TABLE 1.
MICs of 11 antimicrobials tested individually against Mycobacterium abscessus subsp. abscessus and Mycobacterium abscessus subsp. massiliense isolatesa
| Subspecies and drug | MIC (mg/liter) |
Susceptibility breakpoint (mg/liter)b |
||||
|---|---|---|---|---|---|---|
| 50% | 90% | Range | Susceptible | Intermediate | Resistant | |
| M. abscessus subsp. abscessus (n = 13)c | ||||||
| Rifabutin | 16 | 32 | 8 to 32 | ≤2 (0, 0) | >2 (13, 100.0) | |
| Clarithromycin | 4 | 8 | 0.5 to 16 | ≤2 (5, 38.5) | 4 (2, 15.4) | ≥8 (6, 46.2) |
| Amikacin | 32 | 32 | 16 to 64 | ≤16 (2, 15.4) | 32 (10, 76.9) | ≥64 (1, 7.7) |
| Cefoxitin | 32 | 32 | 16 to 64 | ≤16 (1, 7.7) | 32–64 (12, 92.3) | ≥128 (0, 0) |
| Ceftibuten | 256 | 256 | 128 to 256 | ≤16 (0, 0) | 32–64 (0, 0) | ≥128 (13, 100.0) |
| Clofazimine | 1 | 2 | 0.5 to 2 | ≤2 (13, 100.0) | ≥8 (0, 0) | |
| Doxycycline | >64 | >64 | >64 | ≤1 (0, 0) | 2-4 (0, 0) | ≥8 (13, 100.0) |
| Imipenem | 16 | 16 | 8 to 64 | ≤4 (0, 0) | 8–16 (11, 84.6) | ≥32 (2, 15.4) |
| Linezolid | 32 | 32 | 4 to 64 | ≤8 (1, 7.7) | 16 (0, 0) | ≥32 (12, 92.3) |
| Moxifloxacin | 32 | 32 | 8 to 256 | ≤1 (0, 0) | 2 (0, 0) | ≥4 (13, 100) |
| Tigecycline | 0.5 | 1 | 0.25 to 1 | ≤0.5 (10, 76.9) | 1 (3, 23.1) | ≥2 (0, 0) |
| M. abscessus subsp. massiliense (n = 13)d | ||||||
| Rifabutin | 16 | 16 | 2 to 16 | ≤2 (1, 7.7) | >2 (12, 92.3) | |
| Clarithromycin | 0.25 | 2 | <0.03 to >256 | ≤2 (11, 84.6) | 4 (0, 0) | ≥8 (2, 15.4) |
| Amikacin | 32 | 32 | 8 to 64 | ≤16 (3, 23.1) | 32 (9, 69.2) | ≥64 (1, 7.7) |
| Cefoxitin | 32 | 64 | 16 to 128 | ≤16 (2, 15.4) | 32-64 (10, 76.9) | ≥128 (1, 7.7) |
| Ceftibuten | 256 | 256 | 128 to 256 | ≤16 (0, 0) | 32-64 (0, 0) | ≥128 (13, 100.0) |
| Clofazimine | 2 | 2 | 0.5 to 2 | ≤2 (13, 100.0) | ≥8 (0, 0) | |
| Doxycycline | >64 | >64 | 8 to >64 | ≤1 (0, 0) | 2-4 (0, 0) | ≥8 (13, 100.0) |
| Imipenem | 16 | 16 | 8 to 64 | ≤4 (0, 0) | 8–16 (11, 84.6) | ≥32 (2, 15.4) |
| Linezolid | 32 | 32 | 1 to 32 | ≤8 (2, 15.4) | 16 (4, 30.8) | ≥32 (7, 53.8) |
| Moxifloxacin | 32 | 32 | 2 to 128 | ≤1 (0, 0) | 2 (1, 7.7) | ≥4 (12, 92.3) |
| Tigecycline | 0.5 | 1 | 0.06 to 1 | ≤0.5 (10, 76.9) | 1 (3, 23.1) | ≥2 (0, 0) |
a
The results of broth microdilution susceptibility testing are for each antimicrobial tested alone.
b
Data in parentheses represent the number, percent, of isolates with the indicated result. Data in bold indicate the MIC breakpoints applied in this study.
c
There were T28 (n = 10) and C28 (n = 3) sequevars among the 13 isolates. None of the isolates had rrl mutations.
d
A truncated erm41 (n = 12), the C28 sequevar (n = 1), and rrl mutations (A2057G, A2058G; n = 2) were found among the 13 isolates.