302 DISINFECTANTS AND ANTISEPTICS 



peptone, and 0.5 per cent sodium chloride in distilled water with a reaction between pH 6.0 

 and 7.0; the Hopkins strain of B. typhosus is used as the test organism; the temperature of 

 medication is 20° C; o.i cc. of culture is added to 5 cc. of diluted disinfectant; transfer is 

 made into subculture broth at 5, 7.5, 10, 12.5, and 15 minutes; a special spiral loop is used; 

 six phenol dilutions are used in each test instead of one; the phenol coefficient is calculated 

 from the weakest dilutions of disinfectant and phenol killing the test organism in 5, 10, and 

 15 minutes, the average from these three being taken and the figure obtained called the 

 "Hygienic Laboratory phenol coefficient."' 



The "Lancet" method, but little used in America, is also based on the Rideal- 

 Walker test, dififering from it in features somewhat similar to the Hygienic Laboratory 

 method. The use of B. coli instead of B. typhosus as a test organism constitutes one 

 of the chief points of difference between the Lancet method and the other standard 

 procedures. 



In 1 91 8 a committee on standardization of disinfectants appointed by the Lab- 

 oratory Section of the American Public Health Association reported a new method 

 for obtaining a phenol coefficient for disinfectants.^ In this "Report" the committee 

 modified the Hygienic Laboratory test in such a way as to get at least theoretically 

 more accurate results. Since this method has not come into practical use in this coun- 

 try a discussion of the procedures will not be given. However, one suggestion was 

 made which is of interest at this time, namely, that phenol coefficients against dis- 

 ease-producing bacteria other than B. typhosus should be determined. Since the ma- 

 jority of bacteriologists conducting phenol coefficient tests agree that a phenol coef- 

 ficient against one organism only is not of much value, further work on the use of dif- 

 ferent organisms seemed desirable. 



The writer^ suggested that representatives of the various groups of pathogens 

 should be used as test organisms for determining the germicidal efficiency of disin- 

 fectants. The organisms proposed were: B. typhosus (representative of the gram 

 negative, non-sporing bacilli); M. aureus (representative of the suppurative group, 

 and also gram positive cocci) ; B. diphtheriae (representative of granular gram positive 

 group, and diphtheroids) ; B. tuberculosis (representative of the acid fast group) ; Dip. 

 pneumoniae (representative of the encapsulated, gram positive cocci); Strep, he- 

 molyticus (representative of the septicemic pathogens, scarlet-fever organisms, ery- 

 sipelas, etc., gram positive chain-forming cocci). 



At that time the writer made a thorough study of the resistance of M. aureus to 

 phenol and outlined a method for the use of this organism in disinfectant testing. In 

 1927 the writer^ followed out this plan and presented a method for testing disinfect- 

 ants in which these various test organisms would be used. At this time detailed pro- 

 cedures for B. typhosus and M. aureus were given and tentative procedures for the 

 other pathogens were outlined. Objections to the Rideal- Walker and the Hygienic 

 Laboratory tests were discussed in detail. Experience with both of these methods has 

 shown weaknesses and inconsistencies which are responsible for inaccuracies. Both 



' Reprint 675, Pub. Health Rep., 36, 1559. 1921. 



2 "Report of the Committee on Standard Methods of Examining Disinfectants," Am. J. Pub. 

 llcilth, 7, 506. 1918. 



3 Reddish, George F.: Am. J. Pub. Ilealth, is, 534- 1925; ibid., 16, 283. 1926. 

 "• Reddish, George F.: op. cil., i6, 283. 1926. 



