Table 1. Susceptibility to 9 antibiotics, antibiotic minimal inhibitory concentrations (MICs), and serotypes of 56 Streptococcus agalactiae isolates.
| Antibiotic a | Non-susceptibility and MIC b | All isolates | Serotypes | |||||
|---|---|---|---|---|---|---|---|---|
| Ia (n = 10) | Ib (n = 9) | II (n = 3) | III(n = 18) | V (n = 8) | NT (n = 8) | |||
| PEN | MIC50 (μg/mL) | 0.094 | 0.094 | 0.094 | 0.064 | 0.094 | 0.094 | 0.094 |
| MIC90 (μg/mL) | 0.125 | 0.125 | 0.125 | 0.094 | 0.125 | 0.125 | 0.125 | |
| MIC range (μg/mL) | 0.008–0.125 | 0.064–0.125 | 0.064–0.125 | 0.047–0.094 | 0.032–0.125 | 0.008–0.125 | 0.064–0.125 | |
| CRO | MIC50 (μg/mL) | 0.094 | 0.125 | 0.125 | 0.125 | 0.064 | 0.125 | 0.094 |
| MIC90 (μg/mL) | 0.19 | 0.19 | 0.19 | 0.19 | 0.125 | 0.5 | 0.5 | |
| MIC range (μg/mL) | 0.047–0.5 | 0.047–0.25 | 0.064–0.19 | 0.064–0.19 | 0.064–0.19 | 0.094–0.5 | 0.064–0.5 | |
| ERY | I (%) | 7.1 | 10.0 | 0.0 | 0.0 | 5.6 | 0.0 | 12.5 |
| R (%) | 78.6 | 90.0 | 100.0 | 100.0 | 72.2 | 75.0 | 62.5 | |
| MIC50 (μg/mL) | 16 | 12 | ≥256 | ≥256 | 32 | 16 | 4 | |
| MIC90 (μg/mL) | ≥256 | ≥256 | ≥256 | ≥256 | ≥256 | ≥256 | ≥256 | |
| MIC range (μg/mL) | 0.125–≥256 | 0.38–≥256 | ≥256 | ≥256 | 0.125–≥256 | 0.125–≥256 | 0.19–≥256 | |
| CLR | I (%) | 14.3 | 20.0 | 0.0 | 100.0 | 16.7 | 12.5 | 25.0 |
| R (%) | 78.6 | 80.0 | 100.0 | .0 | 72.2 | 75.0 | 62.5 | |
| MIC50 (μg/mL) | ≥256 | 12.0 | ≥256 | ≥256 | ≥256 | 64 | 8 | |
| MIC90 (μg/mL) | ≥256 | ≥256 | ≥256 | ≥256 | ≥256 | ≥256 | ≥256 | |
| MIC range (μg/mL) | 0.125–≥256 | 0.5–≥256 | ≥256 | ≥256 | 0.125–≥256 | 0.25–≥256 | 0.25–≥256 | |
| AZM | I (%) | 10.7 | 0.0 | 0.0 | 0.0 | 11.1 | 0.0 | 12.5 |
| R (%) | 87.5 | 100.0 | 100.0 | 100.0 | 88.9 | 87.5 | 87.5 | |
| MIC50 (μg/mL) | ≥256 | 48 | ≥256 | ≥256 | ≥256 | 32 | 32 | |
| MIC90 (μg/mL) | ≥256 | ≥256 | ≥256 | ≥256 | ≥256 | ≥256 | ≥256 | |
| MIC range (μg/mL) | 0.5–≥256 | 2–≥256 | 64–≥256 | ≥256 | 1–≥256 | 0.5–≥256 | 1–≥256 | |
| CLI | I (%) | 8.9 | 30.0 | 0.0 | 0.0 | 0.0 | 0.0 | 12.5 |
| R (%) | 64.3 | 40.0 | 100.0 | 100.0 | 72.2 | 50.0 | 50.0 | |
| MIC50 (μg/mL) | ≥256 | 0.5 | ≥256 | ≥256 | ≥256 | 0.19 | 0.38 | |
| MIC90 (μg/mL) | ≥256 | ≥256 | ≥256 | ≥256 | ≥256 | ≥256 | ≥256 | |
| MIC range (μg/mL) | 0.125–≥256 | 0.125–≥256 | ≥256 | ≥256 | 0.125–≥256 | 0.125–≥256 | 0.19–≥256 | |
| LVX | I (%) | 3.6 | 20.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| R (%) | 35.7 | 10.0 | 44.4 | 0.0 | 72.2 | 12.5 | 12.5 | |
| MIC50 (μg/mL) | 1.5 | 1.5 | 2 | 0.75 | ≥32 | 0.75 | 1 | |
| MIC90 (μg/mL) | ≥32 | 6 | ≥32 | 1 | ≥32 | ≥32 | ≥32 | |
| MIC range (μg/mL) | 0.25–≥32 | 0.38–≥32 | 0.75–≥32 | 0.75–1 | 0.75–≥32 | 0.25–≥32 | 0.75–≥32 | |
| TCY c | I (%) | 7.1 | 0.0 | 33.3 | 0.0 | 0.0 | 0.0 | 12.5 |
| R (%) | 83.9 | 100.0 | 33.3 | 100 | 100 | 87.5 | 75.0 | |
| TLT c | I (%) | 26.8 | 20.0 | 33.3 | 0.0 | 33.3 | 37.5 | 12.5 |
| R (%) | 3.6 | 0.0 | 11.1 | 33.3 | 0.0 | 0.0 | 0.0 | |
a: PEN, penicillin; CRO, ceftriaxone; ERY, erythromycin; AZM, azithromycin; CLR, clarithromycin; CLI, clindamycin; LVX, levofloxacin; TCY, tetracycline; and TLT, telithromycin.
b: I, intermediate; R, resistant; MIC, minimal inhibitory concentrations.
c: TCY and TLT were tested using the disk-diffusion method.