Table 2.
Comparison of Resistance Testing Results Based on Microbroth Dilution and Agar Disk Diffusion
| |
Spearman's correlation coefficient (ρ) |
Proportional Hazard model |
|
|
|---|---|---|---|---|
| Antimicrobial drug | ρb(95% CI) | Parameter | Hazard ratio (95% CI) | Hazard increase/mma |
| Ampicillin | −0.97 (−0.96; −0.99) | Zone diameter | 1.40 (1.22–1.60) | 40 (22–60) |
| Amoxicillin/clavulanic acid | −0.90 (−0.87; −0.93) | Zone diameter | 1.27 (1.23–1.32) | 27 (23–32) |
| Year (2004 vs. 2005) | 0.43 (0.28; 0.67) | – | ||
| Chloramphenicol | −0.97 (−0.95; −0.99) | Zone diameter | 1.33 (1.22–1.45) | 33 (22–45) |
| Year (2004 vs. 2005) | 0.36 (0.15–0.94) | – | ||
| Gentamicin | −0.38 (−0.26; −0.50) | Zone diameter | 1.29 (1.18–1.42) | 29 (18–42) |
| Kanamycin | −0.69 (−0.61; −0.78) | Zone diameter | 1.20 (1.14–1.26) | 20 (14–26) |
| Streptomycin | −0.96 (−0.95; −0.98) | Zone diameter | 4.58 (1.17–12.25) | 358 (70–1125) |
| Serotype (Newport vs. average)c | 0.01 (0.00–0.25) | – | ||
| Serotype (4,5,12:i:- vs. average)c | 0.03 (0.00–1.48) | – | ||
| Species (Bovine vs. Human) | 0.245 (0.09–0.69) | – | ||
| Tetracycline | −0.90 (−0.86; −0.94) | Zone diameter | 1.26 (1.22–1.31) | 26 (22–31) |
| Sulfisozaxole/trimethoprim | −0.50 (−0.40; −0.60) | Zone diameter | 1.40 (1.27–1.54) | 40 (27–54) |
| Year (2004 vs. 2005) | 0.59 (0.36–0.97) | – | ||
| Serotype (Newport vs. average)c | 1.70 (1.03–2.80) | – | ||
| Serotype (4,5,12:i:- vs. average)c | 0.59 (0.29–1.19) | – | ||
a
Average percent increase in hazard of growth inhibition per unit increase in parameter.
b
Spearman's correlation coefficient (ρ); ρ ranges from −1 to 1; a value of −1 indicates perfect negative correlation; a value of 0 indicates no correlation.
c
Hazard ratio for specified serotype versus average of remaining two serotypes.
95% CI, 95% confidence interval.