TABLE 2.
Agar dilution MICs for 300 strains classified by macrolide susceptibility MIC (μg/ml)
| Drug, macrolide susceptibility,a and resistance mechanism | MIC (μg/ml)
|
||
|---|---|---|---|
| Range | 50% | 90% | |
| Penicillin | |||
| S | 0.016-4.0 | 1.0 | 2.0 |
| R | 0.016-16.0 | 0.5 | 4.0 |
| erm(B) | 0.016-16.0 | 1.0 | 4.0 |
| mef(A) | 0.016-8.0 | 0.06 | 2.0 |
| erm(A) | 0.016-0.03 | ||
| erm(B) + mef(A) | 0.016 | ||
| L4 | 2.0-16.0 | 4.0 | 8.0 |
| 23S rRNA | 0.03-0.25 | ||
| LBM415 | |||
| S | 0.03-4.0 | 0.5 | 1.0 |
| R | 0.03-4.0 | 0.5 | 2.0 |
| erm(B) | 0.06-4.0 | 0.5 | 1.0 |
| mef(A) | 0.03-4.0 | 0.25 | 2.0 |
| erm(A) | 1.0-2.0 | ||
| erm(B) + mef(A) | 1.0 | ||
| L4 | 0.125-4.0 | 0.5 | 2.0 |
| 23S rRNA | 0.25-2.0 | ||
| Amoxicillin | |||
| S | ≤0.016-4.0 | 1.0 | 2.0 |
| R | ≤0.016-16.0 | 0.25 | 8.0 |
| erm(B) | ≤0.016-16.0 | 1.0 | 8.0 |
| mef(A) | ≤0.016-4.0 | 0.06 | 2.0 |
| erm(A) | ≤0.016-0.03 | ||
| erm(B) + mef(A) | 0.03 | ||
| L4 | 0.25-16.0 | 4.0 | 8.0 |
| 23S rRNA | 0.03 | ||
| Amoxicillin-clavulanate | |||
| S | ≤0.016-4.0 | 1.0 | 2.0 |
| R | ≤0.016-16.0 | 0.25 | 4.0 |
| erm(B) | ≤0.016-16.0 | 1.0 | 4.0 |
| mef(A) | ≤0.016-4.0 | 0.06 | 2.0 |
| erm(A) | ≤0.016-0.03 | ||
| erm(B) + mef(A) | 0.03 | ||
| L4 | 0.25-16.0 | 4.0 | 8.0 |
| 23S rRNA | 0.03 | ||
| Imipenem | |||
| S | ≤0.004-0.5 | 0.125 | 0.25 |
| R | ≤0.004-2.0 | 0.06 | 0.25 |
| erm(B) | ≤0.004-2.0 | 0.125 | 0.25 |
| mef(A) | ≤0.004-0.5 | 0.016 | 0.25 |
| erm(A) | ≤0.004-0.008 | ||
| erm(B) + mef(A) | 0.008 | ||
| L4 | 0.125-0.25 | 0.25 | 0.25 |
| 23S rRNA | ≤0.004-0.03 | ||
| Meropenem | |||
| S | 0.008-1.0 | 0.25 | 0.5 |
| R | 0.008-2.0 | 0.125 | 0.5 |
| erm(B) | 0.008-2.0 | 0.25 | 0.5 |
| mef(A) | 0.016-2.0 | 0.03 | 0.5 |
| erm(A) | 0.008-0.016 | ||
| erm(B) + mef(A) | 0.016 | ||
| L4 | 0.125-1.0 | 0.5 | 0.5 |
| 23S rRNA | 0.016-0.06 | ||
| Ceftriaxone | |||
| S | 0.016-4.0 | 0.5 | 1.0 |
| R | 0.008->8.0 | 0.25 | 2.0 |
| erm(B) | 0.016->8.0 | 0.5 | 2.0 |
| mef(A) | 0.016-4.0 | 0.06 | 1.0 |
| erm(A) | 0.03 | ||
| erm(B) + mef(A) | 0.03 | ||
| L4 | 0.5->8.0 | 2.0 | 4.0 |
| 23S rRNA | 0.008-0.125 | ||
| Cefuroxime | |||
| S | 0.016-16.0 | 4.0 | 8.0 |
| R | 0.016-64.0 | 0.5 | 8.0 |
| erm(B) | 0.016-64.0 | 4.0 | 8.0 |
| mef(A) | 0.03-8.0 | 0.125 | 8.0 |
| erm(A) | 0.03 | ||
| erm(B) + mef(A) | 0.03 | ||
| L4 | 4.0-64.0 | 8.0 | 32.0 |
| 23S rRNA | 0.03-0.5 | ||
| Cefpodoxime | |||
| S | 0.03-8.0 | 1.0 | 4.0 |
| R | 0.03-64.0 | 0.5 | 4.0 |
| erm(B) | 0.03-64.0 | 2.0 | 4.0 |
| mef(A) | 0.03-8.0 | 0.06 | 4.0 |
| erm(A) | 0.03 | ||
| erm(B) + mef(A) | 0.03 | ||
| L4 | 2.0-32.0 | 4.0 | 32.0 |
| 23S rRNA | 0.03-0.125 | ||
| Cefdinir | |||
| S | 0.016-16.0 | 4.0 | 8.0 |
| R | 0.03->64.0 | 0.5 | 8.0 |
| erm(B) | 0.03->64.0 | 4.0 | 8.0 |
| mef(A) | 0.03-16.0 | 0.125 | 8.0 |
| erm(A) | 0.06 | ||
| erm(B) + mef(A) | 0.06 | ||
| L4 | 4.0-32.0 | 8.0 | 16.0 |
| 23S rRNA | 0.06-0.125 | ||
| Azithromycin | |||
| S | ≤0.016-0.125 | 0.125 | 0.125 |
| R | 1.0->64.0 | >64.0 | >64.0 |
| erm(B) | 2.0->64.0 | >64.0 | >64.0 |
| mef(A) | 1.0->64.0 | 4.0 | 16.0 |
| erm(A) | 4.0-8.0 | ||
| erm(B) + mef(A) | >64.0 | ||
| L4 | >64.0 | >64.0 | >64.0 |
| 23S rRNA | >64.0 | ||
| Clarithromycin | |||
| S | ≤0.016-0.06 | 0.03 | 0.03 |
| R | 0.5->64.0 | 64.0 | >64.0 |
| erm(B) | 0.5->64.0 | >64.0 | >64.0 |
| mef(A) | 0.5-32.0 | 2.0 | 8.0 |
| erm(A) | 0.5-1.0 | ||
| erm(B) + mef(A) | >64.0 | ||
| L4 | 8.0-64.0 | 32.0 | 64.0 |
| 23S rRNA | 8.0-16.0 | ||
a
S, susceptible (n = 146); R, resistant (n = 154). The 154 resistant isolates had the following resistance mechanisms: erm(B), n = 87; mef(A), n = 40; erm(A), n = 4; erm(B) and mef(A), n = 1; L4 protein mutation (L4), n = 18; and 23S rRNA mutation (23S rRNA), n = 4.