The environmental pathogen Mycobacterium ulcerans grows in amphibian cells at low temperatures

Mycobacterium ulcerans, the etiological agent of Buruli ulcers, is an environmental pathogen. We cultivated it in an amphibian (XTC-2) cell line that grows at 28 degrees C. By counting of Ziehl-Neelsen-stained mycobacteria and by quantitative PCR analysis, we found that M. ulcerans multiplies rapidly in association with XTC-2 cells. Transmission electron microscopy demonstrated the presence of intracellular M. ulcerans microorganisms. These data suggest an intracellular environmental niche, and we propose use of XTC-2 cells for isolation of M. ulcerans from environmental sources.