Early events in the pathogenesis of avian salmonellosis

Salmonellae are gastrointestinal pathogens of man and animals. However, str ains that are host-specific avian pathogens are often avirulent in mammals, and those which are nonspecific are commensal in poultry. The objective of this study was to determine whether host specificity was exhibited by bact erial abilities to invade epithelial cells or resist leukocyte killing. In this study, leukocytes isolated from humans and chickens were used to kill Salmonella in vitro. Both Salmonella pullorum, an avian-specific serotype, and Salmonella typhimurium, a broad-host-range serotype, were sensitive to killing by polymorphonuclear leukocytes isolated from both species. Both se rotypes replicated in cells of the MQ-NCSU avian-macrophage cell line. In c ontrast, S. pollorum was noninvasive for cultured epithelial Henle 407, chi ck kidney, chick ovary, and budgerigar abdominal tumor cells. In the bird c hallenge, however, S. typhimurium rapidly caused inflammation of the intest inal mucosa, but S. pullorum preferentially targeted the bursa of Fabricius prior to eliciting intestinal inflammation. Salmonella serotypes which cau se typhoid fever in mice have been shown to target the gut-associated lymph oid tissue. Observations from this study show that S. pullorum initiated a route of infection in chicks comparable to the route it takes in cases of e nteric fever.