Bacteriological studies: 1. The influence of immune serum on the biological properties of pneumococci.

  • Great Britain. Ministry of Health
Date:
1923
Catalogue details

Licence: Public Domain Mark

Credit: Bacteriological studies: 1. The influence of immune serum on the biological properties of pneumococci. Source: Wellcome Collection.

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    + The question of the stability of the R and § SAUNT will be considered later. In order to produce the variant from a normal strain snidtith the influence of specific serum, it is necessary that growth should occur. No alteration has been observed on plating a culture that has remained in contact with the specific serum at ice- chest temperature, or has been shaken with the serum at room temperature. The variant, therefore, is a new generation in the serum and not one of the original pneumococci altered by contact with the serum. This point is of importance when one compares the action of the serum upon the pneumococci in the animal body and in the test tube. Concentrated serum is not essential for the production of R forms. A dilution of 1 in 256 has caused a partial change of a smooth culture into a rough even with a single treatment. In addition, the blood of a mouse, which has received a dose of 0-2 c.c. of serum, has been collected about 18 hours later, and used as a culture medium. The pneumococci sown into it grew as in a dilute agglutinating serum, and from one such culture, after being incubated a night and then plated, several rough colonies were produced. Heterologous sera, as already stated, have generally no power to produce rough colonies from a smooth culture and numerous experiments have given negative results, even after several passages. I have, however, found one exceptional instance. A Type I. strain grown ina Type II. serum produced rough colonies when plated; these remained rough after many generations in blood broth. Until then it had seemed that the production of rough colonies in a given serum might serve as a test of the serological type. For example, the atypical II. A and II. B strains, which are believed by the American observers to be related to Type II., were grown in undiluted Type IJ. serum. Both strains grew uniformly and not in chains, thus showing the absence of agglutinins for them, and after five consecutive passages in ' Type II. serum the colonies remained of the normal smooth type. I have recorded elsewhere* evidence that the so-called atypical Type IT. strains are serologically distinct from Type II. DESCRIPTION OF THE R AND S Forms or PNEUMOCOCCUS COLONIES. All the serological varieties of pneumococci with the exception of Type III. yield on the same medium colonies which are indis- tinguishable. ‘There is, however, only a difference in degree between the Type III. colonies and the others, and sometimes the colonies of Type IJ. and the atypical strains of Group IV. are equally large and watery. The following description of the normal type of colony applies only to strains which have been * Reports on Pub. Health and Med. Subjects, Ministry of Health, No. 13, 1922.
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