Relation between changes in the stability of Pasteurella tularensi8 suspensions and in its bacterial population. I. The stability of suspensions of Pasteurella tularensis in the presence of electrolytes

Population changes in Pasteurella tularensis were noticed thirty years ago by Francis (1922) who found that serial transfers of a virulent strain on serum-glucose agar resulted in loss of viru-lence. This phenomenon has been confirmed since then by other investigators (Foshay, 1932; Sny-der et al., 1946). In a riecent publication, Eigelsbach, Braun, and Herring (1951) describe the existence of sev-eral types of colonies in P. tularensis; however, they were unable to find a definite correlation between colony appearance and biological prop-erties. In liquid media, a rough variant appeared which became dominant in time. The authors as-sumed that in old cultures toxic factors accumu