Correlation between variable-number tandem-repeat-based genotypes and drug susceptibility in Mycobacterium avium isolates

Little is known about the correlation between genotype and drug susceptibility in Mycobacterium avium (Mav) strains isolated from patients with Mav infections. To examine whether drug susceptibility profile of Mav is associated with genotype, we carried out variable-number tandem-repeat (VNTR) typing and drug susceptibility testing for Mav isolates from Japanese with nodular-bronchiectasis (NB)-type and cavitary disease (CA)-type diseases. We performed M. avium tandem repeat (MATR)-VNTR typing and drug susceptibility testing by the broth dilution method, using macrolides, rifamycins, ethambutol, isoniazid, aminoglycosides, and quinolones, for Mav isolates from patients with NB and CA-type diseases (NB-Mav and CA-Mav). Based on the VNTR genotyping, the Mav strains were grouped into three clusters. There was no difference with respect to the distribution of NB-Mav and CA-Mav among the clusters. We observed a strong association between VNTR genotype and susceptibility to quinolones (levofloxacin, moxifloxacin, gatifloxacin, sitafloxacin, and garenoxacin) and ethambutol. There was essentially no significant difference in drug susceptibility between NB- and CA-Mav strains, although NB-Mav was somewhat more resistant to fluoroquinolones, especially gatifloxacin, than CA-Mav. There was a significant association between VNTR genotype and susceptibility to quinolones and ethambutol in Mav isolates from Japanese patients.