TABLE 4.
In vitro activities of six antimicrobial agents against the 244 nasopharyngeal isolates of S. pneumoniae by agar dilutiona
| Antimicrobial agent | Penicillin-susceptible strains (n = 209)b
|
Penicillin-intermediate and -resistant strains (n = 35)c
|
||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| R (%) | I (%) | MIC50 | MIC90 | MIC range | R (%) | I (%) | MIC50 | MIC90 | MIC range | |
| Erythromycin | 72.1 | 0.5 | 64 | 128 | 0.023–≥128 | 85.3 | 0 | 64 | 128 | 0.023–≥128 |
| Chloramphenicol | 51.0 | 0.5 | 8 | 16 | 1–32 | 29.4 | 0 | 4 | 8 | 2–16 |
| Tetracycline | 86.4 | 3.0 | 32 | 32 | 0.125–64 | 94.1 | 0 | 32 | 64 | 0.125–64 |
| Vancomycin | 0 | 0 | 0.25 | 0.25 | 0.023–0.25 | 0 | 0 | 0.25 | 0.25 | 0.064–0.25 |
| Rifampin | 0 | 0 | ≤0.125 | ≤0.125 | ≤0.125 | 0 | 0 | ≤0.125 | ≤0.125 | ≤0.125 |
| Ofloxacin | 0.5 | 3.5 | 1 | 2 | 0.25–2 | 0 | 2.9 | 1 | 2 | 0.5–4 |
a
All MICs given are in micrograms per milliliter. R, resistant strains; I, intermediate strains.
b
Susceptible, MIC ≤ 0.064 μg/ml.
c
Intermediate, MIC = 0.125 to 1 μg/ml; resistant, MIC ≥ 2 μg/ml.