TABLE 2.
In vitro susceptiblities of 200 isolates of the M. fortuitum group, M. chelonae, and M. abscessus to 15 antimicrobial agents using the broth microdilution method
| Bacterium (no. of isolates tested) and antimicrobial agent | MIC (μg/ml)
|
No. (%) of isolates
|
||||
|---|---|---|---|---|---|---|
| Range | 50% | 90% | Susceptible | Intermediate | Resistant | |
| M. fortuitum group (69) | ||||||
| Amikacin | 1-16 | 1 | 8 | 69 (100) | 0 (0) | 0 (0) |
| Tobramycina | 1-32 | 8 | 16 | 6 (9) | 31 (45) | 32 (46) |
| Cefoxitin | 8->256 | 32 | 64 | 13 (19) | 55 (80) | 1 (1) |
| Ciprofloxacin | 0.25-16 | 0.25 | 8 | 43 (62) | 3 (4) | 23 (33) |
| Moxifloxacinc | 0.06-16 | 0.06 | 16 | 46 (67) | 6 (9) | 17 (25) |
| Gatifloxacinc | 0.06-16 | 0.12 | 8 | 48 (70) | 7 (10) | 14 (20) |
| Levofloxacinc | 0.06-64 | 0.25 | 32 | 44 (64) | 2 (3) | 23 (33) |
| Clarithromycin | 0.12->64 | 2 | 8 | 45 (65) | 10 (15) | 14 (20) |
| Azithromycinc | 1-64 | 8 | 64 | 16 (24) | 16 (24) | 37 (52) |
| Telithromycinc | 0.06->64 | 64 | >64 | —f | — | — |
| Doxycycline | 0.25->32 | 16 | >32 | 9 (13) | 13 (19) | 47 (68) |
| Imipenem | 1-32 | 2 | 8 | 42 (61) | 22 (32) | 5 (7) |
| Meropenemc | 1->64 | 4 | 32 | 35 (51) | 6 (9) | 28 (41) |
| TMP-SMZd | 1->64 | 64 | >64 | 34 (49) | — | 35 (51) |
| Linezolide | 0.12-64 | 8 | 32 | 47 (68) | 5 (7) | 17 (25) |
| M. chelonae (39) | ||||||
| Amikacin | 2-16 | 8 | 16 | 39 (100) | 0 (0) | 0 (0) |
| Tobramycin | 1-16 | 8 | 16 | 12 (31) | 17 (44) | 10 (26) |
| Cefoxitin | 16->256 | 32 | 256 | 2 (5) | 25 (64) | 12 (31) |
| Ciprofloxacin | 2->16 | 16 | >16 | 0 (0) | 1 (3) | 38 (97) |
| Moxifloxacinc | 1-32 | 8 | 8 | 9 (23) | 8 (21) | 22 (56) |
| Gatifloxacinc | 1-16 | 8 | 16 | 8 (21) | 9 (23) | 22 (56) |
| Levofloxacinc | 8->64 | 32 | 64 | 0 (0) | 0 (0) | 39 (100) |
| Clarithromycin | 0.06->64 | 4 | >64 | 19 (49) | 1 (3) | 19 (49) |
| Azithromycinc | 0.25->64 | >64 | >64 | 7 (18) | 5 (12) | 27 (70) |
| Telithromycinc | 0.12->64 | 64 | >64 | — | — | — |
| Doxycycline | 32->32 | >32 | >32 | 0 (0) | 0 (0) | 39 (100) |
| Imipenemb | 2-64 | 16 | 64 | 7 (18) | 12 (31) | 20 (51) |
| Meropenemc | 4-64 | 64 | >64 | 1 (3) | 2 (5) | 36 (92) |
| TMP-SMZd | 64->64 | >64 | >64 | 0 (0) | — | 39 (100) |
| Linezolide | 1-32 | 8 | 16 | 32 (82) | 5 (13) | 2 (5) |
| M. abscessus (92) | ||||||
| Amikacin | 1->128 | 8 | 8 | 88 (96) | 0 (0) | 4 (4) |
| Tobramycina | 1->32 | 8 | 16 | 25 (27) | 39 (42) | 28 (30) |
| Cefoxitin | 8-256 | 32 | 64 | 3 (3) | 85 (92) | 4 (4) |
| Ciprofloxacin | 0.25->16 | 8 | 16 | 3 (3) | 2 (2) | 87 (95) |
| Moxifloxacinc | 0.06-32 | 8 | 16 | 7 (8) | 10 (11) | 75 (82) |
| Gatifloxacinc | 0.06-32 | 8 | 16 | 6 (7) | 16 (17) | 70 (76) |
| Levofloxacinc | 0.5->64 | 16 | 64 | 2 (2) | 2 (2) | 88 (96) |
| Clarithromycin | 0.06->64 | 1 | 8 | 73 (79) | 9 (10) | 10 (11) |
| Azithromycinc | 0.25->64 | 2 | 32 | 48 (52) | 0 (0) | 44 (48) |
| Telithromycinc | 0.5->64 | 32 | >64 | — | — | — |
| Doxycycline | 4->32 | >32 | >32 | 0 (0) | 7 (8) | 85 (92) |
| Imipenemb | 1->64 | 8 | 16 | 11 (12) | 64 (70) | 17 (18) |
| Meropenemc | 8->64 | 32 | 64 | 0 (0) | 1 (1) | 9 (99) |
| TMP-SMZd | 2->64 | >64 | >64 | 1 (1) | — | 91 (99) |
| Linezolide | 1-32 | 16 | 32 | 29 (32) | 24 (26) | 39 (42) |
a
Tobramycin results were recommended to be reported only for M. chelonae isolates.
b
Imipenem results were not recommended to be reported for M. chelonae and M. abscessus isolates.
c
The breakpoints of these antimicrobial agents for RGM have not yet been addressed by the NCCLS (11). The NCCLS breakpoints for Staphylococcus species were used (12).
d
TMP-SMZ, trimethoprim-sulfamethoxazole.
e
The breakpoints of linezolid for RGM proposed by Wallace et al. (18) were used. These breakpoints of linezolid have not yet been addressed by the NCCLS (11).
f
—, no breakpoints are available.