Small-Flaking or “O” Agglutinin After Intravenous Injections of Typhoid Vaccine

Since the introduction of the use of prophylactic typhoid vaccine, confusion has risen in interpreting the Widal agglutination reaction in the diagnosis of typhoid fever. Recently Felix 1 introduced the technic of demonstrating the presence of small-flaking or “O” agglutinin, which he claimed to occur only in infection but not after subcutaneous inoculation of the vaccine. Gardner 2 found that while “O” agglutinin can be produced by subcutaneous inoculation of the vaccine, it very rarely reaches a titer higher than 1:200. We wished to know whether this “O” agglutinin can be produced by repeated intravenous injections of the vaccine and whether its titer would be higher than that occurring after subcutaneous injections. After this work was begun, we noticed that Pijper and Dau had reported the finding of high titer “O” agglutination after oral ingestion of typhoid vaccine. 3

Large-flaking or “H” antigens were prepared by the usual method, namely, agar washings in saline or broth of B. typhosus, B. paratyphosus A and B. paratyphosus B preserved with 0.1% formalin, and used with suitable dilution. Small-flaking or “O” antigen was prepared from B. typhosus (Rawlin's strain) treated with alcohol; a modified Bien's method 4 was used which will be described in detail later.