Antibiotic Resistance 2D: Selection, Mutation & the Dosing Window

Dosing schedule

Full course

Intermittent

Under-dose

No treatment

Parameters

Antibiotic dose 1.5×MIC

Mutation rate 0.50%

Fitness cost of resistance 20%

Initial resistance 0%

Speed 3×

Presets

Full course (cure)

Under-dosing

No treatment

Aggressive

Live Readout

Population

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% resistant

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Generation

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Current dose

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Resistant MIC

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Outcome

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How it works

Each generation, cells above the antibiotic's minimum inhibitory concentration (MIC) are killed with probability scaling with the overshoot; survivors reproduce logistically toward a carrying capacity, and a susceptible offspring can mutate to resistance at the set mutation rate (with a small chance of reversion the other way). Resistant cells pay a fitness cost — slower reproduction — whenever the drug is not present to select for them.

Mutant selection window — the dose range between the susceptible MIC and the resistant MIC (4× higher here). Inside it, susceptibles die but resistant cells face reduced competition and expand — this is exactly what the "Under-dose" schedule holds the population in.
Full course — a steady dose above both MICs kills the colony before resistant mutants can establish a foothold.
Intermittent — six generations of dosing followed by six generations off, modelling poor adherence; it repeatedly re-opens the selection window.

💊 antibiotic active

Susceptible Resistant