THE EFFECTS OF THREONINE ON POPULATION CHANGES AND VIRULENCE OF SALMONELLA TYPHIMURIUM

Abstract

There is considerable evidence that nutrition is capable of modifying infec-tions in experimental animals (Schneider, 1949; Clark, 1950), yet very little is known about the causative mechanisms of these effects. In addition, recent in-vestigations with Brucella (Goodlow, Mika, and Braun, 1950) demonstrated that specific amino acids have a significant effect on bacterial population changes in vitro involving the establishment of variants with different virulence. It was, therefore, of considerable interest to analyze a phenomenon observed in studies (Holtman and Page, 1950) with Salmonella typhimurium,-namely that the ad-ministration of threonine to infected guinea pigs resulted in a significant reduc-tion of survival time. Threonine was used because it had been found by qualita-tive chromatographic analysis that following Salmonella infection the tissues of guinea pigs contained free threonine not detected in similar tissues of nonin-fected animals. The reasons for the virulence-enhancing effect of threonine remained obscure until it was discovered that Salmonella populations recovered from threonine-treated animals contained a high proportion of threonine-re-