Mycobacterium massiliense Type II genotype leads to higher level of colony forming units and TNF-α secretion from human monocytes than Type I genotype.

Recently, we introduced a novel Mycobacterium massiliense Type II genotype from Korean patients, in which all isolates showed only a rough (R) colony morphotype. In this study, we sought to compare clinical factors and virulence potentials of two genotypes of M. massiliense, Type I and Type II. Patients infected with Type II tend to be younger at infection than those infected with Type I (56.7 vs 62.3, p = 0.051). Type II was more significantly related to R colony type than Type I (34.1% vs 94.1%, p < 0.001). The Type II strain showed significantly more colony forming units (CFUs) and higher levels of TNF-α secretion in infection of human monocytes than the Type I strain. The challenge of extracted glycopeptidolipid (GPL) into human monocytes indicated that the loss of GPL from the cell wall of the Type II genotype led to a higher level of TNF-α secretion in a toll-like receptor 2(TLR2)-dependent manner. Taken together, our data suggest that the M. massiliense Type II genotype shows higher virulence than Type I, which may be due to the induction of TNF-α via the loss of GPL from the Type II cell wall.