Pseudomonas aeruginosa infection in cystic fibrosis. Relationship between mucoid strains of Pseudomonas aeruginosa and the humoral immune response.

The occurrence of Pseudomonas aeruginosa in the respiratory tract of 70 cystic 
fibrosis patients and the occurrence of precipitins against Ps. aeruginosa in 
sera from the same patients have been investigated during one year 
by means of monthly bacteriological examinations of tracheal secretions and by 
means of crossed immunoelectrophoresis of a polyvalent Ps. aeruginosa antigen against 
sera from the patients. The one-year period prevalence rate of patients 
harbouring Ps. aeruginosa was 64 per cent. In newly colonized patients 
and in intermittently colonized patients non-mucoid strains were predominating, whereas mucoid 
strains were predominating in chronically colonized patients. The occurrence of mucoid 
strains, especially in chronically colonized patients, was associated with a significantly 
higher number of precipitins against Ps. aeruginosa than the occurrence of 
non-mucoid strains. Males chronically colonized with mucoid strains presented a significantly 
higher number of precipitins than females chronically colonized with mucoid strains 
and the number of precipitins was correlated with the duration of 
the chronic colonization with Ps. aeruginosa in males in contrast to 
females. The results are in accordance with the hypothesis that mucoid 
substance could be a virulence factor because it might inhibit the 
opsonizing effect of the precipitins on the mucoid cells and the 
complement dependent lysis of the cells hereby favouring mucoid strains at 
the expense on non-mucoid strains in the respiratory tract of cystic 
fibrosis patients. 