Table 7

Interpretation of extended clarithromycin susceptibility results for Mycobacterium abscessus

Clarithromycin susceptibility days 3–5Clarithromycin susceptibility day 14Genetic implicationM. abscessus subspeciesMacrolide susceptibility phenotype
SusceptibleSusceptibleDysfunctional erm(41) geneM. a. massilienseMacrolide susceptible
SusceptibleResistantFunctional erm(41) geneM. a. abscessus
M. a. bolletii
Inducible macrolide resistance
ResistantResistant23S ribosomal RNA point mutationAnyHigh-level constitutive macrolide resistance