Catalase-Driven Microflow Displacement for Rapid, Visual Antimicrobial Susceptibility Testing

Rapid and accurate antimicrobial susceptibility testing (AST) is essential for guiding effective antibiotic therapy and combating antimicrobial resistance (AMR). Here, we present an instrument-free phenotypic AST method that integrates catalase-mediated hydrogen peroxide decomposition with microflow tubing displacement for naked-eye readout. The system employs a disposable syringe as the reaction chamber and a micrometer-scale PTFE tube as the displacement scale. Gas generated by bacterial catalase activity drives ink movement within the tubing, enabling visual discrimination between susceptible and resistant strains within ∼60 min. Using <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> as model pathogens, we optimized bacterial inoculum size, hydrogen peroxide concentration, and incubation time to maximize sensitivity. Validation with 63 clinical isolates against four antibiotics following Clinical and Laboratory Standards Institute (CLSI) guidelines demonstrated high concordance with standard AST results. Furthermore, the method successfully distinguished susceptibility in 18 culture-free urinary tract infection samples. This low-cost, rapid, and portable platform has potential for point-of-care AST, particularly in resource-limited settings.