The Differential Diagnosis of Bovine Brucellosis from the Bactericidal Action of Blood Plasma

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Abstract
Brucella abortus organisms were grown on beef liver agar slants for 24 hrs. at 37[degree]C and suspended in dist. water containing 0.05% Tryptose peptone and 0.5% NaCl. This was diluted to a reading of 28 on the Libby Photronreflectome-ter and contained 1.5 X 109 live organisms per ml. It was diluted 1:1000 for final use. Sterile blood plasma samples were collected from normal and immune cattle and from those infected with Br. abortus. They were then prepd. in several dilutions. Each dilution was incubated with live organisms for 48 hrs. at 37[degree]C. The plasma action was measured by the degree of turbidity as compared with control tubes. No infected plasma sample in any dilution inhibited growth. Samples from most young calves inhibited growth in dilutions up to 1:160, probably because of ingestion of colostrum. Samples from heifers and adult cows after natural infection and recovery inhibited growth in a higher dilution than those from normal ones. This inhibition test is an accurate means of identifying infected young and adult cows and where the agglutn. titers range from 1:25 to 1:5000.