Figure 1.

Visual representation of the classical and updated models for development of antibiotic resistance in Mtb. The top portion shows a population of Mtb in the absence of drug selection (- DRUG). In the classical model, pre-existing resistant bacilli (red) in the population grow despite the addition of drug (+ DRUG) and susceptible bacteria (gray) are eliminated over time until only resistant cells remain. In the updated model, pre-existing resistance may still be present, but tolerant bacilli (yellow) may also be present and/or be induced by drug exposure. With drug selection, susceptible bacteria are again eventually eliminated, with resistance dominating the population over time. Figure created with BioRender.com.