Identification and analysis of small molecule inhibitors of FosB from Staphylococcus aureus

Area of Science:

• Biochemistry
• Microbiology
• Drug Discovery

Background:

• Antimicrobial resistance (AMR) is a global health crisis.
• FosB, a Mn²⁺-dependent enzyme, inactivates the antibiotic fosfomycin and is present in pathogens like *Staphylococcus aureus*.
• FosB is a validated drug target, as *fosB* gene knockout reduces fosfomycin's minimum inhibitory concentration (MIC).

Purpose of the Study:

• To identify novel inhibitors of the *Staphylococcus aureus* FosB enzyme.
• To characterize the identified inhibitors through structural, kinetic, and synergy assays.
• To evaluate the potential of these inhibitors in combination therapy to overcome fosfomycin resistance.

Main Methods:

• High-throughput *in silico* screening of the ZINC15 database using structural similarity to phosphonoformate.
• Crystallography to obtain structures of FosB complexes with identified compounds.
• Enzyme kinetics assays to determine inhibitory potency.
• Synergy assays to assess the combined effect of inhibitors and fosfomycin on *S. aureus* growth.

Main Results:

• Eight potential FosB inhibitors were identified through *in silico* screening.
• Crystal structures of FosB-inhibitor complexes were obtained.
• Kinetic characterization confirmed the inhibitory activity of the compounds.
• Synergy assays indicated that some compounds may lower the MIC of fosfomycin in *S. aureus*.

Conclusions:

• Novel inhibitors of the *Staphylococcus aureus* FosB enzyme have been discovered.
• These compounds represent promising leads for developing new strategies against fosfomycin-resistant bacteria.
• The findings provide a foundation for future drug design targeting FosB to combat AMR.