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Journal Article

The Virulence of Old and of Recent Cultures of Bacillus pestis

George W. McCoy
The Journal of Infectious Diseases
Vol. 6, No. 2 (Apr. 1, 1909), pp. 170-180
Published by: Oxford University Press
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Page Count: 11

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Topics: Plague, Lesions, Inoculation, Virulence, Humans, Rats, Spleen, Bacillus, Control loops, Surgeons
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These experiments demonstrate that of eight cultures of B. pestis that have been carried on artificial media for long periods five (5) Jedda, Manila, Glasgow, New York, X, are highly virulent, all of the animals inoculated with these cultures having died. One culture, Reedy Island, is not constantly lethal for animals. Two of these cultures, Frisco and Bombay, are practically avirulent. The cultures isolated in San Francisco in the recent epidemic, Rat No. 66, Rat No. 82, Human No. 171, and Squirrel No. 1, are highly virulent. The size of the dose and the mode of administration of virulent cultures (cutaneously or subcutaneously) have no marked influence upon the length of time an animal will live after inoculation. In the last statement an exception must be made in the case of such a colossal dose as a whole agar culture which generally kills earlier than the smaller doses, but in the case of such a large dose it is not improbable that an intoxication, owing to the large mass of bacilli introduced, plays a part. Varying resistance of different guinea-pigs is of more importance than the dose of culture. Passing the culture through one guinea-pig has no appreciable influence in raising the virulence. These statements as to virulence refer only to guinea-pigs and white rats. Work is now in progress to determine the virulence of these cultures for wild rats (Mus norvegicus).