Role of Alginate O Acetylation in Resistance of Mucoid Pseudomonas aeruginosato Opsonic Phagocytosis

ABSTRACTEstablishment and maintenance of chronic lung infections with mucoid Pseudomonas aeruginosain patients with cystic fibrosis (CF) require that the bacteria avoid host defenses. Elaboration of the extracellular, O-acetylated mucoid exopolysaccharide, or alginate, is a major microbial factor in resistance to immune effectors. Here we show that O acetylation of alginate maximizes the resistance of mucoid P. aeruginosato antibody-independent opsonic killing and is the molecular basis for the resistance of mucoid P. aeruginosato normally nonopsonic but alginate-specific antibodies found in normal human sera and sera of infected CF patients. O acetylation of alginate appears to be critical for P. aeruginosaresistance to host immune effectors in CF patients.