Microfluidic-based observation of local bacterial density under antimicrobialconcentration gradient for rapid antibiotic susceptibility testing

摘要

The need for accurate and efficient antibiotic susceptibility testing (AST) has beenemphasized with respect to the emerging antimicrobial resistance of pathogenic bacteriawhich has increased over the recent decades. In this study, we introduce a microfluidicsystem that enables rapid formation of the antibiotic concentration gradient withconvenient bacterial growth measurement based on color scales. Furthermore, we expandedthe developed system to analyze combinatory effects of antibiotics and measured thecollective antibiotic susceptibility of bacteria compared to single microfluidic ASTmethods. By injecting a continuous flow precisely into the channel, the system enabled theconcentration gradient to be established between two parallel channels of differentantibiotic concentrations within 30 min, before bacteria enter the exponential growthphase. Moreover, the local bacterial growth levels under antibiotic gradient werequantitatively determined by calculating the position-specific grayscale values from themicroscopic images and were compared with the conventional optical density measurementmethod. We tested five antibiotic types on our platform for the pathogenic Gram-negativebacteria strain , and we were able to determine theminimum inhibitory concentration (MIC) at which 90% to 95% of bacterial growth wasinhibited. Finally, we demonstrated the efficacy of our system by showing that most of theantibiotic MICs determined in our platform show good agreement with the MIC rangesuggested by the Clinical and Laboratory Standards Institutes.