TABLE 2.
Susceptibility testing results for β-lactam antibioticsa
| Isolate | Testb | Oxacillin MIC (μg/ml) | Interpretation | Ampicillin MIC (μg/ml) | Interpretation | Penicillin MIC (μg/ml) | Interpretation | Cefoxitin MIC (μg/ml) | Disk zone (mm) | Interpretation |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | MicroScan | ≤0.5 | S | |||||||
| Broth microdilution (Sensititre) | 0.5 | S | 1 | R | 1 | R | ||||
| Reference broth microdilution | 0.5 | S | 2 | R | 4 | 25 | S | |||
| 2 | MicroScan | >2 | R | |||||||
| Broth microdilution (Sensititre) | 4 | R | 2 | R | 4 | R | ||||
| Reference broth microdilution | 0.25 | S | 1 | 4 | 28 | S | ||||
| 3 | MicroScan | >2 | R | |||||||
| Broth microdilution (Sensititre) | >4 | R | 4 | R | 4 | R | ||||
| Reference broth microdilution | 16 | R | >2 | R | 8 | 19 | R |
a
R, resistant; S, susceptible.
b
In the MicroScan, MICs were the same regardless of inoculation method (Prompt inoculum versus turbidity technique). In the Sensititre assay, testing was done in replicate, with no difference in results.