(A) Schematic plot of the fraction of surviving bacteria in batch culture for a resistant strain (solid line), tolerant strain (dashed line) and susceptible strain (dotted line). (B–D) Examples of standard Disk diffusion assay results with ampicillin (10 μg). White dashed lines mark the diameter of the dark zone where the growth of bacteria is prevented by the antibiotics i.e. the “inhibition zone”. (B) Resistant strain (MGZ1-PSA11, Table 1) (MIC > 100 μg/ml). (C) Tolerant strain (tbl3a, MIC = 3 ± 1 μg/ml). (D) Susceptible strain (KLY, Table 1) with the same MIC as the strain shown in (C). The standard Disk diffusion assay does not distinguish between susceptible and tolerant strains. A slightly larger inhibition zone may be seen in tolerant strains because of delayed growth. Disk diameter: 6 mm.