Table 3.
Susceptibility of B. suis to the different antibiotics contained in FM and mTM
| Antibiotic | Concn | Growth of B. suis (no. of CFU/plate [mean ± SD])a |
|---|---|---|
| Nalidixic acid | 5 mg/liter | 71.7 ± 8.1* |
| 10 mg/liter | 2.9 ± 0.6** | |
| Bacitracin | 25,000 IU/liter | 70.9 ± 6.9* |
| 50,000 IU/liter | 13.8 ± 3.7** | |
| Polymyxin B | 5,000 IU/liter | 81.4 ± 7.9 |
| Cycloheximide | 100 mg/liter | 80.8 ± 7.5 |
| Natamycin | 50 mg/liter | 78.8 ± 7.3 |
| Vancomycin | 20 mg/liter | 74.3 ± 9.8 |
| Nystatin | 100,000 IU/liter | 80.1 ± 7.7 |
| Colistin | 7.5 mg/liter | 79.6 ± 7.9 |
| Nitrofurantoin | 10 mg/liter | 80.7 ± 8.1 |
| Amphotericin B | 4 mg/liter | 80.7 ± 6.6 |
| None (control) | 80.5 ± 7.8 |
a
Growth of 40 representative B. suis strains (Table 1) in MHA-YE-CS supplemented with the indicated antibiotics at the concentrations used in FM or mTM. Nalidixic acid and bacitracin were also tested at 2-fold higher concentrations than those in FM or mTM. *, P < 0.001; **, P < 0.0001 with respect to MHA-YE-CS agar control plates without the corresponding antibiotic.