The lipid substances and cytopathic effects in man of BCG strain "Copenhagen" and attenuated vole bacillus strain "Prague".

Both virulent and attenuated acid-fast micro-organisms (including BCG) may provoke in the infected or vaccinated host cytopathic effects characterized by the formation of specific granulation tissue or caseous necrosis. The mycobacterial antigens responsible for these reactions are localized in the lipid substances which are not essential for eliciting immunity to tuberculosis.The lipid contents of 3 mycobacterial strains (BCG-Prague, BCG-Copenhagen, and MP-Prague-the latter an attenuated strain of Myco. microti) were repeatedly analysed during the period 1964-66. The latter 2 strains-of high and low lipid content respectively-were injected intradermally into 2 tuberculin-positive human volunteers and their cytopathic effects studied. The local reaction to MP-Prague was minimal and healed completely after 1 month; severe ulcerous reactions requiring 4 months to heal were observed with BCG-Copenhagen.Electron-microscopic investigation of ultrathin sections showed marked differences in the surface structure of these strains, indicating that they had different ways of disintegrating in vivo.The authors suggest that mycobacterial strains with a low lipid content and established immunogenicity may be more valuable for tuberculosis prophylaxis than BCG or other attenuated mycobacteria.