Characterization of the virulence and antigenic structure of Salmonella typhimurium strains with lipopolysaccharide core defects.

The virulence and antigenic characters of Salmonella typhimurium strains, identical except for known lipopolysaccharide core defects, were compared. Smooth strains multiplied extensively and killed most mice. Deep rough strains containing only heptose I or heptose I and II in the rough core were completely eliminated after 6 h, whereas more superficial rough strains containing additional core sugars could be detected in low numbers (10(4) colony-forming units/g of tissue) for at least 7 days postinjection. Normal human serum exhaustively absorbed with certain rough strains was tested for ability to kill other rough strains. Two strains with the most superficial defects (rfaJ, rfaL) each had a unique serological character; strains with deeper defects showed much cross-reactivity. Similarities between the susceptibility of strains to the bactericidal effect of specifically absorbed serum correlated, in some cases, with similarities in in vivo behavior.