Enterotoxin production and plasmid profiles in Salmonella typhimurium isolated from man

One hundred twenty-six isolates of Salmonella typhimurium from various clinical sources were tested for enterotoxin production and characterization of plasmid profile. Cell-free culture supernates and polymyxin B extracts of all the strains were assayed by rabbit ileal loop and skin permeability tests. Enterotoxic activity was detected in culture supernates of 32 strains. Twenty-one strains by both rabbit ileal loop and skin permeability tests, nine strains by skin permeability test, and two strains by rabbit ileal loop test were positive. Live culture of three enterotoxic strains, positive in culture supernates produced ileal secretion. Polymyxin B extracts from 6 hours and 18 hours broth cultures of all the strains were devoid of enterotoxicity. Ileal mucosa exposed to culture supernate of enterotoxigenic strains showed swollen and blunted villi with submucosal oedema while those exposed to polymyxin B extracts showed shortening of villi and sloughing of epithelial lining. Plasmid profiles of enterotoxigenic strains were heterogenous and grouped into 20 different profiles. No correlation could be established between plasmid profile, R-pattern, and enterotoxin production.