Growth rates of Salmonella colonies.

Most species of Salmonella grow rapidly and luxuriantly on ordinary agar media. In contrast, Salmonella pullorum and a few other species or types such as Salmonella abortus-ovis, Salmonella sendai, and Salmonella typhi-suis develop slowly and sparsely (Kauffmann, 1954). The reasons for the poor growth of these strains are not known. Also, their sparse growth makes isolation more difficult. In the present investigation, the rates of growth of a large number of Salmonella on solid media, and to a limited extent in liquid media, have been determined under a variety of environmental conditions. Particular attention has been given to the slow growth of S. pullorum and to attempts to increase its rate of development.