Mapping of quorum sensing interaction network of commensal and pathogenic staphylococci

Staphylococci utilize secreted autoinducing peptides (AIPs) to regulate group behavior through a process called quorum sensing (QS). For pathogenic staphylococci, such as Staphylococcus aureus, QS regulates the expression of major virulence factors, and QS inhibition has been proposed as an alternative to antibiotics for the treatment of infections with methicillin-resistant S. aureus (MRSA). Here, we surveyed the interaction map between QS systems of the pathogens S. aureus, Staphylococcus epidermidis, and Staphylococcus lugdunensis and all the currently known staphylococcal AIPs, covering 21 different species. We identified six of these ribosomally synthesized and post-translationally modified peptides (RiPPs) in this study and compiled the full collection of AIPs by chemical synthesis. The resulting mapping provided 280 QS interactions that were divided into human- and animal-associated staphylococci, showing substantial differences in inhibitory potencies between the groups. AIPs of the bovine-associated species Staphylococcus simulans displayed potential as QS inhibitors toward the investigated strains and were therefore chosen as a starting point for a structure-activity relationship study. This study provides insights into the requirements for QS interference, yielding the most potent inhibitors reported to date for S. epidermidis and S. lugdunensis. Furthermore, we tested an S. simulans AIP as an anti-virulence agent in an assay to assess the risk of acquired suppression of the inhibitory effect, and we established an assay set-up to successfully monitor agr deactivation of virulent MRSA by the QS inhibitor. Finally, a peptide was shown to attenuate skin infection caused by MRSA in a mouse model. Our results reveal a complex network of staphylococcal interactions and provide further impetus for the investigation of QS modulation in the targeting of antibiotic-resistant pathogens.IMPORTANCEBacteria from the Staphylococcus genus produce macrocyclic peptides, called autoinducing peptides (AIPs), used in inter-cell communication with their kin. Differences in AIP sequence and length produced by different staphylococcal species can result in communication interference, altering the physiology of co-inhabiting staphylococci in complex microbiotas. Opportunistic pathogens like Staphylococcus aureus regulate the expression of toxins using this peptide-mediated communication, and its inhibition has, therefore, been proposed as a strategy to target infections caused by methicillin-resistant S. aureus (MRSA). The systematic mapping of AIP activities, structure-activity relationship studies, and evaluation of resistance development provided in this paper, therefore, serve as a resource for the future discovery of inhibitory peptides for the investigation of bacterial communication.