The effect of Salmonella pullorum infection on amino acids of the chick.

The pathology of pullorum disease has been frequently described, but little information exists concerning the mechanism by which Salmonella pullorum exerts a damaging effect on its host. While the organism becomes quite generally distributed throughout the chick during the course of disease, the fact that it tends to be prevalent in the liver suggests the possibility of. alterations in both protein and carbohydrate metabolism of this animal. It was shown by Holtman and Page in 1950 (unpublished data) that an experimental increase in the blood level of threonine in guinea pigs infected with Salmonella typhimurium resulted in a marked reduction of survival time. This amino acid, in vivo, was later demonstrated by Page, Goodlow, and Braun (1951) to induce significant bacterial population changes resulting in the establishment of variants of increased virulence. Whether this type of amino acid effect occurs during the progress of natural infection has not been determined although it is evident that the free amino acid levels of the blood may be reduced during the course of disease. For example, Woodward, Sbarra, and Holtman (1954) reported a decrease in all free amino acids and the complete disappearance of cysteine, arginine, and phenylalanine in the blood of rats infected with Bacterium tularense. The study reported here was undertaken to determine if changes occur in the free and bound amino acid levels of the blood and liver of chicks infected with S. pullorum. This particular combination was selected because it is a natural host-parasite relationship that can be conveniently studied in the laboratory and, thus, could be useful in shedding light on the alterations in host metabolism during the course of disease.