A method for rapid antibiotic susceptibility testing by tracking sub-micron scale motion of single bacterial cells including obtaining a biological sample from a subject including live bacteria. Different doses of antibiotic are added to a multi-well glass slide and adding portions of the biological sample to the wells. Bacterial cells are tethered onto the surface. The tethered bacterial cells are imaged and tracked. Bacterial sub-micron motion of tethered cells is measured at the different doses. A processor performs statistical analysis on a population of cells for each antibiotic dose to generate an antibiotic dose curve proportional to the motion changes, where the antibiotic dose curve plots data including a decrease in movement over time indicating a proportional effectiveness of an antibiotic applied to a well.