Biochemical characterization and worldwide distribution of serologically distinct lipopolysaccharides of Haemophilus influenzae type b.

The sugar composition and the electrophoretic mobility in SDS-polyacrylamide gel electrophoresis of the various lipopolysaccharides (LPS) from clinical isolates of Haemophilus influenzae type b (Hib) were determined to correlate epidemiologic data with compositional data. Rabbit sera specific in Ouchterlony immunodiffusion for 10 different LPS (LPS 1-10) reacted with 647 or 690 Hib strains isolated from patients with invasive disease in various continents. Serotype 1 was predominant and was found in 550 isolates (80%). None of the Hib isolates reacted with antisera specific for LPS of two nonencapsulated isolates (LPS 5 and 6). Sugar analysis by gas-liquid chromatography of trimethylsilylated methyl glycosides revealed that the LPS of the 10 serotypes contained glucose, galactose, L-glycero-D-mannoheptose, and glucosamine in various proportions. LPS 1, 2, 8, and 9 contained the highest amounts of glucose and galactose relative to L-glycero-D-mannoheptose, which is considered present in constant amounts in H. influenzae LPS. LPS 1, 2, and 9 were most frequently found in invasive disease isolates.