Characterization of spontaneous N. gonorrhoeae mutants: group I, susceptible spontaneous mutants from erythromycin and azithromycin-resistant N. gonorrhoeae strains; group II, erythromycin- and azithromycin-resistant N. gonorrhoeae mutants from susceptible N. gonorrhoeae strains

GroupStrain(s)OriginERY MIC (μg/ml)aAZM MIC (μg/ml)b23S rRNA mutation at position 2611 (E. coli numbering system)cmtr mutationd
Allele 1Allele 2Allele 3Allele 4
I20869Clinical isolate32.0-64.04.0TTCTNo mutation
20870Clinical isolate32.0-64.04.0TTCTNo mutation
LK368Spontaneous mutant of 208694.01.0CTCTNo mutation
LK369Spontaneous mutant of LK3682.00.5CCCTNo mutation
II22831Clinical isolate0.50.125CCCCNo mutation
21305Clinical isolate0.50.125CCCCInsertion T
21855Clinical isolate1.00.125CCCCNo mutation
LK361, LK362Spontaneous mutant of 228318.02.0CCCCDeletion A
LK363, LK364Spontaneous mutant of 2130532.04.0TTTTInsertion T
LK359, LK360Spontaneous mutant of 2185564.08.0TTTTNo mutation
LK366Spontaneous mutant of 2283164.032.0TTTCDeletion A
LK367Spontaneous mutant of 2283164.032.0TTCTDeletion A
  • a ERY, erythromycin.

  • b AZM, azithromycin.

  • c C2599T for alleles 1 and 2 and C2605T for allele 4 (N. gonorrhoeae numbering).

  • d mtr mutation is the single-base-pair (A) deletion in the 13-bp inverted repeat in the mtrR-mtrC promoter region.