Abstract
As a possible means of throwing light on the mode of action of the sulfonamides, the bacteriostatic effect of sulfathiazole, alone and with other drugs, has been studied as a function of temperature. Other such studies have given revealing information concerning the interaction of these substances with luminous bacteria, as well as isolated enzyme systems. 1
With the work of Kohn and Harris 2 as a guide, several experiments have been carried out on Escherichia coli. This organism was chosen because of its susceptibility to the drugs in question, and because it grows well over a rather wide temperature range. Included in this report are data concerning the rate of growth of E. coli, as a function of temperature, and to some extent, of the concentration of the added rate-influencing substances. The substances chosen are among those of current interest, sulfathiazole, p-aminobenzoic acid and urca. 3 These have been studied separately, and in some of the possible combinations. In general, the first results are in line with what one would predict.
In the method chosen, massive inocula of E. coli were added to the water clear SG (salt and glucose) medium, 2 or to this medium containing the indicated quantities of added substances. The large inocula were chosen to give, in a day's time, large turbidity differences, which were measured with a Coleman Universal spectrophotometer with the wave length dial set at 600 mμ. Comparisons were made against a SG medium blank, which had received the same treatment as the other tubes, though this always remained perfectly clear. This turbidity measurement, of course, gives the total number of organisms present, without regard to their viability.
A composite graph of results in Fig. 1 shows the effect of various substances and combinations of these substances on the growth rate of E. coli, as a function of temperature.
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