Action of Gentian Violet on Mucosus capsulatus. 149 



96 (792) 



Action of gentian violet on Mucosus capsulatus group. 



By J. G. Fitzergerald and Gertrude Mackintosh. 



[From the Hearst Laboratory of Pathology and Bacteriology, 

 University of California.] 



It has recently been shown by Churchman 1 in two interesting 

 communications bearing on the subject that the aniline dye, 

 gentian violet, has a selective bactericidal action on certain 

 bacteria. The action of the dye has been spoken of as bacterio- 

 static, indicating that the growth of some species of bacteria is 

 inhibited. In addition to this inhibiting influence, Churchman 

 believes the substance has also a very definite bactericidal action. 

 It was shown in the publications referred to that the action of 

 gentian violet as a bacteriostatic or bactericidal agent presented 

 in a general way a parallelism with the Gram stain. The majority 

 of gram positive bacteria are inhibited by gentian violet, while 

 the majority of gram negative bacteria are not. The action of 

 gentian violet can be observed on the divided plates or by staining 

 with gentian violet and determining subsequently whether the 

 microorganisms so treated will grow on culture media. On divided 

 plates, one half of an ordinary petri dish is covered with plain 

 nutrient agar, the other half with nutrient agar to which has been 

 added an aqueous solution of gentian violet; such a plate when 

 streaked with gram positive bacteria will show a growth only on 

 the side of the plate where there is no gentian violet, while gram 

 negative bacteria usually grow equally well on the plain agar and 

 on gentian violet agar. 



Since it seemed possible that the differentiation of closely 

 related species might be accomplished by the use of divided 

 gentian violet plates, the method has been used in a further study 

 of the Mucosus capsulatus group. In all, thirty-six strains of 

 bacteria have been investigated; they include B. ozcence, B. lactis 

 aerogenes, B. enteriditis, B. pneumonice Friedlander, B. rhino- 

 scleromatis, B. capsulatus, and B. Mucosus capsulatus. All of the 



1 Churchman, Journal Experimental Medicine, Vol. XVI, No. 2, August, 1912, 

 pp. 221-247, and Vol. XVI, No. 6, December, 1912, pp. 822-830. 



