Generation rates of faecal streptococci in various vehicles.

Potassium tellurite media gave the highest detrimental effects on the generation number of all tested faecal streptococci species. This applies to all investigated vehicles. However, drastic tellurite effects became more conspicuous with certain vehicles than with others. This is particularly true with acid and alkaline foods and water, especially with strains like Streptococcus bovis, Str. faecium, and Str. durans. Again, tellurite becomes more influencial with regard to old cells rather than young cells in the logarithmic phase. On the other hand, the use of thallous acetate as a concentration agent secured better results than either the tellurite or azide almost with all tested vehicles. Yet, sodium azide may be regarded as holding an intermediate position between tellurite and thallous acetate in terms of vehicles, Streptococcus species, and age of pollution. A lower number of generation resulted with all tested faecal streptococci species, using liquid media bearing more than one concentrating agent. This applied to water and milk examination.