The virulence of pathogenic bacteria is to some degree dependent on or modified by their environment, and, as the result of experiment, it is known that the virulence of such organisms may be raised by their passage through animals. On the other hand, it has been stated that the virulence of some is lost in a comparatively short time when cultivated on artificial media.1 Different strains of the same organism may differ to a marked degree in this respect, and conclusions in regard to a class of organisms should not be based on results obtained unless the organisms are from several sources.
Bacillus mallei is an organism handled frequently by many laboratory workers; consequently any fallacy in regard to loss of virulence in old cultures should be corrected, since, if one strain has proved virulent, all should be regarded as such unless proved to be otherwise.
At the Boston
ARMS BL. THE VIRULENCE OF OLD CULTURES AND SUBCULTURES OF BACILLUS MALLEI. JAMA. 1910;LIV(9):699. doi:10.1001/jama.1910.92550350001001h