A novel highly charged exopolysaccharide produced by two strains of Stenotrophomonas maltophilia recovered from patients with cystic fibrosis

► Stenotrophomonas maltophilia emerging pathogen for cystic fibrosis patients. ► Mucoid strains produce abundant exopolysaccharides. ► First structural definition of S. maltophilia exopolysaccharides. ► Tetrasaccharide repeating unit: 2 GalA, 1 GlcA, 1 Glc, 1 lactate, 2 O-acetyl groups. ► Highly negatively charged polymer similar to alginate produced by P. aeruginosa.