TABLE 4.
Comparison of susceptibilities of various macrolide-resistant strains of MSSA
| Test agent | None (n = 76) |
ermA (i)a (n = 13) |
ermA (c)b (n = 4) |
ermB (c) (n = 1) |
ermC (i) (n = 5) |
|||||
|---|---|---|---|---|---|---|---|---|---|---|
| MIC range (μg/ml) | % I and Rc | MIC range (μg/ml) | % I and R | MIC range (μg/ml) | % I and R | MIC range (μg/ml) | % I and R | MIC range (μg/ml) | % I and R | |
| Modithromycin | ≤0.063-0.125 | NC | ≤0.063-0.125 | NC | 16->64 | NC | >64 | NC | 0.125 | NC |
| Telithromycin | ≤0.063-0.125 | 0 | ≤0.063-0.125 | 0 | >64 | 100 | >64 | 100 | ≤0.063-0.125 | 0 |
| Clarithromycin | ≤0.063-0.25 | 0 | 64->64 | 100 | >64 | 100 | >64 | 100 | >64 | 100 |
| Azithromycin | 0.25-1 | 0 | >64 | 100 | >64 | 100 | >64 | 100 | >64 | 100 |
| Clindamycin | ≤0.063-8 | 1.3 | ≤0.063-0.125 | 0 | >64 | 100 | >64 | 100 | ≤0.063-0.25 | 0 |
a
i, inducible resistance phenotype.
b
c, constitutive resistance phenotype.
c
The percentages of intermediate-resistant (I) and resistant (R) strains are shown. The CLSI breakpoint criteria are as follows: telithromycin, 2 and ≥4 μg/ml; clarithromycin, 4 and ≥8 μg/ml; azithromycin, 4 and ≥8 μg/ml; clindamycin, 1 to 2 and ≥4 μg/ml. NC, not calculated (the breakpoints of modithromycin have not been determined).