11
Table 5. Treatment Regimens for Mycobacterium abscessus
by Macrolide Susceptibility (Mutational and
Inducible Resistance)
Macrolide
Susceptibility Pattern
No. of
Drugs
c
Preferred Drugs
Frequency of
Dosing Mutational
a
Inducible
b
Susceptible Resistant Continuation
phase ≥2
Oral/inhaled
(choose 2–3)
Azithromycin
(clarithromycin)
e
Clofazimine
Linezolid
Inhaled amikacin
Resistant Susceptible
or resistant
Initial phase
≥4
Parenteral
(choose 2–3)
Amikacin
Imipenem (or
Cefoxitin)
Tigecycline
Oral (choose 2–3)
Azithromycin
(clarithromycin)
e
Clofazimine
Linezolid
Daily (3 times
weekly may
be used for IV
aminoglycosides)
Continuation
Phase ≥2
Oral/inhaled
(choose 2–3)
Azithromycin
(clarithromycin)
e
Clofazimine
Linezolid
Inhaled amikacin
a
Mutational resistance: None present—Isolate determined to be phenotypically susceptible at 3–5
days of incubation in culture. Present—Isolate determined to be phenotypically resistant at 3–5
days of incubation or sequencing identifies rrl mutation know to confer resistance.
b
Inducible resistance: Functional erm(41) gene—Isolate determined to be resistant aer 14 days of
incubation or sequencing identifies functional gene sequence. Nonfunctional erm(41) gene—Isolate
determined to be susceptible aer 14 days of incubation or sequencing identifies truncated sequence
or C28 mutation (in subspecies abscessus).
c
Initial phase refers to the time that the parenteral agents are being given. Continuation phase refers
to the subsequent phase of therapy that typically includes oral antimicrobial agents sometimes
paired with inhaled agents.
d
Azithromycin (clarithromycin) is active in this setting and should be used whenever possible.
e
Azithromycin (clarithromycin) activity is unlikely but can be added for its immunomodulatory
effects but should not be counted as active against M. abscessus with a functional erm(41) gene. In
this setting, frequent sputum cultures should be obtained to detect potentially new organisms like
M. avium complex.
(cont'd)
