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

Abstract

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.