Pathogenic Microbes Seen in Sputum of Adults With Stable Asthma

NEW YORK (Reuters Health) Jul 12 - A minority of adults with stable asthma
harbor pathogenic microbes in sputum and pharyngeal secretions, which
correlate with decreased lung function and frequent asthma symptoms, Finnish
researchers report.

Respiratory infection with microorganisms, such as rhinovirus and Chlamydia
pneumoniae, has been shown to trigger asthma flares, but the role of these
pathogens in adults with stable disease was unclear.

To investigate, Dr. T. H. Harju, from the University of Oulu, and colleagues
tested induced sputum samples and pharyngeal swab specimens for the presence
of various pathogens in 103 patients with asthma and 30 healthy controls.
The findings are reported in the July issue of Thorax.

Rhinovirus was detected in sputum samples from 6.7% of controls, 9.4% of
mild asthmatics, and 16.0% of moderate asthmatics. The presence of this
microbe was linked to more asthma symptoms and with a reduced FEV1.

Bordetella pertussis positivity, which was detected in 16.7% of controls,
28.3% of mild asthmatics, and 20% of moderate asthmatics, showed a similar
association with asthma symptoms and FEV1.

C. pneumoniae, by contrast, was more commonly detected in healthy controls
than in asthmatics -- 36.6% vs. 20.8% in mild asthmatics and 22% in moderate
asthmatics -- but like the other microbes, seemed to adversely affect lung
function.

"Our study has shown that there is an association between pathogen
positivity and clinical symptoms in patients with asthma," the authors
conclude. "Rhinovirus RNA as well as C. pneumoniae and B. pertussis DNA are
commonly present in the sputum or pharyngeal swab specimens of asthmatic
patients without ongoing infection or asthma exacerbation, as well as in
healthy controls."

Thorax 2006;61:579-584.

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