Bacilli Resembling the Typhoid Bacillus 663 



BACILLI RESEMBLING THE TYPHOID BACILLUS. 



Bacillus typhosus is one of a group of organisms pos- 

 sessing a considerable number of common characteristics, 

 each member of which, however, can be differentiated by 

 some one fairly well-marked peculiarity. At one end of 

 the series is the typhoid bacillus, which we conceive to be 

 devoid of the power to liquefy gelatin, ferment sugars, form 

 indol, coagulate milk, or progressively form acids. At the 

 other extreme stands Bacillus coli, an organism whose 

 typical representatives coagulate milk, form indol, ferment 

 dextrose, lactose, saccharose, and maltose with the forma- 

 tion of hydrogen 'and carbon dioxid in the proportion of 



H 2^ 



coT ~ i- 



Between these extremes are numerous organisms known 

 as "intermediates." It is usually a simple matter to dif- 

 ferentiate these forms from the typical species at the two 

 ends of the series, but it is quite difficult to differentiate 

 them from one another. Whether they are of sufficient 

 importance to make it worth while to pay much attention 

 to them is, as yet, uncertain; and, indeed, we do not know 

 whether they are to be regarded as variations from the 

 type species or separate and distinct organisms. The fact 

 that some of them are associated with serious and fatal 

 disorders paracolon bacillus and bacillus of psittacosis 

 proves them, at least, to be important. 



In his careful review of the intermediate forms thus far 

 described, Buxton* summarizes the main points of difference 

 as follows: 



B. coli com- 



munis. Intermediates. B. typhosus. 



Coagulation of milk -+- 



Production of indol -j- 



Fermentation of lactose with gas .... -j- 



Fermentation of glucose with gas. . . -j- + 



Agglutination by typhoid serum .... -f- 



The characteristics of the three groups as shown by the 

 fermentation-test stand thus:f 



Gas upon Gas upon Gas upon 



dextrose. lactose. saccharose. 



Bacillus typhosis 



Intermediates + 



Bacillus coli communis -j- -f- 



Bacillus coli communior -j- -j- + 



c "Journal of Medical Research," vol. vm, No. i, June, 1902, p. 201. 

 t Hiss and Zinsser, "Text-book of Bacteriology," 1910, p. 429. 



