The relationship of phenotype changes in Pseudomonas aeruginosa to the clinical condition of patients with cystic fibrosis.

Strains of Pseudomonas aeruginosa, isolated from the sputum of relatively fit patients with cystic fibrosis (CF) who had been recently colonized by the organism, showed typical cultural and serologic characteristics. The majority of strains of P. aeruginosa isolated from CF patients with chronic bronchopulmonary infection had 3 distinctive features, loss of 0 serotype reaction, expression of a new somatic antigen, and sensitivity to normal human serum. Patients with organisms with one or two of these features were more severely affected by the disease. The appearance of these variants may represent a critical stage in the progression of CF.