Abstract
The serological identity of “normal” cultures of the porcine and bovine strains of Brucella abortus has been shown by Traum. 1
The “R” variants of the porcine strain, although culturally and morphologically similar to those of the bovine strains previously reported, 2 appear to be more widely separated serologically from the bovine “R” cultures than are the parent cultures.
“R” variants of 7 strains of bovine source, 8 strains of porcine source and one strain from a spontaneously-infected laboratory guinea pig, were obtained by growing the cultures in broth plus 10% anti-Brucella abortus rabbit serum. These cultures included old stock cultures and recently-isolated cultures of both strains as well as cultures originally isolated in widely separated localities. Cells for absorption were obtained by growing the several cultures on 1% glucose-2% glycerine agar in sealed Blake bottles.
The absorption was accomplished by the addition to anti-serum of the same quantity of the various antigen suspensions which had been standardized to 1.5 mm. on the Gates opacimeter. In further absorption of the same serum, definite quantities of the standard suspensions were centrifuged until clear and the packed cells added to the serum.
Brucella abortus antisera from rabbits, cows and guinea pigs were used with results similar to those below. However, relatively low-titered anti “R” rabbit sera were most satisfactory for this differentiation. The absorbed sera were tested for agglutinins with our stock agglutinating fluid prepared from culture 80.
Table I shows the results of agglutination tests after the addition of several small absorbing doses of representative “R” antigens to anti 80 R serum.
The “R” variants of bovine source, with the exception of No. 80, removed the Brucella abortus agglutinins, while similar quantities of the “R” variant of porcine strains showed a much smaller absorbing capacity .
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