Rifaximin intake leads to emergence of rifampin-resistant staphylococci

Summary Objectives Rifaximin is a poorly absorbed non-systemic antimicrobial agent used in various gastrointestinal disorders. Rifampin is pivotal for the treatment of staphylococcal foreign body infections and resistance develops rapidly during monotherapy. The close structural relation of rifaximin to rifampin may lead to cross-resistance. The aim of our study was to determine whether rifampin-resistance emerges in human skin staphylococci during or after oral intake of rifaximin. Methods Rifampin resistance of skin staphylococci in healthy volunteers during and after intake of rifaximin was determined by E-Test. Results Seven out of eleven volunteers developed rifampin-resistant staphylococci after intake of rifaximin. A total of eleven rifampin-resistant and three rifampin-intermediate staphylococcal isolates were found. Before or during intake no resistant isolate was detected. Shortly after discontinuation the rifampin-resistant strains were primarily isolated from the perianal skin, a few weeks later they were found more frequently on the skin of the hands and lower arms. Conclusion Our data show that rifampin-resistant staphylococci emerge after intake of rifaximin. Since rifampin resistance is associated with treatment failure in staphylococcal foreign body infections, we conclude that rifaximin should be avoided in patients at risk for these infections.