Curcumin reduces the expression of ahyI, quorum sensing gene, in A. Hydrophila

Background and Aim: Aeromonas hydrophila is a Gram-negative bacterium that can infect a variety of aquatic and terrestrial animals, including humans, with different disease outcomes. In fish, it affects several species, where it causes fatal hemorrhagic septicemia, a major freshwater disease affecting aquaculture worldwide. Also, the transmission of A. hydrophila infections from diseased fish to humans through the consumption of contaminated water and raw or undercooked seafood has been reported. In humans, it can cause a number of infections including bacteremia, bronchopulmonary infections, cellulitis, food-borne gastroenteritis, meningitis, peritonitis and wound infections. Pathogenicity of A. hydrophila is multifactorial which is controlled by the Quorum sensing (QS) system. QS is a mechanism of cell-to-cell signaling via the production of signal molecules known as autoinducers that allow a bacterium to ‘‘sense’’ its own population. Quorum sensing regulates several functions such as conjugation, secretion of virulence factors, antibiotics production and biofilm formation. In A. hydrophila N-acyl homoserine lactone (C۴HSL), acts as the QS signal molecule. This molecule is produced by acyl-homoserine synthase that is encoded by the ahyI gene. C۴HSL affects the expression of several virulence factors including hemolysins, lipases, and proteases. Anti QS potential of curcumin has been reported, previously. Curcumin is a yellow pigment that is found in Curcuma lunga. It’s a polyphenol compound with anti-inflammatory, anti-QS, Anti-bacterial, Antiviral, anti-oxidant and anti-tumor properties. This study was conducted to evaluate the effect of curcumin on the expression of the ahyI QS gene in A. hydrophila.Methods: A. hydrophila, isolated from diseased fish, were cultured in Muller Hinton Agar medium. The MIC (Minimum Inhibitory Concentration) of curcumin against A. hydrophila was determined. A.hydrophila was grown Lauria broth medium containing a sub-MIC concentration of curcumin. After reaching the late exponential phase, the bacteria were harvested from the medium and subjected to total RNA extraction and cDNA synthesis. The control cells were grown in the media lacking curcumin. Finally, the expression of the ahyI gene was investigated by quantitative Polymerase Chain Reaction (qPCR) using gene-specific primers. In addition, the ۱۶s rRNA gene was used as an internal reference gene.Results: The MIC of curcumin was determined ۱۲۸ µg/mL and thus, bacteria grown in the media containing curcumin with a concentration of ۶۴ µg/mL (as ½ sub-MIC) was selected for further experiments. Our results showed that the expression of ahyI among curcumin-treated cells reduced by ۷۰% , compared to the control cells Conclusion: In this study, we showed that curcumin significantly reduced the expression of the ahyI gene, which can result in the reduced production of the C۴HSL autoinducer molecules in A. hydrophila. Since the proper expression of a variety of virulence factors are dependent on the concentration of C۴HSL, attenuation of ahyI by curcumin can reduce bacterial infectivity and pathogenicity. Thus, curcumin could be regarded as a promising anti-QS agent to be used against A. hydrophila infections.

کلیدواژه ها:

Aeromonas hydrophila ، Quorum sensing ، curcumin ، ahyI