Bacterial colonisation and infection of the lower airways in cystic fibrosis : a microbiological and clinical study

Abstract

Pulmonary deterioration has remained the major cause of mortality in cystic fibrosis (C17) patients despite the considerable improvement of their survival due to more efficient therapy and centralised care. The progression of the CF lung disease is correlated to inflection with a limited number of colonising bacterial species. An inflammatory reaction in the lung occurs early. The general aim of this thesis was to study the bacterial colonisation in the lower airways of CF patients, and the concomitant inflammatory reaction.

Paper I is a retrospective study of the chronic bacterial colonisation with Stenotrophomonas maltophilia in 12 CF patients during 1983-1992. No background factors for chronic colonisation could be verified in our material. An epidemiologic outbreak was not seen. The patients were older at the time of first isolation of S. maltophilia compared to that of Pseudomonas aeruginosa. Chronic colonisation implied a deterioration of the lung function during follow-up. The lung function of the patients was significantly worse at first isolation of S. maltophilia compared to controls colonised with P. aeruginosa at similar ages. Chronic colonisation and repeated antibiotic treatments resulted in rapid development of antimicrobial resistance. Thus, S. maltophilia is a pathogenic bacterium in patients with CF and a marker of lung disease.

Paper II evaluates multiplex PCR-based detection of P. aeruginosa, S. maltophilia and Burkholderia cepacia in 90 sputum specimens compared to culture. Our data indicate high sensitivity (93%) regarding the detection of P. aeruginosa and high specificity regarding all three genera examined. The greatest gains with this method could be made when used for the early detection of P. aeruginosa in sputum-producing CF patients.

Paper III describes typing of 39 clinical isolates of B. cepacia, which is an important pathogen, often associated with deterioration of the CF lung status. It exhibits a considerable phenotypic polymorphism. Typing by arbitrarily primed (AP)-PCR. using ERIC primer was performed for epidemiologic subtyping. Genetic changes were detected by analysis of shifts in the band patterns that were individual. Partial species identification could effectively be obtained by sequencing the V3 region of the 16S RNA gene. Heterogeneity of the bases was revealed in the same region in 10 of 37 strains, indicating at least two different types of 16S rRNA in the same cell. Most of the 14 CF patients, to whom 33 of the isolates belonged, developed severe lung disease after colonisation with Burkholderia, irrespective of the typing results.

Paper IV investigates TN17-oc and IL-8 levels of sputum in 10 CF patients during exacerbation and the baseline levels of IL-8 in 48 sputum-producing CF patients. High IL-8 and TNF-[alpha] values in sputum seemed to correlate with clinical symptoms of deterioration and could be valuable diagnostic parameters. Our data also indicated a correlation between current bacterial colonisation with either P. aeruginosa or S. aureus in the lower airways and IL-8 concentrations in sputum. IL-8 in the sputum of CF patients seems to be a useful marker of both current bacterial colonisation and the degree of lung damage.

Paper V evaluates the effect of 14-day ibuprofen therapy with special regard to IL-8 levels in sputum of 19 CF patients in clinically stable condition. The study was performed double-blinded, placebo-controlled in a crossover manner. Ibuprofen therapy did not result in significantly decreased IL-8 concentrations in the sputum of these CF patients with relatively advanced pulmonary disease. Slightly lower levels during day 8-14 of ibuprofen therapy were seen. Prescribing ibuprofen for this group of CF patients may need individual evaluation and will probably not be a general alternative.