ASTHMA

Pathogenic bacteria and viruses in induced sputum or pharyngeal secretions of adults with stable asthma

T H Harju¹, M Leinonen², J Nokso-Koivisto², T Korhonen², R Räty², Q He², T Hovi², J Mertsola³, A Bloigu², P Rytilä⁴, P Saikku^2,5

¹ Department of Internal Medicine, University of Oulu, Oulu, Finland
² National Public Health Institute, Oulu, Turku and Helsinki, Finland
³ Department of Pediatrics, Turku University Hospital, Turku, Finland
⁴ Department of Allergy, Skin and Allergy Hospital, Helsinki University Central Hospital, Helsinki, Finland
⁵ Department of Medical Microbiology, University of Oulu, Oulu, Finland

Correspondence to:
Dr T H Harju
Department of Internal Medicine, P O Box 5000, 90014 University of Oulu, Finland; terttu.harju{at}oulu.fi

Background: Respiratory infections are well known triggers of asthma exacerbations, but their role in stable adult asthma remains unclear.

Methods: 103 asthmatics and 30 control subjects were enrolled in the study. Sputum was induced by inhalation of 3% NaCl solution. Oropharyngeal swab specimens were obtained from the posterior wall of the oropharynx. Respiratory specimens were analysed by RT-PCR for rhinovirus, enterovirus and respiratory syncytial virus and by PCR for adenovirus, Chlamydia pneumoniae, Mycoplasma pneumoniae and Bordetella pertussis.

Results: Sputum samples from two of the 30 healthy controls (6.7%), five of 53 patients with mild asthma (9.4%), and eight of 50 with moderate asthma (16.0%) were positive for rhinovirus. Rhinovirus positive asthmatic subjects had more asthma symptoms and lower forced expiratory volume in 1 second (FEV₁) (79% predicted) than rhinovirus negative cases (93.5% predicted; p = 0.020). Chlamydia pneumoniae PCR was positive in 11 healthy controls (36.6%), 11 mild asthmatics (20.8%), and 11 moderate asthmatics (22%), and PCR positive asthmatics had lower FEV₁/FVC than negative cases (78.2% v 80.8%, p = 0.023). Bordetella pertussis PCR was positive in 30 cases: five healthy controls (16.7%), 15 mild asthmatics (28.3%), and 10 moderate asthmatics (20%). Bordetella pertussis positive individuals had lower FEV₁/FVC (77.1% v 80.7%, p = 0.012) and more asthma symptoms than B pertussis negative cases.

Conclusions: Rhinovirus, C pneumoniae, and B pertussis are found in the sputum or pharyngeal swab specimens of asthmatic subjects without concurrent symptoms of infection or asthma exacerbation, as well as in some healthy controls. Positivity is associated with lower lung function and more frequent asthma symptoms.

Abbreviations: CRP, C-reactive protein; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; PCR, polymerase chain reaction; RSV, respiratory syncytial virus

Keywords: asthma; rhinovirus; Chlamydia pneumoniae; Mycoplasma pneumoniae; Bordetella pertussis

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