The Selective Bactericidal Action of Gentian Violet

During the course of an experimental study of bacteriuria, specimens of urine thought to contain Bacillus prodigiosus which had been injected into the circulation became contaminated with Bacillus subtilis. In an effort to rid them of this contamination, the effect on the two organisms of a number of common dyes was studied and a striking selective power possessed by gentian violet was brought to light. It is the purpose of this paper to record the original observations and to report an extension of the study to other bacteria. In my first experiments the dye was applied directly to the organisms, and its effect was noted after transplanting the stained bacteria to agar. Five drops of a saturated aqueous solution of gentian violet 1 were added to a forty-eight hour broth culture of the organism to be tested. The mixture was shaken well and allowed to stand for one hour. Transplants were then made to agar, a control inoculation of unstained organisms being made at the same time upon agar in a second tube. After twenty-four hours' incubation at 37 ° C. a striking selective property of the dye had asserted itself. When Bacillus prodigiosus was the organism used, no difference was observed between the tu~be inoculated with the stained, and that inoculated with the unstained organisms; growth was equally luxuriant in ,both (figure I). In the case of Bacillus subtilis, however, the results were quite different, for the stained subtilis failed to grow (figure 2).