Screening of Dietary Substances: New Blockade Strategy on Quorum Sensing
The increasing occurrence of multiresistant pathogenic bacterial strains has gradually rendered traditional antimicrobial treatment ineffective. Quorum sensing, which is ubiquitous in bacteria, is the cell density dependent expression of species in bacteria mediated by hormone like compounds called autoinducers. Quorum quenching, which is the ability to disrupt quorum sensing, has a great therapeutic potential. The observation that quorum sensing is linked to virulence factor production, suggest that many virulent microbes could potentially be rendered nonpathogenic by inhibition of their quorum sensing systems. Though antimicrobial properties of dietary phytochemicals are well known, their ability as quorum sensing modulators is less studied. The primary objective of this investigation was to determine the quorum sensing inhibition activity of common fruit extracts, viz., Ananas cosmosus, Citrus sinensis, Vitis Concord Seedless, Punica granatum, Phyllanthus emblica, Anacardium occidentale, Lycopersicon esculentum, Malus domestica, Vitis muscat and Vitis vinifera. The bacterial strain used was Chromobacterium violaceum MTCC 2656. Loss of purple pigment in Chromobacterium violaceum is indicative of quorum sensing inhibition by the fruit extract introduced. The experiments were done in triplicate using standard methods. 6 fruit extracts, viz., Ananas cosmosus, Citrus sinensis, Vitis Concord Seedless, Punica granatum, Lycopersicon esculentum and Vitis muscat expressed quorum quenching activity. Phyllanthus emblica showed antimicrobial activity. Quantitative assessment of pigment inhibition indicated that the quorum quenching activity of the fruits is concentration dependent. Citrus sinensis showed lowest quorum quenching activity. The molecules within the extracts that are involved in the inhibition of quorum sensing and the mechanism of quorum quenching are to be studied as a future prospect in order to exploit the wide possibilities of quorum quenching as a possible future treatment scenario for infections caused by bacteria which regulate pathogenocity by means of quorum sensing.