Molecular basis of fusB-mediated resistance to fusidic acid in Staphylococcus aureus

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Fusidic acid resistance in Staphylococcus aureus is a growing clinical concern.
• The genetic basis and molecular mechanisms of fusidic acid resistance, particularly the fusB determinant, remain incompletely understood.

Purpose of the Study:

• To clone, sequence, and characterize the fusB gene responsible for fusidic acid resistance in S. aureus.
• To elucidate the mechanism by which the FusB protein confers resistance to fusidic acid.

Main Methods:

• Cloning, sequencing, and overexpression of the fusB gene from plasmid pUB101.
• Bioinformatic analysis, reporter gene fusions for regulatory studies, and protein purification.
• In vitro assays using staphylococcal and E. coli translation systems to assess FusB protein function and binding to EF-G.

Main Results:

• The single gene fusB was identified and cloned, capable of conferring fusidic acid resistance in S. aureus.
• FusB encodes a 25 kDa cytoplasmic protein, with homologues found in other Gram-positive bacteria.
• Resistance expression is regulated by translational attenuation; purified FusB protein specifically binds staphylococcal EF-G and protects against fusidic acid inhibition.

Conclusions:

• The fusB gene is sufficient to confer fusidic acid resistance in S. aureus.
• FusB functions by directly interacting with the staphylococcal elongation factor G (EF-G), the drug's target.
• The findings provide a molecular understanding of fusidic acid resistance mediated by FusB, crucial for combating antibiotic resistance.