M. catarrhalis, a
"Harmless" Bacterium Found to Cause 10 Percent of COPD Flare-Ups
Jul 21, 2005 - 11:22:38 PM
A ubiquitous bacterial strain thought to be uninvolved in chronic obstructive pulmonary disease (COPD) in fact is responsible for 2-4 million flare-ups of the condition that occur annually in the United States, researchers from the University at Buffalo have shown.
The bacterium, Moraxella catarrhalis or M. catarrhalis, often is present in sputum of adults with COPD. However, its potential role in the disease was ignored for decades, because studies in the early 1950s had found it to be relatively harmless.
A study published in the July 15 issue of the American Journal of Respiratory and Critical Care Medicine reports that M. catarrhalis was found to be responsible for approximately 10 percent of exacerbations of COPD. Timothy F. Murphy, M.D., professor of medicine and microbiology in the UB School of Medicine and Biomedical Sciences, was lead author on the study.
"This paper is the first to study the involvement of M. catarrhalis in a prospective way in adults with COPD," Murphy said. "Using rigorous methods, our work has shown that acquiring M. catarrhalis is strongly associated with the onset of symptoms of an exacerbation.
"People with COPD, estimated to be about 20 million in the U.S., experience one to two exacerbations per year," said Murphy, chief of the UB medical school's Infectious Diseases Division and a pioneer in vaccine development for respiratory disease. "If 10 percent of all exacerbations are caused by M. catarrhalis, that translates to 2-4 million exacerbations annually."
COPD is the fourth leading cause of death in the U.S. and many of those deaths occur during exacerbations, he said. "Exacerbations also cause enormous morbidity and health-care costs. They lead to physician visits, emergency room visits, hospital admissions and respiratory failure requiring mechanical ventilation."
In addition to showing that M. catarrhalis is involved in exacerbations of COPD, the researchers also found that patients make immune responses to the bacterium when they acquire it.
"Both of these observations provide lines of evidence that M. catarrhalis is a pathogen for these patients and provide a strong rationale for pursuing the development of vaccines to prevent M. catarrhalis infections in people with COPD," Murphy said.
The study involved 104 adults with COPD who were seen at the outpatient clinic at the Buffalo Veterans Affairs Medical Center over 81 months. During this period, patients made 3,009 clinic visits, 560 of which were during exacerbations. Sputum samples were collected at each clinical visit and molecular typing of organisms was conducted, as well as assays to measure immune response.
Researchers identified 120 episodes of M. catarrhalis infections in 50 patients, nearly half of which were associated with flare-ups of COPD. There was no evidence that exacerbations were associated with acquisition of a new strain of another pathogen.
"We know that M. catarrhalis causes ear infections in children," said Murphy. "With these new observations regarding the importance of the bacterium in adults with COPD, we have even more reason to forge ahead with developing a vaccine to prevent M. catarrhalis infections."
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