The antagonism of sulfonamide inhibition of certain lactobacilli and enterococci by pteroylglutamic acid and related compounds.

Several lines of evidence have indicated an interrelation between pteroic acid derivatives (Lactobacillus casei factor, folic acid, etc.) and sulfonamides in bacterial metabolism. Teply et al. (1) demonstrated that the inhibition of Lactobacillus arabinosus by sulfapyridine was reversed by a factor in liver extract which resembled folic acid. Also, Miller (2) found the synthesis of folic acid by Escherichia coli to be inhibited by sulfanilamide. Finally, Angier et al. (3) recently demonstrated that the PABA’ moiety occurs in the pteroic acid molecule. PABA is known to antagonize sulfonamides competitively (4). We have studied the effect of sulfonamides on the metabolism of pteroic acid derivatives both in organisms requiring the preformed molecules for growth and in those able to synthesize their own requirements. We have also investigated the possible antagonism of sulfonamides by these compounds and the mechanism of this antagonism where observed. In this paper, the results obtained with certain lactobacilli and enterococci are presented. A preliminary report of a portion of this work has previously been published (5).