The value of different serological tests in serotyping of Actinobacillus pleuropneumoniae strains

Immune sera were raised in rabbits against 12 serotypes of Actinobacillus pleuropneumoniae biotype I in order to compare serological tests for simplicity and sensitivity in serotype determination. The serological tests included the tube agglutination test with and without 2-mercaptoethanol addition, the indirect haemagglutination test with and without 2-mercaptoethanol, the immunodiffusion test and the coagglutination test. All these tests proved suitable for serotype determination with the reference strains; however, cross-reactions of varying degree were observed in all of them. Owing to its simplicity, rapidity and specificity, the coagglutination test appears to be the most suitable for primary serotyping. A more definite answer to the question could be obtained by serotyping strains isolated from field cases.