ALTERNATE ROUTES OF INVASION MAY AFFECT PATHOGENESIS OF SALMONELLA-TYPHIMURIUM IN SWINE

Transmission of Salmonella typhimurium in swine is traditionally belie ved to occur by the fecal-oral route, with invasion through the intest inal wall and Peyer's patches. However, involvement of the upper respi ratory tract may be equally important, An esophagotomy was performed o n 6- to 8-week-old pigs. Esophagotomized pigs were challenged intranas ally with 10(9) CFU of S. typhimurium cells and necropsied at 3, 6, 12 , and 18 h postinoculation (p.i.), By 3 h p.i., S. typhimurium was rec overed from cecum, colon, head, and thoracic tissues and from the midd le ileum involving a large number of Peyer's patches, The ileocolic ly mph nodes and ileocolic junction were not positive for S. typhimurium until 6 and 12 h p.i., respectively. Additional pigs were inoculated t ransthoracically with 10(9) CFU of S. typhimurium and necropsied at 3 and 18 h p.i. By 3 h p.i., all tissues were positive for S. typhimuriu m. Tonsil explants seeded,vith 10(9) CFU of S. typhimurium indicated t hat within 6 h p.i., S. typhimurium was located within the tonsilar cr ypts. These data show that after intranasal inoculation, S. typhimuriu m rapidly appears in the gut tissues and suggest that the tonsils and lung may be important sites for invasion and dissemination of Salmonel la species.