Fusidic acid, a fusidane that interferes with protein synthesis via the translocase enzyme, is mainly notable for its activity against staphylococci, coagulase-positive and negative, whether or not they are resistant to methicillin and related penicillins. It is also active against corynebacteria and against many genera of strict anaerobes and microaerophiles. Mutants showing resistance, by more than one mechanism, may readily be selected in vitro. Combination of fusidic acid with other antibiotics generally gives addition or indifference, but also delays emergence of resistant mutants.