Comparison of Various Media for the Growth and Isolation of Brucella

Abstract

SUMMARY A basal medium containing 0·5 per cent (v/v) Tween 40 was able to support the growth of 80 per cent of the Brucella abortus Wilson type II cultures studied. The other strains of Brucella abortus, Brucella suis, Brucella melitensis and intermediate types grew on the basal medium either with or without the addition of Tween 40. The Tween agar medium containing the antibiotics bacitracin, polymyxin and actidione with or without ethyl violet, as well as the Albimi-antibiotic medium, would not support the growth of Brucella abortus type II strains. Serum dextrose agar plus antibiotics was the only selective medium which supported the growth of all the brucella cultures studied. Milks from 45 cows artificially infected with Brucella abortus Strain 544 (which is known to grow well on selective media) were cultured on various media. Of milks that were culturally positive on one or more of the media used, 80 per cent were culturally positive on Albimi-antibiotic (A.A.), 66 per cent on serum dextrose-antibiotic (S.D.A), 80 percent on Tween-antihiotic-ethyl violet (T.A.E.), 34 per cent on thio blood agar + antibiotics, 34 per cent on Morris’s medium and 30 per cent on serum dextrose agar + dyes media The addition of 15 viable Brucella abortus cells to 10 ml. of negative milk resulted in the isolation of the organism from 4 of the 12 plates when two 5-mm. loopfuls of the cream-deposit mixture were cultured.