Gulf Coast tests confirm deadly tropical soil bacterium is now endemic to the United States

<Em data-recalc-dims=Burkholderia pseudomallei cultured on sheep blood agar for 24 hours. B. pseudomallei is an aerobic Gram-negative bacterium, and it is the causative agent of melioidosis. “/>

Enlarge / Burkholderia pseudomallei cultured on sheep blood agar for 24 hours. B. pseudomallei is a Gram-negative aerobic bacterium, and it is the causative agent of melioidosis.

For years, health officials in the United States have noted sporadic and mysterious cases of a foreign bacterial infection, called melioidosis. The infection – which is difficult to diagnose, tricky to treat and often fatal – was thought to only strike travelers or those who had come into contact with contaminated imported goods or animals. Yet every once in a while an American would fall inexplicably ill – no recent travel, no clear connections.

Now health officials have a definitive explanation. And that confirms a long-dreaded suspicion: the deadly bacteria is no longer foreign. Rather, he is a permanent resident of the United States entrenched on American soil.

Three samples taken from soil and water from puddles in the Gulf Coast region of southern Mississippi tested positive for the bacteria, Centers for Disease Control and Prevention officials said Wednesday. The sampling was part of an investigation into two mystery cases in the region that occurred in 2020 and 2022. The positive test results mark the first time investigators have caught the deadly germ in U.S. environmental samples, though have been looking for him for years.

It is not known how long the bacterium has resided in the United States or how widespread its distribution has become. But CDC modeling suggests that environmental conditions in Gulf Coast states are conducive to the growth of the bacteria. The agency requested extensive environmental sampling.

Although the discovery explains the puzzling cases, the most important thing now is for health officials to spread the word. It is no longer a traveler’s disease. In a health advisory released yesterday, the CDC noted that its advisory “serves to alert clinicians and public health officials across the country to consider melioidosis in patients whose clinical presentation is consistent with the signs and symptoms of disease, regardless of their history of travel to international disease-endemic areas, as melioidosis is now considered locally endemic in areas of the Mississippi Gulf Coast region.”

New resident

The bacterium in question is Burkholderia pseudomallei, which lives in soil and water in tropical and subtropical regions and causes rare but dangerous sporadic infections. The most endemic areas are in Southeast Asia and northern Australia, but it has also appeared in parts of Southwest Asia, Africa, the Pacific, and the Americas, such as Peru, Brazil, Haiti and some US territories, including Puerto Rico.

B. pseudomallei causes melioidosis by being transmitted in a variety of ways, all involving direct contact with contaminated soil and water. People can become infected if they ingest contaminated soil, water or food; if they breathe in contaminated dust or water droplets; or if contaminated soil or water comes in contact with a break in the skin. People at greater risk of melioidosis than others are those with specific conditions, such as diabetes, excessive alcohol consumption, chronic lung disease, chronic kidney disease, and conditions that weaken immune responses. The good news is that the infection rarely spreads from person to person.

The ensuing symptoms of melioidosis may depend on the route B. pseudomallei takes in the body. If it enters through a skin wound, it can cause pain, swelling and an abscess. If it gets into the blood, it can cause joint pain, abdominal discomfort, and disorientation. If it enters through the lungs, it can cause coughing and chest pain. And if it becomes systemic, it can lead to weight loss, brain infection, and seizures. Overall, the symptoms may seem nebulous and can easily be mistaken for other conditions. It has been described as “the great imitator” due to the frequency and ease with which it is mistaken for other serious infections, such as tuberculosis.

Its indistinct nature contributes to its deadly character. B. pseudomallei is naturally resistant to many commonly used antibiotics. Any delay in an accurate diagnosis can allow the bacteria to cause more serious illness. According to the CDC, melioidosis is fatal in 90% of people who are not properly treated. When people are treated with the right antibiotics, the mortality rate drops below 40%. And if patients have access to intensive care and the right drugs, the death rate drops to around 20%.

For all these reasons, the US government considers B. pseudomallei a bioterrorist threat, listing it as a level 1 selective agent along with the anthrax bacterium (Bacillus cereus Biovar anthracite) and the Ebola virus.

American cases

According to the CDC, the United States averages about 12 cases of melioidosis per year, most of which are travel-related. But there have been notable and puzzling exceptions over the years.

Last year, melioidosis made headlines when four people in four states were infected with the same strain of B. pseudomallei. The first unexplained cases, which were fatal, occurred in an adult in Kansas in March. Then another adult from Minnesota survived and a 4-year-old child from Texas suffered brain damage. Finally, a child in Georgia was identified as a case through a post-mortem examination.

In October, investigators announced a pause in the puzzling outbreak: the strain of B. pseudomallei causing the infections was found in an aromatherapy room spray, made in India, which contained “precious stones”. Specifically, it was the Better Homes & Gardens Lavender & Chamomile Essential Oil Infused Aromatherapy Room Spray with Gems, sold by Walmart.

Although investigators suspected an imported product from the outset, the cluster drew attention to other puzzling cases in the United States – cases that had raised concerns that B. pseudomallei prowled on American soil. In 2015, for example, CDC researchers investigated all 34 cases of human melioidosis in the United States between 2008 and 2013, finding that cases seemed to increase every year during that time. The study, published in the CDC Morbidity and Mortality Weekly Report, concluded that B. pseudomallei may be an emerging infectious disease in the United States.

“It should be noted that three cases of melioidosis occurred in U.S. residents with no history of travel outside the United States or to areas where melioidosis is endemic, possibly indicating unrecognized sources of exposure in the United States. United,” the researchers wrote. “Therefore, being aware that this infection can be seen in people without a clear history of travel to places where B. pseudomallei is endemic is important.”

The warning came back in a case report published in 2020, also authored by CDC researchers and published in the journal Emerging Infectious Diseases. The report documented a puzzling 2018 case of melioidosis in a 63-year-old man from Atascosa County, Texas, which is in the Gulf Coast region. The man had no relevant travel history, reporting only a trip to Mexico 30 years before his illness.

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