Abstract
Results given previously 1 have shown that bovine serum displayed a greater bactericidal activity against Brucella abortus than did a comparable amount of whole blood. Trials have accordingly been made to determine whether an increase in the titer of the serum bactericidins was to be found in individuals which had recovered from an infection with this organism.
The technic employed was essentially the same as that previously described. 1 2 The serum was taken from, (a) cows which had previously been artificially infected with Br. abortus, and from whose blood practically all agglutinins for the organisms had disappeared (i.e., “recovered”) and (b) from other animals which, insofar as was known, had had no contact with the organism (i.e., “normal”).
A uniform quantity (0.3 cc) of serum, or of dilutions of serum, from an individual was added to each of a series of small tubes into which had been placed 0.05 cc of decimal dilutions of a 36- or 48-hour culture of a standardized saline suspension of Br. abortus. To each of the tubes containing diluted serum was then added 0.2 cc of complement of beef serum. (The complement was obtained by absorbing beef serum, with heat-killed cells of Br. abortus, at 0 °C for 20-30 minutes.) Following incubation for 22-24 hours, the contents of each tube were poured into a petri dish with fluid pork-infusion agar, and incubated 5 or 6 days. For the bacterial control, 0.05 cc of each of the different dilutions was mixed with the fluid medium and poured into petri dishes. In these tests the number of organisms in the final dilution (-7) was generally between 10 and 50. Heated serum (0.3 cc). complement (0.3 cc), and the combination of heated serum (0.3 cc) and complement (0.2 cc), respectively, were treated in the same manner as the serum and diluted serum above.
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