Toxins, putative cell adhesins and fibronectin binding properties of Salmonella dublin

Fifty Salmonella dublin strains isolated from cattle and human diarrhoeal cases were assayed for toxin production, haemagglutination, cell-surface hydrophobicity and fibronectin-binding properties. Most strains (65% of tested) produced cytotonic toxins and cytotoxic factors when tested on Chinese hamster ovary (CHO) cells and rabbit skin test. However, only three strains produced a skin-permeability factor as determined in pig skin intra-dermal tests. None of the strains were positive in pig intestinal loop tests. Six of the 32 strains tested for 125I-fibronectin and its 125I-29 kDa N-terminal domain binding showed 10-17% and 6-10% binding, respectively. Most of the strains expressed mannose-sensitive haemagglutination (MSHA) (76%) and high cell-surface hydrophobicity (74%) when grown at 37 degrees C. At 20 degrees C the expression of MSHA and especially the expression of high cell-surface hydrophobicity were reduced. Twelve strains grown at 37 degrees C did not haemagglutinate erythrocytes from five animal species used in this study, while six of these strains expressed high cell-surface hydrophobicity. Salmonella dublin strains isolated in Denmark appeared to express a higher frequency of fimbriae type 1 (MSHA) and a lower frequency of high cell-surface hydrophobicity than the strains from external sources.