Optimising Droplet Microfluidics for Antibiotic Drug Discovery

Abstract

Antimicrobial resistance (AMR) represents a critical global health challenge that threatens the efficacy of modern medical procedures and our ability to treat infectious diseases. In 2019 alone, AMR was associated with more than 4.95 million deaths worldwide and by 2050, AMR could impose an additional healthcare burden of 1 trillion US dollars globally. Innovative approaches in drug discovery and development are required to improve current in vitro antibiotic susceptibility tests (AST). Droplet microfluidics have promising future applications in microbiology to miniaturise antibiotic screening platforms at the single-cell level. Here picodroplet technology was optimised for future droplet-based AST. Novel metal compounds were assessed for their activity against ESKAPE pathogens and mycobacterial species. Broad-spectrum activity was demonstrated, however when comparing two standard AST methods, results varied. Picodroplet technology was tested as an alternative to bulk cultures by producing monodisperse water-in-oil picodroplets of varying surfactant concentrations, culture media types, and droplet volumes. This study successfully demonstrated the generation of droplets with high monodispersity containing single or multiple MRSA bacterial cells, the maintenance of bacterial viability and proliferation within droplets, the observation of droplet shrinkage during bacterial growth, and the detection of differences in antibiotic susceptibility between the droplet and bulk cultures. Finally, dendrimer-based surfactants were assessed for their ability to prevent small molecule leakage out of the droplet bilayer to ensure antibiotics would not crosstalk between each droplet bioreactor. These optimisation investigations advances knowledge in the development of a rapid in vitro antibiotic susceptibility test which will reduce animal models and replicate the human infection environment for improved clinical translation.