TABLE 1.
Susceptibility of isolate collections by methoda
| Collection and method | % (no.) of isolates that were: |
MIC50/90 (μg/ml) | MIC range (μg/ml) | ||
|---|---|---|---|---|---|
| Susceptible | Intermediate | Resistant | |||
| Entire collection (n = 198) | |||||
| AD | 59.6 (118) | 25.8 (51) | 14.6 (29) | 64/256 | <1 to >256 |
| Etest | 59.1 (117) | 17.7 (35) | 23.2 (46) | 64/>1,024 | 0.5 to >1,024 |
| DD | 85.9 (170) | 6.6 (13) | 7.6 (15) | NAb | NA |
| BMD | 49.0 (97) | 27.3 (54) | 23.7 (47) | 128/256 | <2 to >256 |
| U.S. collection (n = 126) | |||||
| AD | 61.1 (77) | 25.4 (32) | 13.5 (17) | 64/256 | <1 to >256 |
| Etest | 57.1 (72) | 21.4 (27) | 21.4 (27) | 64/512 | 0.5 to >1,024 |
| DD | 88.1 (111) | 7.1 (9) | 4.8 (6) | NA | NA |
| BMD | 44.4 (56) | 27.0 (34) | 28.6 (36) | 128/256 | <2 to >256 |
| Australian collection (n = 72) | |||||
| AD | 56.9 (41) | 26.4 (19) | 16.7 (12) | 64/256 | 8 to >256 |
| Etest | 62.5 (45) | 11.1 (8) | 26.4 (19) | 64/>1,024 | 1 to >1,024 |
| DD | 81.9 (59) | 5.6 (4) | 12.5 (9) | NA | NA |
| BMD | 56.9 (41) | 27.8 (20) | 15.3 (11) | 64/256 | 8 to >256 |
a
Isolates were deemed susceptible if the MIC was ≤ 64 μg/ml, intermediate if the MIC was 128 μg/ml, and resistant if the MIC was ≥ 256 μg/ml according to the CLSI E. coli breakpoints.
b
NA, not applicable.