Inhibition of Fosfomycin Resistance Protein FosA from Pseudomonas aeruginosa

Antimicrobial resistance is an urgent issue in modern-day medicine. One way to address this problem is to repurpose and restore the function of older antibacterials through the specific targeting of antibiotic-modifying enzymes produced by bacteria. Fosfomycin is an antibiotic that is attractive for repurposing because it has been previously approved for use in uncomplicated urinary tract infections (UTIs) and is widely regarded as safe with no known off-target interactions. The primary limitation to fosfomycin usage has been the emergence of fosfomycin resistance enzymes. FosAPa is the fosfomycin resistance enzyme from Pseudomonas aeruginosa. We identified and evaluated several potential inhibitors of FosAPa using high-throughput virtual screening (HTVS) and 31P-NMR. In addition, we obtained X-ray crystal structures of FosAPa with the inhibitors bound in the active site to gain insights into important protein-ligand interactions necessary for the potential structure-based drug design. Preliminary cell-based assays were performed to evaluate the effect that the inhibitors have on the minimum inhibitory concentration (MIC) of fosfomycin in P. aeruginosa. Our results provide an initial scaffold for structure-activity relationships and future compound modifications for combating fosfomycin resistance in P. aeruginosa and other FosA-containing Gram-negative pathogens.