Table 2.

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

StrainaMIC (μg/ml) ofb:MutationHeterozygosity
AZIERYCLARSPIRLINCCLINSTREP BTELIPEN
Parent 1T00.200.050.020.390.200.051.560.0060.01None4C:0A
Mutant 1Az3.120.780.781.560.390.20500.010.02C2611A1C:3A
Parent 6T00.100.050.020.101.560.050.780.0030.01None4C:0G
Mutant 6Az12.5>1001000.786.250.20>1000.390.01C2611G0C:4G
Parent 3T00.020.020.010.100.200.021.560.0030.02None4A:0G
Mutant 3Az>20012.53.12>1001.560.201.560.010.02A2059G2A:2G
Parent 8T00.100.050.050.390.200.103.120.010.05None4A:0G
Mutant 8Az>200>1001006.25253.1212.50.100.05A2058G2A:2G
ATCC 496190.120.0300.030.200.39≤0.203.120.010.39NDcND
  • 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.