Summary
- Melioidosis is an emerging infectious disease in the United States caused by Burkholderia pseudomallei.
- Neurologic melioidosis can lead to serious symptoms such as fever, headache, seizures, weakness, and brain abscesses.
- A recent outbreak in the United States linked to an aromatherapy spray imported from India resulted in 4 confirmed cases of melioidosis.
- Inhaled B. pseudomallei can enter the central nervous system through various portals, causing neurologic issues.
- The ATS2021 strain of B. pseudomallei showed robust biofilm production, considerable virulence in mouse models, and affected oligodendrocytes associated with brain function.
In the United States, there is an emerging infectious disease known as melioidosis. It is caused by a bacterium called Burkholderia pseudomallei. This disease is prevalent in areas where the bacterium causes pneumonia and severe bacteremia, which can be fatal depending on various factors such as the standard of care and underlying health conditions like diabetes. Melioidosis can present in various ways, from asymptomatic to acute pulmonary illness. In some cases, about 1.5% to 5% of patients, the infection can lead to serious neurologic melioidosis. This form of the disease is characterized by symptoms such as fever, headache, seizures, weakness, and brain abscesses.
In 2021, there were four confirmed cases of melioidosis in the United States where the patients had not traveled internationally. Further investigation linked the source of the infection to an aromatherapy spray imported from India. Two of the patients developed neurologic melioidosis, with one unfortunately passing away and the other experiencing long-term complications. Additionally, a pet raccoon that had contact with the contaminated spray also exhibited neurologic symptoms before passing away. Although viable bacteria were not recovered from the raccoon, PCR testing detected the presence of Burkholderia pseudomallei DNA in tissue samples.
Studies have shown that Burkholderia pseudomallei can enter the central nervous system through various portals, such as the nasal mucosa or olfactory epithelium. Neurologic disease caused by this bacterium is associated with a specific protein called Burkholderia intracellular motility factor A (BimA), which enables the bacteria to move within host cells and evade the immune system. Some strains of Burkholderia pseudomallei possess a variant of the BimA gene, known as bimABm, which is linked to neurologic complications.
A particular strain of Burkholderia pseudomallei, ATS2021, was characterized in a study to test medical countermeasures against melioidosis. The research involved growing the bacteria in different types of media, assessing biofilm formation, and exposing mice to aerosolized bacteria to determine the 50% lethal dose (LD50). The results showed that ATS2021 was highly virulent in mouse models of inhalational melioidosis, causing rapid neurologic invasion and significant health effects.
Further investigations included genetic analyses of ATS2021, which revealed the presence of virulence factors typically associated with Burkholderia pseudomallei strains. The strain displayed robust biofilm production at 37°C, which may contribute to the difficulty in treating melioidosis with antibiotics. Histopathologic analyses in mice exposed to ATS2021 showed lesions in various organs, including the brain, spinal cord, and vertebral bone marrow. Immunohistochemical analyses corroborated these findings, highlighting the impact of the infection on different tissues.
One significant observation from the study was the effect of ATS2021 on oligodendrocytes in the brain. Oligodendrocytes are crucial for myelination in the central nervous system, and the research showed a significant decrease in oligodendrocyte activity in mice exposed to high doses of aerosolized bacteria. This dysregulation of oligodendrocytes could potentially explain some of the clinical symptoms observed in animal models, such as muscle weakness and sensitivity to touch.
Overall, the study highlights the importance of understanding the virulence and pathogenic mechanisms of emerging infectious diseases like melioidosis. With the increasing prevalence of melioidosis in the United States, it is essential for clinical laboratories to remain vigilant and for researchers to develop novel medical countermeasures and diagnostic strategies to combat this infectious disease. By studying isolates like ATS2021, scientists can gain insights into the hazards associated with these pathogens and work towards effective prevention and treatment strategies.
Infectious Diseases, Public Health & Prevention