TABLE 3.
Identification of 151 fastidious GNR by MALDI-TOF MS: comparison of three sample preparation methods and different score value cutoffs
| MALDI-TOF MS method | No. (%) of isolates identified using a species score value cutoff of: |
No. (%) of isolates identified using a genus score value cutoff of: |
|||||
|---|---|---|---|---|---|---|---|
| 2.0 | 1.9 | 1.8 | 1.7 | 1.7 | 1.6 | 1.5 | |
| Direct colony transfer | |||||||
| Species identification | 65 (43.0) | 85 (56.3) | 92 (60.9) | 98 (64.9) | |||
| Genus identification | 49 (32.5) | 29 (19.2) | 22 (14.6) | 8 (5.3) | 116 (76.8) | 125 (82.8) | 115 (76.2) |
| No identification | 35 (23.2) | 35 (23.2) | 35 (23.2) | 35 (23.2) | 35 (23.3) | 26 (17.2) | 36 (23.8) |
| Misidentification | 2 (1.3) | 2 (1.3) | 2 (1.3) | 10 (6.6) | 0 (0) | 0 (0) | 0 (0) |
| Direct transfer plus formic acid preparation | |||||||
| Species identification | 70 (46.4) | 86 (57.0) | 95 (62.9) | 101 (66.9) | |||
| Genus identification | 46 (30.5) | 29 (19.2) | 17 (11.3) | 8 (5.3) | 118 (78.1) | 128 (84.8) | 119 (78.8) |
| No identification | 33 (21.9) | 33 (21.9) | 33 (21.9) | 33 (21.9) | 33 (21.9) | 23 (15.2) | 32 (21.2) |
| Misidentification | 2 (1.3) | 3 (2.0) | 6 (4.0) | 9 (6.0) | 0 (0) | 0 (0) | 0 (0) |
| Ethanol-formic acid extraction | |||||||
| Species identification | 81 (53.7) | 89 (58.9) | 100 (66.2) | 105 (69.5) | |||
| Genus identification | 39 (25.8) | 27 (17.9) | 16 (10.6) | 9 (6.0) | 122 (80.8) | 124 (82.1) | 128 (84.8) |
| No identification | 29 (19.2) | 29 (19.2) | 29 (19.2) | 29 (19.2) | 29 (19.2) | 27 (17.9) | 23 (15.2) |
| Misidentification | 2 (1.3) | 6 (4.0) | 6 (4.0) | 8 (5.3) | 0 (0) | 0 (0) | 0 (0) |