LOS ANGELES: Researchers have found the presence of a disease-causing bacterium in people with a rare immune disorder, chronic granulomatous disease (CGD) that leaves them exposed to fungal and bacterial infections, sometimes deadly.
The researchers at the U.S. National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda identified the new bacterium, which they named granulobacter bethesdensis, in the inflamed lymph nodes of a 39-year-old man suffering from CGD.
They said the patient was having fever, chills, fatigue and night sweats for nearly three months, which did not respond to normal treatments and he was referred to the U.S. National Institutes of Health (NIH), where he was unresponsive to antibiotics. After two months, he had developed swelling in the lymph nodes at the base of his neck and a biopsy of the matter from the nodes established that the infection was caused by the bacterium.
The researchers have published their findings in the latest issue of journal PLoS Pathogens.
Scientists have since genetically analyzed the bacterium and found it to belong to the Acetobacteraceae family, which includes several species found in the environment and also used in the making of vinegar. It is for the first time that a member of this family in found to cause an infection in humans.
The NIAID researchers have isolated the bacterium in two more patients with CGD.
NIH director Elias Zerhouni said discovery of new bacteria is not uncommon, but discovering an organism that causes human illness is certainly unique. He said it calls for intensive study.
CGS is caused as a result of a genetic defect in an enzyme called phagocyte NADPH oxidase, used in immune cells to generate hydrogen peroxide to kill bacteria and fungi.
To establish that the bacterium had specifically caused the infection in the lymph nodes, the researchers inoculated healthy mice and mice genetically altered to carry CGD with various amounts of the bacterium. Lymph nodes recovered from the CGD-infected mice revealed a similar condition to those of the patient with CGD. The lymph nodes of the disease-free mice appeared normal. Subsequent genetic sequencing confirmed that the bacterium found in the mice was identical to the organism isolated from the patient. The bacterium was not fatal in the CGD patient nor the infected mice.
NIAID's chief of Laboratory of Clinical Infectious Diseases Steven M Holland said almost 50 per cent of infections in people with CGD could not be diagnosed. Some of these patients were subjected to surgery and others with broad spectrum drugs. He said, "This newly identified organism could help us identify the source of those infections and allow for the development of targeted and curative therapies."
The lead author of the study David E. Greenberg said further studies would be needed to compare the immune response to the new bacterium in healthy people and in those with CGD and to determine how the bacterium causes infection in people with CGD.
