Determined with about 150 clinical isolates of Streptococcus pneumoniae. Source of data: J. Blondeau

The data in the previous slide can be expressed as time above MPC. When this is done, comparing the compounds is straightforward. The logic is that mutant growth is restricted by concentrations above MPC. The longer the threshold is exceeded, the better.

It may be that lethal activity for mutants will lower the threshold, but we don’t know that yet: the selection window hypothesis does not include consideration of lethal activity in order to cover compounds that only exhibit bacteriostatic activity.