Table 1.

MICs of 14 antibiotics for 396 erythromycin-resistant and 141 erythromycin-susceptible S. pyogenes isolates

Erythromycin resistance phenotype (no. of isolates tested)Antimicrobial agentMIC (μg/ml)a% Resistant
50%90%Range
M (242)Erythromycin882–16100
Clindamycin0.0640.0640.032–0.1250
Clarithromycin480.5–16100
Roxithromycin16162–64100
Azithromycin482–16100
Spiramycin0.250.50.064–0.50
Josamycin0.250.50.064–10
Cephalothin0.1250.250.064–0.50
Tetracycline0.250.250.064–160
Chloramphenicol240.5–40
Vancomycin0.50.50.25–0.50
Penicillin0.0080.0080.008–0.0160
Ciprofloxacin0.510.25–20
Quinupristin-dalfopristin0.250.50.125–10
IR (150)Erythromycin481–>64100
Clindamycin0.1250.50.064–161
Clarithromycin240.5–>64100
Roxithromycin16322–>64100
Azithromycin16322–>64100
Spiramycin480.25–>6463
Josamycin480.125–>6460
Cephalothin0.250.50.125–0.50
Tetracycline32320.125–6493
Chloramphenicol442–323
Vancomycin0.50.50.25–0.50
Penicillin0.0160.0160.008–0.0160
Ciprofloxacin0.50.50.25–10
Quinupristin-dalfopristin0.50.50.016–0.50
CR (4)Erythromycin>64>644–>64100
Clindamycin>64>64>64100
Clarithromycin>64>642–>64100
Roxithromycin>64>6416–>64100
Azithromycin>64>6432–>64100
Spiramycin>64>6432–>64100
Josamycin>64>648–>64100
Cephalothin0.1250.50.125–0.50
Tetracycline32640.25–6475
Chloramphenicol442–40
Vancomycin0.50.50.25–0.50
Penicillin0.0160.0160.008–0.0160
Ciprofloxacin0.50.50.25–0.50
Quinupristin-dalfopristin0.50.50.25–0.50
Erythromycin-susceptible isolates (141)Erythromycin0.0320.0640.032–0.1250
Clindamycin0.0640.0640.032–0.1250
Clarithromycin0.0320.0640.032–0.0640
Roxithromycin0.1250.250.064–0.250
Azithromycin0.1250.250.064–0.250
Spiramycin0.250.50.125–0.50
Josamycin0.250.250.125–0.50
Cephalothin0.1250.50.125–20
Tetracycline0.25320.125–6416
Chloramphenicol241–324
Vancomycin0.50.50.25–0.50
Penicillin0.0080.0160.008–0.0160
Ciprofloxacin0.510.25–20
Quinupristin-dalfopristin0.250.50.125–10
  • a 50% and 90%, MICs at which 50 and 90% of isolates are inhibited, respectively.