Pseudomonas aeruginosa is a Gram-negative bacterium widely distributed in nature and causing opportunistic infections in humans. P. aeruginosa is an important bacterial pathogen of nosocomial (hospital derived) infections, and it can also cause life threatening diseases in patients with cancer, burn wounds, cystic fibrosis and those that have received immunosuppressive therapy. Lipopolysaccharide (LPS) is an integral component of the P. aeruginosa cell envelope, occupying the outer leaflet of the outer membrane in this pathogen. The outer core of P. aeruginosa LPS is composed of one d-galactosamine (GalN), one l-Rha, and three or four d-glucose (GlcI–GlcIV) residues. It exists in two structurally distinct glycoforms, called “uncapped” and “capped” which basically differ in position and linkage of an l-Rha residue in each structure