The influence of cultural conditions on the production of diphtheria toxin / A.F. Watson and Elsie Langstaff.

  • Watson, A. F.
Date:
[1927?]
Catalogue details

Licence: In copyright

Credit: The influence of cultural conditions on the production of diphtheria toxin / A.F. Watson and Elsie Langstaff. Source: Wellcome Collection.

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    heating effects must not be excluded. Although this cannot be demonstrated with every batch of medium, cases have been encountered during the course of the work. Five bottles of digest medium from a large number of preparations were autoclaved in fixed parts of the same autoclave. They were then sown with C. diphtherias from the same culture in isothermal positions in the incubator. At the end of ten days’ growth the cultures were carefully examined for purity and the filtrates tested for their flocculation value with antitoxin. The results of four of these experiments are collected in table XIII. Table XIII. Variations in the toxin production of individual filtrates from bottles of culture medium sterilised together in different parts of the same autoclave. Position in autoclave. Average Lf units per c.c. after 10 days’ growth. B. 2231. B. 2238. B. 2261. B. 2265. A 2 11 14 9 B 10 12 17 10 C 8 14 17 9 D 1 13 • • e 10 F 10 4 14 10 Percentage “variability”* of autoclaved group 90 71 18-3 10 Percentage “variability” of control filtered group 10*5 10-5 ?0 • • « * “Variability” (Max. Lf - Min. Lf) X 100 Max. Lf. The variations from filtrate to filtrate were greater in the autoclaved media than the control group which were filtered, and since all the other factors were kept constant this increased variability could be attributed only to uneven heating effects during autoclaving. If we accept this fact of the uneven distribution of heat in a large loaded autoclave, the variations of the media autoclaved at pH 8’0 can be understood. At this pH few media remain quite clear after autoclaving and the precipitation which occurs no doubt contributes to the variation. The sterilisation of media at pH 8'0 by methods involving increasing amounts of heat. The gradual destruction of the 'toxin-inducing powers of media adjusted to pH 8*0 by increasing heat as involved in different methods of sterilisation is shown in table XIY. There is a grading in the value of the filtrates, the over-autoclaved media being of little or no value. Heat may affect the growth- promoting powers of the media as well as the toxin-inducing properties, though this is not always the case. Growth-promoting “ substances ”
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