Q&A: CDC alerts US clinicians about cases of melioidosis unrelated to travel
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The CDC recently issued a health advisory regarding three cases of melioidosis in the United States that appear to be unrelated to travel.
Melioidosis, which is caused by the gram-negative bacterium Burkholderia pseudomallei, can be difficult to diagnose because it is often mistaken for diseases like tuberculosis, the CDC noted.
The three cases were reported in Kansas, Minnesota and Texas. The first one, identified in March 2021, was fatal, the CDC reported.
The CDC said genomic analysis indicated that the three patients may have shared a common source of exposure. According to the alert, none of the patients’ families reported traveling outside the U.S.
Melioidosis is predominantly found in tropical climates, especially in Southeast Asia and northern Australia, according to the CDC, but an analysis published in 2016 in Nature Microbiology found that it is likely endemic in more countries than initially thought.
In 2019, experts argued that melioidosis should be considered a major neglected tropical disease because of its large global burden.
To prevent spread of melioidosis, the CDC recommends the following:
- Consider melioidosis in patients with a compatible illness despite a travel history to a disease-endemic country.
- If melioidosis is suspected, a culture of blood, throat swab, urine or respiratory specimens, abscesses or wounds should be taken.
- When cultures are ordered, the lab should be advised that the cultures may grow B. pseudomallei and lab personnel should observe safety precautions.
- Patients with melioidosis should be treated with IV antibiotics for at least 2 weeks up to 8 weeks.
- Physicians should consider re-evaluating patients with isolates that were identified by automated systems.
- If a case of melioidosis is suspected or confirmed, the local health department should be contacted immediately.
We spoke with Jill Weatherhead, MD, MS, DTMandH, FAAP, assistant professor of tropical medicine and infectious disease at Baylor College of Medicine, about the CDC alert and what clinicians need to know about melioidosis.
Healio: Is it strange that three cases of melioidosis were reported from three different U.S. states?
Weatherhead: We know that B. pseudomallei, which causes melioidosis, is associated with certain climates. It is particularly common in tropical and subtropical climates. To see new cases emerge in different regions around the country is a little unique. However, based on the report, it suggested that the exposure for these three individuals is potentially from the same source, which may be from a tropical and subtropical climate, which is how the individuals were exposed in the first place.
Healio: The CDC alert says the patients may potentially share a common source of exposure. What could that be?
Weatherhead: Transmission of this bacteria is from contaminated soil and water. The bacteria will thrive in soil and water in warmer, tropical and subtropical climates. Typically, the mode of transmission with that contaminated water or soil is inhalation of the organisms — which is how people go on to develop lung disease — or through the skin. For example, cuts in the skin then get contaminated with the infected water or soil. It's really the soil and water that's contaminated with the bacteria, which is how humans would subsequently be infected because, although it has been reported, transmission from human to human is very rare.
Healio: What should clinicians be on the lookout for, and what should they do if they suspect a case of melioidosis?
Weatherhead: It still is a rare disease in the United States. Melioidosis can present with a range of symptoms. Most commonly patients have lung disease like pneumonia, bronchitis, or even cavitary lung lesions but it can also cause blood infection and disseminate to other organs, including, rarely, the brain. Additionally, some patients might have skin lesions, abscesses or nodules, if they are infected through skin inoculation. Because patients with melioidosis can present with a variety of symptoms, when evaluating a nontraveling patient who lives in a non-endemic region melioidosis is not typically a disease that healthcare providers will think about first. It has a very broad set of signs and symptoms of infection.
If you have a patient who has these symptoms — though they are broad — if you get cultures from wherever the infection seems to be isolated, whether it's from the blood or from the lungs or other sites, you can culture the organism in the lab. They can grow it and identify it in order to confirm the diagnosis. It's really just knowing where patients are coming from. If they're coming from highly endemic regions, they certainly should be moved toward the top of the list. But in the U.S., it really is the due diligence of getting the cultures necessary to identify the organism.
One thing I will point out is it can be confused or mistaken for pulmonary TB because it can form what are called cavitary lesions in the lungs that look like TB. If you're seeing that appearance in the lungs and the patient does not have TB, this would be another diagnosis to think of. It's important to alert your laboratory staff that this is an organism that you are considering because, although it is very rarely transmitted from human to human, in the lab there are certain procedures that are aerosolized. Laboratory workers can be at risk in those situations. We want to alert our laboratory workers that it is a potential pathogen we're concerned about. The next step is starting antibiotics when you see a patient who is ill who may have the disease, and contacting your local health department.
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CDC. Multistate investigation of non-travel associated Burkholderia pseudomallei infections (melioidosis) in three patients: Kansas, Texas, and Minnesota – 2021. https://emergency.cdc.gov/han/2021/han00444.asp. Accessed July 13, 2021.
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