Fusidic Acid Resistance Mechanisms in Staphylococcus aureus

Staphylococcus aureus resistance to fusidic acid arises via several complementary strategies. The most common involves mutations in the fusA gene encoding elongation factor G (EF-G), which reduce drug binding and lock EF-G onto the ribosome, thereby preventing the antibiotic from exerting its inhibitory effect. These point mutations often confer high-level resistance but can impose a fitness cost that bacteria may offset through compensatory adaptations. Another major pathway is the acquisition of fusB-family genes, which produce proteins that bind EF-G and displace fusidic acid, restoring normal translation even in the presence of the drug. These protective genes are frequently located on plasmids or staphylococcal chromosomal cassettes, facilitating horizontal transfer across strains. Additional mechanisms, such as altered uptake or efflux and enzymatic modification, have been described but appear less prevalent clinically. The combined action of these pathways has led to a global rise in fusidic acid resistance among both methicillin-susceptible and methicillin-resistant S. aureus, undermining a key topical and systemic therapy. Ongoing research into the molecular basis of resistance, its fitness implications and potential chemical inhibitors is guiding more effective surveillance, stewardship and treatment strategies.

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Fusidic Acid Resistance Mechanisms in Staphylococcus aureus publication trend

The graph below shows the total number of articles in fusidic acid resistance mechanisms in staphylococcus aureus across all publications each year (not limited to Nature Index journals).

Technical terms

Elongation factor G (EF-G): A GTP-dependent ribosomal translocase essential for polypeptide elongation and recycling, and the primary target of fusidic acid.

fusA/fusB genes: fusA encodes EF-G; mutations in fusA reduce drug binding. fusB encodes a protective protein that dislodges fusidic acid from EF-G.

Minimum inhibitory concentration (MIC): The lowest concentration of antibiotic that prevents visible bacterial growth in vitro.

Transcriptomics: The large-scale study of RNA transcripts to assess global changes in gene expression under defined conditions.

Metabolomics: The comprehensive analysis of small-molecule metabolites within a biological sample, revealing shifts in metabolic pathways.

References

1. The global prevalence of fusidic acid resistance in clinical isolates of Staphylococcus aureus: a systematic review and meta-analysis. Antimicrobial Resistance & Infection Control (2021).
2. Structure and function of FusB: an elongation factor G-binding fusidic acid resistance protein active in ribosomal translocation and recycling. Open Biology (2012).
3. Transcriptomic and Metabolomic Analysis of a Fusidic Acid-Selected fusA Mutant of Staphylococcus aureus. Antibiotics (2022).
4. The Prevalence and Determinants of Fusidic Acid Resistance Among Methicillin-Resistant Staphylococcus aureus Clinical Isolates in China. Frontiers in Medicine (2021).