Autoinducers modulation as a potential anti-virulence target of bacteria by phenolic compounds.

• Phenolics showed bacterial anti-virulence potential by modulating autoinducers. • Pomegranate extract showed the highest potential as quorum quencher at low doses. • Grape extract showed a noted inhibition against bacterial biofilms and motility. • Persimmon extract exhibited strong growth inhibition against Klebsiella pneumoniae. • Persimmon and pomegranate extracts caused bacterial membrane damage after exposure. The goal of this study was to determine the effects of phenolic extracts from grape (GrPE), pomegranate (PoPE), and persimmon (PePE) by-products on bacterial virulence activities such as biofilms, motility, energy-dependent efflux pumps, and β-lactamase activity, which are modulated primarily by quorum sensing (QS), defining their potential applications. The microdilution method was used to determine the minimum inhibitory concentration (MIC) and sub-inhibitory concentrations (SICs) of the extracts against reference pathogenic bacteria. The antibacterial mode of action was determined by labelling bacterial cells in in vivo cell-tracking experiments. Antibiograms showed that PoPE inhibited bacteria at lower concentrations, and PePE had a stronger effect against Klebsiella pneumoniae. Both extracts caused significant cell membrane damage (CMD), whereas GrPE did not. At SICs, all extracts showed anti-QS activity, especially PePE, which inhibited violacein and pyocyanin production at 1/128 × MIC. Additionally, QS autoinducers found in Chromobacterium violaceum and Pseudomonas aeruginosa were modulated by the extracts; PePE showed the highest modulation. Antibiofilm assays revealed that GrPE, at MIC and 2 × MIC, acted as a potent antibiofilm agent against biofilms of Pseudomonas putida, Bacillus cereus , and Staphylococcus aureus , which was related to disruption of swarming motility by GrPE. All extracts, especially PoPE, exerted a potent effect against the activation of efflux pumps of P. aeruginosa as well as β-lactamase activity in K. pneumoniae. Results suggest that the anti-virulence potential of the extracts may be related to their effect as extracellular autoinducer modulators. This study allowed to define potential applications of these extracts. [Display omitted] [ABSTRACT FROM AUTHOR]