TABLE 2.

First- and second-step and compensatory mutations associated with mupirocin resistance and their associated effects on resistance and competitive fitness in S. aureusa

Mutant and amino acid substitution in IleRSbMupirocin MIC (μg/ml)Competitive fitness
Wild type0.0161.00
First-step mupirocin-resistant mutants
    G593V10.92 ± 0.02
    G593V20.94 ± 0.05
    V631F20.99 ± 0.08
    V631F21.00 ± 0.03
    V588F80.94 ± 0.04
    V588F80.95 ± 0.01
    V588F80.93 ± 0.01
    V588F80.96 ± 0.05
    V588F160.99 ± 0.03
    V588F160.94 ± 0.04
Second-step mupirocin-resistant mutants
    G593V, V631F160.63 ± 0.03
    V631F, V588F320.57 ± 0.03
    V588F, R816C640.32 ± 0.06
    V588F, F563L1280.24 ± 0.08
    V588F, H67Q1280.33 ± 0.01
Fitness-restored mutants
    G593V, V631F, A196V20.99 ± 0.02
    G593V, V631F, A196V20.94 ± 0.07
    G593V, V631F, E190K21.00 ± 0.00
    G593V, V631F, E190K21.00 ± 0.01
    V631F, V588F, none321.01 ± 0.05
    V588F, R816C, E195K40.95 ± 0.01
    V588F, R816C, A196V80.93 ± 0.08
    V588F, F563L, none80.98 ± 0.01
    V588F, H67Q, Q67H80.96 ± 0.05
    V588F, H67Q, H396Q80.79 ± 0.07
    V588F, H67Q, H396Q160.79 ± 0.07
  • a The table is based on data presented elsewhere (48).

  • b The mutations in IleRS occurring at each stepwise selection are shown in boldface.