence agent and inhibit V. cholerae toxin production. Methods: Two standard strains V.cholerae ATCC 14035 and V. cholerae PTCC 1611 were used in this study. Minimum Inhibitory Concentration (MIC) of capsaicin was determined by broth micro dilution method. Based on MIC results the bacteria were cultured in the presence of sub-MIC concentrations of capsaicin and a negative control without capsaicin. Real-time PCR was carried out to determine the expression level of toxin genes of V.choleraein each concentration. Results: MIC results showed that 200mgmL-1 of capsaicin in 2% Dimethyl sulfoxide (DMSO) could inhibit the growth of the two standard type strains of V. cholerae. The expression level of V.choleraetoxin genes showed a great reduction under sub-MIC concentrations of capsaicin using Real-time PCR. Conclusion: Capsaicin showed great inhibitory effect against cholera toxin and Zot production in the tested standard type strains of V. cholerae. The results showed promising insights for capsaicin to be developed as an antivirulence agent.

Keywords:

Vibrio cholerae , antivirulence agents , capsaicin , toxin gene expression