Although using the mutant selection window hypothesis to restrict the development of de novo resistance is conceptually straightforward, it is politically difficult. This is because we must generally use drug concentrations that are higher than necessary to cure; thus patient altruism is required. We cannot ask someone to take more personal risk for the sake of people as a whole if no clinical studies have been done to support the idea. With S. pneumoniae we are running out of time, since resistance to one quinolone predisposes the bacterium to developing resistance to other quinolones.The next step is to conduct animal studies to relate the in vitro dimensions of the selection window to those occurring in vivo.