Mutant Selection Window Hypothesis Describes Emergence of Spontaneous Resistance

Antibiotic-resistant mutations occur spontaneously: They arise whether we treat with antibiotic. If we do not treat, no selective pressure exists to enrich and preferentially amplify the mutants. The pathogen population will contain a tiny subpopulation of resistant mutants that will remain small. Selective pressure exists when we use enough antibiotic to interfere with the growth of the majority, susceptible population. Then the mutants have a growth advantage. The minimal amount of antibiotic needed for mutant enrichment is difficult to determine accurately, but the minimal concentration that blocks the growth of 99% of the dominant, susceptible population serves as a slight overestimate. This value is easily measured by applying a known....