Lipopolysaccharide is composed of three distinct domains, lipid A, a short core of oligosaccharide and the O-antigen polysaccharide (Fig. 1) . The lipid A domain is the bioactive component and is recognized during human infection. The composition of the O-antigen varies between different Gram-negative bacterial strains. The presence or absence of O chains determines whether LPS is considered rough or smooth (3) . Full length O chains would render the LPS smooth while the absence or reduction of O-chains would make the LPS rough (3, 4) .