Table 2.

Growth rate and MIC results

Group and mutationGrowth rateCLAa MIC (μg/ml)
InitialAfter subculture on CLA-free media
On CLA-free mediabOn CLA (2 μg/ml)c4 passages21 passages
In vitro mutants
 No mutation (WT)+++No growth<0.016<0.016<0.016
 A-2142 to G++++++>256>256>256
 A-2143 to G++++++643248
 A-2142 to C++++++>256>256>256
 A-2143 to C++++64164
 A-2142 to T++++64164
 A-2143 to T+No growth0.5<0.016<0.016
Clinical isolates
 No mutation (pretreatment)+++ND<0.016<0.016<0.016
 A-2142 to G+++ND>256>256>256
 A-2143 to G+++ND>256>256>256
  • a CLA, clarithromycin.

  • b For in vitro mutants, relative to the growth rate for the WT (NCTC 11637) (100%); for clinical isolates, relative to the growth rate for the paired pretreatment Clas isolate (100%). +++, 95 to 100%; ++, 95 to 70%; +, 50 to 70%.

  • c Relative to the growth rate for the Clar NCTC 11637 mutant with a mutation from A-2142 to G (100%). +++, 90 to 100%; ++, 70 to 90%. ND, not done.