DETERMINING THE GERMICIDAL EFFICIENCY OF DISINFECTANTS

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Abstract
Current methods of examining disinfectants are reviewed and it is shown that in these tests germicidal efficiency against only a single test organism is determined. Since disinfectants generally are used to kill many pathogens other than the test organism used in these methods, it is suggested that pathogens representative of the more important groups of disease-producing microorganisms be used and a greatly simplified procedure employed. The following pathogens are suggested: B. typhosus, M. aureus, B. diphtheriae, B. tuberculosis, Dip. pneumoniae, Strep. hemolyticus and B. pestis. Cultures of these organisms must show normal resistance against some germicidal agent, and phenol has been arbitrarily chosen for this purpose. A standard resistance for M. aureus and Strep. hemolyticus, based on studies by the author, are given. Strains of M. aureus suitable for test purposes must not be killed by 1-70 phenol in 10 minutes, nor by 1-80 phenol in 15 minutes at 20[degree]C. when 0.5 cc. of broth culture is added to 5 cc. of diluted phenol. Strep. hemolyticus strains should not be killed by 1-90 phenol in 15 minutes nor by 1-80 phenol in 5 minutes under the same conditions. It is suggested that similar standards for the other pathogens listed as suitable for test organisms be determined and that only such cultures as show normal resistance be used in testing the germicidal efficiency of disinfectants.

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