A real-time simultaneous measurement on a microfluidic device for individual bacteria discrimination

Rapid detection of pathogenic bacteria is one of the important social issues for preventing and identifying cause of problems affecting human health. Ionic current sensing through pores has shown the ability to electrically measure bacteria. However, there is an inherent limitation to discriminate chemical characteristics of bacteria for existing ionic current sensing methods Here we propose a real-time simultaneous measurement method, which combines ionic current sensing and fluorescence observation on a microfluidic device. Our method can detect not only the size of individual bacteria passing through a micropore but also observe their stainability based on chemical properties of bacterial cell surface within 300 ms. We succeeded in discriminating each bacterium in a solution mixture including contaminant particles by combining highly accurate ionic current sensing which can detect a size difference of 70 nm, and fluorescence observation which can discriminate internal structures such as those that define bacteria as gram-positive or gram-negative. Our method can be applied to not only on-site bacteria detection but also to screening technology.