Investigation of Cell-wall Targeting Strategies to Combat Antibiotic Resistance in Staphylococcus Aureus
Antibiotic resistant Staphylococcus aureus (S. aureus) includingmethicillin resistant S. aureus (MRSA) and vancomycin intermediate resistant S. aureus (VISA) are a major concern in world health care. MRSA is one of the most prevalent pathogens and causes severe infections in hospital and community settings. It is responsible for over 300,000 cases of MRSA infection globally every year. Though significant progress has been made in drug discovery, few novel antibiotics have been developed in the last decade or so. Reasons for this are partly because new targets are hard to find, partly because they are expensive to develop and partly because they come with a low return on investment and because there is extremely fast development of resistance even to new antimicrobials. This research aims to explore novel therapeutic and mechanistic approaches focused on cell wall regulation that overcome resistance. Following a detailed investigation, a β-lactam enhancer was identified and investigated for its mechanism of action in MRSA. It was observed that chemical 1 showed a strain-dependent and antibiotic-dependent enhancement in multiple MRSA strains. Mechanistic investigation demonstrated that chemical 1 reduced the availability of D-Ala-D-Ala precursor and altered the autolytic activity in MRSA strains. This suggested disruption of the cell wall potentially by reducing D-alanine availability. The second approach focused towards understanding the development of resistance in VISA strains. The VISA resistance phenotypes are often associated with mutations in two-component system like WalKR. This study made an attempt to investigate biochemical mechanism of the mutations in iv causing the resistant phenotypes. The wild-type WalK and WalR proteins were successfully expressed and purified for future biochemical characterization. Together, these results point to the importance of cell wall regulation in antibiotic resistance and show the promise of targeting the physiology and regulatory mechanisms of bacteria. This work offers a platform for developing new treatments based on adjuvants that will restore the efficacy of existing antibiotics.
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