The present invention relates to methods and compositions for preventing and treating Staphylococcus aureus in a subject. Therapeutic compositions of the present invention comprise leukocidin E and/or D proteins or polypeptides and anti-leukocidin E and/or D antibodies. The invention further relates to methods of identifying inhibitors of LukE/D cytotoxicity and inhibitors of LukE/D-leukocyte binding.