Distribution of Salmonella in the carcases of normal cattle at slaughter.

Lymph nodes and other tissues from a number of sites in the viscera, carcase and head were collected from 28 cattle which had been held for at least four days before slaughter. Salmoinella was isolated from 21 of these cattle, but in al except three of them it was confined to the gastrointestinal tract and the mesenteric lymph nodes. There was no evidence, in any of the animals, of spread beyond these nodes via the circulatory system. The distribution of infection suggested that the ileum and perhaps the caecum were the primary sites for invasion of the animal. Individual mesenteric nodes were collected from a further 85 cattle, and the number of salmonellae present in each was estimated by direct plating. Salmonella was isolated from 61 of these animals, and in each of 29 animals at least one node contained more than 5000 organisms per g. The predominant serotype in the mesenteric lymph nodes was Salmonella typhimurium.