Abstract
The results of an investigation on the development process of the human Mycobacterium tuberculosis, using the single cell method of approach, were reported. 1 Single organisms or small groups of from 2 to 6 were isolated in micro-droplets of Long's medium. These micro-droplets were preserved in such a manner that periodic observations could be made on identical individuals for several days or weeks. While variation did occur, the most usual type of reproductive process was the segmenting of the rod into 3 or more ovoid units, the reduction of these units into fine granules from which, later, extremely fine and delicate rods were found to develop. These rods elongated and thickened with varying rapidity until they became of the size and shape of what may be called the mature acid-fast tubercle bacillus. In the fine granule phase of the development process, as well as in the case of the exceedingly small and delicate rods which were observed to evolve from the granules, the organisms appear distinctly non-acid-fast.
The changes which were described are seemingly not allied to those recently described by Mellon and his coworkers 2 for the avian M. tuberculosis, in which a filterable phase is involved. In a recent study of one of us (K) no positive results with human M. tuberculosis, as far as filterability is concerned, have been obtained by culture or animal inoculation when the N, V, or W Berkefeld candles are employed, or with the neutrally charged membrane filters of Zsigmondy-Bachman. An occasional filtrate was found to become clouded with coccoid and diplococcoid types after long incubation, but upon critical examination the organism which grew up was found to be a non-pathogenic member of the diphtheroid group, which at times produces a considerable amount of acid-fast material and therefore could possibly be mistaken for Mycobacterium tuberculosis.
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