Table 3. Agreement between amphotericin B MIC results obtained by the CLSI method and each of the Etest methods for 136 clinical isolates of Aspergillus species.
| Species (N of isolates tested) |
Test method | MIC (µg/mL) | Essential agreement (%)* | N (%) of isolates with MIC>ECV† | Categorical agreement (%)† | % of categorical discrepancies‡ | |||
|---|---|---|---|---|---|---|---|---|---|
| Range | MIC50 | MIC90 | Very major | Major | |||||
| A. fumigatus (56) | CLSI | 0.25-2 | 0.5 | 2 | 0 (0.0) | ||||
| Etest-MH | 0.032-4 | 1 | 3 | 91.1 | 3 (5.4) | 94.6 | 0.0 | 5.4 | |
| Etest-RPG | 0.012-4 | 0.5 | 2 | 91.1 | 2 (3.6) | 96.4 | 0.0 | 3.6 | |
| A. lentulus (2) | CLSI | 4 | NA | NA | 2 (100) | ||||
| Etest-MH | 32 | NA | NA | 0.0 | 2 (100) | 100.0 | 0.0 | 0.0 | |
| Etest-RPG | 32 | NA | NA | 0.0 | 2 (100) | 100.0 | 0.0 | 0.0 | |
| Total, A. fumigatus complex (58) | CLSI | 0.25-4 | 1 | 2 | 2 (3.4) | ||||
| Etest-MH | 0.032-32 | 1 | 2 | 87.9 | 5 (8.6) | 98.3 | 0.0 | 1.7 | |
| Etest-RPG | 0.012-32 | 0.75 | 2 | 87.9 | 4 (6.9) | 98.3 | 0.0 | 1.7 | |
| A. niger (7) | CLSI | 0.5-1 | 0.5 | 1 | 0 (0.0) | ||||
| Etest-MH | 1-6 | 3 | 3 | 57.1 | 4 (57.1) | 42.9 | 0.0 | 57.1 | |
| Etest-RPG | 0.016-2 | 0.38 | 0.75 | 85.7 | 0 (0.0) | 100.0 | 0.0 | 0.0 | |
| A. awamori (15) | CLSI | 0.25-1 | 0.5 | 1 | 0 (0.0) | ||||
| Etest-MH | 0.25-4 | 1 | 3 | 73.3 | 3 (20.0) | 80.0 | 0.0 | 20.0 | |
| Etest-RPG | 0.016-0.75 | 0.38 | 0.75 | 93.3 | 0 (0.0) | 100.0 | 0.0 | 0.0 | |
| A. tubingensis (10) | CLSI | 0.06-0.25 | 0.25 | 0.25 | 0 (0.0) | ||||
| Etest-MH | 0.25-3 | 0.25 | 0.75 | 90.0 | 1 (10.0) | 90.0 | 0.0 | 10.0 | |
| Etest-RPG | 0.125-2 | 0.25 | 0.5 | 90.0 | 0 (0.0) | 100.0 | 0.0 | 0.0 | |
| Total, A. niger complex (32) | CLSI | 0.06-1 | 0.25 | 1 | 0 (0.0) | ||||
| Etest-MH | 0.25-6 | 1 | 3 | 75.0 | 8 (25.0) | 75.0 | 0.0 | 25.0 | |
| Etest-RPG | 0.016-2 | 0.38 | 0.75 | 90.6 | 0 (0.0) | 100.0 | 0.0 | 0.0 | |
| A. flavus/A. oryzae (22) | CLSI | 1-4 | 2 | 4 | 2 (9.1) | ||||
| Etest-MH | 0.19-16 | 4 | 16 | 63.6 | 15 (68.2) | 40.9 | 0.0 | 59.1 | |
| Etest-RPG | 1-16 | 4 | 16 | 63.6 | 17 (77.3) | 31.8 | 0.0 | 68.2 | |
| A. tamarii (2) | CLSI | 0.25-1 | NA | NA | 0 (0.0) | ||||
| Etest-MH | 0.19-0.75 | NA | NA | 100.0 | 0 (0.0) | 100.0 | 0.0 | 0.0 | |
| Etest-RPG | 0.25 | NA | NA | 100.0 | 0 (0.0) | 100.0 | 0.0 | 0.0 | |
| Total, A. flavus complex (24) | CLSI | 0.25-4 | 2 | 2 | 2 (8.3) | ||||
| Etest-MH | 0.19-16 | 4 | 16 | 66.7 | 15 (62.5) | 45.8 | 0.0 | 54.2 | |
| Etest-RPG | 0.25-32 | 4 | 16 | 66.7 | 17 (70.8) | 37.5 | 0.0 | 62.5 | |
| A. terreus (15) | CLSI | 0.5-4 | 2 | 4 | 0 (0.0) | ||||
| Etest-MH | 0.25-12 | 1.5 | 8 | 86.7 | 4 (26.7) | 73.3 | 0.0 | 26.7 | |
| Etest-RPG | 0.25-32 | 0.75 | 8 | 80.0 | 2 (13.3) | 86.7 | 0.0 | 13.3 | |
| A. sydowii (5) | CLSI | 1-2 | 2 | 2 | 0 (0.0) | ||||
| Etest-MH | 0.5-3 | 1.5 | 3 | 100.0 | 1 (20.0) | 80.0 | 0.0 | 20.0 | |
| Etest-RPG | 0.25-0.75 | 0.5 | 0.75 | 80.0 | 0 (0.0) | 100.0 | 0.0 | 0.0 | |
| A. versicolor (1) | CLSI | 1 | NA | NA | 0 (0.0) | ||||
| Etest-MH | 3 | NA | NA | 100.0 | 1 (100) | 0.0 | 0.0 | 100.0 | |
| Etest-RPG | 0.75 | NA | NA | 100.0 | 0 (0.0) | 100.0 | 0.0 | 0.0 | |
| Total, A. versicolor complex (6) | CLSI | 1-2 | 2 | 2 | 0 (0.0) | ||||
| Etest-MH | 0.5-3 | 2 | 3 | 100.0 | 2 (33.3) | 66.7 | 0.0 | 33.3 | |
| Etest-RPG | 0.25-0.75 | 1 | 1 | 83.3 | 0 (0.0) | 100.0 | 0.0 | 0 | |
| A. calidoustus (1) | CLSI | 4 | NA | NA | |||||
| Etest-MH | 4 | NA | NA | 100.0 | NA | NA | NA | NA | |
| Etest-RPG | 3 | NA | NA | 100.0 | NA | NA | NA | NA | |
| Total (136) | CLSI | 0.06-4 | 1 | 2 | 4 (3.0) | ||||
| Etest-MH | 0.032-32 | 1 | 8 | 81.6 | 34 (25.2) | 77.8 | 0.0 | 22.2 | |
| Etest-RPG | 0.012-32 | 1 | 4 | 83.8 | 23 (17.0) | 85.9 | 0.0 | 14.1 | |
*Essential agreement (±2 log2 dilutions) between the CLSI method and each of the Etests; †The recently published ECVs (2 µg/mL for the A. fumigatus, A. niger, A. flavus, and A. versicolor complexes and 4 µg/mL for the A. terreus complex) were used for analysis of categorical agreement [8,13]; ‡Discrepancies were considered to be very major when an isolate classified as non-WT (above the ECV) by the CLSI method was categorized as WT by one of the Etests and major when an isolate classified as WT by the CLSI method was classified as non-WT by one of the Etests.
Abbreviations: MIC, minimum inhibitory concentration; Etest-MH, Etests using Mueller-Hinton agar; Etest-RPG, Etests using RPMI agar; ECV, epidemiological cutoff values; NA, not analyzed; WT, wild type.