Abstract
A chemically defined culture medium for Streptococcus pyogenes C-203 is described. The addition of DNA ∗ ∗ The following abbreviations are used: PGA, pteroylglutamic acid; CF, citrovorum factor; PABA, ρ-aminobenzoic acid; TSB, trypticase soy broth; DNA, deoxyribose nucleic acid; RNA, ribose nucleic acid; CoA, coenzyme A. and acetate, but not of pteroylglutamic acid or leucovorin, to this medium reverses the inhibitory effect of 1:2-dihydro- s-triazines on this organism. RNA supplemented with acetate is inactive in this reversal but a combination of deoxyguanylic acid and thymidine is nearly as active as DNA. 1:2-Dihydro- s-triazines are synergistic with sulphonamides against S. pyogenes in the defined medium but not in crude media. DNA or its constituent deoxyribosides reverse this synergism but PABA is ineffective. S. pyogenes remains sensitive to 1:2-dihydro- s-triazines after repeated transfers in a defined culture medium containing no thiamine, and develops very little tolerance to these compounds following the addition of acetate and guanine to the medium; but the further addition of thiamine causes a greatly increased tolerance. This increase in tolerance of S. pyogenes to 1:2-dihydro- s-triazines, which develops with repeated transfers and is caused by the addition of acetate, guanine, and thiamine to the defined medium, is blocked by sulphonamides.
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