Growth rates of susceptible and resistant M. tuberculosis strains during growth in vitro in single cultures and competitionsa

StrainMutationMIC (μg/ml)Single cultureCompetition culture
Doubling time (h)No. of divisionsRelative fitnessDoubling time (h)No. of divisionsRelative fitness
MutantWild typeMutantWild type
Ser531→Trp (TCG→TGG)>3231.610.60.71 ± 0.0936.324.39.413.90.67 ± 0.06
His526→Tyr (CAC→TAC)>3226.212.80.86 ± 0.0330.627. ± 0.05
Ser522→Leu (TCG→TTG)>1623.614.20.95 ± 0.0244.423.87.713.70.54 ± 0.03
H37RaNone (wild type)0.2524.513.70.91 ± 0.05
H37RvNone (wild type)0.2524.813.50.90 ± 0.05
  • a Data shown represent the average of two to three independent replicate experiments for each of two independent isolates of the same mutant type. Standard errors for relative fitness are indicated. In single and competition cultures, the doubling time was estimated from a plot of ln(CFU) = f(time), where the slope is ln2/doubling time (hours). The relative fitness is the ratio of doubling time (wild type)/doubling time (mutant).