Anti-quorum sensing effects of licochalcone A and epigallocatechin-3-gallate against <i>Salmonella</i> Typhimurium isolates from poultry sources.

Abstract

Quorum sensing (QS) is a cell density-dependent mechanism used by many pathogenic bacteria for regulating virulence gene expression. Inhibition or interruption of QS by medicinal plant remedies has been suggested as a new strategy for fighting against antibiotic-resistant bacteria. This study aimed to assess the impact of sub-inhibitory concentrations of licochalcone A (LAA) and epigallocatechin-3-gallate (EGCG) as natural plant products on the QS<i>-</i>associated genes (<i>sdiA</i> and <i>luxS</i>) expression. The PCR test was used to confirm the presence of <i>sdiA</i> and <i>luxS</i> genes in 23 <i>S</i>. Typhimurium isolates from poultry. The quantitative real-time PCR assay was used to analyze the expression of <i>sdiA</i> and <i>luxS</i> in <i>S</i>. Typhimurium isolates in response to the treatment with sub-inhibitory concentrations of LAA and EGCG at 45-min time point. All <i>S</i>. Typhimurium isolates showed the presence of <i>sdiA</i> and <i>luxS</i> genes (100%). As result, the expression of QS-related genes was significantly reduced in <i>S.</i> Typhimurium isolates following treatment with LAA and EGCG. In conclusion, LAA and EGCG showed anti-QS activity with down-regulation of both <i>sdiA</i> and <i>luxS</i> genes in <i>S.</i> Typhimurium, suggesting potential therapeutic use of them against salmonellosis. However, it must be pointed out that the safety and efficiency of these compounds need more thorough research.