174 CLINICAL BACTERIOLOGY. 



Bacteriologic Diagnosis of Typhoid Fever (Differentia- 

 tion of Typhoid-bacilli and Bacterium Coli Commune). 



The bacteriologic diagnosis of typhoid fever is usually 

 complicated by so many difficulties that it can not be con- 

 sidered as an aid in the clinical diagnosis. Isolation of the 

 typhoid-bacillus in the feces is a matter of great difficulty by 

 reason of the extraordinary resemblance of the bacillus to the 

 bacterium coli commune a resemblance that is so marked 

 that some observers (particularly the Lyons school) have 

 considered the two microorganisms identical. The micro- 

 scopic appearances, the agar-culture and the gelatin-culture 

 of both bacteria are absolutely alike. Potato-cultures 

 are, generally, though by no means always, different : the 

 bacterium coli gives rise to a thick, raised, circumscribed, 

 greasy, brownish deposit ; the typhoid-bacillus, on the 

 other hand, to an invisible, extensive coating. In using 

 potatoes for differential diagnostic purposes one-half of the 

 surface must be inoculated with the suspected bacteria, and 

 the other half with actual typhoid-bacilli. If the same 

 growth takes place on each half of the potato, it is highly 

 probable, providing there is agreement in other respects, 

 that the suspected organism is really the specific Eberth- 

 Gaffky bacillus. Among further points of differential 

 diagnosis as between typhoid-bacilli and coli-bacilli are the 

 following: (i) The bacterium coli coagulates milk; the 

 typhoid-bacillus does not. (2) The bacterium coli gener- 

 ates gas in nutrient media containing peptone, and especi- 

 ally in those containing grape-sugar, after exposure in 

 the thermostat for even a few hours ; the typhoid-bacillus 

 does not. It must, however, not be overlooked that, 

 though quite seldom, there occur varieties of coli-bacilli 

 that do not coagulate milk and do not cause fermentation 

 of grape-sugar, and thus can not, by any of the methods 

 thus far known, be absolutely differentiated from the 

 Eberth-Gaffky bacillus. A further point of differentiation 

 consists in the fact that the typhoid-bacillus does not yield the 

 indol-reaction, whereas the bacterium coli does. There is, 

 however, a variety of bacterium coli that does not generate 

 indol. The differentiation between the two bacteria thus re- 

 mains extremely difficult, and only such bacteria can be 

 decided with perfect certainty to be typhoid-bacilli as 

 possess all of the peculiarities described, and as have 

 been cultivated from the spleen of human beings who 



