ANALYSIS OF THE VIRULENCE OF THE PLAGUE MICROBE AND PREPARATION OF LIVE PLAGUE VACCINES. REPORT 2. STUDY OF THE CELL COMPOSITION OF VIRULENT PLAGUE STRAINS OF DIFFERENT ORIGIN
ARMY BIOLOGICAL LABS FREDERICK MD
Pagination or Media Count:
The microbial population of highly virulent standard strains of the plague microbe are heterogeneous in cell composition. Individual colonies of the same strain differ from one another in virulence, immunogenicity, and fermenting activity. The most stable over a period of years and most alike in virulent properties are the rat and marmot strains, both freshly isolated and stored for a long time on nutrient media. A freshly isolated gerbil strain is less stable and uniform in cell composition. When stored on nutrient media without subculturing, the number of individuals with marked decrease in virulence grows from year to year. Virulent plague strains belonging to the continental variety contained colonies incapable of utilizing glycerin. Two glycerin-negative variants were isolated from strain 363 one, from strain 380. The glycerin-negative variant in the gerbil strain proved to be unstable. In the highly virulent strains, no close relationship was noted between the capacity of the colonies to ferment rhamnose or glycerin and virulence. Colonies that fermented rhamnose but not glycerin were highly virulent. The stability of all the basic characteristics, chiefly virulence, in the standard plague strains is largely determined by the nature of the strain, i.e., by the source from which it is isolated.