Cost of resistance (%) | No. of generations for: | |
---|---|---|

Fixation by compensatory mutation^{a} | Elimination^{b} | |

2 | 912 | 1,139 |

5 | 359 | 449 |

10 | 175 | 218 |

20 | 83 | 103 |

↵

*a*Assuming a frequency of 10^{−6}of a compensatory mutation restoring fitness; the values are the number of generations (*t*) required for the compensated resistance genotype to become fixed, i.e., to represent 99% of the drug-resistant population, determined by the following formula:*t*= ln[(*rc*/_{t}*r*)/(_{t}*rc*/_{t−1}*r*_{t−1})]/ln(1 − cost per generation), where*rc*and_{t}*rc*_{t−1}are absolute numbers of resistant mutants with a compensatory mutation.↵

*b*Calculated for a ratio of resistant to susceptible organisms of 99:1 at time zero; the values are the number of generations (*t*) to reach levels of spontaneous drug resistance frequency (10^{−8}) determined by the following formula:*t*= ln[10^{−8}(*r*_{0}/*S*_{0})]/ln(1 − cost per generation).