Effectiveness of a multifaceted prevention programme for melioidosis in diabetics (PREMEL): A stepped-wedge cluster-randomised controlled trial

Burkholderia pseudomallei and melioidosis

Burkholderia pseudomallei, the causative agent of melioidosis, is found in soil and water of tropical and subtropical regions globally. Modelled estimates of the global burden predict that melioidosis remains vastly under-reported, and a call has been made for it to be recognized as a neglected tropical disease by the World Health Organization. Severe weather events and environmental disturbance are associated with increased case numbers, and it is anticipated that, in some regions, cases will increase in association with climate change. Genomic epidemiological investigations have confirmed B. pseudomallei endemicity in newly recognized regions, including the southern United States. Melioidosis follows environmental exposure to B. pseudomallei and is associated with comorbidities that affect the immune response, such as diabetes, and with socioeconomic disadvantage. Several vaccine candidates are ready for phase I clinical trials. In this Review, we explore the global burden, epidemiology and pathophysiology of B. pseudomallei as well as current diagnostics, treatment recommendations and preventive measures, highlighting research needs and priorities.

Melioidosis Vaccines (MeVa): Attitudes to vaccines, melioidosis and clinical trials in key stakeholders in Ubon Ratchathani, Thailand

Background: Melioidosis is a bacterial infection which kills an estimated 89,000 people per year in tropical and sub-tropical regions, chiefly affecting the poorest. Diabetes is the primary risk factor, conferring a 12-fold increase in risk. Despite limited funding compared to other neglected tropical diseases, melioidosis vaccine development has generated several candidates for clinical development. CPS-CRM 197/Hcp1 is a promising vaccine candidate developed at the University of Nevada, Reno which is due to enter a Phase I clinical trial in Oxford, UK in 2024. As we move closer to the possibility of field trials of a melioidosis vaccine, it is critical to work in parallel to understand perceptions toward a vaccine among those living where melioidosis rates are high. Reasons for vaccine acceptance versus hesitancy are complex, and include perceived risk of the target disease, concern about side effects, and above all trust in government, scientists, the pharmaceutical industry and other authorities. Methods: We will carry out a qualitative study in Ubon Ratchathani, Thailand, an endemic region for melioidosis, as groundwork for a potential future melioidosis vaccine efficacy study, and in the longer-term vaccine introduction. This study seeks to explore knowledge and attitudes in three main areas; 1) melioidosis disease, 2) vaccines, and 3) participation in clinical vaccine trials. In-depth interviews and focus group discussions will take place in five participant groups of different risks and exposure to melioidosis. Purposive, convenience sampling will be used, also snowball sampling to reach some participant groups. Sample size will be based on participant's experience, to inform the line of enquiries of study, or until data saturation, expecting 66-90 participants across all groups. Discussion: The findings of this study will be written up and published in an open access journal, and will be valuable to inform future design of clinical trials as well as engagement and communications associated with future vaccine rollout.

Characteristics and One Year Outcomes of Melioidosis Patients in Northeastern Thailand: A Prospective, Multicenter Cohort Study

Background

Melioidosis is a neglected tropical infection caused by the environmental saprophyte Burkholderia pseudomallei.

Methods

We conducted a prospective, observational study at nine hospitals in northeastern Thailand, a hyperendemic melioidosis zone, to define current characteristics of melioidosis patients and quantify outcomes over one year.

Findings

2574 individuals hospitalised with culture-confirmed melioidosis were screened and 1352 patients were analysed. The median age was 55 years, 975 (72%) were male, and 951 (70%) had diabetes. 565 (42%) patients presented with lung infection, 1042 (77%) were bacteremic, 442 (33%) received vasopressors/inotropes and 547 (40%) received mechanical ventilation. 1307 (97%) received an intravenous antibiotic against B. pseudomallei. 335/1345 (25%) patients died within one month and 448/1322 (34%) of patients died within one year. Most patients had risk factors for melioidosis, but patients without identified risk factors did not have a reduced risk of death. Of patients discharged alive, most received oral trimethoprim-sulfamethoxazole, which was associated with decreased risk of post-discharge death; 235/970 (24%) were readmitted, and 874/1015 (86%) survived to one year. Recurrent infection was detected in 17/994 patients (2%). Patients with risk factors other than diabetes had increased risk of death and increased risk of hospital readmission.

Interpretation

In northeastern Thailand patients with melioidosis experience high rates of bacteremia, organ failure and death. Most patients discharged alive survive one year although all-cause readmission is common. Recurrent disease is rare. Strategies that emphasize prevention, rapid diagnosis and intensification of early clinical management are likely to have greatest impact in this and other resource-restricted regions.

Funding

US NIH/NIAID U01AI115520.

Limited Awareness of Melioidosis in High-risk Populations Despite an Increasing Incidence of the Disease in Far North Queensland, Australia

The incidence of melioidosis, an opportunistic infection caused by Burkholderia pseudomallei, has recently doubled in Far North Queensland (FNQ), Australia. This contrasts with the local burden of dengue, which is nearing elimination, and the stable incidence of leptospirosis. This questionnaire-based study assessed the awareness of melioidosis among people in FNQ with risk factors for the disease, using awareness of leptospirosis and dengue as comparators. There were 427 respondents; 361 (85%) reported one or more risk factors for melioidosis. Only 69 of 361 (19%) had heard of melioidosis compared with 301 of 361 (83%) who had heard of dengue (P < 0.001) and 137 of 361 (38%) who had heard of leptospirosis (P < 0.001). In FNQ, Australia, there is an increasing local incidence of melioidosis, but there is limited awareness of the disease among high-risk individuals. Greater community awareness of melioidosis is necessary to implement strategies to prevent disease and expedite the presentation of patients with this life-threatening infection.

Melioidosis in the remote Katherine region of northern Australia

Melioidosis is endemic in the remote Katherine region of northern Australia. In a population with high rates of chronic disease, social inequities, and extreme remoteness, the impact of melioidosis is exacerbated by severe weather events and disproportionately affects First Nations Australians. All culture-confirmed melioidosis cases in the Katherine region of the Australian Top End between 1989–2021 were included in the study, and the clinical features and epidemiology were described. The diversity of Burkholderia pseudomallei strains in the region was investigated using genomic sequencing. From 1989–2021 there were 128 patients with melioidosis in the Katherine region. 96/128 (75%) patients were First Nations Australians, 72/128 (56%) were from a very remote region, 68/128 (53%) had diabetes, 57/128 (44%) had a history of hazardous alcohol consumption, and 11/128 (9%) died from melioidosis. There were 9 melioidosis cases attributable to the flooding of the Katherine River in January 1998; 7/9 flood-associated cases had cutaneous melioidosis, five of whom recalled an inoculating event injury sustained wading through flood waters or cleaning up after the flood. The 126 first-episode clinical B. pseudomallei isolates that underwent genomic sequencing belonged to 107 different sequence types and were highly diverse, reflecting the vast geographic area of the study region. In conclusion, melioidosis in the Katherine region disproportionately affects First Nations Australians with risk factors and is exacerbated by severe weather events. Diabetes management, public health intervention for hazardous alcohol consumption, provision of housing to address homelessness, and patient education on melioidosis prevention in First Nations languages should be prioritised.

Melioidosis, caused by the environmental bacterium Burkholderia pseudomallei, disproportionately affects Australian First Nations peoples in the Northern Territory of Australia. The Katherine region has some of the highest rates of homelessness in Australia, and social inequity impacts health outcomes for First Nations people whose access to care is further complicated by remoteness. In this study, we describe the clinical features and epidemiology of melioidosis in the Katherine region over a 32-year period. Almost three quarters of melioidosis cases were First Nations Australians, over half lived in a very remote region, and diabetes and hazardous alcohol consumption were common risk factors. Following a severe flooding event in the region in 1998, a spike in cases of melioidosis was seen, the majority presenting as skin and soft tissue infections. The B. pseudomallei isolates in the study were extremely genetically diverse, reflecting the large geographic area of the Katherine region. With predicted climate change-driven increases in severe weather events and subsequent increases in melioidosis cases, public health priorities in the region should include addressing high rates of homelessness and hazardous alcohol consumption, optimisation of diabetes management, and ongoing education in First Nations languages regarding prevention of B. pseudomallei exposure.