MIC distributions of 35 antibiotics for 54 clinical isolates of Mycobacterium lentiflavum

Background: Mycobacterium lentiflavum is one of the non-tuberculosis mycobacteria (NTM) which can cause cervical lymphadenitis and pulmonary infection, and the isolation frequency from laboratories over Japan in 2014 is estimated to be 1.1%, in the eighth place of NTMs (Takaki A. IJTLD 20 (11); 2016: S457). It will be useful to have the MIC profile of antibiotics against M. lentiflavum clinical isolates for the practical management of the patients. Methods: A total of 54 M . lentiflavum isolates were collected over Japan through 2002 to 2015, and identified by 16S rRNA, rpoB , hsp65 sequencing. MICs of 35 antibiotics for one type strain and those 54 isolates were determined according to CLSI M24-A2 (CAMHB+5%OADC at 30˚C). Results: The mode MICs of clofazimine (CFZ), trimethoprim/sulfamethoxazole (TMP/SMX) and clarithromycin (CLR) were low; ≤0.12 µg/ml, 0.5/9.5 µg/ml and 4 µg/ml, respectively, while two isolates showed high MIC for CLR, >32 µg/ml, and the other two also showed 4/76 µg/ml for MIC of TMP/SMX. The mode MICs of four quinolones [ofloxacin (OFX), levofloxacin (LFX), moxifloxacin (MFX), sitafloxacin (SFX)] and rifabutin (RFB) were relatively low; 8 µg/ml, 4 µg/ml, 2 µg/ml, 2 µg/ml and 1 µg/ml, respectively. One isolate showed high MIC for OFX (>64 µg/ml) and LFX (64 µg/ml). Ten anti-tuberculosis drugs, 10 s-lactams, 4 tetracyclines, 2 aminoglycosides and linezolid showed high MICs. Discussion and Conclusion: Our data suggested that CFZ, TMP/SMX and CLR could be effective against M. lentiflavum, though some guidelines indicate the use of rifamycin, ethambutol and CLR as standard combination.