Diffusion–Convection Hybrid Microfluidic Platform for Rapid Antibiotic Susceptibility Testing
Ann V. Nguyen, Morteza Azizi, Mohammad Yaghoobi, Belgin Dogan, Shiying Zhang, Kenneth W. Simpson, Alireza Abbaspourrad
Abstract
Conventional antibiotic susceptibility testing (AST) assays such as broth microdilution and Kirby–Bauer disk diffusion are time-consuming (e.g., 24–72 h) and labor-intensive. Here, we present a microfluidic platform to perform AST assays with a broad range of antibiotic concentrations and controls. A culture medium stream was serially enriched with antibiotics along the length of the platform via diffusion and flow-directing mass convection mechanisms, generating a concentration gradient captured in a series of microchamber duplicates. We observed an agreement between the simulated and experimental concentration gradients and applicability to a variety of different molecules by changing the loading time according to a simple linear equation. The AST assay in our platform is based on bacterial metabolism, indicated by resazurin fluorescence. The small reaction volume enabled a minimum inhibitory concentration (MIC) to be determined in 4–5 h. Proof-of-concept functionality testing, using human isolates and clinically important antibiotics from different classes, indicated a high rate of agreement (94%: MIC within ±1 two-fold dilution of the reference method) of on-chip MICs and conventional broth microdilution. Overall, our results showed that this microfluidic platform is capable of determining antibiotic susceptibility in a rapid and reliable manner.