Developing Tadpole as a Comparative Animal Model to Study Pathogenicity.

is an emerging, nontuberculosis mycobacterium (NTM) that infects humans. has two morphotypes, smooth (S) and rough (R), related to the production of glycopeptidolipid (GPL), that differ in pathogenesis. To further understand the pathogenicity of these morphotypes in vivo, the amphibian was used as an alternative animal model. infections have been previously modeled in zebrafish embryos and mice, but are cleared early from immunocompetent mice, preventing the study of chronic infection, and the zebrafish model cannot be used to model a pulmonary infection and T cell involvement. Here, we show that tadpoles, which have lungs and T cells, can be used as a complementary model for persistent infection and pathogenesis. Intraperitoneal (IP) inoculation of S and R morphotypes disseminated to tadpole tissues including liver and lungs, persisting for up to 40 days without significant mortality. Furthermore, the R morphotype was more persistent, maintaining a higher bacterial load at 40 days postinoculation. In contrast, the intracardiac (IC) inoculation with S induced significantly greater mortality than inoculation with the R form. These data suggest that tadpoles can serve as a useful comparative experimental organism to investigate pathogenesis and host resistance to .