Neutralization of Sulphonamide Inhibition of Yeast Growth by p-Aminobenzoic Acid

Abstract

FROM the many theories concerning the mode of action of sulphonamides, one by Fildes1 has recently emerged which, because of the volume of evidence brought forth in its support, is now considered the most logical explanation of sulphonamide bacteriostasis. Fildes has suggested that inhibitors of microbial growth are effective as a result of interference with an “essential metabolite”, a substance which he denned as having an essential part in the chain of synthesis necessary for growth. Woods2 was able to show that p-aminobenzoic acid nullified the growth-inhibitory action of sulphanilamide for a number of bacteria. Studies in this laboratory3 have confirmed Woods's original observations. It was found that the in vitro bacteriostatic effect of sulphanilamide, sulphapyridine, and sulphathiazole on streptococci, pneumococci, and staphylococci respectively was neutralized by p-aminobenzoic acid. Dimond4 has recently reported similar growth-inhibition of the fungus Trichophyton purpureum by sulphanilamide and neutralization of this inhibition by p-amino-benzoic acid. The present report describes the application of Woods's findings to yeast growth and suggests the importance of p-aminobenzoic acid in yeast metabolism.