Hemagglutinating and hydrophobic surface properties of salmonellae producing enterotoxin neutralized by cholera anti-toxin

Abstract

Eleven Salmonella strains known to produce enterotoxin under aerobic culture conditions in deferrated (DF) medium at 37 degrees C were shown to produce enterotoxin with and without aeration at 22, 28, 37 and 42 degrees C. Heat-labile enterotoxin was generally produced with growth temperatures up to 37 degrees C irrespective of aeration. Heat-stable enterotoxin was produced up to 42 degrees C, mainly aerobically, as indicated by infant mouse assay (IMA), by six of the eleven strains tested. Nine strains produced heat-stable rapid permeability factor (RPF) in rabbit skin. Cholera anti-toxin neutralized reactivities of Salmonella heat-labile enterotoxin in four different biological assays. Mixed gangliosides also neutralized this activity in the cell-test systems. With guinea-pig erythrocytes, all strains underwent mannose-resistant hemagglutination (MRHA) irrespective of growth temperatures, i.e. 22 and 37 degrees C or medium, i.e., DF, tryptose soy broth (TSB) and colonization factor antigen (CFA) agar. At both growth temperatures, CFA agar-grown cells of each strain caused MRHA of bovine erythrocytes. Excepting three Salmonella typhimurium strains, DF broth-grown cells gave MRHA of bovine, chicken and human group A erythrocytes, CFA agar-grown cells caused MRHA of chicken and human blood, whereas TSB-grown cells caused few MRHA reactions. Salmonellae producing both heat-stable, (ST) and heat-labile, (LT) enterotoxins adsorbed to Phenyl Sepharose whereas salmonellae that produced only LT enterotoxin did not. The presence of MRHA adhesions did not correlate with cell-surface hydrophobicity. However, mannose-resistant hemagglutinins may occur more commonly among salmonellae than has been previously recognized.