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APPLICATION OF THE SINGLE-DOSE ASSAY TECHNIQUE TO PSITTACOSIS
FORT DETRICK FREDERICK MD
Pagination or Media Count:
When suspensions of psittacosis organisms were injected intracerebrally into groups of mice, a nearly linear relationship was observed between the concentration of the agent injected and the mean time to death of the mice. Thirty-four psittacosis preparations were assayed and by plotting the relationship between the reciprocal time to death for mice given the 10 to the minus 3 power dilution of agent and the MICLD sub 50 values for the preparations, a reference curve was established. This reference curve made it possible to estimate directly the LD sub 50 value of a psittacosis suspension of unknown concentration from the mean reciprocal time to death of a group of mice injected with a single dilution. In this work, the number of mice used was reduced by 62.5, the titrations were complete in 3 to 5 days compared with the usual 12 days, three to four times as many assays could be done in a day, and no assays had to be repeated because end points were not missed. In addition, the precision of the single-dilution assay compared favorably with that of the LD sub 50 titration.
APPROVED FOR PUBLIC RELEASE