Fatty acid composition of mycobacterial lipids as an index of pathogenicity.

Five species of Mycobacterium were analyzed for the fatty acid composition of total and neutral lipids and of individual classes of phosphatides. The methyl esters of fatty acids were analyzed using the technique of gas liquid chromatography. It was found that myristic, palmitic, palmitoleic, and tuberculostearic acids were the major fatty acids present in all of the lipid components of these strains of tubercle bacilli. The ratio of unsaturated to saturated fatty acids is lowest in the most pathogenic strain, indicating a progressive increase in this ratio, and the highest ratio is represented by a saprophytic strain. An avian pathogenic organism falls in the center of this classification among the examined strains of mycobacteria. These results indicate that the ratio of unsaturated to saturated fatty acids of lipids can be used to determine and establish the pathogenic species of mycobacteria.