NUTRITION OF THE HOST AND NATURAL RESISTANCE TO INFECTION : II. THE DIETARY EFFECT AS CONDITIONED BY THE HETEROGENEITY OF THE TEST PATHOGEN POPULATION.

The property of a diet of whole wheat and whole dried milk to promote a higher survival rate among a stock of heterogenetic, outbred W-Swiss mice subjected to S. enteritidis infection, over that promoted by a "synthetic" diet, has been shown to be a function of the infecting bacterial population. Broth cultures so prepared as presumably to yield S. enteritidis organisms of uniform character have consistently failed to reveal an effect of diet on natural resistance, even though the parent bacterial populations revealed a dietary effect. The dietary difference effect on natural resistance could not be demonstrated with an avirulent culture of S. typhimurium, or with a freshly prepared virulent culture of S. typhimurium presumably uniform in character. The dietary effect on natural resistance was demonstrated by employing a 1:1 mixture of avirulent and virulent cultures of S. typhimurium.