VARIATION OF SALMONELLA PULLORUM 49 



The birds were maintained in separate cages. Each was inoculated intraperi- 

 toneal^ with 0.5 cc. of a saline suspension of the organism having a turbidity 

 equal to tube 2 of McFarland's nephelometer. Their sera were tested at frequent 

 intervals with known pullorum antigen, and in some instances with an antigen 

 prepared from Strain VIII, which represents the parent strain of variant Vlll-a. 

 (See Table 4.) In Table 17 are given the reactions of the different sera with known 

 pullorum antigen and with their homologous antigens nine days after the first 

 injection of the different strains. It will be seen that only one serum (Bird 3) 

 produced with the typical strain reacted with pullorum antigen. The reaction 

 appeared similar to that produced with the homologous antigen. The reaction 

 between the serum of Bird 1 and its homologous antigen (C) did not appear as 

 typical agglutination in the lower dilutions, and in the higher dilutions the 

 character of the settling was the same as in the antigen control. A similar observa- 

 tion was made with the serum of Bird 4, while the serum of Bird 2 did not react 

 with its homologous antigen. It appears from these results that the three variants 

 employed do not possess antigenic power equal to that of the typical normal 

 strain. 



Table 17. — Agglutination titres of sera tested with homologous and 



HETEROLOGOUS S. pullorum ANTIGEN. 



*Variants 

 **Normal strain 



Legend: 4' — complete agglutination 



3 — incomplete agglutination 

 2 — partial agglutination 

 1 — slight agglutination 

 — no agglutination 

 ? — not typical agglutination 

 S— settling of cells 



In a second experiment Strain VIII and its variant VHI-a were inoculated into 

 three and five mature birds, respectively. Each bird was inoculated intraperi- 

 toneally with 2 cc. of live antigen, with a turbidity equal to that of tube 2 of 

 McFarland's nephelometer. Six consecutive daily doses were administered to each 

 bird, except the birds inoculated with the variant, which received seven con- 

 secutive daily doses approximately one month after the first inoculation. Table 

 18 shows that the three birds injected with the normal strain developed a titre 

 within eight days after the first inoculation, while the birds receiving the variant 

 gave no agglutinin response until after the second series of inoculations. Further- 

 more, the agglutinin response observed in the birds receiving the variant was 

 extremely feeble. All birds were necropsied at the end of a period of 190 days. 

 While the titres at necropsy were considerably lower than those observed earlier, 

 the decrease in titre does not necessarily mean freedom from infection, since 

 S. pullorum was recovered from Bird 18950, which possessed a titre of 1:20. 



