Surotomycin is an investigational oral antibiotic. This antibiotic is under investigation by Merck & Co (who acquired Cubist Pharmaceuticals) for the treatment of life-threatening Diarrhea, commonly caused by the bacterium Clostridium difficile. Surotomycin is an investigational oral antibiotic. This antibiotic is under investigation by Merck & Co (who acquired Cubist Pharmaceuticals) for the treatment of life-threatening Diarrhea, commonly caused by the bacterium Clostridium difficile.