Estimation of the biological activity (potency) of batches of brucellin prepared from a mucoid strain of Brucella abortus.

A study was conducted to determine the repeatability of a procedure used to prepare brucellin from a mucoid strain of Brucella abortus, and to determine the biological activity of those brucellins. The brucellins were standardized to contain 1 mg protein/ml, and their potency was estimated according to the European pharmacopoeia norm for tuberculin. Estimation of the potency was done in cattle that have been sensitized with living or killed brucellae. A brucellin that effectively detected acute and chronic brucellosis in cattle with experimentally induced brucellosis was used as reference brucellin. Results show that five of the nine batches of brucellin equalled the potency of the reference brucellin. Three brucellins had 79-88% potency of the reference brucellin and one had only 59%. Since the potency of various brucellins may vary it is suggested to estimate the potency of the brucellins according to the European pharmacopoeia norm for tuberculin.