ABSTRACT
We describe a 57-year-old man with steroid-dependent myasthenia gravis and progressive ulcerating leg nodules due to clarithromycin-resistant Mycobacterium chelonae. The patient was successfully treated with linezolid.
Subject(s)
Acetamides/therapeutic use , Anti-Bacterial Agents/therapeutic use , Mycobacterium Infections, Nontuberculous/drug therapy , Mycobacterium chelonae/isolation & purification , Oxazolidinones/therapeutic use , Humans , Linezolid , Male , Middle Aged , Mycobacterium Infections, Nontuberculous/microbiology , Treatment OutcomeABSTRACT
Linezolid was tested by broth microdilution against 140 clinical Nocardia isolates belonging to seven species. The MIC at which 50% of the strains are inhibited (MIC50) and MIC90 for all species other than Nocardia farcinica were 2 and 4 microg/ml. Linezolid is the first antimicrobial agent demonstrated to be active against all Nocardia species.
Subject(s)
Acetamides/pharmacology , Anti-Bacterial Agents/pharmacology , Nocardia/drug effects , Oxazolidinones/pharmacology , Linezolid , Microbial Sensitivity Tests , Species SpecificityABSTRACT
Linezolid is an oxazolidinone available as an oral drug which has activity against most gram-positive bacteria. However, few species of the genus Mycobacterium have been studied. We tested 249 clinical isolates and 10 reference strains of rapidly growing mycobacteria for susceptibility to linezolid by broth microdilution. Clinical species included the Mycobacterium fortuitum group (n = 74), M. abscessus (n = 98), M. chelonae (n = 50), M. mucogenicum (n = 10), and M. fortuitum third biovariant complex (10). The modal MIC for M. mucogenicum was 1.0 microg/ml, and the MIC at which 90% of the isolates tested are inhibited (MIC(90)) was 4 microg/ml; the modal MIC for the M. fortuitum group was 4 microg/ml, and the MIC(90) was 16 microg/ml; the modal MIC for the M. fortuitum third biovariant complex was 4 microg/ml, and the MIC(90) was 8 microg/ml; the modal MIC for M. chelonae was 8 microg/ml, and the MIC(90) was 16 microg/ml; and the modal MIC for M. abscessus was 32 microg/ml, and the MIC(90) was 64 microg/ml. Based on peak levels of linezolid in serum of 15 to 20 microg/ml, we propose the following broth MIC breakpoints for these species: susceptible, < or = 8 microg/ml; moderately susceptible, 16 microg/ml; and resistant, > or =32 microg/ml). These studies demonstrate the excellent potential of linezolid for therapy of rapidly growing mycobacteria.
