The Influence of Subculture and of Streptococcal Extracts on the Growth Rates of Hemolytic Streptococci.

In a previous paper (Lewandowski and Stahly, 1944) it was shown that the growth rate of a group C hemolytic streptococcus, adapted to artificial media, became constant after a number of subcultures in an apparently favorable medium. It is the purpose of this paper to give a description of the materials and methods used and to present the growth rates of a group of strains maintained by passage through mice. The influence of streptococcal extracts on the growth rates of hemolytic streptococci also was investigated and the results are included in this paper. Relatively few studies concerning the growth rates of hemolytic streptococci have been reported. Mason (1935) calculated generation times for streptococci from a few growth curves which he obtained from the literature. Foster (1921), working with a single strain of hemolytic streptococcus, graphically indicated the change of pH in a standard broth medium during the growth of the organism. Beckwith and Rose (1925) observed that a strain of hemolytic streptococcus, which had been maintained by pleural passage in rabbits and was extremely virulent for these animals, proliferated more rapidly in infusion broth than a strain of the organism which had been maintained in artificial media and had become attenuated. Blundell (1942) suggested that an extract of the washings of a group A streptococcus may act as a growth factor in increasing the virulence of this bacterium for mice.