Anne S. Youmans

Effect of the h37ra strain of m. Tuberculosis and of a mycobacterial rna fraction on tumor growth.

Summary Data are presented to show that both an H37Ra strain of Mycobacterium tuberculosis and a ribosomal RNA fraction from this strain are effective inhibitors of tumor growth in mice. Mice were pretreated with tubercle bacilli or RNA fraction and challenged 5 weeks later with mixtures of tumor cells and the respective pretreatment agents. Comparative data with BCG are presented. Inhibition did not appear to be due to any direct toxic effect of tubercle bacilli or ribosomal RNA fraction on tumor cells. The necessity, for an inhibitory effect, of tuberculin hypersensitivity was deemed unlikely because the ribosomal RNA fraction neither induces nor provokes tuberculin hypersensitivity. The inhibition realized with mycobacterial extract avoids the risk to the tumor-bearer of viable organisms.

Immunogenicity of particles isolated from Mycobacterium tuberculosis.

Summary 1. By following a carefully standardized procedure highly immunogenic particles uniformly were obtained by ultra-centrifugation from ground extracts of the H37Ra strain of Mycobacterium tuberculosis var. hominis. These particles, which ranged in size from 20-200 mμ, were just as effective as the living whole cells of this strain in protecting mice against a severe tuberculous infection. 2. The sediment comprised of the particles prepared from H37Ra cells was red in color and therefore has been termed the “red fraction.” The immunogenic activity of this fraction was almost eliminated when the particles were diluted 5 times or more with 0.25 M sucrose buffer, autoclaved at 126°C for 15 minutes, or filtered through a Berkefeld filter. However, lyophilization in 0.25 M sucrose buffer significantly reduced their immunogenic activity while lyophilization in 0.88 M sucrose buffer did not. Sonic oscillation appeared to have no significant effect on the activity of the particles. When the cells were washed 3 times with sucrose buffer the immunogenic activity was not affected. 3. In contrast to these findings, even though the same preparation procedures were followed, the fraction containing the particles when prepared from BCG cells was not always immunogenically active. The sediment containing the particles appeared grey in color, and the immunogenic activity was reduced by sonic vibration and by washing with sucrose buffer. 4. A chemical analysis of the particles from both H37Ra and BCG showed that they contain large amounts of lipid and no DNA. The significance of these findings is discussed.

Tuberculostatic action of chloromycetin in vitro and in vivo.

Summary and Conclusions The antibiotic Chloromycetin has been found to be only moderately bacteriostatic for virulent human type tubercle bacilli in vitro as compared with streptomycin or para-aminosalicylic acid. The majority of 19 human type strains studied were completely inhibited in their growth by between 6.25 and 12.5 micrograms or more of the drug in the presence of serum. One bovine strain was equally sensitive. This degree of bacteriostatic activity was not markedly affected by the number of tubercle bacilli present nor was the bacteriostatic activity of para-aminosalicylic acid or streptomycin enhanced by the addition of Chloromycetin. When administered subcutaneously, Chloromycetin has been shown to be ineffective, whereas, when admixed with the diet in concentrations of 0.5 and 0.25%, it was slightly effective for the suppression of experimental murine tuberculosis.

The Effect of Streptomycin on Well-Established Experimental Tuberculosis of Mice.

Conclusion Streptomycin to the amount of 3000 fig per day had a favorable effect upon the course of experimental tuberculosis in mice when treatment was initiated 7, 14 and 21 days following infection.

Response of mice to standard infecting doses of Mycobacterium tuberculosis var. hominis.

Summary 1. Over a 5-year period, 1950 through 1954, one to 6 groups per month of 10 to 30 mice each were infected intravenously with a 1 mg inoculum of the H37Rv strain of Mycobacterium tuberculosis var. hominis. 2. The median survival times of 177 (98.3%) of the 180 groups infected during this period fell between the 10th and 16th day inclusive. Statistical analyses revealed that there was no significant difference between the yearly means of the median survival times nor was there significant difference between the monthly means of the median survival times.

Effect of Mycobacterial Cell Components upon Susceptibility of Mice to Infection with M. tuberculosis.

Summary When virulent mycobacteria are mixed with large numbers of viable attenuated mycobacterial cells and injected intravenously into mice the susceptibility to tuberculous infection is markedly increased. By mixing different mycobacterial components, prepared by differential centrifugation of mechanically ruptured attenuated mycobacterial cells, and injecting these into mice, the resistance lowering factor was localized in the intracellular particulate material which sedimented at 144,000 × g. Subfractions, prepared by differential centrifugation, of this particulate fraction, were usually inactive but gained resistance lowering activity when any two were recombined. The particulate fraction is composed of cell membranes, enzymatically active particles and ribosomes.

The development in vitro of an avirulent, immunogenic variant of Mycobacterium tuberculosis var. hominis.

Summary A variant of the H37Rv strain of Mycobacterium tuberculosis var. hominis which appears to be avirulent for mice and guinea pigs, was developed in vitro by continual subculture over 3 years on a nitrogen-free synthetic medium. This new strain, designated H37RaN, resembled the parent H37Rv strain both macroscopically and microscopically, but differed metabolically from the parent strain in its reduced ability to utilize for growth carbon compounds related to the tricarboxylic acid cycle. This strain immunized mice as well as the frequently used immunogenic strains, H37Ra and BCG.