The Selective Action of Gentian Violet on Closely Related Bacterial Strains

In a previous communication 1 a selective bactericidal p roper ty possessed by gentian violet was described, and observations were reported to indicate the nature of this chemical affinity as exhibited in a study of a large number of representative bacteria. It was shown that bacteria could be sharply divided into two groups by their behavior toward gentian violet, either by staining the organisms directly, and then transplanting them to ordinary media, or by growing the unstained organisms on media containing the dye. In one of the groups of bacteria thus distinguished, gentian violet prevented growth; in the other it was without effect. The first group contained such organisms as B. subtills, B. anthracis, B. mycoides, M. aureus, M. albus, Streptococcus, and B. diphtheri~; in the other group fell B. typhosus, B. paratyphosus, B. coil communis, B. pyocyaneus, B. prodigiosus, B. cholerce suis, and many others. Organisms whose growth was inhibited by the dye were referred to as violet positive, while those whose growth was uninfluenced were termed violet negative. The selective action of the dye was well demonstrated by the use of divided plates, so made as to contain plain agar in one half and gentian violet agar in the other. A divided plate across which two violet positive and two violet negative organisms have been stroked is shown in figure I, which illustrates the selective action of the dye and the technique of its demonstration. The effect of the dye on a violet positive organism is shown in figure 2, which represents a divided plate that has been stroked with seropurulent material from a suppurating parotltis in typhoid fever. On the plain agar side of the plate a number of discrete colonies of M. aureus are seen growing, while the gentian violet side of the plate has remained sterile, though the track of the inoculating needle is plainly marked on the plate by a film of dried bloody serum. In smears from the gentian violet half of the plate, no organisms were to be found.