Table 1.

Agar dilution MICs for 207 quinolone-susceptible pneumococcal strainsa

Drug and strain typebMIC range (μg/ml)MIC50 (μg/ml)MIC90 (μg/ml)
Penicillin
 Penicillin S≤0.008–0.060.0160.03
 Penicillin I0.125–1.00.251.0
 Penicillin R2.0–16.04.04.0
Gemifloxacin
 Penicillin S≤0.008–0.1250.030.03
 Penicillin I≤0.008–0.250.030.06
 Penicillin R0.004–0.1250.030.06
Ciprofloxacin
 Penicillin S0.25–4.01.02.0
 Penicillin I0.25–4.01.02.0
 Penicillin R0.5–4.01.04.0
Levofloxacin
 Penicillin S0.125–4.01.02.0
 Penicillin I0.5–4.01.02.0
 Penicillin R1.0–2.01.02.0
Sparfloxacin
 Penicillin S≤0.03–1.00.51.0
 Penicillin I0.06–2.00.50.5
 Penicillin R0.06–1.00.50.5
Grepafloxacin
 Penicillin S≤0.03–1.00.1250.5
 Penicillin I≤0.03–0.50.1250.5
 Penicillin R≤0.03–0.50.250.5
Trovafloxacin
 Penicillin S0.03–0.50.1250.25
 Penicillin I0.016–1.00.1250.25
 Penicillin R0.03–0.250.1250.25
Amoxicillin
 Penicillin S≤0.008–0.250.0160.06
 Penicillin I0.016–4.00.1251.0
 Penicillin R0.5–8.02.04.0
Cefuroxime
 Penicillin S≤0.008–2.00.030.25
 Penicillin I0.125–8.00.52.0
 Penicillin R0.5–32.08.016.0
Azithromycin
 Penicillin S≤0.008–>128.00.1250.5
 Penicillin I≤0.008–>128.00.125>128.0
 Penicillin R0.03–>128.04.0>128.0
Clarithromycin
 Penicillin S≤0.008–>128.00.030.06
 Penicillin I≤0.008–>128.00.0332.0
 Penicillin R0.008–>128.02.0>128.0
  • a Strains with ciprofloxacin MICs of ≤4.0 μg/ml.

  • b S, susceptible; I, intermediate; R, resistant.