JOHNE'S BACILLUS 441 



Johne's Bacillus 



This organism was found by Johne and Frothingham (1895) in a chronic disease 

 of cattle characterized by massive infiltration of the intestinal tract. It was 

 believed at first to be an avian type of tubercle bacillus, but subsequent work has 

 rendered it clear that it is a different species of organism. 



Morphologically it is a short, thick rod, 1-2 /^ long, generally straight, with 

 rounded ends and parallel or slightly bulging sides ; it is non-motile. Gram- 

 positive, and strongly acid-fast. Staining is generally uniform, but may 

 occasionally be granular. It was first isolated in pure culture by Twort in 1910, 

 on a glycerine egg medium containing dead tubercle bacilli (Twort and Ingram 

 1912, 1913). Subsequently it was found that the saprophytic acid-fast 

 bacilli could replace the tubercle bacilli, and that a glycerine extract of the 

 organisms, or even liquid tuberculin, could be used (M'Fadyean et al. 1912). 

 Twort and Ingram advise the following medium : Cultures of Myco. phlei are 

 killed by steaming ; the growth is scraped ofi and dried ; the bacilli are then 

 ground in a mortar, and added in 0-5-1 -0 per cent, concentration to Dorset's egg 

 medium containing 4 per cent, of glycerine. On this medium primary cultures of 

 Johne's bacillus consist of tiny, dull-white colonies, rarely visible to the naked eye 

 in less than 4 weeks ; they are more or less circular in shape, and may be dis- 

 crete or confluent. As they grow older, they increase in size, become more elevated, 

 and turn a dull yellowish-white colour ; the edges remain thin, and from them 

 numerous irregular striations rise towards the central peak. In subcultures the 

 growth is more copious, more confluent, and may be slightly wrinkled. If the 

 saline in Dorset's egg medium is replaced by peptone beef broth, the growth is 

 still better ; and if sheep's brain broth or horse liver extract is used, the growth 

 cannot be distinguished from a Dorset's egg culture of human tubercle bacilli. 

 On glycerine agar containing phlei extract the growth is slower and less \agorous. 

 In glycerine broth with phlei extract added growth occurs in the form of a thin 

 surface film, which may later show irregular areas of thickening. After several 

 subcultures growth is more profuse, and may even occur in plain glycerine broth 

 without the addition of phlei extract. Growth occurs between 28° C. and 43° C., 

 the optimum temperature being 39° C. In culture the bacilli are very short, 

 often only about 1 jli in length ; there is no branching, but occasional club forms 

 are seen. Primary cultures are best made by treating the washed intestinal 

 mucosa with 20 per cent, antiformin for about 30 minutes, and seeding on to 

 a glycerine egg medium containing dead phlei or tubercle bacilli (see Minett 1942). 

 In what way the added organisms serve to promote the growth of Johne's bacillus 

 is not known ; they probably provide some nutrient substance, or enzyme, neces- 

 sary for its metabolism ; but that this substance is not specific to acid-fast bacilli 

 is shown by the fact that alcoholic extracts of such diverse substances as currant- 

 grapes, figs, oats, linseed, and the fungus Cantharellus aurantiacus, are all able 

 to replace the acid-fast bacilli (Twort and Ingram 1914). 



Whether the bacilli giving rise to Johne's disease in sheep are identical with 

 those in cattle is not clear. Apparently they are more difficult to grow, and in 

 primary culture may take 6 or 7 months to develop (Dunkin and Balfour-Jones 

 1935). On the other hand McEwen (1939) claims to have infected calves by 

 feeding them with material from diseased sheep, so that the difference between 

 the bovine and ovine bacilli may be less than Dunkin (1936) suggests. 



