Enterotoxin production by Salmonella typhimurium strains of different virulence

1 Departments of Microbiology * Physiology, University of Birmingham, P. O. Box 363, Birmingham B15 2TT Institute of Child Health, Francis Road, Birmingham B16 8ET 4 Correspondence should be sent to Dr J. Stephen. Received March 18, 1985 Accepted April 15, 1985 Six strains of Salmonella typhimurium (TML, W118, LT7, SL1027, M206 and Thax-1) of known virulence and ability to induce fluid secretion when inoculated into the rabbit ileum were examined for enterotoxin production. Enterotoxic activity, assayed in the rabbit ileal-loop test, was detected in polymyxin-B extracts from all strains (with the possible exception of Thax-1) cultured for 6 h in casamino acid-yeast extract medium. The extracts were inactive in tissue-culture assays with CHO, Y-1 adrenal and Vero cells, and in the infant mouse assay for enterotoxin. There was no correlation between enterotoxigenicity in vitro and the ability of whole organisms to induce fluid secretion in vivo. The significance of these results in relation to salmonellosis is discussed.