Table 2.

Phenotypic analysis of passage-derived strains with mutations in 23S rRNA

StrainaMIC (μg/ml) ofb:MutationHeterozygosity
Parent 1T00.
Mutant 1Az3.120.780.781.560.390.20500.010.02C2611A1C:3A
Parent 6T00.
Mutant 6Az12.5>1001000.786.250.20>1000.390.01C2611G0C:4G
Parent 3T00.
Mutant 3Az>20012.53.12>1001.560.201.560.010.02A2059G2A:2G
Parent 8T00.
Mutant 8Az>200>1001006.25253.1212.50.100.05A2058G2A:2G
ATCC 496190.120.0300.030.200.39≤
  • a Strains designated nT0 are the parental, macrolide-susceptible strains; strains designated asnAz are the mutants that were characterized following passage in azithromycin (29). ATCC 49619 is the control strain suggested by the NCCLS (25).

  • b AZI, azithromycin; ERY, erythromycin; CLAR, clarithromycin; SPIR, spiramycin; LINC, lincomycin; CLIN, clindamycin; STREP B, streptogramin B; TELI, telithromycin (HMR-3647); PEN, penicillin G. The 14-membered macrolides used are erythromycin and clarithromycin, the 15-membered macrolide is azithromycin, the 16-membered macrolide is spiramycin, the lincosamides are lincomycin and clindamycin, and the ketolide is telithromycin.

  • c ND, not done.