Detection of mycobacterial lipids in skin biopsies from leprosy patients

Thin-layer chromatography was used to compare lipid extracts from lepromatous skin biopsies with those from normal skin and from Mycobacterium leprae purified from armadillo spleen. Several lipids were found in infected skin which were absent from normal skin but corresponded to lipids present in the purified M. leprae. These included mycolic acids, a 6-deoxyhexose-containing lipid (glycolipid I) and a wax ester (possibly related to the Mycobacterium tuberculosis wax, phthiocerol dimycocerosate). Unlike Mycobacterium lepraemurium, M. leprae contained no C-type mycosides. In terms of lipid profile, M. leprae from armadillo spleen showed the same characteristics as bacilli from human skin samples. Quantitative analysis of mycobacterial lipids in lepromatous skin biopsies indicated that their concentrations were much higher than would be predicted from the number of acid-fast bacilli present. Accumulation of lipid debris from dead M. leprae could provide a protective environment in infected cells for remaining viable bacilli.