The Effect of Aromatic Diamidines on Bacterial Growth: II. The Antagonism of Nucleic Acids and Polyamines.

It is generally accepted that the composition of the medium exerts an important influence on the action of antibacterial substances on microorgani. Many workers have succeeded in paralyzing the effect of antibacterials by the addition to the media of substances such as organ extracts, peptone, and bacterial extracts. Thus, Mcllwain (1941) counteracted the antibacterial effect of acriflavin on Escherichia coli and on hemolytic streptococci by the addition of nucleotides and of a concentrate of amino acids. Lockwood (1938) inhibited the action of sulfonamides on hemolytic streptococci by the addition of serum and peptone. Stamp (1939) observed a similar effect after the addition of heated suspensions of hemolytic streptococci, and Woods (1940) after the addition of yeast extracts. The asumption that the activity of these substances is associated with the presence of antagonists served as a starting point for the isolation and determination by Woods (1940) of para-aminobenzoic acid as the antagonist of sulfonamides. In a preliminary paper (1944) we reported the antagonistic effect of peptone, meat extract, yeast extract, and particularly of nucleotides against the antibacterial activity of aromatic diamidines. Since then Snell (1944) has reported on the antagonistic effect of some polyamines against the antibacterial action of propamidine on lactobacilli. The mechanism of the action of nucleotides against the antibacterial action of diamidines is the subject of the present study.