The capsular polysaccharide was isolated from Escherichia coli 010 : K5 : H4; it could not be obtained from a uncapsulated ( K Y ) mutant. It contains N-acetylglucosamine and glucuronic acid in a molar ratio of 1 : 1. Acid hydrolysis of the acidic polysaccharide as well as Smith degradation and degradation by deamination of the carboxyl-reduced polysaccharide suggested that the polysaccharide is composed of a disaccharide repeating unit. The data obtained by methylation analysis and nuclear magnetic resonance spectroscopy indicated that the repeating sequence of the capsular polysaccharide is the 4-fi-glucuronyl-I ,4-a-N-acetylglucosaminyl unit. This structure is similar to that of desulfo-heparin.It has been shown previously that pathogenicity of Escherichia coli bacteria correlated with the chemical and physical properties of their surface polysaccharide antigens [I, 21. E. coli strains with certain capsular polysaccharide antigens (K antigens) are frequently associated with urinary tract infections, especially in children [2 -41. The K antigens which are most prominent in these extraintestinal infections are KI, K2, K3, K5, K12 and K13. Encapsulated bacteria give rise to antibodies against K antigens in man and experimental animals. However, antibodies against the K5 polysaccharide antigen are only very rarely found after immunization with E. coli exhibiting the K5 antigen. It was therefore desirable to elucidate the structure of the K5 antigen in the hope that structural considerations may help to explain the poor immunogenicity of this important bacterial surface antigen.The following structural information of the above-mentioned K antigenic capsular polysaccharides of E. coli is available : the K1 antigen is a homopolysaccharide consisting of cc-2,S-linked neuraminic acid [5], the K2 antigen is a teichoicacid-like polymer consisting of galactopyranosyl-glycerol phosphate and galactofuranosyl-glycerol phosphate units in a molar ratio of 2: 1 [6] and the K13 antigen is a heteropolysaccharide with a repeating sequence of 3-linked ribose and 7-linked 2-keto-3-deoxy-manno-octulosonic acid (dOclA) [7]. In preliminary studies we have found that the K12 antigen consists of L-rhamnose and dOclA in a molar ratio of 2: 1 (unpublished results). In this publication we report the structure of the KS antigen from E. coli 010 : K5 : H4, compare it with similar bacterial polysaccharides and discuss the low immunogenicity of this capsular polysaccharide. MATERIALS AND METHODS Bacteria and CultivationEscherichia coli strain Bi 8337-41 (010 : K5 : H4) was used. It was obtained by Drs I. and F. Qrskov of the International Abbreviation. dOclA, 2-kelo-3-deoxy-~-manno-octulosonic acid Enzyme. b-Glucuronidase (EC 3.2.1.31).Escherichia Centre, Copenhagen. The growth conditions for the isolation of the capsular polysaccharide have been described previously [6,7]. Isolation and Purijication qf the Capsular PolysaccharideThe acidic capsular polysaccharide and the bacterial cells were precipitated from the liquid cultures by the additi...

The relationship of capsular types of Staphylococcus aureus to type of infection, carrier state, and phage type was studied in a collection of 477 isolates from 380 infection sites. Capsular polysaccharides were demonstrated by precipitation and agglutination with 11 monospecific antisera. When only one isolate from each infection was considered, 63% were of type 8 and 16% were of type 5. Of all the isolates tested, over 90% were encapsulated. We did not demonstrate any marked difference in the distribution of capsular types between isolates from the blood stream or purulent processes and isolates from healthy carriers or food. Most isolates from bovine mastitis milk had nontypeable capsules. The capsular type seemed stable in culture, and encapsulation had no apparent influence on susceptibility to phages. Of 27 phage-propagating strains maintained via culture transfer on artificial media over many years, 16 (59%) produced capsules. A striking association between certain phage patterns and capsular types was demonstrated.

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