CHAPTER 16 

 MYCOBACTERIUM 



D EFINITION. Mycobacterium. 



Slender rods, which are stained with difficulty, but which, when once stained, 

 are acid-fast. Cells are sometimes swollen, clavate, cuneate, or even branched. 

 Non-motile. Gram-positive. No endospores. Growth on media slow. Aerobic. 

 Several species are pathogenic to animals. 



Tj^e species is M ycohacterium tuberculosis. 



The Acid-fast Bacteria. — The acid-fast bacteria are so called because of their 

 ability, when once stained, to resist subsequent decolorization by mineral acids. 

 The degree of acid-fastness varies with different members of the group, and in 

 any single member is liable to alteration with changed environmental conditions ; 

 these differences are never so distinct or so constant as to serve as a reliable means 

 of differentiating between the members of the group. 



The first member to be discovered was the leprosy bacillus in 1868 (see Hansen 

 1874). In 1882 came the discovery by Koch of the mammalian tubercle bacilli. 

 The work of Smith (1898), Vagedes (1898), Ravenel (1901), Kossel, Weber and 

 Heuss (1904, 1905), the English Royal Commission (Report 1911), and Park and 

 Krumwiede (1910), during the years 1898-1910, showed that these mammalian 

 bacilli could be divided into two types — the human and the bovine. 



The discovery of the avian type of tubercle bacillus was due largely to the 

 work of Rivolta (1889), Maffucci (1890, 1892), Cadiot, Gilbert and Roger (1890), 

 Sibley (1890), and Straus and Gamaleia (1891), during the years 1889 to 1891. The 

 work of Sibley (1889), Bataillon, Dubard and Terre (1897), Ledoux-Lebard (1898, 

 1900), Friedmann (1903), and Kuster (1905) from 1889 to 1905 served to differentiate 

 a fourth type of tubercle bacillus — the cold-blooded type. In 1895 Johne and 

 Frothingham described the organism which is now known as Johne's bacillus, and 

 which is responsible for a chronic enteritis in cattle. The rat leprosy bacillus 

 was discovered by Stefansky (1903) in 1901 at Odessa. During the years 1885 

 to 1906 a number of workers demonstrated the existence of the saprophytic acid- 

 fast bacilli — a group which, though able, under experimental conditions, to give 

 rise in mammals to lesions closely simulating those of tuberculosis, does not appear 

 capable of causing a definitely progressive disease. Amongst these bacilli the 

 most important are (i) the butter bacillus Myco. butyricum — isolated by Rabino- 

 witsch in 1897 from 23 out of 80 sj^ecimens of market butter examined in Germany, 

 and since then by numerous other workers (Petri 1898, Korn 1899, 1900, Tobler 

 1901, Beck 1905, Pellegrino 1906) ; (ii) Moeller's Grass bacilli i and ii. Moeller 

 isolated his first bacillus in 1898 from timothy-grass (Phleum pratense) ; hence 

 it is generally referred to as Mycobacterium phlei i, or more familiarly as the 



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