Environmental detection of Burkholderia pseudomallei and associated melioidosis risk: a molecular detection and case-control cohort study
Abstract
Background: Environmental acquisition of Burkholderia pseudomallei can cause melioidosis, a life-threatening yet underreported disease. Understanding environmental exposure is essential for effective public health interventions, yet existing tools are limited in their ability to quantify exposure risks.
Methods: We conducted two complementary studies across a 15,118 km2 area of northeast Thailand to improve detection methods and investigate risk factors for melioidosis. In the first study, we compared a newly developed, equipment-light CRISPR-based assay (CRISPR-BP34) with conventional culture methods using both spiked samples and real water samples from household and community sources (November 2020 - November 2021). The second study involved a case-control analysis of 1,135 participants (October 2019 - January 2023) to evaluate the association between environmental exposure to B. pseudomallei (detected in Study 1) and melioidosis risk.
Findings: The CRISPR-BP34 assay demonstrated improved sensitivity (93.52% vs 19.44% for conventional methods) and specificity (100% vs 97.98%), allowing for more accurate detection of B. pseudomallei and exposure risk quantification. Environmental exposure to B. pseudomallei in water sources within a 10 km radius of participants’ households was significantly associated with increased melioidosis risk (OR: 2.74 [95% CI 1.38-5.48]). This risk was also heightened by known factors: occupational exposure among agricultural workers (4.46 [2.91-6.91]), and health factors like elevated hemoglobin A1c, indicating diabetes (1.35 [1.19-1.31]).
Interpretation: Our findings underscore the impact of environmental contamination on melioidosis risk. The robust association between contaminated water sources, including piped water systems, and clinical cases highlights the urgent need for improved water sanitation to mitigate melioidosis risk.
Lay summary
Melioidosis is a neglected tropical disease caused by the bacterium Burkholderia pseudomallei, which can be acquired from the environment through contact with soil or water. However, no previous studies established a statistically significant relationship between B. pseudomallei in the local environment and melioidosis cases, mostly because of low abundance of the bacterium and inconsistent sampling methods.
We recently developed a CRISPR-based method to detect B. pseudomallei and compared it with conventional microbial culture methods on how well it detects the bacterium in water samples from northeast Thailand. We found that our method is far more sensitive (able to pick up the bacterium in most samples with it) and equally specific (able to rule out the bacterium in most samples without it) compared to culture-based methods.
Additionally, we collected water samples, clinical information, and demographic information associated with people in the endemic area. We found exposure to B. pseudomallei in water sources, being an agricultural worker, and diabetes increased the risk of melioidosis.
My role
I performed a literature search which shows that molecular-based techniques (detecting DNA or RNA) had twice the test positivity rate as culture-based techniques (growing the bacterium on agar and finding colonies by eye).
I also processed and analysed the clinical data: I grouped the study participants’ occupation codes and produced a summary of the demographic characteristics of the population (ages, sexes, BMIs, blood glucose level, etc.).
