Table 3. Minimum inhibition concentrations (MICs) distribution and resistance rates of 60 A. viridans strains.
| No. of isolates for which the MIC (mg/L) were: | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Antimicrobials | ≤0.12 | 0.25 | 0.5 | 1 | 2 | 4 | 8 | 16 | 32 | 64 | 128 | ≥256 | MIC a 50 | MIC 90 | R.S b % |
| Penicillin | 25 | 19 | 5 | 6 | 2 | 0 c | 0 | 0 | 1 | 2 | 0 | 0 | 0.25 | 1 | 5.0 |
| Ampicillin | 32 | 17 | 1 | 2 | 1 | 3 | 0 | 0 | 0 | 0 | 1 | 2 | ⩽0.12 | 4 | 5.0 |
| Ceftiofur | 18 | 30 | 2 | 1 | 1 | 5 | 0 | 0 | 0 | 2 | 1 | 0 | 0.25 | 4 | 5.0 |
| Erythromycin | 11 | 13 | 17 | 8 | 4 | 3 | 1 | 0 | 1 | 2 | 0 | 0 | 0.5 | 4 | 31.6 |
| Clindamycin | 3 | 8 | 4 | 5 | 6 | 12 | 10 | 4 | 3 | 2 | 3 | 0 | 4 | 32 | 56.7 |
| Chloramphenicol | 1 | 4 | 3 | 4 | 5 | 12 | 8 | 6 | 3 | 7 | 3 | 4 | 8 | 128 | 38.3 |
| Tetracycline | 0 | 2 | 3 | 5 | 4 | 7 | 16 | 5 | 8 | 2 | 5 | 3 | 8 | 128 | 65.0 |
| Kanamycin | 0 | 0 | 2 | 2 | 6 | 7 | 18 | 13 | 8 | 2 | 1 | 1 | 8 | 32 | 6.7 |
| Gentamicin | 0 | 5 | 3 | 8 | 9 | 14 | 13 | 3 | 2 | 3 | 0 | 0 | 4 | 16 | 13.3 |
| Vancomycin | 0 | 6 | 5 | 4 | 7 | 10 | 19 | 8 | 0 | 1 | 0 | 0 | 4 | 16 | 1.7 |
| Ciprofloxacin | 21 | 14 | 8 | 10 | 3 | 4 | 0 | 0 | 0 | 0 | 0 | 0 | 0.25 | 2 | 6.7 |
| Norfloxacin | 0 | 14 | 10 | 5 | 2 | 5 | 0 | 10 | 8 | 6 | 0 | 0 | 2 | 32 | 40.0 |
| Streptomycin | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 12 | 32 | 14 | 128 | ≥256 | 96.7 |
| SXT d | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 28 | 29 | 128 | ≥256 | 100 |
aMIC, Minimum inhibition concentrations
bR.S, Resistant strains
cThe number of isolates for each antimicrobial agent MICs breakpoint is highlighted by bold text.
dSXT, Trimethoprim-sulfamethoxazole