Serodiagnosis of Corynebacterium Pseudotuberculosis Infections in Sheep.

Abstract

In a serodiagnostic investigation on CorYnebacterium pseudotuberculosis infection in sheep, the phenomenon of synergistic haemolytic activity of metabolites from £. pseudotuberculosis and C. egui was investigated. It was found that sheep erythrocytes were more rapidly haemolysed when first treated with £. Rseudotuberculosis metabolite than when first treated with £. egui metabolite. It was concluded that Q. Rseudotuberculosis metabolite altered the erythrocytes in such a manner as to make them be subsequently lysed by C. egui metabolite. Neither the metabolite of Q. £seudotuberculosis nor that of £. egui alone haemo Lysed erythrocytes.. The haemolysis was inhibited by antiserum to either Q. egui metabolite or to £. pseudotuberculosis "bacterium. In ox blood agar the activities of the metabolites were identical to those of the respective bacterial cultures, but in addition to partial haemolysis, Q. l?seudotuberculosis culture had a betahaemolytic activity. This beta-haemolysis was not inhibited by 9... I2seudotubercu1osis bacterial antiserum. VThen fractionated by gel chromatography f the active substance of £. egui metabolite eluted homogeneously but that of Q. J2,seudotuberculosis - x - metabolite eluted in a profile suggestive of an aggregate of different molecules. In agar gel immunodiffusion, there was cross-reaction between £. egui metabolite and an antigen of £. Eseudotuberculosis but there was none between the metabolites. Sheep sera were then tested for antibodies to £. Eseudotuberculosis using bacterial agglutination test (BAT) and a modified haemolysis inhibition test (HIT). A C. Eseudotuberculosis strain passaged in artificial media was found to give an antigen stable enough for use in BAT. Any sheep serum however, was found to agglutinate this antigen. Treatment of serum with Staphylococcal protein A, 2 mercaptoethanol or adsorption with C. Eseudotuberculosis cells did not prevent this agglutination. Agglutination of C. pseudotuberculosis by sheep serum was therefore concluded to be non-specifico Cross-reaction between C. Eseudotuberculosis and Co £Iogenes in the agglutination test was not detected. BAT titres were found to increase generally with age of animals and possibly with infection. There was no relationship between BAT and HIT titres but HIT positive samples also had high BAT titres. In either test, there was a high positive correlation between age and the prevalence of seropositive cases in the sheep flocks. - xi - An enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to Q. ~seudotuberculosis exotoxin was performed and found slightly more sensitive than the HIT. Such a test would be a simple and rapid test for screening sheep for Q. ~seudotuberculosis~infection.