TABLE 4.
Correlation of mecA PCR test results with MIC category results for current and proposed oxacillin breakpoints
| Organism group (no. of tests) | % Correct values with the indicated medium by MIC breakpointa
|
|||||||
|---|---|---|---|---|---|---|---|---|
| Proposed (≤0.25 = S; ≥0.5 = R)
|
Current (≤2.0 = S; ≥4.0 = R)
|
|||||||
| CDC Difco | MScan Difco | CDC Acumedia | MScan BDMS | CDC Difco | MScan Difco | CDC Acumedia | MScan BDMS | |
| mecA positive | ||||||||
| S. epidermidis (198) | 95.5 | 96.0 | 94.4 | 93.4 | 52.5 | 8.1 | 72.3 | 40.9 |
| Other species (120) | 90.8 | 90.8 | 66.7 | 93.3 | 65.0 | 55.0 | 40.8 | 51.7 |
| All strains | 93.7 | 94.0 | 84.0 | 93.4 | 57.2 | 25.8 | 62.3 | 45.0 |
| mecA negative | ||||||||
| S. epidermidis (99) | 100 (97)b | 100 (98) | 99.0 (97) | 100 (99) | 100 (97) | 100 (98) | 100 (97) | 100 (99) |
| Other species (132) | 52.7 (129) | 55.0 (131) | 60.9 (126) | 66.4 (131) | 97.7 (129) | 100 (131) | 96.9 (126) | 100 (131) |
| All strains | 73.1 | 74.3 | 77.4 | 80.9 | 98.7 | 100 | 98.2 | 100 |
a
For mecA-positive strains, MICs must be ≥0.5 μg/ml for proposed breakpoints or ≥4.0 μg/ml for current breakpoints to be considered correct; for mecA-negative strains, MICs must be ≤0.25 μg/ml for proposed breakpoints or ≤2.0 μg/ml for current breakpoints to be considered correct. MScan, MicroScan; S, susceptible; R, resistant.
b
Number given in parentheses is the total number of results used for calculations. Differences were due to growth failures in some MIC plates.