Question 1

How do tolerance, persistence and resistance differ?

Accepted Answer

Resistance raises the concentration needed to inhibit growth. Tolerance leaves that concentration unchanged but slows killing across the whole population. Persistence describes a subpopulation surviving while the majority dies quickly. The three call for different measurements, and using the words interchangeably makes a result hard to place against existing work.

Question 2

What does a biphasic killing curve show?

Accepted Answer

That the population is not uniform in its response. A rapid initial decline followed by a slower phase indicates a surviving fraction behaving differently. Seeing it requires sampling densely enough and over a long enough period, with a detection limit low enough that the second phase is not lost at the floor.

Question 3

How is persistence confirmed rather than assumed?

Accepted Answer

By regrowing the survivors and retesting susceptibility. If the regrown population is as susceptible as the original, the survival was phenotypic rather than genetic. Skipping this step leaves open the possibility that a resistant mutant was selected, which is a different phenomenon with different consequences.

Question 4

Are persisters simply dormant cells?

Accepted Answer

The association with slow growth is real but not absolute, and treating dormancy as the definition overstates what has been shown. Some survivors are metabolically active. Framing dormancy as one contributing state rather than as the mechanism keeps the interpretation aligned with the available evidence.

Question 5

Why is single-cell observation useful here?

Accepted Answer

Because the phenomenon is defined by a minority. Population measurements average over cells behaving differently, so a small surviving fraction is invisible in bulk data. Microfluidic observation tracks individual cells before, during and after exposure, showing when the state arises and whether it reverses.

Question 6

How strong is the evidence for treatment failure?

Accepted Answer

Suggestive rather than settled. The laboratory phenomenon is well established and animal work supports a contribution, but direct human evidence linking a surviving subpopulation to a specific relapse is limited. Stating the strength of the link honestly is more defensible than presenting it as established.

Question 7

Does the growth medium influence results?

Accepted Answer

Substantially. Carbon source, stationary phase entry, inoculum preparation and prior starvation all shift the surviving fraction, sometimes by orders of magnitude. Reporting culture history in full is therefore necessary for comparison between studies, and variation between laboratories often traces back to exactly this.

Microbiology

Microbiology

Research Frontiers in Antibiotic Persistence and Phenotypic Tolerance