TABLE 1.

MIC ranges, MIC50sa, MIC90s, and resistance rates of 82 erythromycin A-resistant pneumococcal isolates from seven European countries

AntibioticbMIC rangeMIC50MIC90SusceptibleIntermediateResistant
No.%No.%No.%
All strains (n = 82)
    Erythromycin A1-≥32≥32≥32000082100
    Roxithromycin0.5-≥32≥32≥320011.28198.8
    Clarithromycin1-≥32≥32≥32000082100
    Azithromycin1-≥32≥32≥320056.17793.9
    Spiramycin0.03-≥32≥32≥32NDNDNDNDNDND
    Clindamycin0.06-≥3216≥321720.711.26478.0
    Telithromycin≤0.03-0.5≤0.030.25821000000
    Q-D0.03-20.518097.622.400
    Penicillin G0.016-2111923.25769.567.3
    Cefotaxime0.016-2117895.144.900
    Amoxicillin0.016-211821000000
    Tetracycline0.06-≥3216≥3289.81214.66275.6
    Ciprofloxacin0.06-211NDNDNDNDNDND
    Vancomycin0.125-0.50.250.25821000000
    Teicoplanin0.06-0.250.060.125NDNDNDNDNDND
Erm(B)-positive strains (n = 64)
    Erythromycin A4-≥32≥32≥32000064100
    Roxithromycin4-≥32≥32≥32000064100
    Clarithromycin2-≥32≥32≥32000064100
    Azithromycin1-≥32≥32≥320011.66398.4
    Spiramycin2-≥32≥32≥32NDNDNDNDNDND
    Clindamycin2-≥32≥32≥32000064100
    Telithromycin≤0.03-0.5≤0.030.25641000000
    Q-D0.03-20.516296.923.100
    Penicillin G0.016-2111625.04468.846.3
    Cefotaxime0.016-20.516296.923.100
    Amoxicillin0.016-212641000000
    Tetracycline0.125-≥3216≥320034.76195.3
    Ciprofloxacin0.06-211NDNDNDNDNDND
    Vancomycin0.125-0.50.250.25641000000
    Teicoplanin0.06-0.250.060.125NDNDNDNDNDND
mef(A)-positive strains (n = 18)
    Erythromycin A1-828000018100
    Roxithromycin0.5-16480015.61794.4
    Clarithromycin1-1628000018100
    Azithromycin1-1621600422.21477.8
    Spiramycin0.03-824NDNDNDNDNDND
    Clindamycin0.06-0.50.060.251794.415.600
    Telithromycin≤0.03-0.1250.030.06181000000
    Q-D0.25-10.51181000000
    Penicillin G0.016-212316.71372.2211.1
    Cefotaxime0.016-2111688.9211.100
    Amoxicillin0.016-211181000000
    Tetracycline0.06-32832738.9950.0211.1
    Ciprofloxacin0.25-20.52NDNDNDNDNDND
    Vancomycin0.03-0.250.250.25181000000
    Teicoplanin0.03-0.1250.060.125NDNDNDNDNDND
  • a MIC50 and MIC90, MICs at which 50 and 90% of isolates, respectively, are inhibited.

  • b Breakpoints (intermediate and resistant) are as follows according to NCCLS (19): erythromycin A, 0.5 μg/ml and ≥1 μg/ml; clarithromycin, 0.5 μg/ml and ≥1 μg/ml; azithromycin, 1 μg/ml and ≥2 μg/ml; clindamycin, 0.5 μg/ml and ≥1 μg/ml; telithromycin, 2 μg/ml and ≥4 μg/ml, quinupristin-dalfopristin (Q-D), 2 μg/ml and ≥4 μg/ml; penicillin G, 0.1 to 1 μg/ml and ≥2 μg/ml; cefotaxime (nonmeningitis), 2 μg/ml and ≥4 μg/ml; amoxicillin, 4 μg/ml and ≥8 μg/ml; tetracycline, 4 μg/ml and ≥8 μg/ml; vancomycin (susceptible), ≤1 μg/ml. Roxithromycin breakpoints are not NCCLS approved. The breakpoints ≤1 μg/ml and ≥2 μg/ml were used. Ciprofloxacin, spiramycin, and teicoplanin breakpoints are not available. ND, not determined.