440 M YCOBACTERI UM 



not yet been cultivated. Agglutination tests carried out with the serum of lepers 

 do not help in determining the aetiological significance of these organisms, for it has 

 been found that tubercle bacilli and saprophytic acid-fast bacilli are agglutinated 

 as well as the bacilli cultivated from leprosy (Duval and Wellman 1912). And 

 since it is impossible to reproduce typical leprosy in laboratory animals by 

 inoculation even with ground-up leprous material, it is clear that animal inocula- 

 tion tests are likewise useless in deciding this question. 



There is reason to believe that the non-chromogenic acid-fast bacilli cultivated 

 by various workers were in fact the real leprosy bacillus. Examination, however, 

 of the records reveals the fact that, though colonial development was obtainable 

 in the first two or three subcultures, attempts to carry on the bacilli indefinitely 

 in subculture almost invariably failed. Even in Soule and McKinley's work, which 

 incidentally Schlossmann (1933), Duval and Holt (1934a), Holt (1934a, b), and 

 Dharmendra and Lowe (1938) have failed to confirm, more and more difficulty 

 was experienced in obtaining growth with each successive subculture. Duval 

 (1910) many years ago brought evidence to show that leprosy bacilli were able 

 to grow in artificial media only so long as some of the original human leproma- 

 tous tissue persisted in the culture, and that the bacilli derived their nutriment 

 almost entirely from the autolytic products of this human protein material (see 

 also Duval 1934). These findings are supported by the more recent work of 

 Schlossmann (1933). If they are correct, they seem to afford an explanation 

 of many of the observed facts. Whether it will be possible, as Duval and Holt 

 (19346) anticipate, to replace the natural autolytic tissue products by protein- 

 split substances derived from other sources, is still doubtful. We may con- 

 clude tentatively that the leprosy bacillus has been grown in culture, but that 

 its indefinite subcultivation in artificial media has never been unequivocally 

 demonstrated. 



In these circumstances it is regrettable that a number of stock cultures in 

 various collections are labelled Mycobacterium leprce., and that so much work has 

 been expended in studying the various properties of these so-called leprosy bacilli. 

 Many of the strains are undoubtedly ordinary saprophytic acid-fast bacilli, and 

 their description under a false name can do nothing but cause confusion in the 

 literature. (For attempts at experimental reproduction of leprosy, see Chapter 60.) 



The Rat Leprosy Bacillus 



This organism was first described by Stefansky (1903) in 1901 at Odessa, where 

 it was giving rise to a leprosy-like disease in rats. The organisms, which have 

 never yet been definitely cultivated, are 3-5 /u long, are often slightly curved, and 

 have rounded ends. They are Gram-positive and strongly acid-fast, withstanding 

 5 per cent. H2SO4 and 95 per cent, alcohol for at least 5 minutes. Staining is often 

 granular. According to Marchoux (1933) the rat leprosy bacillus is killed by 

 exposure to moist heat at 60° C. for 15 minutes. It cannot withstand drying, 

 but it remains viable for 2 years or more in infected organs preserved in 40 per cent, 

 glycerol at 0-6° C. From the fact that human leprosy cannot be conveyed to 

 rats, it is probable that the leprosy and the rat leprosy bacilli are different. There 

 is reason to believe that some cases of human leprosy may be caused by the rat 

 leprosy bacillus (see Chapter 60). (For experimental reproduction of the disease 

 in rats, see Chapter 60.) 



