Burkholderia refers to a genus of bacteria. The genus is important from the standpoint of infectious disease because several species cause illness in humans and animals. Burkholderia cepacia can cause a lung infection in people who have cystic fibrosis. B. pseudomallei causes melioidosis, an infection of the blood that can result in pain and tissue destruction at different sites in the body. B. mallei causes an illness known as glanders, a respiratory illness that occurs primarily in horses, mules, and donkeys and can be transmitted to humans. Glanders infection is often lethal in people.
Infections such as meliodoisis are reaching epidemic levels in various regions of the world, and the respiratory infection caused by B. cepacia is a main health threat in those with cystic fibrosis. Adding to the concern about Burkholderia, several species are worrisome because of their documented use as biological warfare agents.
B. cepacia was discovered in the 1940s by Cornell University researcher Walter Burkholder during an investigation into a disease outbreak in New York State. By the 1980s, the organism was recognized as being able to colonize and form an infection in the lungs of people with cystic fibrosis. Then, the infection was regarded as being minor, compared to that caused by Pseudomonas aeruginosa. Indeed, at first the organism was not recognized as a unique genus, and was called Pseudomonas cepacia. However, only a decade later, the uniqueness and seriousness of B. cepacia in cystic fibrosis had been recognized.
The lung infection caused by B. cepacia can become chronic. Over years, even decades, the infection will alternately become severe, leading to difficulty in breathing, and less severe, when it is managed more effectively by antibiotics and other forms of therapy. The lung infection is not contagious.
Glanders is another lung infection that, in contrast, can be spread from person to person by coughing. If not treated, the infection can be lethal within days. A less invasive form of the infection can require months from which to fully recover.
Glanders is not a significant health concern currently in North America and Europe, as imported livestock is monitored for the disease. However, it is still prevalent in Africa, Asia, the Middle East, Central America, and South America.
Melioidosis is a third Burkholderia-mediated disease that is caused by B. pseudomallei. It is also a disease of the respiratory tract; indeed, it displays symptoms that are similar to glanders. However, melioidosis and glanders differ in how they are acquired.
Melioidosis is prevalent in tropical climates. For example, the disease is endemic—it is frequently present year-round—in the Southeast Asian countries of Cambodia, Thailand, Vietnam, Laos, Malaysia, and Myanmar, and is also prevalent in the northern portion of Australia. As well, the disease is present but less prevalent in the South Pacific, India, Africa, and the Middle East.
Elsewhere in the world, melioidosis does occur, but only sporadically. Cases have been reported from Mexico, Equador, Panama, Haiti, Brazil, Peru, and in the U.S. states of Hawaii and Georgia. In the U.S., only a few cases are reported each year, according to the Centers for Disease Control and Prevention, and these typically involve people who have been traveling in areas where melioidosis is prevalent.
Many animals are susceptible to melioidosis including horses, sheep, cattle, goats, dogs, and cats. The disease can be transferred from the infected animals to humans, hence it is a zoonosis. As well, the disease can be spread from person to person. The disease can also be acquired by drinking contaminated water or coming into contact with contaminated water in a crop field.
Melioidosis can occur just in the respiratory tract or, if the blood becomes infected, can become more widespread in the body. The symptoms of fever, muscle or bone ache, headache, and weight loss may appear in only a few days, or may take years to become evident.
WORDS TO KNOW
ANTIBIOTIC RESISTANCE: The ability of bacteria to resist the actions of antibiotic drugs.
BIOLOGICAL WARFARE: Biological warfare, as defined by The United Nations, is the use of any living organism (e.g. bacterium, virus) or an infective component (e.g., toxin), to cause disease or death in humans, animals, or plants. In contrast to bioterrorism, biological warfare is defined as the “state-sanctioned” use of biological weapons on an opposing military force or civilian population.
COLONIZE: Colonize refers to the process where a microorganism is able to persist and grow at a given location.
ZOONOSES: Zoonoses are diseases of microbiological origin that can be transmitted from animals to people. The causes of the diseases can be bacteria, viruses, parasites, and fungi.
IN CONTEXT: BIOLOGICAL WEAPON THREATS
B. mallei and B. pseudomallei are considered potential biological weapons. Horses and other animals used in the transport of troops and military gear were deliberately infected with glanders during World War I (1915–1918), and it was used by the Japanese to infect prisoners during World War II (1939–1945).
Burkholderia are common environmental organisms and so are common in many areas of the world.
Some types of Burkholderia infections are at epidemic proportions in tropical regions and are less common, but nevertheless present, elsewhere in the world. The distribution of B. cepacia is global. It is a health threat in persons with cystic fibrosis worldwide.
Melioidosis is diagnosed by isolating the organism from the blood, urine, sputum, or from sores on the skin. The illness is treated using antibiotics. As of 2007, no vaccine exists to protect people from melioidosis. Prevention consists of minimizing contact with potential sources of the organism.
Similarly, B. cepacia lung infections and glanders are treated using appropriate antibiotics and, in the case of cystic fibrosis, other treatments designed to lessen the clogging of the lungs with the overproduced mucous.
Melioidosis is an important disease in some tropical regions of the world. The more persistent form of the illness can be debilitating, disrupting family life and making it impossible for a person to work.
B. cepacia is an important disease-causing organism for millions of people who have cystic fibrosis. The lung infection can persist for decades, and the long-term attempts by the host's immune system to destroy the infection can progressively damage the lungs to such an extent that survival is threatened.
B. cepacia lung infections also can similarly and progressively lessen lung function. Additionally, the attempts to eradicate the infection using antibiotics can be less than effective, which can result in the development of bacteria that are resistant to the antibiotics being used. This can make subsequent treatment more difficult and, as more potent antibiotics may be necessary, increasingly expensive.
B. mallei and B. pseudomallei are considered potential biological weapons. Both organisms can be resistant to a variety of antibiotics, which can make it more difficult to treat the infections they cause. Also, because they can infect both livestock and humans, they have been exploited during wartime.
Some species of Burkholderia are beneficial. In particular, B. cepacia and B. fungorum are able to degrade certain pesticides that otherwise tend to persist in the environment and cause ecological damage. This environmental benefit comes with the risk that those exposed to, for example, sprays containing the organisms, could be at risk to develop illness. However, under controlled conditions of use, Burkholderia can be useful in reducing pesticide contamination.
Black, Jacquelyn. Microbiology: Principles and Explorations. New York: John Wiley & Sons, 2004.
DiClaudio, Dennis. The Hypochondriac's Pocket Guide to Horrible Diseases You Probably Already Have. New York: Bloomsbury, 2005.
Centers for Disease Control and Prevention. “What You Should Know about Burkholderia cepacia infection.” <http://www.cdc.gov/ncidod/dbmd/diseaseinfo/blastomycosis_t.htm> (accessed March 25, 2007).