Label-free single-particle imaging approach for ultra-rapid detection of pathogenic bacteria in clinical samples

Rapid detection of pathogenic bacteria within a few minutes is the key to control infec-tious disease. However, rapid detection of pathogenic bacteria in clinical samples is quite a challenging task due to the complex matrix, as well as the low abundance of bacteria in real samples. Herein, we employ a label-free single-particle imaging approach to address this challenge. By tracking the scattering intensity variation of single particles in free solu-tion, the morphological heterogeneity can be well identified with particle size smaller than the diffraction limit, facilitating the morphological identification of single bacteria from a complex matrix in a label-free manner. Furthermore, the manipulation of convec-tion in free solution enables the rapid screening of low-abundance bacteria in a small field of view, which significantly improves the sensitivity of single-particle detection. As a proof of concept demonstration, we are able to differentiate the group B streptococci (GBS)-positive samples within 10 min from vaginal swabs without using any biological reagents. This is the most rapid and low-cost method to the best of our knowledge. We believe that such a single-particle imaging approach will find wider applications in clinical diagnosis and disease control due to its high sensitivity, rapidity, simplicity, and low cost.

Automated summary

This study presents a label-free single-particle imaging approach for rapid detection of pathogenic bacteria in complex matrix. By tracking the scattering intensity variation of single particles in free solution, the morphological heterogeneity of bacteria can be identified. The manipulation of convection in free solution enables the rapid screening of low-abundance bacteria. As a proof of concept, the technique successfully differentiated positive samples within 10 minutes without using any biological reagents.