AGGLUTININS IN TYPHOID FEVER 113 



characteristics of the general class of bacteria to which they belong, but are 

 not agglutinated by their respective serum; as, for example, a strain of 

 typhoid bacilli, which are not agglutinated by any typhoid serum. The 

 only positive proof that they are typhoid bacilli is the ability to produce by 

 their injection into animals an active immunity against fully virulent 

 typhoid bacteria. 



Non-agglutinable strains of bacteria can be isolated especially from the lower ani- 

 mals. At times, however, they regain their agglutination property when they are 

 grown in artificial media and frequently subplanted. Possibly, the reason that the 

 bacteria become inagglutinable at all, is that they undergo immunization within the 

 organism against the existing agglutinins. By growing bacteria in agglutinating serum 

 for a certain time, one can obtain non-agglutinable strains. 



i. Agglutinins for typhoid and paratyphoid A and B, can, not 

 Agglutina- infrequently, be demonstrated in the patient's serum as early 

 T^h kl as t ^ ie ^i 1 ^ ^ a y> but as a rule, at about the beginning of the 

 and Para- secon d week of the disease. Moreover, they remain within 

 typhoid, the serum for several weeks after the illness and disappear 

 only gradually. A positive agglutination test does not, how- 

 ever, mean the existence of the corresponding disease. A healthy bacillus 

 carrier can also have an agglutinating serum. Some cases of icterus catar- 

 rhalis even give a positive Widal test. But in order to assign to this last 

 a correct explanation, one must remember that typhoid bacilli may remain 

 in the gall-bladder for years and thus lead to catarrhal inflammation and 

 stone formation. 



Partial agglutinins from coli infections must always be considered. 

 Some authorities mention a positive Widal, in connection with endocarditis 

 maligna, sepsis, malaria, phthisis, and miliary tuberculosis. 



An absence of the agglutination test, especially at the early part of an 

 illness, should not influence a negative diagnosis of typhoid too greatly, 

 inasmuch as many cases are known where the reaction appeared for the 

 first time during the period of convalescence. In the employment of this 

 test as an aid for the differential diagnosis between several bacterial in- 

 fections, it is best to titrate the serum to its limit, as the higher titer for 

 one class of bacteria generally speaks in favor of the infection by the same. 

 Paratyphoid serum agglutinates typhoid bacilli only slightly, while true 

 typhoid agglutinates both typhoid and paratyphoid bacteria with almost 

 equal strength. In severe and difficult cases, Castellani's test should be 

 performed. Paratyphoid B . serum always gives the limit of its agglutinat- 

 ing titer both with the pathogenic mouse typhoid and hog cholera bacillus. 



2. Cholera. Only rarely has the agglutination test been employed with 

 the serum of patients infected with cholera. On the other hand, if cultures 

 from a cholera stool are made upon a plate, the identification of the suspi- 

 cious colonies grown here is regularly conducted by means of this test. For 



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