Sulfanilamide Bacteriostasis in the Presence of Mercuric Chloride and p-Aminobenzoic Acid.

The fact that urethane, a structurally unrelated compound, can inhibit sulfanilamide action has caused Johnson (1942) to question the competitive metabolite hypothesis developed by McIntosh and Whitby (1939), Stamp (1939), Fildes (1940), Green (1940), Woods (1940) and Woods and Fildes (1940). He would explain the antagonism of p-aminobenzoic acid on the basis of the well-known fact that narcotics in low concentration may be stimulative. Johnson has demonstrated stimulation and inhibition by p-aminobenzoic acid on the luminescence and growth of the luminous bacteria. Sulfanilamide itself is capable of stimulating bacterial growth (Finklestone-Sayliss et al., 1937; Johnson, 1942; Green et al., 1942; Lamanna, 1942) and in this property is related to narcotics in general. McIlwain (1942) has reported that the antagonism of p-aminobenzoic acid and urethane is not comparable in all respects and that the competition with essential metabolite hypothesis remains, therefore, fundamentally unchallenged. The present study presents relevant data describing the influence of p-aminobenzoic acid on the growth-stimulating concentration of sulfanilamide, and the mutual antagonism of mercuric chloride and sulfanilamide. A strain of Escherichia coli was used which gave abundant growth on the synthetic medium employed. The medium was copied after McLeod (1940).