AGGLUTININS AND PRECIPITINS 



97 



The three rows of tubes are set up so as to use suspensions in each row 

 of bacillus typhosus, paratyphosus A, and paratyphosus B. The dilutions 

 may be carried further if necessary. The tubes are incubated in a water bath 

 at 55 C. for two hours, are read immediately, and, if desired, again after 

 twenty-four hours in the refrigerator. The standard method of Dreyer may 

 be adapted to other methods of dilution and incubation, but must be the 

 same in the study of every case. 



In unvaccinated individuals agglutination in a dilution of 1-25 

 against bacillus typhosus justifies suspicion, and if marked in dilu- 

 tion of 150 is nearly always diagnostic. Browning offers the fol- 

 lowing table as indicating positive reactions in each of the 

 diseases indicated. 



Organism 



B. typhosus 



B. paratyphosus A. 



B. paratyphosus B. 



Serum dilution 

 I-IOO 



1-50 (or even lower 1-20) 

 1-200 



These criteria are not applicable to vaccinated persons or those 

 who have previously had typhoid or paratyphoid fever. Martin and 

 Upjohn examined seventy-five persons from; seven to fourteen 

 months after typhoid vaccination and found that the serum of two- 

 thirds agglutinated bacillus typhosus in serum dilutions of 1-200, 

 and that of one-tenth agglutinated in dilutions of 1-800. These are 

 higher levels than are usually reached by unvaccinated persons dur- 

 ing the course of the disease. Vaccination with typhoid vaccine 

 produces minor agglutinins for para A and B, but in very low con- 

 centration. Triple vaccines produce agglutinins for para A and B, 

 but rarely in dilutions exceeding 1-50 or i-ioo. The following 

 chart, taken from Mackie and Wiltshire, as quoted by Browning, 

 illustrates the change in titer of blood serum in the course of infec- 

 tion with bacillus paratyphosus A. 





The first test in this patient was strongly suggestive, since it is 

 rare in a vaccinated individual to find the titer for either para A or B 

 to exceed that of typhosus. In our experience typhoid in the vac- 

 cinated is likely to show titers in the first week of 1-500 for typhosus, 

 i-ioo for para A, and 1-50 for para B ; toward the end of the 

 second week they are likely to be, respectively, 1-2500, 1-750, 

 1-250; and in the third week 1-3000 or higher for typhosus with 

 slight increases for para A and B. The titers then subside. It will 

 be noted that infection increases not only the major but also the 

 minor agglutinins. 

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