A system for and method of antimicrobial susceptibility testing includes detecting a resonance peak of a sensor provided with live microbes on a surface thereof; applying a substance to the live microbes; detecting a resonance peak of said sensor after application of said substance; determining a width of a top of each of said resonance peaks before and after application of the substance from one of: (1) a phase angle versus frequency plot where the phase angle is the phase angle of the electrical impedance of said sensor. (2) a real part of a plot of an electrical impedance versus frequency of said sensor. (3) a plot of a magnitude of electrical impedance versus frequency of said sensor, and (4) a phase angle versus frequency plot where the phase angle is the phase angle between an output voltage and an input voltage of said sensor, and comparing the determined widths of tops of said resonance peaks or standard deviations of the frequency of said resonance peaks to determine antimicrobial susceptibility including the minimum inhibitory concentration (MIC).