Single-Bacterium Diagnosis via Terahertz Near-Field Dielectric Nanoimaging.

Single-bacterium diagnostic methods with unprecedented precision and rapid turnaround times are promising tools for facilitating the transition from empirical treatment to personalized anti-infection treatment. Terahertz (THz) radiation, a cutting-edge technology for identifying pathogens, enables the label-free and non-destructive detection of intermolecular vibrational modes and bacterial dielectric properties. However, this individual dielectric property-based detection and the mismatched spatial resolution are limited for the single-bacterium identification of various species of pathogens. Here, we demonstrate a single-bacterium THz dielectric nanoimaging (STDN) strategy by customized THz scattering-type scanning near-field optical microscopy. The THz nanoimages of bacteria are explained and confirmed by theoretical modeling and near-field measurement. By synchronously tracking the bacterial intrinsic dielectric property and extrinsic morphology, the strategy achieved 99.3% and 91.6% accuracy in species identification and antibiotic susceptibility testing with the trained classifier within 2 hours. This proof-of-concept STDN strategy may propel precise bacterial infection management and help to counteract antibiotic resistance.