The profile of respiratory pathogens in induced sputum of elderly and non-elderly asthmatics

Introduction
Respiratory pathogens are thought to be involved in the pathogenesis and exacerbations of asthma at all ages; however, little is known about the airway microbiome in the elderly.

Aim of the study
To identify respiratory pathogens in the induced sputum (IS) of elderly asthmatics, and to determine the association between pathogens and the markers of asthma activity.

Material and methods
Twenty-nine subjects with stable asthma, 15 above 65 years of age and 14 aged 30-49 years, underwent clinical evaluation, fractional exhaled nitric oxide measurement, and sputum induction. Pathogens were detected by multiplex reverse transcription polymerase chain reaction. The periostin concentration of IS supernatants was measured by enzyme-linked immunosorbent assay. Serum eosinophil cationic protein and total IgE levels were measured by Immun^oCAP.

Results
Elderly patients, as compared to non-elderly, had significantly higher eosinophilia in IS, although other markers of eosinophilic inflammation were comparable. Half of the subjects were positive for Haemophilus influenzae. Chlamydophila pneumoniae was found in two subjects. Respiratory viruses were detected in more than 70% of patients. The detection rates and profiles of atypical bacteria and respiratory viruses were similar in both groups. Only in the elderly asthmatics was influenza A positivity associated with lower predicted FVC%, RSV A positivity connected with decreased tIgE concentration, and RSV B positivity related to a lower percentage of lymphocytes in IS.

Conclusions
Despite the existence of differences in some clinical and inflammatory characteristics of asthma between elderly and non-elderly asthmatics, the pathogen detection rates in the IS from the two groups are similar.