The lethal effect of tryptone-soya broth

Overnight cultures of V. cholerae, V. el tor, non-cholera vibrio, and Streptococcus pneumoniae in tryptone-soya broth (with 5% blood added for the last-named) failed to grow on subculture despite visible growth in all tubes. Viable counts and pH determinations of overnight cultures of various species in tryptone-soya broth, brain-heart infusion broth, and Lab-Lemco peptone broth show that death in tryptone-soya broth is associated with the drop in pH resulting from fermentation of glucose in the medium and that this drop is greater than that produced by the same amount of glucose in brain-heart infusion broth. Some strains of pneumococci failed to grow in brain-heart infusion broth and it is suggested that both these media are unsuitable for blood cultures.