Introduction: To determine the characteristics of Mycobacterium avium in Japan, we compared the genetic properties of M. avium isolated in different countries.
Methods: A Mycobacterium avium tandem-repeat variable-number tandem-repeat (MATR-VNTR) analysis was performed using South Korean strains (n = 119) and Japanese strains (n = 76). In addition, we compared the frequencies of a new insertion sequence, ISMav6.
Results: A phylogenetic analysis identified different clusters between the two countries' strains. The prevalence of ISMav6 was significantly different between them, i.e., 75.0% in Japanese strains and 59.8% in the Korean ones (P < 0.035). The frequency of strains with IS Mav6 in the Shine-Dalgarno (SD) sequence of the cfp29 gene that is involved in the interferon-gamma induction was also different, with stronger significance (Japan: 38.2%, Korea: 12.4%, P < 0.001).
Discussion: It is possible that M. avium strains prevalent in Japan and in Korea are genetically distinct. The analyses of the presence of ISMav6, as well as the VNTR patterns of M.avium strains from many different countries would be a promising methodology in elucidating the causes of the recent increase in cases of pulmonary MAC diseases.