Somayyeh Hosseinzadeh - Department of Microbiology, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
Habib Dastmalchi Saei - Department of Microbiology, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
Malahat Ahmadi - Department of Microbiology, Faculty of Veterinary Medicine, Urmia University, Urmia, Iran
Taghi Salehi - Department of Microbiology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran

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-۳-gallate (EGCG) as natural plant products on the QS-associated genes(sdiA and luxS)expression. The PCR test was used to confirm the presence of sdiA and luxS genes in ۲۳ S. Typhimurium isolates from poultry. The quantitative real-time PCR assay was used to analyze the expression of sdiA and luxS in S. Typhimurium isolates in response to the treatment with sub-inhibitory concentrations of LAA and EGCG at ۴۵-min time point. All S. Typhimurium isolates showed the presence of sdiA and luxS genes (۱۰۰%). As result, the expression of QS-related genes was significantly reduced in S. Typhimurium isolates following treatment with LAA and EGCG. In conclusion, LAA and EGCG showed anti-QS activity with down-regulation of both sdiA and luxS genes in S. 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.

Epigallocatechin-۳-gallate, Licochalcone A, luxS gene, sdiA gene, Salmonella typhimurium, Quorum Sensing