Abstract
The characteristic attributes of both the rough and the smooth phases of the human tubercle bacillus have been amply recorded, but there has been no indication of the existence of a mucoid phase such as occurs in the dissociative pattern of many other microörganisms. 1 The isolation and subsequent growth of a mucoid phase in the human tubercle strain, H-37, is therefore briefly presented.
The parent strain was a stock culture of H-37 (intermediate rough phase) on Petragnini egg-medium kept under paraffin seal at room temperature 4 months. The growth was dry, rough, crumbly; the organisms were pleomorphic rods, some being hooked or curved, others showing Y-formation or lateral budding. Many rods contained large granules and all organisms were strongly acid-fast.
The first experimental transfers from this growth were made to 3 liquid mediums: (1) a synthetic medium, pH 7.2, (2) 5% glycerol broth, pH 7.6; (3) a double-strength veal-infusion broth, resterilized, with 2% neopeptone (Difco), 5% glycerol, 0.04% asparagin-1, pH 8.0. The transfers were made, not to the surface, but to the bottom of each flask of liquid. In the first 2 mediums the growth was very slow and finely granular, with no later turbidity or pellicle-formation. The organisms were coherent or discrete beaded acid-fast rods. Repeated transfers from these mediums to a variety of solid mediums produced the dry, rough growth only, typical of culture H-37 containing short acid-fast rods.
The growth in neo-peptone glycerol-broth, pH 8.0, at first resembled that in the other 2 mediums. On the 9th day of incubation at 37°C, however, there developed a slight cloud above the granular growth, and on the 10th day the fluid was turbid. A needle withdrawn from the fluid carried with it material that formed a filament 2 feet long before snapping from the surface of the broth.
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