TABLE 1.
The 14 S. pyogenes test strains used, their antimicrobial susceptibilities, and their macrolide resistance phenotypes and genotypes
| Strain | MICa (μg/ml)
|
Macrolide resistance
|
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| ERY | CLR | AZM | JOS | JOS (ind.) | TEL | TEL (ind.) | CLI | CLI (ind.) | Phenotyeb | Genotype | |
| iB1 | >128 | >128 | >128 | 0.03 | >128 | ≤0.015 | 8 | 0.06 | >128 | iMLS-B | erm(A) |
| iB2 | >128 | >128 | >128 | 0.03 | >128 | ≤0.015 | 8 | 0.03 | >128 | iMLS-B | erm(A) |
| iB3 | >128 | >128 | >128 | 0.03 | >128 | ≤0.015 | 4 | 0.12 | >128 | iMLS-B | erm(A) |
| iB4 | >128 | >128 | >128 | 0.06 | >128 | ≤0.015 | 8 | 0.06 | >128 | iMLS-B | erm(A) |
| iC1 | 2 | 0.5 | 8 | 0.06 | 16 | ≤0.015 | 0.06 | 0.03 | >128 | iMLS-C | erm(A) |
| iC2 | 1 | 0.5 | 4 | 0.06 | 8 | ≤0.015 | 0.06 | 0.03 | >128 | iMLS-C | erm(A) |
| iC3 | 2 | 1 | 4 | 0.03 | 16 | ≤0.015 | 0.06 | 0.06 | >128 | iMLS-C | erm(A) |
| iC4 | 1 | 0.5 | 4 | 0.06 | 8 | ≤0.015 | 0.06 | 0.03 | >128 | iMLS-C | erm(A) |
| iA1 | >128 | >128 | >128 | >128 | >128 | 4 | 16 | 0.25 | >128 | iMLS-A | erm(B) |
| iA2c | >128 | >128 | >128 | >128 | >128 | 2 | 8 | 0.06 | >128 | iMLS-A | erm(B) mef(A) |
| c1 | >128 | >128 | >128 | >128 | >128 | 4 | 8 | >128 | >128 | cMLS | erm(B) |
| c2c | >128 | >128 | >128 | >128 | >128 | 2 | 4 | >128 | >128 | cMLS | erm(B) mef(A) |
| M1 | 16 | 8 | 16 | 0.06 | 0.12 | 0.25 | 0.25 | 0.03 | 0.03 | M | mef(A) |
| s1 | ≤0.015 | 0.03 | 0.03 | 0.06 | 0.06 | ≤0.015 | ≤0.015 | 0.06 | 0.06 | Susceptible | |
a
ERY, erythromycin; CLR, clarithromycin; AZM, azithromycin; JOS, josamycin; TEL, telithromycin; CLI, clindamycin; ind., after induction by growth in 0.05 μg of erythromycin per ml.
b
According to Giovanetti et al. (9).
c
Isolates iA2 and c2 were chosen, among the strains of their phenotypes (iMLS-A and cMLS, respectively), because of the presence of an amplification product in preliminary PCR experiments targeting the mef(A) gene.