Since quorum sensing (QS) is linked to the establishment of bacterial infection, its inactivation represents one of the newest strategies to fight bacterial pathogens. LsrK is a kinase playing a key role in the processing of autoinducer-2 (AI-2), a quorum-sensing mediator in gut enteric bacteria. Inhibition of LsrK might thus impair the quorum-sensing cascade and consequently reduce bacterial pathogenicity. Aiming for the development of a target-based assay for the discovery of LsrK inhibitors, we evaluated different assay set-ups based on ATP detection and optimized an automation-compatible method for the high-throughput screening of chemical libraries. The assay was then used to perform the screening of a 2000-compound library, which provided 12 active compounds with an IC50 ≤ 10 µM confirming the effectiveness and sensitivity of our assay. Follow-up studies on the positive hits led to the identification of two compounds, harpagoside and rosolic acid, active in a cell-based AI-2 QS interference assay, which are at the moment the most promising candidates for the development of a new class of antivirulence agents based on LsrK inhibition.
Keywords: antivirulence agent; bacterial communication; harpagoside; rosolic acid; virulence.