Letter | Published:

Presence in Raw Cow's Milk of a Bactericidal Substance Specific for Certain Strains of Coliform Organisms

Naturevolume 155page22 (1945) | Download Citation



DURING the course of an investigation as to the reason why certain strains of coliform organisms when inoculated into raw 'sterile' milk did not reduce methylene blue or resazurin, it was found that these organisms were actually destroyed in milk held at 37° C. for six hours1. As all the tests for the presence of a bacteriophage in the raw milk were negative, it was considered that the destruction of the organisms might be due to a specific bactericidal substance in the milk. The destruction of the organisms appeared to be closely correlated with the temperature at which the milk was held, so it was considered that the substance was probably not thermostable and further work was undertaken to find out the effect of heat on the substance. To do this, 'sterile' raw milk which had been heated to temperatures varying from 52° to 53° C. for half an hour was inoculated with young broth cultures of the susceptible strains of coliform organisms, so as to give an approximate inoculation count on MacConkey's agar of 500,000–2,000,000 organisms per ml.

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  1. 1

    Morris, C. S., J. Dairy Res., 13, 115 (1943).

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  1. Advisory Dairy Bacteriological Department, Seale-Hayne Agricultural College, Newton Abbot, Devon

    • C. S. MORRIS


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