Virulence in Relation to Early Phases of the Culture Cycle

Abstract

In view of the many physiological characteristics of bacteria which have been found to vary in different phases of the culture cycle, it was thought worth while to see if virulence for the animal host would also show correlation with “physiological youth.”

A strain of Salmonella enteritidis (pathogenic for mice by mouth) was cultivated in a one per cent peptone medium continuously aerated with the apparatus devised in this laboratory by H. H. Walker. The lag-period of this organism in this medium; was one hour and the period of logarithmic increase extended from the second to the sixth hour with decline setting in after the eighth hour.

Cultures in the first, fifth and sixth hours were used for the intraabdominal injection of 95 mice, one cc. amounts containing either 10,000 or 100,000 organisms being employed. All mice died in periods varying from one to 15 days. The mean time of survival was as follows:

There seems no evidence of any appreciable difference in virulence in the early phases of the culture cycle.