Usefulness of variable numbers of tandem repeats typing in clinical strains of Mycobacterium avium

Abstract

We evaluated the usefulness of Variable Numbers of Tandem Repeats (VNTR) analysis, which was recently reported as a new typing method of Mycobacterium avium strains of animal origin, for strain differentiation of clinical isolates of M. avium in comparison with the standard IS1245-RFLP typing method. In addition, forty M. avium isolates recovered from sputum samples of same patient in different times were analyzed with VNTR typing method. The subjects were twenty-four clinical isolates of M. avium stocked at Higashi Nagoya National Hospital and discriminatory power was evaluated with Hunter Gaston Discriminatory Index (HGDI). Furthermore, forty M. avium isolates recovered from sputum samples of one patient obtained at four different times were analyzed by using this VNTR typing method. VNTR typing showed better discriminatory power for twenty-four clinical isolates than IS1245-RFLP method (HGDI: 0.975 vs 0.866). In the second study, polyclonal infection of four genotype strains with different allele profiles were detected. The ratio of mixture of the four different genotype strains varied during clinical course. We considered that VNTR typing method was very useful for discriminatory examination of M. avium.