Prevalence and persistence of polyagglutinable Pseudomonas aeruginosa in isolates from cystic fibrosis patients.

During the 17 years from 1972 to 1988 1010 Pseudomonas aeruginosa isolates from sputum samples of 183 cystic fibrosis patients attending the Danish Cystic Fibrosis Centre at Rigshospitalet were serogrouped and phage typed. The patients were chronically infected with Pseudomonas aeruginosa (range of duration of infection: 1-17 years). They attended the Centre monthly and since 1976 all had been hospitalized for 14 days every three months. The number of patients with Pseudomonas aeruginosa infection increased from 29 to 123 during the period 1972 to 1988 and the number of isolates typed ranged from 14 to 197 a year. About half of the patients had one to five monoagglutinable isolates before they had polyagglutinable isolates. The prevalence of polyagglutinable isolates each year increased during the observation period (range: 24% to 88%). In all, three quarters of the patients had polyagglutinable isolates in their last typed sample. During the 17-year period 81% of the patients harboured polyagglutinable isolates. 77% of these patients, however, were for periods colonized with monoagglutinable isolates (0-3, 0-6, 0-1, 0-2 (including 0-2, 0-5, 0-2/5 due to cross-reactions between 0-2 and 0-5) and 0-9 were most prevalent) either alone or concurrent with polyagglutinable isolates, whereas 5% harboured polyagglutinable isolates exclusively during the whole observed period of infection. Polyagglutinable isolates with a short phage pattern were more frequent than those with a long phage pattern during the entire period from 1972 to 1988, and the prevalence increased during the period. Twenty-eight percent of the patients had a persistent phage pattern for an average of seven years in spite of change of serogroup. Twenty-seven percent of the patients had a persistent monoagglutinable serogroup and phage pattern for an average of eight years. The increasing prevalence and persistence of polyagglutinable strains correlate with the improved survival of the patients and thereby with the increased duration of the infection. The reason for this is discussed.