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Melioidosis is a bacterial infection caused by Burkholderia pseudomallei, which was formerly known as Pseudomonas pseudomallei. B. pseudomallei is a Gram-negative bacterium that typically lives in soil and water in regions with tropical and subtropical climates such as South and Southeast Asia, northern Australia, parts of Central and South America, the U.S. Virgin Islands, and Puerto Rico. B. pseudomallei can infect both animals and humans through direct contact with non-intact skin or mucous membranes, inhalation, or ingestion. It is not considered to be transmissible via respiratory droplets in non-laboratory settings. The risk of spread from person to person is considered extremely low, but can occur through sexual transmission, breastfeeding, and birth.

The CDC receives an average of 12 reports of melioidosis per year.  Most cases have occurred in people with recent travel to a country where B. pseudomallei is known to be endemic. On July 27, 2022, the Centers for Disease Control and Prevention (CDC) detected B. pseudomallei for the first time during environmental sampling of soil and water in the Gulf Coast region of southern Mississippi during an investigation of two human melioidosis cases. Both patients had been hospitalized with pneumonia and sepsis. Neither had traveled outside of the United States. Genetic sequencing revealed the same novel strain of B. pseudomallei in both patients.

In the majority of cases, symptoms occur 1 to 21 days from exposure, with an average of 7 days. In about 5% of cases, symptoms can develop from latent-activated infections much later than the typical 21-day window.

Melioidosis may present as a localized infection, pneumonia, bacteremia, or disseminated infection and can infect any organ, including the brain. Pneumonia is the most common clinical presentation. Signs and symptoms of melioidosis often mimic other diseases such as community-acquired pneumonia or tuberculosis. Other clinical presentations include skin ulceration, gastrointestinal ulceration, sepsis, or abscesses. Medical conditions that predispose persons for melioidosis include diabetes mellitus, alcoholism, chronic lung disease, chronic renal disease, liver disease, hematologic malignancy, thalassemia, cancer, long-term steroid use, and other non-HIV-related immune suppressed condition.

Early diagnosis and treatment is critical in reducing the mortality rate from this disease, which can approach 90% in septic patients with delayed diagnosis and treatment. Melioidosis is confirmed by culture of B. pseudomallei from blood, urine, sputum, throat swabs, abscesses or wounds.

Testing must be conducted by trained personnel because some automated identification methods in clinical laboratories may misidentify B. pseudomallei as a different bacterium. 

Automated identification algorithms using MALDI-TOF, 16s, or VITEK-2 may misidentify B. pseudomallei as another bacterium such as Burkholderia spp. (specifically B. cepacia and B. thailandensis), Chromobacterium violaceum, Ochrobactrum anthropic, and, possibly, Pseudomonas spp., Acinetobacter spp., and Aeromonas spp.

Treatment of melioidosis consists of two phases: an intensive phase, followed by an eradication phase. The intensive phase involves intravenous antimicrobial therapy for at least two weeks with ceftazidime or meropenem. The eradication phase consists of oral therapy with trimethoprim-sulfamethoxazole (TMP/SMX) for 3 to 6 months.

Healthcare personnel are generally not at risk if they follow standard precautions. Laboratory personnel are at increased risk because some lab procedures may aerosolize particles and release B. pseudomallei into the air.

Melioidosis is a Nationally Notifiable Disease. B. pseudomallei is a Tier 1 select agent, which is defined as biological agents and toxins that have been determined to have the potential to pose a severe threat to both human and animal health, to plant health, or to animal and plant products. State or local public health department should be contacted immediately if B. pseudomallei is suspected or identified. The health department should forward the isolate to the closest state laboratory or to a Laboratory Response Network (LRN) laboratory for confirmation. State and LRN laboratories should send presumptive positives to CDC for confirmation for whole genome sequencing.


CDC Health Alert Network, Melioidosis Locally Endemic in Areas of the Mississippi Gulf Coast after Burkholderia pseudomallei Isolated in Soil and Water and Linked to Two Cases – Mississippi, 2020 and 2022, July 27, 2022, CDCHAN-00470

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