Fusidic acid’s Resistance

Because the drug is not licensed for use in the U.S., there are no Clinical and Laboratory Standards Institute standard definitions of fusidic acid resistance. However, in vitro susceptibility studies of U.S. strains of several bacterial species such as S. aureus, including MRSA and coagulase negative Stahylococcus, indicate potent activity against these pathogens^。

In the UK and Australia, susceptibility is defined as a minimum inhibitory concentration (MIC) of 0.25 mg/l or 0.5 mg/l or less. Resistance is defined as an MIC of 2 mg/l or more. In laboratories using disc diffusion methods, susceptibility for a 2.5 µg disc is defined as a zone of 22 mm or more, and resistance is defined as a zone of 17 mm or less; intermediate values are defined as intermediate resistance.

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