Immunochemistry of the K Antigens of Escherichia coli

From Echerichia coli O8:K87(B?):H19 an acidic polysaccharide was extracted with 45% aqueous phenol and purified by ultracentrifugation and fractional precipitation with cetyltrimethylammonium bromide (cetavlon). The acidic polysaccharide was homogenous as judged by ultracentrifugation analysis. It has a molecular weight ( S 20, w °/D) of 280 000, a sedimentation constant ( S ° 20,w ) of 3.07×10 −13 sec and a diffusion constant (D) of 0.85×10 −7 cm per sec. The acidic polysaccharide consists of equimolar amounts of l ‐fucosamine, glucosamine, glucose, galactose and glucuronic acid. It contains one O ‐acetyl group per 5 sugar units. Using periodate oxidation, hydrazinolysis, carboxyl reduction, methylation and partial acid hydrolysis it was found that the polysaccharide is built from about 270–300 of pentasaccharide repeating units which have the following structure:The linkage between the repeating units is a galactosyl‐(1,4)‐glucuronic‐acid bond. The O ‐acetyl groups are bound in the 2 position of either glucose or galactose of each repeating unit. With the acid of bacterial agglutination, passive haemagglutination and immune precipitation it was established that the acidic polysaccharide represents the K87 antigen of E. coli O8 : K87(B?) : H19. As determined by serological inhibition studies, the non‐reducing glucose units and O ‐acetyl groups (on the 2‐position of either glucose or galactose) are essential parts of the determinant group(s).