High-Throughput Screening of Inhibitors Targeting Agr/Fsr Quorum Sensing in Staphylococcus aureus and Enterococcus faecalis

Staphylococcus aureus and Enterococcus faecalis employ cyclic peptide-mediated quorum sensing (QS) systems, termed agr and fsr respectively, to regulate the expression of a series of virulence genes. To identify quorum sensing inhibitors (QSIs) that target agr/fsr systems, an efficient screening system was established. In addition to the gelatinase-induction assay to examine E. faecalis fsr QS, the use of an S. aureus agr reporter strain that carries luciferase and green fluorescence protein genes under the agr P3 promoter facilitated the development of a high-throughput screen (HTS) for QSIs. As a result of screening of 906 actinomycetes culture extracts, four showed QSI activity against the agr and fsr systems without growth inhibitory activity. The extracts were purified on a small scale, and three HPLC peaks were obtained with obvious QSI activity. In sum, the established HTS system is a promising strategy for the discovery of anti-pathogenic agents targeting cyclic peptide-mediated QS in Gram-positive pathogens.