Polyagglutinability due to loss of O-antigenic determinants in Pseudomonas aeruginosa strains isolated from cystic fibrosis patients.

O-polyagglutinable P. aeruginosa are prevalent among chronically infected cystic fibrosis patients. In the present work, one O-group 3, one O-group 9 and one polyagglutinable 0–3/9 strain were analysed by use of both corresponding group specific antisera against the O-antigen and polyspecific antisera against all extractable antigens of the 3 strains. Quantitative immunoelectrophoresis and classical tube-agglutination methods were employed in the analysis. The results showed that the polyagglutinable strain contained 0.1% and the 0–9 strain 1%, respectively, of the O-antigen-containing LPS present in the 0–3 strain. It is discussed whether these differences represent a gradual antigenic adjustment to the defence mechanisms of the chronically infected patients.