Isolation of Salmonella from mesenteric lymph nodes of healthy cattle at slaughter.

Salmonella was sought in 100 normal, slaughtered cattle, most of which had been held for at least four days before slaughter. The organism was isolated from 76 cattle: from the rumen contents of 62, the ruminal lymph nodes of two and the mesenteric lymph nodes of 54. The mesenteric nodes of 35 of the cattle yielded salmonellae by direct plating; plate counts indicated that some nodes contained over 2500 organisms per gram. S typhimurium was the most prevalent serotype in the mesenteric nodes but not in the rumen; up to seven serotypes were isolated from one animal. In animals which have travelled or been held for several days before slaughter, the mesenteric lymph nodes may be a source of contamination for meat and edible offal in the abattoir.