Table 3. Minimum inhibitory concentration (MIC) values of selected antibiotics against Clostridium difficile isolates by E-tests
| Antibiotics | MIC (μg/mL) breakpoints | Number of C. difficile isolates (%) | MIC values (μg/mL) of C. difficile isolates and control |
| S | I | R | S (%) | I (%) | R (%) | Isolate (1) | Isolate (2) | Isolate (3) | Isolate (4) | Isolate (5) | Isolate (6) | Isolate (7) | Isolate (8) | Isolate (9) | Isolate (10) | Isolate (11) | Isolate (12) | Isolate (13) | Isolate (14) | Isolate (15) | ATCC 9689 |
| Vancomycin1) | ≤2 | - | >2 | 15 (100) | 0 (0) | 0 (0) | 0.5 | 1.0 | 0.5 | 0.5 | 0.25 | 0.25 | 1.0 | 0.25 | 2.0 | 0.5 | 1.0 | 1.0 | 0.5 | 0.25 | 0.25 | 0.5 |
| Metronidazole2) | ≤8 | 16 | ≥32 | 15 (100) | 0 (0) | 0 (0) | 0.5 | 0.5 | 0.25 | 1.0 | 0.03 | 8.0 | 0.5 | 1.0 | 0.5 | 0.5 | 0.06 | 4.0 | 8.0 | 0.25 | 1.0 | 2.0 |
| Tetracycline2) | ≤4 | 8 | ≥16 | 10 (66.7) | 5 (33.3) | 0 (0) | 8.0 | 0.25 | 0.015 | 0.25 | 4.0 | 8.0 | 2.0 | 0.03 | 8.0 | 0.03 | 8.0 | 0.015 | 0.06 | 8.0 | 4.0 | 4.0 |
| Clindamycin2) | ≤2 | 4 | ≥8 | 11 (73.3) | 4 (26.7) | 0 (0) | 0.5 | 4.0 | 4.0 | 2.0 | 4.0 | 0.5 | 1.0 | 4.0 | 2.0 | 1.0 | 0.25 | 0.25 | 0.25 | 1.0 | 0.25 | 1.0 |
| Moxifloxacin2) | ≤2 | 4 | ≥8 | 6 (40.0) | 6 (40.0) | 3 (20.0) | 0.5 | 4.0 | 8.0 | 4.0 | 8.0 | 0.25 | 4.0 | 0.25 | 0.25 | 4.0 | 1.0 | 4.0 | 8.0 | 4.0 | 0.25 | 2.0 |
The breakpoints defined by European Committee for Antimicrobial Susceptibility Testing (EUCAST).
The breakpoints defined by Clinical and Laboratory Standards Institute (CLSI).
S, sensitive; I, intermediate; R, resistant.