Adjunctive use of rifampin for the treatment of Staphylococcus aureus infections

Background: Staphylococcus aureus causes severe life-threatening infections and has become increasingly common, particularly methicillin-resistant strains. Rifampin is often used as adjunctive therapy to treat S aureus infections, but there have been no systematic investigations examining the usefulness of such an approach. Methods: A systematic review of the literature to identify in vitro, animal, and human investigations that compared single antibiotics alone and in combination with rifampin therapy against S aureus. Results: The methods of in vitro studies varied substantially among investigations. The effect of rifampin therapy was often inconsistent, it did not necessarily correlate with in vivo investigations, and findings seemed heavily dependent on the method used. In addition, the quality of data reporting in these investigations was often suboptimal. Animal studies tended to show a microbiologic benefit of adjunctive rifampin use, particularly in osteomyelitis and infected foreign body infection models; however, many studies failed to show a benefit of adjunctive therapy. Few human studies have addressed the role of adjunctive rifampin therapy. Adjunctive therapy seems most promising for the treatment of osteomyelitis and prosthetic device-related infections, although studies were typically underpowered and benefits were not always seen. Conclusions: In vitro results of interactions between rifampin and other antibiotics are method dependent and often do not correlate with in vivo findings. Adjunctive rifampin use seems promising in the treatment of clinical hardware infections or osteomyelitis, but more definitive data are lacking. Given the increasing incidence of S aureus infections, further adequately powered investigations are needed.