Identification of a S. aureus virulence factor by activity-based protein profiling (ABPP)

Serine hydrolases play diverse roles in regulating host-pathogen interactions in a number of organisms, yet few have been characterized in the human pathogen Staphylococcus aureus. Here, we describe a chemical proteomic screen that identified 10 previously uncharacterized S. aureus serine hydrolases that mostly lack human homologues. We termed these enzymes Fluorophosphonate-binding hydrolases (FphA-J). One hydrolase, FphB, can process short fatty acid esters, exhibits increased activity in response to host cell factors, is located predominantly on the bacterial cell surface in a subset of cells, and is concentrated in the division septum. Genetic disruption of the fphB gene confirms that the enzyme is dispensable for bacterial growth in culture but crucial for establishing infection in distinct sites in vivo. A selective small molecule inhibitor of FphB effectively reduces infectivity in vivo, suggesting that it may be a viable therapeutic target for the treatment or management of Staphylococcus infections.