Figure 5. Selection of de novo resistant mutants at sub-inhibitory concentrations of antibiotics.
A total of 20 independent lineages of S. typhimurium were serially passaged in Mueller-Hinton medium containing 1 µg/ml streptomycin. Every 100 generations approximately 105 cells were plated onto LB agar containing different concentrations of streptomycin and the fractions of resistant mutants were calculated. The data points are grouped by number of generations of growth and resistance level, and in each of these data sets one data point represents the fraction of cells present in one lineage capable of growth at the specified antibiotic concentrations. Please note that data points at the baseline will overlap.