A Dehydrated Bacterial Agglutination Antigen (Bang's Disease). ∗ †

This is a preliminary report on the use of a dehydrated bacterial antigen for agglutination testing. The studies reported are confined to Bact. abortus antigen used in the diagnosis of Bang's disease of cattle.

Preparations of bacterial agglutination antigens for use in macroscopic methods of agglutination testing for disease have universally been made by suspending the bacteria in salt solution. The early workers 1 in this field considered the salt solution as essential for the agglutination phenomenon. This conclusion is known now 2 , 3 to be erroneous.

We are studying a method of agglutination testing in which a washed, dehydrated antigen preparation is mixed in measured quantities with fixed amounts of agglutination serum. The bacterial suspension, in distilled water, is evaporated to dryness in petri dishes in the incubator at 37.5°C. A film results which is transparent, amber colored and quite brittle. The antigen is kept in the dehydrated form until needed for use.

A satisfactory method of conveying the dehydrated antigen to the agglutinating serum in the necessary minute measured amounts has been effected by resuspending the antigen in distilled water. By suspending weighed quantities of the dehydrated antigen in definite amounts of water and pipetting this suspension, it is possible to measure precise amounts of the antigen onto a suitable glass plate. The water is again removed by evaporation before an electric fan. The antigen adheres to the glass plate.

Measured amounts of agglutinating serum are mixed with the dried antigen. This can be accomplished conveniently by stirring with an ordinary wooden toothpick. Macroscopic agglutination takes place rapidly, within one to several minutes, when the serum contains specific agglutinins.