Long-term inhaled corticosteroid (ICS) therapy increases sputum bacterial load, according to a prospective open-label blinded end point study published in the European Respiratory Journal.
Researchers randomly assigned 60 patients with stable moderate chronic obstructive pulmonary disease (COPD) to receive one inhalation of salmeterol 50 μg plus fluticasone propionate 500 μg or salmeterol 50 μg twice daily for 12 months. The primary end point was change in sputum bacterial load during treatment.
The study results showed that compared with salmeterol monotherapy, the combination of salmeterol plus fluticasone was associated with a significant increase in sputum bacterial load (P =.005). Furthermore, patients treated with ICS therapy also experienced a modification of sputum microbial composition and increased airway load of potentially pathogenic bacteria. However, this increase in bacterial load was detected only in patients receiving ICS who had low baseline sputum or blood eosinophil levels (≤2%) but not in those who had higher baseline levels of eosinophils. No change was found in respiratory viruses detected.
The authors stated that this latter finding might be the result of different mechanisms that are involved in fighting off bacterial and viral infections of the airways, resulting in different susceptibility to ICS.
ICS therapy given in combination with long-acting beta-2 agonists (LABAs) is recommended for patients at high risk for exacerbations. Other studies have suggested that blood eosinophilia can predict a greater efficacy of this combination in preventing exacerbations. The results of the current study support those findings and suggest that increased bacterial load or the change in airway microbial composition in patients with COPD who are receiving ICS/LABA combination therapy is associated with low sputum or blood eosinophil levels.
The authors noted that the study was not powered to detect clinical outcomes, and the question as to whether or not this increase in bacterial load is associated with increased infection must be evaluated in properly designed studies.
Contoli M, Pauletti A, Rossi MR, et al. Long-term effects of inhaled corticosteroids on sputum bacterial and viral loads in COPD [published online October 5, 2017]. Eur Respir J. doi:10.1183/13993003.00451-2017