Gradient-Based Microfluidic Platform for One Single Rapid Antimicrobial Susceptibility Testing

Antimicrobial resistance is a growing problem, necessitating rapid antimicrobial susceptibility testing (AST) to enable effective in-clinic diagnostic testing and treatment. Conventional AST using broth microdilution or the Kirby-Bauer disk diffusion are time-consuming (e.g., 24-72 h), labor-intensive, and costly and consume reagents. Here, we propose a novel gradient-based microchamber microfluidic (GM(2)) platform to perform AST assay for a wide range of antibiotic concentrations plus zero (positive control) and maximum (negative control) concentrations all in a single test. Antibiotic lateral diffusion within enriched to depleted (C-max and zero, respectively) cocurrent flowing fluids, moving alongside a micron-sized main channel, is led to form an antibiotic concentration profile in microchambers, connected to the depleted side of the main channel. We examined the tunability of the GM(2) platform, in terms of producing a wide range of antibiotic concentrations in a gradient mode between two consecutive microchambers with changing either the loading fluids' flow rates or their initial concentrations. We also tested the GM(2) platform for profiling bacteria associated with human Crohn's disease and bovine mastitis. Time to result for performing a complete AST assay was similar to 3-4 h in the GM(2) platform. Lastly, the GM(2) platform tracked the bacterial growth independent of an antibiotic mechanism of action or bacterial species in a robust and easy-to-implement fashion.

Automated summary

This study proposed a novel gradient-based microchamber microfluidic platform for rapid antimicrobial susceptibility testing, which can cover a wide range of antibiotic concentrations in a single test with a short time to results. The platform demonstrated good tunability and applicability for profiling different bacteria, and tracked bacterial growth independently of antibiotic mechanism or bacterial species in a robust and easy-to-implement manner.