Gas-chromatographic screening of capsular polysaccharides of Neisseria meningitidis

Abstract

Thirteen systemic strains, i e strains isolated from systemic infections, and 77 carrier isolates of Neisseria meningitidis were serogrouped by agglutination and analyzed by gas chromatography (GC) of phenol extracts. For systemic strains the sugar patterns were in accordance with their group-specific capsular polysaccharides (CPS). Some carrier isolates revealed unexpected GC profiles. Upon immunological retesting with new sera, GC results were generally confirmed. Occasional isolates initially serogrouped as B or Y completely lacked neuraminic acid. Some non-groupable isolates were shown by ultracentrifugation and GC to have significant amounts of this sugar likely to originate from CPS of known composition or from unknown polysaccharides. One such originally non-groupable isolate showed a weak agglutination reaction specifically with group B antiserum when reexamined. Generally, carrier isolates had lower amounts of CPS than systemic strains of the same group. Five successive isolates from one carrier were first serogrouped as X, Z or non-groupable, but they had high amounts of galactosamine and 2-keto-3-deoxy octonate, sugars characterizing CPS of serogroup 29E. These isolates were confirmed by agglutination with recently available group 29E antiserum to be of this serogroup, which has not been reported before in Norway. Ultracentrifugation revealed the presence of unknown polysaccharides containing glucose, galactose or glucosamine, but further purification of these polymers is required to determine their composition and immunological importance.