EXPLOITING BACTERIAL NUTRIENT STRESS IN THE TREATMENT OF ANTIBIOTIC-RESISTANT PATHOGENS

Abstract

To revitalize the antibiotic pipeline, it is critical to identify and validate new antimicrobial targets. An uncharted area of antibiotic discovery can be explored by inhibiting nutrient biosynthesis. Herein, we investigate the potential of inhibiting biotin biosynthesis in monotherapy and combination therapy approaches to treat multidrug-resistant Gram-negative pathogens. In chapter 2, we validate biotin biosynthesis as a viable target for Gram-negative pathogens. Historically, biotin biosynthesis was overlooked as a target in Gram-negative pathogens as there was no observed fitness cost associated with its inhibition in standard mouse infection models. We discovered traditional mouse models do not accurately represent the biotin levels in humans. We developed an innovative mouse model to account for this discrepancy, validating biotin biosynthesis as an antimicrobial target in the presence of human-mimicking levels of biotin. Exploiting this sensitivity, we show that an inhibitor of biotin biosynthesis, MAC13772, is efficacious against Acinetobacter baumannii in a systemic murine infection model. In chapter 3, we continue to investigate the potential of targeting biotin biosynthesis in a combination therapy approach. In this work, we identify the ability of MAC13772 to synergize with colistin exclusively against colistin-resistant pathogens. The first committed step of fatty acid biosynthesis requires biotin as a cofactor; therefore, it is indirectly inhibited through the action of MAC13772. We propose that the inhibition of fatty acid biosynthesis leads to changes in membrane fluidity and phospholipid composition, restoring colistin sensitivity. The combination of a fatty acid biosynthesis inhibitor and colistin proved superior to either treatment alone against mcr-1 expressing Klebsiella pneumoniae and colistin-resistant Escherichia coli murine infection models. Together, these data suggest that biotin biosynthesis is a robust antibiotic target for further development in monotherapy and combination therapy approaches.