Slide-agglutination test of Haemophilus gallinarum antigen treated by trypsin to inhibit spontaneous agglutination.

Spontaneous agglutination of Haemophilus gallinarum (HG) cells cultured in Kato's broth was inhibited by trypsin treatment. The treated cell had the same antigenicity as the common antigen prepared from chicken meat infusion broth. Trypsinized antigen could be used in the slide-agglutination test to detect HG antibody in chicken serum.