IN VITRO SELECTION OF VARIANTS WITH VACCINAL PROPERTIES FROM VIRULENT STRAINS OF P. PESTIS
ARMY BIOLOGICAL LABS FREDERICK MD
Pagination or Media Count:
Subcultures with vaccine properties from virulent strains of the plague microbe may be selected according to the following features On the Jackson-Burrows medium they should grow in the form of pigmentless colonies, on magnesium-oxalate agar of Higuchi--Smith they should form colonies of the III order and should not disclose a tendency for a loss of residual virulence they should be nonvirulent for mice in doses of 1x10 to the 7th power bacteria, and under the influence of ferrous salts their virulence should be raised but without the restoration of the capability for pigment formation and without the restoration of virulence in a dose of 5000 bacteria they should cause immunity in 80--90 of white mice and guinea pigs in respect to virulent plague bacteria in a dose of 200 Dc1. A final judgement of the selected subcultures is decided following their approval on laboratory animals based on those tests which at the present time are accepted for evaluating vaccine strains of the plague microbe.