Studies on Infection and Immunity in Experimental Typhoid Fever: VIII. Intravenous and Intra-Lymph Node Challenge of Chimpanzees with Salmonella typhi

The responses of chimpanzees to intravenous or intramesenteric lymph node challenge with Salmonella typhi were essentially the same as those following oral administration of the organisms. Bacteremia, fever, elevated sedimentation rates, increased C-reactive protein levels, positive stool cultures, antibody production, and clinical symptoms of disease (anorexia, lethargy, constipation, and dehydration) were manifested by the parenterally challenged animals. Differences in observed responses concerned the number and time of appearance of positive stool cultures and the degree of antibody formation. Stools were positive in fewer intravenously challenged animals and, when they did occur, appeared later than in orally infected animals. Antibody titers, on the other hand, were not only much higher in the parenterally challenged chimpanzees but reached a peak earlier than in animals infected via the oral route. These studies indicate that typhoid fever can be successfully established without initial involvement of the gastrointestinal tract. The implications of these findings for the pathogenesis of the disease are discussed briefly.