Abstract: A method for antibacterial susceptibility testing includes preparing a set of two or more samples of a plurality of bacterial cells from a patient; adding a different amount of a selected drug to each sample; illuminating at least a portion of a sample using a coherent illumination source; capturing a series of speckle images over time of at least a portion of the illuminated sample; and determining an inhibition status of the sample using a machine-learning classifier applied to the series of speckle images. The steps of illuminating the sample, capturing a series of images, and determining an inhibition status are repeated for each sample of the set of two or more samples. The method may include transforming the series of speckle images to a frequency series of speckle images; and determining the inhibition status of the sample uses the machine-learning classifier applied to the frequency series of speckle images.