Figure 1. Conceptual illustration of the diffusometry-enabled technique for AST.

(A) Fluorescent particles are measured by diffusometry and analyzed with the spatial cross-correlation algorithm for the information of diffusivity. Theoretically, a broad correlation width indicates strong diffusivity. The target microorganisms are captured based on immunoreactions. Motile or non-motile bacteria can lead to different diffusivity changes. (B) In the AST tests, motile bacteria, such as P. aeruginosa, boost the diffusivity initially owing to the bacterial motility. After more bacteria attach to particles, the diffusivity drops all the way down if the bacteria are resistant to antibiotics; otherwise, the diffusivity stops declining at a certain time point. By contrast, non-motile bacteria have no increased diffusivity along time. Apart from this difference, their other responses to antibiotics are similar to their motile counterpart.