Mechanisms of activity, resistance and toxicity
Understanding the mechanisms of action, resistance and toxicity are critical for the discovery, development and optimal use of antimicrobials. D4's research allows the rational design of new antimicrobials by enhancing antimicrobial activity, overcoming common resistance mechanisms and minimising host toxicity. Furthermore, this knowledge is crucial for optimising clinical use of antimicrobials in patients.
D4 researchers employ a range of cutting-edge techniques to explain mechanisms of action, resistance and toxicity. These include:
- molecular imaging
- structural biology
- molecular biology
- computational biology
- mechanism-based modelling
Most clinically-used treatments for malaria and human African trypanosomiasis act by unknown mechanisms, and many newly discovered anti-parasitic compounds have no known mode of action.
D4 research in this area combines parasite cultures of Plasmodium falciparum or Trypanosoma brucei with metabolomics and other biochemical techniques to investigate the mechanisms of action, resistance and toxicity of common classes of antimalarial and antitrypanosomal compounds.
While the bactericidal action of the polymyxin antibiotics is thought to be initiated by their interaction with lipopolysaccharide (LPS) of the outer membrane of Gram-negative bacteria, subsequent steps in the killing action are largely unknown.
D4 research in this area has addressed many aspects of the mechanisms of resistance to polymyxins, such as those that involve changes to the chemical composition or loss of LPS. However, many questions remain unanswered about the mechanisms of polymyxin resistance.
Importantly, nephrotoxicity is the major dose-limiting factor with intravenous polymyxins. Even though polymyxin-induced nephrotoxicity is related to apoptosis of kidney tubular cells, the detailed mechanism is not clear.
Ongoing studies aim to elucidate the molecular mechanisms of activity and resistance of polymyxins in Gram-negative bacteria and nephrotoxicity. To address these questions, our laboratory employs cutting-edge techniques such as molecular imaging, structural biology, molecular biology, genomics, transcriptomics, proteomics, metabolomics, lipidomics, computational biology and bioinformatics.
Cell wall synthesis inhibitors
All bacteria use different penicillin-binding proteins (PBPs) and a series of other enzymes to synthesise and remodel the cell wall. These enzymes are critical for bacterial viability. However, significant gaps exist in the understanding of the biochemical function(s) and molecular interactions of these enzymes. This is especially true for extremely common scenarios where multiple enzymes are bound by an antibiotic and thereby inactivated.
D4 research in this area is developing and applying innovative experimental and mechanism-based modelling approaches to identify the most important PBPs and other enzymes involved in cell wall synthesis of critical bacterial pathogens. D4 researchers are using static and latest dynamic in vitro infection models (including the hollow fibre system) to maximise bacterial killing and minimise emergence of resistance over clinically relevant durations of therapy.
This research includes the development of innovative combination dosage regimens to eradicate non-replicating persisters and minimise resistance. Our research projects on cell wall synthesis inhibitors are performed in collaboration with leading experts on bacterial genomics and molecular and clinical microbiology.
Aminoglycosides are important members of our therapeutic armamentarium to combat bacterial superbugs. These antibiotics have predictable pharmacokinetics with high plasma concentrations, negligible plasma protein binding and primarily renal elimination. Aminoglycosides provide rapid and extensive bacterial killing. However, emergence of resistance during monotherapy can be extensive. Therefore, aminoglycosides are most commonly used in combination therapies.
Synergistic and extensive bacterial killing without emergence of resistance is often found for combinations of an aminoglycoside plus another antibiotic (such as a beta-lactam). However, the mechanisms of bacterial killing by aminoglycosides are still not fully understood and very few studies assessed the mechanisms of synergistic killing and resistance prevention.
D4 research in this area is clarifying these mechanisms for aminoglycosides by an integrated experimental and mechanism-based modelling strategy.