Eiko Kondo

AN ATTEMPT TO CULTIVATE MYCOBACTERIA IN SIMPLE SYNTHETIC LIQUID MEDIUM CONTAINING LECITHIN-CHOLESTEROL LIPOSOMES

An attempt was made to cultivate mycobacteria in a simple synthetic liquid medium containing lecithin-cholesterol liposomes. This lipid complex showed a marked growth-promoting effect on the submerged growth of M. tuberculosis and M. bovis. The role of lecithin as nutrient was suggested. The bacillary growth in such environment retained good viability, strong acid-fastness, and high virulence in mice. An avirulent strain of tubercle bacilli, H37Ra, did not respond to lecithin-cholesterol liposomes unlike the parent virulent strain, H37Rv. However, this was not a general rule for virulence, as a highly virulent strain of M. bovis (Ravenel) and an attenuated strain (BCG) both grew well in the presence of lipsomes. Lipid analysis showed that cholesterol in the liposome medium was esterified to some extent during the bacterial growth. It was discussed that the culture in the liposome-containing medium may present an experimental model for the study of interaction between mycobacteria and the macrophage membrane.

An electron microscopy study of intra-cellular mycobacteria in experimental mouse tuberculosis

Ultra-thin sections for electron microscopy (EM) were prepared from granulomatous lungs which developed in mice in response to experimental infection by a highly virulent strain of M. bovis. A subsidiary study was made of the EM appearance of mycobacteria separated from the lung tissue homogenate by differential centrifugation and trypsin-digestion. Examination of many micrographs showed that the phagosomal membrane may, at least partly, be in close contact with the cell wall of ingested mycobacteria. Such areas of contact often produce an electron-dense granularity or a row of evenly-spaced minute granules, accompanying the damage to the inner structure of the bacterial cell. A variety of disintegrating bacterial figures were observed, characterized by inward detachment of the plasma membrane, shrinkage and digestion of the cytoplasm, and occasional rupture of the cell wall. Various forms of lamellated and osmophilic inclusion bodies were present in macrophages, but their relation to ingested mycobacteria was uncertain.