Acute lobar pneumonia : prevention and serum treatment / by Oswald T. Avery [and others].

Date:
1917
Catalogue details

Licence: Public Domain Mark

Credit: Acute lobar pneumonia : prevention and serum treatment / by Oswald T. Avery [and others]. Source: Wellcome Collection.

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    Cultural Characteristics —While growth may be obtained on the usual simple media, pneumococcus is, nevertheless, sensitive to slight variation in composition and reaction of the media. On media prepared from meat extract, growth is irregular and at best sparse and delicate. The pneumococcus colony on the surface of meat in- fusion agar, which has been enriched by the addition of a small amount of sterile defibrinated rabbit blood, presents certain charac- teristic features. The colony is small, moist, translucent, discrete, and round, with well defined edges, greenish in color, with a checker- like or ringed topography. The colony is finely granular, with a darker center, surrounded by lighter ringed areas. Pneumococcus on blood media produces a greenish zone of discoloration about the colonies. In broth pneumococcus grows diffusely, producing a uniform tur- bidity without pellicle and with a slight flocculent sediment. The turbidity of broth cultures begins to clear up after 24 hours’ incuba- tion, corresponding to the period of beginning autolysis and the passing into solution of the disintegrating bacterial protein. Gelatin is not liquefied; this medium, however, is not well adapted for the cultivation of pneumococcus, since no growth of this organism occurs at temperatures below 25°C. In milk and inulin serum water pneumococcus produces acid and coagulation of the medium. Inulin fermentation by pneumococcus is of differential value in distinguishing this organism from strepto- coccus. In studying the fermentation of inulin by pneumococcus, various irregularities are encountered. Although fermentation is the rule, it is not uncommon to find strains that fail to ferment this carbohydrate, and, in addition, the same strain may ferment it at one time, and fail to ferment it at another. The failure to ferment inulin in many instances may be due to the fact that not all prepara- tions of inulin are fermentable by pneumococcus, and not infrequently different lots of media, prepared from the same inulin, vary in their suitability for growth. Therefore, while inulin fermentation is of value in differential diagnosis of pneumococcus from other organ- isms, this reaction should be considered only as confirmatory evidence. The addition of simple carbohydrates to culture media enhances the initial growth of pneumococcus. However, the amount of acid