Disease progression of Mycobacterium avium pulmonary infection and the mycobacterial variable number tandem repeat (VNTR) typing.

Nontuberculous mycobacteriosis may progress to fatal chronic respiratory infections. Some cases remain stable over a relatively long period of time. With no well established progression predictors yet available, we conducted a retrospective analysis of the association between mycobacterial variable numbers of tandem repeat (VNTR) and clinical progression in 37 patients who were seen at the Department of Respiratory Medicine, Tohoku University Hospital between 2005 and 2006 and from whose respiratory tract specimens M. avium was isolated and cultured. The disease type in the 15 patients who began an antimicrobial therapy within 1 year after a bacteriological diagnosis was defined as progressive, and that in the 9 patients who began an antimicrobial therapy 2 years or longer after diagnosis was defined as stable. A cluster analysis of the mycobacterial VNTR genotypes showed concentrations of the progressive-type isolates and the stable-type isolates in different clusters. Furthermore, the study demonstrated that multiple logistic regression analysis can be used to construct a model for estimating, with statistical significance, progression of nontuberculous mycobacteriosis based on the mycobacterial VNTR genotype. These results indicated that whether a nontuberculous mycobacteriosis is progressive can be estimated by the VNTR genotyping of the nontuberculous mycobacterium.