Abstract
The emergence of multidrug-resistant bacteria stimulates the search for new substitutes to traditional antimicrobial agents, especially molecules with antivirulence properties, such as those that interfere with quorum sensing (QS). This study aimed to evaluate the potential of phenolic compounds for QS inhibition in a QS biosensor strain (Chromobacterium violaceum) and three foodborne bacterial species (Aeromonas hydrophila, Salmonella enterica serovar Montevideo, and Serratia marcescens). Initially, an in silico molecular docking study was performed to select the compounds with the greatest potential for QS inhibition, using structural variants of the CviR QS regulator of C. violaceum as target. Curcumin, capsaicin, resveratrol, gallic acid, and phloridizin presented good affinity to at least four CviR structural variants. These phenolic compounds were tested for antimicrobial activity, inhibition of biofilm formation, and anti-QS activity. The antimicrobial activity when combined with kanamycin was also assessed. Curcumin, capsaicin, and resveratrol inhibited up to 50% of violacein production by C. violaceum. Biofilm formation was inhibited by resveratrol up to 80% in A. hydrophila, by capsaicin and curcumin up to 40% in S. Montevideo and by resveratrol and capsaicin up to 60% in S. marcescens. Curcumin completely inhibited swarming motility in S. marcescens. Additionally, curcumin and resveratrol increased the sensitivity of the tested bacteria to kanamycin. These results indicate that curcumin and resveratrol at concentrations as low as 6μM are potential quorum sensing inhibitors besides having antimicrobial properties at higher concentrations, encouraging applications in the food and pharmaceutical industries.
Highlights
The microbial communication system called quorum sensing (QS) is used by a wide variety of bacteria allowing them to collectively modify their behavior in response to changes in cell density
This study evaluated the ability of some phenolic compounds to inhibit bacterial quorum sensing regulated phenotypes
Phenolic compounds have potential to inhibit quorum sensing in foodborne bacteria
Summary
The microbial communication system called quorum sensing (QS) is used by a wide variety of bacteria allowing them to collectively modify their behavior in response to changes in cell density This communication is mediated by small molecules accumulated during microbial multiplication and involves the production, secretion, and detection of extracellular signaling molecules, known as autoinducers (AI; Mukherjee and Bassler, 2019). In Gram-positive organisms, communication is mediated by autoinducer peptides which are usually secreted by ABC-type carrier proteins (Monnet et al, 2014; Lima et al, 2020) In addition to these main QS autoinducers, the furanosyl borate diester, known as autoinducer-2 (AI-2), is associated with both Gram-positive and Gram-negative bacteria allowing intra and interspecific communications (Chen et al, 2002). A number of other extracellular bacterial metabolites that function as signals in a range of microorganisms have been discovered recently (Vanetti et al, 2020)
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