Studies of a genomic fosfomycin resistance protein from Pseudomonas aeruginosa

Abstract

CHEMISTRY

STUDIES OF A GENOMIC FOSFOMYCIN RESISTANCE PROTEIN FROM PSEUDOMONAS AERUGINOSA

RACHEL PHARRIS RIGSBY

Dissertation under the direction of Professor Richard N. Armstrong In the last two decades it has become increasingly clear that the efficacy of antibiotics for the treatment of infectious diseases is in jeopardy due to the appearance of drug resistant strains of microorganisms. Understanding the mechanisms of antimicrobial resistance is crucial for effective patient care in the clinic and essential for developing strategies to enhance biodefense against intentionally disseminated pathogens. Fosfomycin, (1R, 2S)-expoxypropylphosphonic acid, is a potent, broad-spectrum antibiotic effective against both Gram-positive and Gram-negative microorganisms. A decade after its introduction, plasmid-mediated resistance to fosfomycin was observed in the clinic. Previous investigations established that resistance was due to a metalloenzyme (FosA) that catalyzes the addition of glutathione to the antibiotic, rendering it inactive. Similar resistance elements have now been identified in the genomes of several pathogenic microorganisms. Genomic and biochemical analyses suggest that there are three distinct subgroups of metalloenzymes, termed FosA, FosB, and FosX, that confer resistance through somewhat different chemical mechanisms. The objectives of this research were to characterize a genomically encoded FosA protein from Pseudomonas aeruginosa involved in microbial resistance to fosfomycin and to elucidate the underlying structural and mechanistic enzymology of resistance. Particular attention was focused on development of enzyme inhibitors and characterization of several active-site mutants. The evolution of the resistance proteins was also investigated.

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