The development of antibiotic-resistant bacteria is a worldwide health-related emergency that calls for new tools to study the bacterial metabolism and to obtain fast diagnoses. Indeed, the conventional analysis timescale is too long and affects our ability to fight infections. Slowly growing bacteria represent a bigger challenge, since their analysis may require up to months. Among these bacteria, Mycobacterium tuberculosis, the causative agent of tuberculosis has caused, only in 2016 more than 10 million new cases and 1.7 million deaths. We employed a particularly powerful nanomechanical oscillator, the nanomotion sensor, to characterize rapidly and in real time a tuberculous and a non-tuberculous bacterial species, Bacillus Calmette-Guérin and Mycobacterium abscessus exposed to different antibiotics. Here, we show how high speed and high sensitivity detectors, the nanomotion sensors, can provide a rapid and reliable analysis of different mycobacterial species, obtaining qualitative and quantitative information on their response to different drugs.