Epidemiological investigations of the respiratory tract bacteriology in patients with cystic fibrosis.

Seventy patients with cystic fibrosis treated as out-patients in a cystic fibrosis 
clinic have been followed during one year by monthly bacteriological examinations 
of tracheal secretions. The daily impression obtained in the laboratory is 
expressed by the mean point prevalence rate of Pseudomonas aeruginosa: 44 
per cent, Staphylococcus aureus: 39 per cent, Haemophilus influenzae: 17 per 
cent, Diplococcus pneumoniae: 8 per cent, and miscellaneous other bacteria, mainly 
Enterobacteriaceae: 8 per cent. The fluctuations of the bacteriology are described 
by additional epidemiological terms: At one or more examinations during the 
study (period prevalence rate), 90 per cent of the patients harboured 
St. aureus, 64 per cent Ps. aeruginosa (mainly mucoid strains), 64 
per cent H. influenzae, 37 per cent D. pneumoniae, and 30 
per cent miscellaneous other bacteria, mainly Enterobacteriaceae. This pattern was found 
in all age groups with minor age-dependent modifications, especially as regards 
Enterobacteriaceae. Ps. aeruginosa was predominating as regards chronic colonization which reflects 
the most difficult therapeutic problems, the period prevalence rate being 39 
per cent in contrast to St. aureus: 10 per cent, and 
H. influenzae: 1 per cent. St. aureus was predominating as regards 
new colonization and recolonization which reflect the problems of prevention, the 
incidence rate of new colonization and recolonization per risk group being 
84 per cent, followed by H. influenzae: 62 per cent, Ps. 
aeruginosa: 43 per cent, and D. pneumoniae: 30 per cent. The 
results show that the bacteriological problems in cystic fibrosis are still 
considerable as regards therapy as well as prevention. Although many species 
may colonize the respiratory tracts of these patients, the main clinical 
problems concern Ps. aeruginosa and St. aureus; the reason why is 
discussed. 