Bacterial alterations source of persistent COPD lung infections

August 14, 2002

BUFFALO, N.Y. - Clever bacteria populations may be changing just enough to keep ahead of patients' immune systems, causing a mysterious intensification of Chronic Obstructive Pulmonary Disease (COPD) -- the fourth leading cause of death in the United States. More commonly know as chronic bronchitis and emphysema, COPD affects nearly 15 million people in this country.

Researchers at the Veterans Affairs (VA) Medical Center in Buffalo, NY have ended decades of controversy by proving populations of infectious bacteria are changing constantly in the lungs of COPD patients, allowing the bacteria to strike again and again - sometimes with deadly results. Their findings, appearing in the August 15th issue of The New England Journal of Medicine, may explain why healthy immune systems cannot prevent these recurring infections.

Intensified COPD symptoms deprive patients of oxygen through severe shortness of breath and coughing that produces thick, sticky sputum (phlegm). Researchers studied samples of sputum from 81 patients over a period of 56 months. Findings show patients were fighting populations of bacteria that repeatedly changed over time, possibly keeping one step ahead of immune defenses.

Many of the COPD patients' immune systems seemed to be working normally, yet bacterial infections rebounded after apparently being eliminated. This prompted researchers to look more closely at the nature of the bacteria. Instead of simply measuring the size and intensity of a bacterial infection, Drs. Sanjay Sethi, and Tim Murphy led a VA investigation of the bacteria's molecular identity.

They suspected acquiring a new strain of bacteria brought on the dangerous infections, causing the already sick patients to cough, choke and experience severe shortness of breath. Proving this would require a new way to identify one strain of bacteria from another.

"This study applied state of the art technology to tell whether the bacterial infections that kept cropping up were just one strain of bacteria lingering in the body for months or years, or whether different strains of the same bacteria would come and go," said Murphy.

The study successfully recovered about 4000 separate strains of bacteria. New technology involving DNA testing enabled investigators to study the molecular signature of the bacteria, resulting in extremely accurate identification.

"People with COPD may have nothing wrong with their immune systems but they keep getting these recurrent infections - our findings may explain why this happens. It appears that when a person gets an infection and makes a good immune response, that response is only good for that particular bacteria strain," said Sethi.

Investigators believe their findings may lead to novel ways to treat bacterial infection. "We can use these observations to understand the immune response to bacteria and possibly develop vaccines that keep pace with the changing strains," said Murphy.

There are 50 patients actively involved in this ongoing study, and enrollment continues. VA's Medical Research Service, will support the project through 2004.
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VA research provides improved medical care for veterans, as well as the general population. Through its unique affiliation with medical schools, VA plays a crucial role in educating future physicians in research and clinically oriented areas.

Veterans Affairs Research Communications

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