Macrolide and occult infection in asthma

Abstract

A small percentage of asthma exacerbations are linked with infection by an atypical bacterium, such as Chlamydia pneumoniae or Mycoplasma pneumoniae. These bacteria also have been proposed to cause occult chronic lower airway inflammation and to initiate nonatopic asthma in adults. Consequently, the logical procedure would be to eliminate these pathogens as soon and as thoroughly as possible using antibiotics. Nonetheless, antibiotics are not recommended even for the treatment of acute asthma exacerbations except as needed for comorbid conditions. These discrepancies highlight the need to define the role, if any, of antimicrobials that are active against atypical pathogens, mainly macrolides, but also tetracyclines and fluoroquinolones, in the treatment of asthma. Macrolides are antibiotics with both antimicrobial and antiinflammatory activities. Some studies have documented that these agents could be useful in the treatment of occult infection in asthma because of their antimicrobial activity against atypical pathogens. They could also lead to reduction of the airways inflammation by decreasing the transcription of mRNA for a variety of cytokines and inhibiting interleukin-8 release by eosinophils, and therefore improvement of symptoms and pulmonary function. These effects are not caused by bronchodilation, elevation of serum theophylline level, or steroid-sparing mechanism. The available clinical evidence seems to support use of macrolides in the treatment of asthma because of their antimicrobial activity. However, studies that may confirm this hypothesis are scarce and with limited scientific value because of their open, uncontrolled design.