A Comparison of Virulence of Vibrio Cholerae Strains for the Embryonated Egg

The$LD_{50}$dose of Vibrio choleyae in the 13-day embryonated egg has been used as an index of variational differences in strains from different patients and from individual patients at different times during the course of infection. The$LD_{50}$doses for primary isolates early in an epidemic in Calcutta in 1953 were distributed over a wide range of values, which is suggestive of multiple sources of infection. The$LD_{50}$of daily isolates from individual patients indicates that the infecting strain may remain stable in some cases, but in others it appears to reflect temporary or progressive selection of mutants which arise during the course of infection. The results suggest, also, that the embryo$LD_{50}$might be used to investigate phenomena assoiated with epidemics. The avirulence of R strains for the embryonated egg and certain data with S strains indicate that embryo virulence of V. choleyae may be associated to an uncertain degree with its human virulence.