Murray McGregor said:

> Your scenario relies on the assumption that resistance is the only
> variable at play and this is simply incorrect. Most cases are down to
> inefficiency and inconsistency of the delivery system of the treatment.
> Genetic difference is certainly a possibility, but not as you indicate,
> a certainty.

> Resistance is certainly selected for, but to say that exposure to
> treatment gives rise to new strains automatically is a leap too far.

A very good point.  I should not have used the word "certainly" and/or
should have added a qualification, such as "over time", "over multiple
treatment periods", or "on average over a large number of colonies".

        jim