TABLE 1.
Class | Genotype or phenotype | No. of isolates | MIC (μg/ml)
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Nalidixic acid
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Ciprofloxacin
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Tetracycline
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Chloramphenicol
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Range | GMM | Mode | MIC50 | MIC90c | Range | GMM | Mode | MIC50 | MIC90 | Range | GMM | Mode | MIC50 | MIC90 | Range | GMM | Mode | MIC50 | MIC90 | |||
A | Nals Cips | 8a (11) | 4-8 | 7.5 | 8 | 8 | 8 | 0.03-0.25 | 0.06 | 0.03 | 0.03 | 0.06 | 1-256 | 49.2 | 2 | 2 | 128 | 4-256 | 42 | 16 | 16 | 16 |
B | Nalr Cips | 125a (148) | 16-256 | 223.2 | 256 | 256 | 256 | 0.03-0.5 | 0.25 | 0.25 | 0.25 | 0.5 | 1-256 | 28.5 | 1 | 2 | 128 | 2-256 | 12.7 | 4 | 4 | 32 |
C | Nalr Cipr | 14a (23) | 256 | 256 | 256 | 256 | 256 | 1-2 | 1.21 | 1 | 1 | 2 | 1-32 | 5.29 | 4 | 4 | 8 | 4-32 | 15.14 | 16 | 16 | 32 |
1 | WT gyrA WT parC | 20a (24) | 4-256 | 90.6 | 256 | 32 | 256 | 0.03-1 | 0.17 | 0.12 | 0.12 | 0.25 | 1-256 | 24.6 | 8 | 4 | 32 | 1-256 | 31.4 | 32 | 16 | 32 |
2 | WT gyrA parC | 19 | 8-256 | 116.6 | 256 | 16 | 256 | 0.03-0.25 | 0.11 | 0.12 | 0.12 | 0.25 | 1-256 | 33.6 | 4 | 4 | 64 | 4-32 | 17.9 | 16 | 16 | 32 |
3 | gyrA WT parC | 43a (74) | 128-256 | 253 | 256 | 256 | 256 | 0.03-2 | 0.49 | 0.25, 0.5 | 0.5 | 1 | 1-256 | 35.2 | 1 | 2 | 128 | 4-128 | 19.1 | 4 | 4 | 16 |
4 | gyrA parC | 65 | 256 | 256 | 256 | 256 | 256 | 0.12-2 | 0.34 | 0.25 | 0.25 | 0.5 | 1-256 | 21.3 | 1 | 1 | 128 | 2-32 | 5.3 | 4 | 4 | 8 |
All isolates | 147a (182) | 4-256 | 241.6 | 256 | 256 | 256 | 0.015-2 | 0.33 | 0.25 | 0.25 | 0.5 | 1-256 | 27.4 | 1 | 2 | 128 | 2-256 | 14.5 | 4 | 4 | 32 |
Excludes serovar Typhimurium isolates DT104 and DT193. Numbers in parentheses include these isolates.
Nals, MIC of nalidixic acid ≤8 μg/ml; Nalr, MIC of nalidixic acid, ≥16 μg/ml; Cips, MIC of ciprofloxacin, ≤0.5 μg/ml; Cipr, MIC of ciprofloxacin, ≥1 μg/ml; gyrA, mutation within QRDR of gyrA; parC, mutation within QRDR of parC; WT, wild type (no mutation within QRDR); GMM, geometric mean.
MIC90, MIC for 90% of strains tested.