TABLE 2.
Antimicrobial agents and susceptibility breakpoints (MICs) for testing rapidly growing mycobacteriaa
| Antimicrobial agent | MIC (μg/ml) |
Comment | ||
|---|---|---|---|---|
| Susceptible | Intermediate | Resistant | ||
| Amikacin | 16 | 32 | ≥64 | M. abscessus complex isolates with MIC of ≥64 μg/ml should be retested and/or the 16S rRNA gene sequenced to check for mutation |
| Cefoxitin | 16 | 32–64 | ≥128 | |
| Ciprofloxacin | ≤1 | 2 | ≥4 | Ciprofloxacin and levofloxacin are interchangeable, but both are less active than the newer B-methoxy-fluoroquinolones |
| Clarithromycin | ≤2 | 4 | ≥8 | See text for information on the erm gene; clarithromycin and azithromycin are interchangeable clinically |
| Doxycycline | ≤1 | 2–4 | ≥8 | |
| Imipenem | ≤4 | 8–16 | ≥32 | All isolates of M. fortuitum, M. smegmatis, and the M. mucogenicum group are presumed imipenem susceptible; imipenem MICs do not predict meropenem or ertapenem susceptibility |
| Linezolid | ≤8 | 16 | ≥32 | |
| Meropenem | ≤4 | 8–16 | ≥32 | |
| Moxifloxacin | ≤1 | 2 | ≥4 | |
| Tigecycline | Insufficient data to establish breakpoints; only MIC should be reported | |||
| Tobramycin | ≤2 | 4 | ≥8 | Predominantly for M. chelonae; if MIC > 4 μg/ml, the test should be repeated and/or the identification confirmed by rpoβ gene sequencing |
| TMP-SMX | ≤2/38 | ≥4/76 | MIC is 80% inhibition | |
a
CLSI M24, 3rd ed., 2018 (2).