On the inhibitory action of certain anilin dyes upon bacterial development

Abstract

The triamino triphenyl methanes possess a well-marked inhibitory power over the development of certain pathogenic organisms, notably staphylococci, streptococci, pneumococci and meningococci, besides the anthrax bacillus and actinomyces. This is quite pronounced, even in a dilution of 1 : 100,000. The common pathogenic bacilli are not affected by the dyes in question, in this concentration.

The inhibitory effect is referable to the underlying chromophoric group, and the presence of the basic auxochromic groups. If the basicity of the dye is diminished by the replacement of the basic by acid auxochromic groups, or if such groups are introduced in addition to the basic groups, the inhibitory effect is destroyed.

Of the other classes of anilin dyes an inhibitory effect is produced only by those which contain the chromophonic radicles:

and here also, only by those which contain basic auxochromic radicles. Acid dyes possess no inhibitory properties. The most active inhibitory dyes are the triamino triphenyl methanes, while the indamins, the oxazins, the thiazins and azins are on the whole less active in this respect.

The inhibitory effect does not depend upon the color of the dye, as there are violet acid dyes which are non-inhibitory, and red basic dyes which are markedly inhibitory; similarly there are green dyes which are active and others which are inactive in this respect. The essential common factor evidently is the absence of acid and the presence of basic auxochromic groups. Not all representatives of the sensitive groups of organisms are equally influenced by the dyes in question, nor even by a single dye, nor are the different groups affected to the same extent. Certain dyes will inhibit the growth of all the different sensitive groups, while the effect of others is less extensive.