Potentially pathogenic bacteria cultured from the sputum of stable asthmatics are associated with increased 8-isoprostane and airway neutrophilia

Abstract

Potential bacterial pathogens are found in the airways in several diseases that are associated with neutrophilic inflammation. The aim of this study was to characterize subjects with stable asthma, with no symptoms of respiratory infection, to assess whether key potentially pathogenic bacteria were present in significant quantities in the airways and to correlate this with the pattern of airway inflammation and oxidative stress. Subjects with stable asthma (n = 115) and healthy controls (n = 8) underwent clinical assessment, including hypertonic saline challenge combined with sputum induction. A significant load of potentially pathogenic bacteria (> 10⁶ cfu/mL) was cultured from the sputum of 17 (15%) subjects with stable asthma and was associated with higher total cell counts, proportion and number of neutrophils, sputum IL-8 and 8-isoprostane concentrations. The role of bacteria in potentiating neutrophilic asthma warrants further investigation. Therapies such as antibiotic and antioxidant treatment may be most effective in this sub-group of patients.

Keywords::

• Airway inflammation
• asthma
• bacteria
• IL-8
• 8-isoprostane
• oxidative stress

Acknowledgements

Assistance with collection and analysis of samples was received from the Respiratory Research team, in particular Rebecca Oldham, Hunter Medical Research Institute, John Hunter Hospital, Newcastle, NSW, Australia.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

This paper was first published online on Early Online on 13 November 2009