Isolation and identification of mycolic acids in Mycobacterium leprae and Mycobacterium lepraemurium

Mycolic acids with a characteristic structure were isolated by high performance-liquid-chromatography (HPLC) and mass-spectrometry from a foot pad of a nude mouse inoculated with Mycobacterium leprae. Mycolic acids with the same structure were also obtained from mycobacteria collected from the liver of an armadillo with experimental leprosy. Mycolic acids were isolated from Mycobacterium lepraemurium grown both in vivo and in vitro and these mycolic acids had different structures from those of M. leprae. Mycolic acid structures have great taxonomical significance. The methods used for isolating and analyzing mycolic acids appear applicable for the rapid identification of M. leprae in samples containing at least 10(9)-10(10) mycobacterial cells. Using our method, mycolic acids with the same structure were found in mycobacteria from armadillos experimentally infected with M. leprae and from armadillos with naturally acquired leprosy-like disease. It is likely, therefore, that the pathogenic mycobacteria of the naturally acquired disease are the same as, or at least closely related to, M. leprae. The present work suggests that M. leprae has a special position in mycobacterial phylogeny.