The use of a selective medium in the growth-agglutination test for chronic Erysipelothrix insidiosa infections in swine.

The use of a phosphate-buffered horse-meat infusion broth (pH 7.8) containing neomycin sulphate 50 pg/ml, kanamycin 400xg/ml and vancomycin 25 pg/ml was compared with the medium without antibiotics in the E. insidiosa growth-agglutination test on sterile and contaminated, positive and negative swine and rabbit serums. The addition of the inhibitory agents to the medium caused no visible growth depression on the 2 antigen strains employed — regardless of the percentage (S 40 %) of specific hyperimmune serum content. The use of the selective medium in testing hyperimmune serum revealed no significant difference in the recorded antibody titer as compared to the ordinarily used medium. The presence of some contaminants in the agglutinating system did not influence the results — provided that the multiplication of these organisms was inhibited (Table 1). The inhibitory efficiency was tested on 161 contaminated sw’ine serum samples and on 12 contaminated rabbit serums. None of the selective broth dilutions of these serums showed multiplication of contaminants during a 24 hrs. preincubation period or in a control tube after 48 hrs. incubation. The inhibitors allow bacteriologic aseptic technique in the procedure of the growth-agglutination test to be deviated to a certain limit. This limit was not exceeded in this material by applying a serum dilution technique otherwise used in agglutination tests with killed antigen. As the described method eliminates the demand of complete aseptic bleeding and serum preparation procedures or an elaborious sterile filtration procedure, and since the test can be used by any laboratory without previous preparation and testing of a killed antigen, the growth-agglutination test is recommended as a fast and reliable aid in the differential diagnosis of erysipelas arthritis on herd basis in swine.