Antigenic relationship of Brucella ovis to Brucella abortus and Brucella melitensis using the complement fixation test.

WORTHINGTON, R. W. & MULDERS, MARIAS. G. Antigenic relationship of Brucellaovis to Brucella abortus and Brucella melitensis using the complement fixation test. Onderstepoort J. vet. Res., 36 (2) , 191-1 98, 1969. The CF test was used to investigate the serological relationship of Br. avis to Br. abortus and Br. melitensis. A definite antigenic relationship between Br. avis and Br. abortus could be demonstrated. Definitive results were obtained by absorbing sera with Br. avis , Br. melitensis a nd Br. abortus before testing. INTRODUCTION The aetiological agent of the most important cause of infectious epididymitis in rams was first isolated by Buddie & Boyes (1953) in New Zealand and by Simmons & Hall (1953) in Austra lia . Buddie (1956) described the organism and named it Brucella ol'is. The Subcommittee on the Taxonomy of Brucella of the International Committee on Bacteriological Nomenclatu re was not satisfied that the organism was correctly classified as a Brucella (according to Diaz, Jones & Wilson, 1967). The main objection was apparently that no serological relationship to smooth Brucella was revealed by aggl utination tests (Meyer & Cameron, 1956). More recent studies have shown that there are definite antigenic similarities between Br. avis and Brucella melitensis (Hughes, 1892), especially when Br. melitensis in the rough phase is used (Diaz, Jones & Wilso n, 1967). There seems little doubt, therefore, that the organism will now be accepted as a member of the genus Brucella. The question remaining is probably whether it is classed as a biotype of Br. melitensis or whether it is accepted as a separate species. In our experience the most valuable serological test for the detection of Br. avis antibodies in sheep is the complement fixation (CF) test. The object of the presen t study was to use the CF test to investigate the serological relationship between strains of Br. avis, iso lated in South Africa and in other countries, to smooth phase Br. melitensis and Br. abortus (Schmidt & Weiss , 1901). A furthe r object was to di scover whether there were antigenic differences between various South African strains of Br. ol'is. MATERIALS AND METHODS Strains: The Brucella strains used and details of their origin are li sted in Table I. Cultivation of organisms and preparation of cell suspensions Br. avis strains were grown in the liq uid medium described by Lawrence & Jones (1961) in large Ro ux flasks under a 15 per cent ca rbon dioxide atmosphere. The flasks were shaken on a shaking machine during incubation at 3rC for 72 hours. Cultures were then tested for purity, bulked, killed in a waterbath at 60 °C for 1 hour, washed twice in 0.85 per cent saline containing 0.5 per cent phenol, suspended in a small amount of phenol saline and used immediately for antigen production or stored at 4 °C until required for serum absorption tests. Similar washed suspensions of Br. abortus and Br. melitensis were prepared from cultures grown on potato agar medium in Roux flasks . TABLE I. Strains used in the investigation