"We believe that antibiotics may become an important addition to the therapeutic options for some patients with asthma," said Richard Martin, M.D., Professor of Medicine at National Jewish and co-author of the paper. "However, diagnosis of chlamydia or mycoplasma infection requires an invasive procedure. At the present time only select centers can appropriately perform the necessary tests. We are working on simpler methods to make the diagnosis easier."
The researchers took multiple tissue samples from the upper and lower airways of 55 adults with mild to moderate asthma. They looked for evidence of bacterial infections by culturing tissue samples and performing genetic analyses. None of the tissue cultures grew any bacteria, but DNA from Mycoplasma pneumoniae or Chlamydia pneumoniae were detected in samples from 31 of the 55, or 56%, of the patients.
Before antibiotic treatment began, there were no significant differences in lung function between those showing evidence of bacterial infection and those showing none. Lung function was evaluated by measuring the amount of air patients could exhale in one second, called forced expiratory volume in one second or FEV1.
Twenty-six of the patients then took 500 milligrams of the antibiotic clarithromycin twice a day for six weeks while continuing their standard asthma medications. Twenty-six other asthma patients continued their standard asthma medications and a placebo instead of the antibiotic treatment. Three patients were excluded from the treatment analysis due to scheduling and compliance problems. Patients with no evidence of bacterial infection who were randomized to the antibiotic group showed no significant change in their lung function after treatment. The lung function of patients with evidence of bacterial infection, however, improved after the antibiotic treatment. Their average FEV1 rose 200 milliliters.
"That is a clinically significant improvement," said co-author Monica Kraft, M.D., Associate Professor of Medicine at National Jewish. "Those patients noticed an improvement in their breathing ability."
It is not clear how a bacterial infection influences chronic asthma. There is evidence that it can exacerbate existing asthma. But the National Jewish researchers also believe that it may contribute to the development of the disease. They are currently conducting experiments in mice to better understand the role of bacterial infections in asthma.
Although the clarithromycin did improve lung function in mild to moderate asthmatics with evidence of bacterial infections, Drs. Martin and Kraft do not advocate its widespread use for asthma. When properly used, standard asthma medications can control symptoms in the vast majority of asthma patients. Overuse of antibiotics in general has led to an increase in drug-resistant bacteria around the world.
The antibiotic helped only those who showed evidence of bacterial infections. Detection of bacterial infection requires invasive procedures, such as bronchoscopy, that are difficult to perform, unpleasant for the patient, and pose slight hazards themselves. But for patients who do not achieve control of their asthma even with maximum doses of standard medications, Dr. Martin believes physicians should consider evaluating their patients for bacterial infections and treating with antibiotics if the lungs do appear infected.
National Jewish is a nonprofit, nonsectarian institution dedicated to the research, treatment and prevention of respiratory, allergic and immune system diseases. For more information visit our Web site at www.nationaljewish.org.
Chest is a peer-reviewed journal published by the American College of Chest Physicians. It is available online each month at www.chestjournal.org. ACCP represents more than 15,000 members who provide clinical, respiratory, and cardiothoracic patient care in the U.S. and throughout the world. ACCP's mission is to promote the prevention and treatment of diseases of the chest through leadership, education, research and communication.