Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2024

The effective use of antibiotics as curative and preventative measures to combat bacterial infections is being threatened due to the spread of resistant pathogens worldwide. In 2019, approximately 1.3 million deaths were directly attributable to resistant bacteria aligning with predictions that without appropriate action by 2050, we could expect to see up to 10 million annual deaths from resistant pathogens. Designing novel antibiotics to treat resistant infections is ideal, although, the development process is long and arduous. To bridge the gap until new antibiotics are discovered, an alternative option is to delve deeper into the understanding of currently approved antibiotics. By uncovering novel interactions, we can lay the groundwork for future drug development and enhance their effectiveness in clinical settings. Through advancements in medicinal chemistry, antibiotics can be modified to broaden their applications, extracting further insights and potentially utilizing them beyond their traditional role of infection treatment.

This work describes the use of a fluorescent daptomycin probe, synthesised in our group, to investigate the mode of action and resistance mechanisms of daptomycin, while evaluating the potential use of the probe as a rapid diagnostic tool. Flow cytometry, confocal microscopy and microfluidics have enabled us to investigate interactions between this fluorescent probe and a range of bacterial species under various conditions relating to it’s mode of action, resistance mechanisms and use in diagnostics.

Initial susceptibility testing of the probe showed consistent and substantial retention of potency compared to daptomycin across various susceptible and resistant bacterial species. We observed varied localisation profiles between susceptible and resistant bacterial species, providing insights into the effects daptomycin elicits in certain species. While assessing binding to bacteria, we showed that the probe was able to distinguish between resistant and susceptible Staphylococcus spp based on fluorescent signal. Within these resistant species, the probe appeared to be able to distinguish between two major mechanisms of daptomycin resistance, while also providing evidence of substantial binding variation between single-cells of resistant Staphylococcus aureus.