Bacteria and viruses are mainly responsible for exacerbations of COPD. Approximately 40% of exacerbations are caused by bacteria, 40% by viruses, and in 20% both bacteria and virus are isolated.

The most common bacteria isolated are H.influenzae, S.pneumoniae and M.catarrhalis. The most common viruses are the common cold rhinovirus, influenza and parainfluza viruses and adenovirus.

Bacteria not only cause exacerbations of COPD, they also colonise the airways of these patients. In many studies it has been shown that airways colonisation leads to worsening of symptoms and increasing exacerbation rates. It has also been linked with current smoking status. H.influenzae is possibly the greatest threat to the well being for patients with COPD. It is linked with higher inflammatory levels (CRP) and a more prolonged exacerbation.

At present we do not have any recommended treatments for those exacerbations with a viral aetiology (although influenza vaccine can help to prevent them and reduce morbidity), but treatments are currently in development.

Antibiotic cover must be adequate to cover the 3 most common bacteria that cause exacerbations and the choice should be made based on local antibiotic resistance data.

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Management