Studies on a New Medium for Primary Isolation of Corynebacterium
Diphtheriae from the View Point of the Morphological Characteristics
1959 Volume 32 Issue 11 Pages 847-858
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1959 Volume 32 Issue 11 Pages 847-858
At present the bacteriological diagnosis of diphtheria is based on the gross appearance of the colonies on various kinds of tellurite-blood-agar media and the morphology on Loeffler serum medium. However, Corynebacterium diphtheriae on tellurite-blood-agar medium requires over 48 hours incubation for an accurate differentiation and not always shows a typical morphology. Also Loeffler medium, inspite of the important advantage of rapid growth and typical microscopic appearance of the organism, is not so simple to prepare.
In order to correct this disadvantage of both media, and to satisfy the clinical requirement of rapid diagnosis by visual image, morphological characteristics of the organism were studied, using beef heart infusion blood medium, added 0.5 % cow milk treated with several enzymes. The addition of cow milk treated with pancreatic ferment was found to develop the typical forms of the organism. And when compared the viable cell count of 10-6 mg/m1 suspension (each 6 strains of gravis, mitis and intermedius) on Loeffler medium and beef heart infusion blood medium, supplemented by pancreatic digestion of cow milk, the latter is remarkably superior.
Furthermore, a new beef heart infusion blood medium was prepared incorporating pancreatic digestion of cow milk, sodium fluoride and sodium arizarinate as used by Bregman for screening the suspicious colonies from their coloration. This new medium was found to be as satisfactory as Loeffler medium in regard to the morphology, appearance frequency of metachromatic bodies even in the primary isolation from patient, diameter of colony and also the detecting rate of a small number of organisms, decreasing at local lesion by antibiotic treatment.
It is pointed out that this new medium is superior to the Loeffler medium, in that the former is uniform in its quality, reproducible in its results, easy to prepare and longer preservability.
