TABLE 1.
MIC90, range of MICs, and susceptibility for 786 isolates of S. pyogenes obtained from pharyngeal exudate samples
| Anti-microbial | MIC90 (μg/ml) | Range of MICs (μg/ml) | No. (%) of strains
|
||
|---|---|---|---|---|---|
| Susceptible | Intermediatec | Resistantc | |||
| Penicillina | ≤0.015 | ≤0.015–0.06 | 786 (100.0) | 0 (0) | 0 (0) |
| Cefotaxime | ≤0.25 | ≤0.25–≤0.25 | 786 (100.0) | 0 (0) | 0 (0) |
| Cefaclor | ≤1 | ≤1–≤1 | −a | −a | −a |
| Cefixime | ≤0.25 | ≤0.25–4 | NAb | NAb | NAb |
| Cefuroxime | ≤0.25 | ≤0.25–≤0.25 | −a | −a | −a |
| Erythromycin | 4 | ≤0.1–≥16 | 573 (72.9) | 3 (0.4) | 210 (26.7) |
| Ciprofloxacin | 1 | ≤0.5–4 | NAb | NAb | NAb |
a
All the strains susceptible to penicillin can be susceptible to amoxicillin, amoxicillin clavulanate, cefuroxime, and cefaclor (11). Amoxicillin clavulanate was tested on a 2:1 basis.
b
NA, not applicable. No breakpoint criteria have been established by the National Committee for Clinical Laboratory Standards.
c
The breakpoints (μg/ml) for intermediate strains and resistant strains were respectively 0.5 and ≥1 for erythromycin and clarithromycin, 1 and ≥2 for azithromycin, ceftriaxone, and cefotaxime, and 0.25 and ≥4 for penicillin (11).