Longitudinal studies of virulence factors of Pseudomonas aeruginosa in cystic fibrosis.

Among 111 strains of Pseudomonas aeruginosa from 49 children with cystic fibrosis, duration of colonization correlated with bacterial phenotype. We confirmed that P. aeruginosa from chronically colonized patients tended to be less motile, produce lower levels of protease and elastase, to be more sensitive to normal serum and to be polyagglutinating or untypable with standard antisera. We also showed that phospholipase and heat-stable hemolysin, concerned in metabolism of inorganic phosphate, and exotoxin A, were lower in these isolates. In longitudinal studies there was a decrease in virulence properties when isolates from the same patient were compared. No reversion from altered phenotype to 'wild-type' characteristics was found.