Sialic acid in the lipopolysaccharide of Haemophilus influenzae: strain distribution, influence on serum resistance and structural characterization

Mol Microbiol. 1999 Aug;33(4):679-92. doi: 10.1046/j.1365-2958.1999.01509.x.


A survey of Haemophilus influenzae strains indicated that around one-third of capsular strains and over two-thirds of non-typeable strains included sialic acid in their lipopolysaccharides (LPS). Mutation of the CMP-Neu5Ac synthetase gene (siaB) resulted in a sialylation-deficient phenotype. Isogenic pairs, wild type and siaB mutant of two non-typeable strains were used to demonstrate that sialic acid influences resistance to the killing effect of normal human serum but has little effect on attachment to, or invasion of, cultured human epithelial cells or neutrophils. We determine for the first time the site of attachment of sialic acid in the LPS of a non-typeable strain and report that a small proportion of glycoforms include two sialic acid residues in a disaccharide unit.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Adhesion / genetics
  • Bacterial Proteins / genetics
  • Carbohydrate Sequence
  • Cell Line
  • Disaccharides / chemistry
  • Drug Resistance / genetics
  • Haemophilus influenzae / enzymology
  • Haemophilus influenzae / genetics*
  • Lipopolysaccharides / chemistry*
  • Molecular Sequence Data
  • Mutation
  • N-Acetylneuraminic Acid / analysis
  • N-Acylneuraminate Cytidylyltransferase*
  • Neutrophils
  • Oligosaccharides / chemistry


  • Bacterial Proteins
  • Disaccharides
  • Lipopolysaccharides
  • Oligosaccharides
  • N-Acylneuraminate Cytidylyltransferase
  • SiaB protein, Neisseria meningitidis
  • N-Acetylneuraminic Acid