Immunochemical investigations on lipopolysaccharides and acidic polysaccharides from serum-sensitive and serum-resistant strains of Escherichia coli isolated from urinary-tract infections

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Abstract
Factors that may determine the variable resistance of urinary strains of E. coli to the bactericidal activity of normal human serum were analyzed. No statistically significant difference was found in the amount of lipopolysaccharide (LPS) that could be extracted from serum-sensitive and serum-resistant strains by the phenol-water or warm-saline techniques. The ratio of LPS O-side-chain sugars to core sugars was not significantly greater in serum-resistant than in serum-sensitive strains. A sugar resembling D-glycero-D-mannoheptose was found in LPS from some of the strains; in 1 case the sugar was associated with the O-side-chain moiety. Lipopolysaccharides from all but 2 strains contained the E. coli R1 core structure. No consistent difference was observed between serum-sensitive and serum-resistant strains in the amount of acidic polysaccharide extracted or its red-cell agglutination-inhibiting activity; nor was a clear relationship found between sensitivity to serum and sensitivity to R-specific bacteriophages [FO, Br2, Br10, Fp1, 6SR, C21]. No one mechanism of serum resistance explains the response to serum of the E. coli strains examined in this study.