Figure 4: Colonies detected with the TDtest are typically not due to resistant mutants. | Scientific Reports

Figure 4: Colonies detected with the TDtest are typically not due to resistant mutants.

From: TDtest: easy detection of bacterial tolerance and persistence in clinical isolates by a modified disk-diffusion assay

Figure 4

(A) The inhibition zone after the first step of the TDtest (exposure to antibiotics only- Imipenem 2.5 μg). The dashed lines mark the diameter of the inhibition zone. (B) The inhibition zone after the second step of the TDtest (replacement of the antibiotic disk with a glucose-containing disk). Appearance of colonies inside the inhibition zone occurs after a few hours and indicates tolerant/persistent bacteria. (C) A colony that grew inside the inhibition zone (panel B, white arrow) was picked and retested for the same antibiotic after overnight growth. The dashed lines mark the diameter of the inhibition zone, same as in panel A. Similar results were obtained on more colonies and also for ampicillin (Supplementary Fig. S3), see also Supplementary Fig. S4. Disk diameter: 6 mm.

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