This disclosure describes pharmaceutical compositions and methods that involve the use of a polyhydroxyanthraquinone to inhibit quorum sensing in a microbe. In some embodiments, the polyhydroxyanthraquinone may be effective to antagonize AgrA function in a microbe. In other embodiments, the polyhydroxyanthraquinone may be effective for prophylactic and/or therapeutic treatment of a skin and soft tissue infection (SSTI) of a subject by a microbe. In still other embodiments, the polyhydroxyanthraquinone may be effective to reduce, limit progression, ameliorate, or resolve, to any extent, a symptom or clinical sign of infection by a microbe.
