BACTERICIDAL ACTION OF CR INDICATOR 87 



are quite as resistant to its action as are the other Gram-negative 

 bacteria. 4 



CONCLUSIONS 



The bactericidal power of CR (China blue-Rosolic acid) is due 

 entirely to the action of Rosolic acid. Moreover, the inhibition 

 of growth seems to be directed only against Gram-positive bac- 

 teria. Almost all Gram-negative bacteria tested grow readily on 

 a medium containing twenty-five times the amount of Rosolic 

 acid which is inhibitive for Gram-positive organisms. This 

 apparent selective action of Rosolic acid, coupled with its failure 

 to inhibit the growth of B. dysenteriae render this dye particularly 

 suitable for the preparation of selective media to be used for 

 the isolation of intestinal bacteria. 



REFERENCES 



Bailstein, F. 1896 Handbuch der Organische Chemie, 2, 1121. 



Bronfenbrenner, J. 1918 J. Med. Research, 39, 25. 



Churchman, J. W. 1912 J. Exp. Med., 16, 221. 



Churchman, J. W. 1913 J. Exp. Med., 17, 373. 



Holleman, A. F. 1911 Traits de Chimie Organique. Paris, p. 446. 



Kligler, I. J. 1918 J. Exp. Med., 27, 463. 



Krumwiede, C, and Pratt, J. S. 1914 J. Exp. Med., 19, 501. 



4 In this connection it is of interest to compare the chemical constitution of 

 rosolic acid with that of fuchsin, which is closely related to brilliant green, 

 malachite green, methyl and crystal violet, etc. Fuchsin has the formula: 



/C6H 3 CH 3 NH 2 

 C.c— C 6 H 4 NH 2 and is usually considered a derivative of triphenylmethane: 

 ^C 6 H 4 NH 2 C1 

 /CeHe 

 H — Cs— C 6 H 6 from which it can be prepared. Fuchsin is a substituted triamino 



\C 6 H 6 

 triphenylmethane, namely, a triamino tolyldiphenylmethane (5). Rosolic acid, 

 on the other hand, contains no amino group; its formula (Beilstein) (6) is: 



/C 6 H 3 CH 3 CH 

 C^— C 6 H 4 OH and it may be considered as a triphydroxy tolyl diphenyl- 



^C 6 H 4 = O 

 methane. It differs from fuchsin in containing hydroxy radicals in place of 

 amino radicals. It would seem, therefore, that this substitution is responsible 

 for the difference in action of the respective dyes upon the Dysentery bacillus. 



