Fig. 8. Impact of collateral IC90 changes on the evolution of drug resistance.
(A) If two drugs display collateral resistance (such as Tet and Chl), a combination of the two drugs will not effectively reduce resistance development, because they both will select for the same mutational profile. (B) In contrast, if the two drugs display collateral sensitivity (such as Amk and Chl), a combination of the two will be effective at reducing evolution of resistance because of suppressed fixation of resistance mutations in the population.