Drivers of melioidosis endemicity: epidemiological transition, zoonosis, and climate change

A rare case of infectious aortitis caused by Burkholderia pseudomallei

INTRODUCTION

Melioidosis is caused by Burkholderia pseudomallei and primarily affects non-vascular organ systems. We present a case of a melioidotic penetrating aortic ulcer (PAU) with unusual clinical features of vascular infection. The patient was successfully treated with a single-stage neoaortoiliac system procedure, highlighting the challenges in managing melioidotic aortic infections.

PRESENTATION OF CASE

We present a case of melioidotic PAU that was successfully treated using a single-stage neoaortoiliac system procedure. A 70-year-old male with type 2 diabetes and ischemic heart disease presented with acute abdominal and back pain, later found to have an infrarenal PAU without aneurysmal changes. Following an emergency endovascular aortic repair (EVAR), blood cultures revealed Burkholderia pseudomallei bacteraemia, leading to the diagnosis of melioidosis-associated aortitis. The patient underwent a complex surgical procedure to remove the infected aorta and reconstruct it using a neoaortoiliac system, followed by a challenging recovery that included wound infection, prolonged antibiotic therapy, and subsequent hospitalization for sepsis. Despite complications, the patient remains alive and functionally independent 15 months post-surgery.

DISCUSSION

Burkholderia pseudomallei, found in contaminated soil and water, can lead to severe infections, including mycotic aneurysms, with a high mortality rate despite treatment. Management of vascular involvement is complex, often requiring emergency interventions like EVAR to enable survival for definitive treatment.

CONCLUSION

This case emphasizes the importance of recognizing melioidosis as a potential cause of infectious aortitis, particularly in patients with a travel history to endemic regions.

Countering Zoonotic Diseases: Current Scenario and Advances in Diagnostics, Monitoring, Prophylaxis and Therapeutic Strategies

Human life and health have interacted reciprocally with the surrounding environment and animal fauna for ages. This relationship is evident in developing nations, where human life depends more on the animal population for food, transportation, clothing, draft power, and fuel sources, among others. This inseparable link is a potent source of public health issues, especially in outbreaks of zoonotic diseases transmitted from animals to humans. Zoonotic diseases are referred to as diseases that are naturally transmitted between vertebrate animals and humans. Among the globally emerging diseases in the last decade, 75% are of animal origin, most of which are life-threatening. Since most of them are caused by potent new pathogens capable of long-distance transmission, the impact is widespread and has serious public health and economic consequences. Various other factors also contribute to the transmission, spread, and outbreak of zoonotic diseases, among which industrialization-led globalization followed by ecological disruption and climate change play a critical role. In this regard, all the possible strategies, including advances in rapid and confirmatory disease diagnosis and surveillance/monitoring, immunization/vaccination, therapeutic approaches, appropriate prevention and control measures to be adapted, and awareness programs, need to be adopted collaboratively among different health sectors in medical, veterinary, and concerned departments to implement the necessary interventions for the effective restriction, minimization, and timely control of zoonotic threats. The present review focuses on the current scenario of zoonotic diseases and their counteracting approaches to safeguard their health impact on humans.

Latent melioidosis activation presenting with urinary tract infection and bacteremia

We report a rare case of latent melioidosis activation in a patient with a distant travel history to an endemic region. Melioidosis is an infection caused by Burkholderia pseudomallei which is highly endemic in Southeast Asia and northern Australia. The patient exhibited common clinical risk factors, presenting with urinary tract infection and bacteremia. The treatment course was complicated by the adverse effect of trimethoprim/sulfamethoxazole. This case underscores the importance of early detection and appropriate treatment of melioidosis, particularly given its expanding global distribution.

Paediatric melioidosis

Melioidosis is a tropical infectious disease caused by the saprophytic gram-negative bacterium Burkholderia pseudomallei. Despite the infection being endemic in southeast Asia and northern Australia, the broad clinical presentations and diagnostic difficulties limit its early detection, particularly in children. Melioidosis more commonly affects the immunocompromised and adults. Melioidosis is increasingly being diagnosed around the world and whole-genome sequencing indicates that these cases are not linked with travel to endemic areas. Research has concentrated on the adult population with limited experience reported in the care of this uncommon, but potentially fatal condition in children presenting with bacteraemia and pneumonia.

Development of an Antigen Capture Lateral Flow Immunoassay for the Detection of Burkholderia pseudomallei

Early diagnosis is essential for the successful management of Burkholderia pseudomallei infection, but it cannot be achieved by the current gold standard culture technique. Therefore, this study aimed to develop a lateral flow immunoassay (LFIA) targeting B. pseudomallei capsular polysaccharide. The development was performed by varying nitrocellulose membrane reaction pads and chase buffers. The prototype LFIA is composed of Unisart CN95 and chase buffer containing tris-base, casein, and Surfactant 10G. The assay showed no cross-reactivity with E. coli, S. aureus, P. aeruginosa, and P. acne. The limit of detections (LODs) of the prototype LFIA was 107 and 106 CFU/mL B. pseudomallei in hemoculture medium and artificial urine, respectively. These LODs suggest that this prototype can detect melioidosis from positive hemoculture bottles but not straight from urine. Additionally, these LODs are still inferior compared to Active Melioidosis Detect (AMDTM). Overall, this prototype holds the potential to be used clinically with hemoculture bottles. However, further improvements should be considered, especially for use with urine samples.

Exploring the Relationship between Melioidosis Morbidity Rate and Local Environmental Indicators Using Remotely Sensed Data

Melioidosis is an endemic infectious disease caused by Burkholderia pseudomallei bacteria, which contaminates soil and water. To better understand the environmental changes that have contributed to melioidosis outbreaks, this study used spatiotemporal analyses to clarify the distribution pattern of melioidosis and the relationship between melioidosis morbidity rate and local environmental indicators (land surface temperature, normalised difference vegetation index, normalised difference water index) and rainfall. A retrospective study was conducted from January 2013 to December 2022, covering data from 219 sub-districts in Northeast Thailand, with each exhibiting a varying morbidity rate of melioidosis on a monthly basis. Spatial autocorrelation was determined using local Moran's I, and the relationship between the melioidosis morbidity rate and the environmental indicators was evaluated using a geographically weighted Poisson regression. The results revealed clustered spatiotemporal patterns of melioidosis morbidity rate across sub-districts, with hotspots predominantly observed in the northern region. Furthermore, we observed a range of coefficients for the environmental indicators, varying from negative to positive, which provided insights into their relative contributions to melioidosis in each local area and month. These findings highlight the presence of spatial heterogeneity driven by environmental indicators and underscore the importance of public health offices implementing targeted monitoring and surveillance strategies for melioidosis in different locations.

Climate change and its impact on infectious diseases in Asia

ABSTRACT

Climate change, particularly increasing temperature, changes in rainfall, extreme weather events and changes in vector ecology, impacts the transmission of many climate-sensitive infectious diseases. Asia is the world's most populous, rapidly evolving and diverse continent, and it is already experiencing the effects of climate change. Climate change intersects with population, sociodemographic and geographical factors, amplifying the public health impact of infectious diseases and potentially widening existing disparities. In this narrative review, we outline the evidence of the impact of climate change on infectious diseases of importance in Asia, including vector-borne diseases, food- and water-borne diseases, antimicrobial resistance and other infectious diseases. We also highlight the imperative need for strategic intersectoral collaboration at the national and global levels and for the health sector to implement adaptation and mitigation measures, including responsibility for its own greenhouse gas emissions.

Melioidosis Knowledge Awareness in Three Distinct Groups in the Tropical Northern Territory of Australia

Melioidosis is a potentially life-threatening infection. This study aimed to assess the melioidosis knowledge among distinct participant groups in the tropical Top End of the Northern Territory (NT) of Australia. Participants were categorised into three groups: NT medical students and health research staff (Group 1: Hi-Ed), Aboriginal Rangers and Aboriginal Healthcare Workers (Group 2: Rangers/AHWs), and patients with a history of melioidosis infection (Group 3: Patients). A questionnaire was developed to collect data on demographics, risk and protective factor awareness, and knowledge acquisition sources. We used responses to calculate indices for risk knowledge (RKI), protective knowledge (PKI), overall melioidosis knowledge (MKI), and information sources (ISI). We found that 93.6% of participants in Group 1 (Hi-Ed) said that they had heard of melioidosis, followed by 81.5% in Group 3 (Patients), and 72.0% in Group 2 (Rangers/AHWs). Group 1 (Hi-Ed) participants demonstrated greater knowledge of risk-increasing behaviours but had gaps in knowledge of clinical risks like diabetes. Multiple regression revealed that the number of resources used was the only significant predictor of MKI. There are varying melioidosis knowledge levels across different NT participant groups. Targeted educational interventions are needed to enhance melioidosis awareness. A weblink with an interactive summary of our analysis can be found under Results part.

Isolation of Burkholderia pseudomallei from a goat in New Caledonia: implications for animal and human health monitoring and serological tool comparison

BACKGROUND

Melioidosis is a serious bacterial infection caused by Burkholderia pseudomallei, a gram-negative bacterium commonly found in soil and water. It can affect both humans and animals, and is endemic in regions such as Southeast Asia and Northern Australia. In recent years, there have been reports of an emergence of human melioidosis in other areas, including New Caledonia.

RESULTS

During standard laboratory analysis in New Caledonia in 2021, a strain of B. pseudomallei was isolated from a goat. The strain was characterized using both MLST and WGS techniques and was found to cluster with previously described local human strains from the area. In parallel, several serological tests (CFT, ELISA, Luminex (Hcp1, GroEL, BPSS1840), arrays assay and a latex agglutination test) were performed on animals from the farm where the goat originated, and/or from three other neighboring farms. Using two commercial ELISA kits, seropositive animals were found only on the farm where the infected goat originated and tests based on recombinant proteins confirmed the usefulness of the Hcp1 protein for the diagnosis of melioidosis in animals.

CONCLUSIONS

Despite the regular reports of human cases, this is the first confirmed case of melioidosis in an animal in New Caledonia. These results confirm the presence of the bacterium in the region and highlight the importance of vigilance for both animal and human health. It is critical that all health partners, including breeders, veterinarians, and biologists, work together to monitor and prevent the spread of the disease.

Burkholderia pseudomallei Complex Subunit and Glycoconjugate Vaccines and Their Potential to Elicit Cross-Protection to Burkholderia cepacia Complex

Burkholderia are a group of Gram-negative bacteria that can cause a variety of diseases in at-risk populations. B. pseudomallei and B. mallei, the etiological agents of melioidosis and glanders, respectively, are the two clinically relevant members of the B. pseudomallei complex (Bpc). The development of vaccines against Bpc species has been accelerated in recent years, resulting in numerous promising subunits and glycoconjugate vaccines incorporating a variety of antigens. However, a second group of pathogenic Burkholderia species exists known as the Burkholderia cepacia complex (Bcc), a group of opportunistic bacteria which tend to affect individuals with weakened immunity or cystic fibrosis. To date, there have been few attempts to develop vaccines to Bcc species. Therefore, the primary goal of this review is to provide a broad overview of the various subunit antigens that have been tested in Bpc species, their protective efficacy, study limitations, and known or suspected mechanisms of protection. Then, we assess the reviewed Bpc antigens for their amino acid sequence conservation to homologous proteins found in Bcc species. We propose that protective Bpc antigens with a high degree of Bpc-to-Bcc sequence conservation could serve as components of a pan-Burkholderia vaccine capable of protecting against both disease-causing groups.

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.

A Graphical Overview of the Histopathology of Human Melioidosis: A Case Series

Background

Melioidosis, caused by the Gram-negative bacterium Burkholderia pseudomallei, has a major global health impact and a wide range of different disease manifestations. Histopathological descriptions of melioidosis remain limited. Granulomatous inflammation with multinucleated giant cells are considered classic features. We aim to present a graphical overview of histopathological manifestations of melioidosis, serving as an aid in diagnosing this disease.

Methods

We performed a retrospective international multicenter laboratory-based analysis of formalin-fixed paraffin-embedded (FFPE) tissue from culture-confirmed melioidosis autopsy and biopsy cases. Available FFPE tissue was stained with hematoxylin and eosin and immunostainings including a monoclonal antibody targeting the capsular polysaccharide (CPS) of B pseudomallei. Tissue with site-specific cultures and/or positive CPS staining were included in the graphical histopathological overview.

Results

We identified tissue of 8 autopsy and 5 biopsy cases. Pneumonia and soft tissue abscesses were the leading foci of disease displaying mainly necrosis and suppuration. Infrequent disease manifestations included involvement of bone marrow and adrenal glands in an autopsy case and biopsied mediastinal tissue, the latter being the only case in which we identified multinucleated giant cells. Using the CPS staining, we demonstrated granulomata as part of rare gastric tissue involvement.

Conclusions

We found fatal melioidosis to be a necrotizing and suppurative inflammation, usually without multinucleated giant cell formation. Gastric and mediastinal involvement points to ingestion and inhalation as possible routes of infection. The CPS staining proved beneficial as an aid to establish a histopathological diagnosis. Our graphical overview can be used by infectious diseases specialists, microbiologists, and pathologists.

Travel-associated melioidosis: a narrative review

BACKGROUND

Melioidosis, caused by Burkholderia pseudomallei, may be considered a neglected tropical disease that remains underdiagnosed in many geographical areas. Travellers can act as the sentinels of disease activity, and data from imported cases may help complete the global map of melioidosis.

METHODS

A literature search for imported melioidosis for the period 2016-22 was performed in PubMed and Google Scholar.

RESULTS

In total, 137 reports of melioidosis associated with travel were identified. The majority were males (71%) and associated with exposure in Asia (77%) (mainly Thailand, 41%, and India, 9%). A minority acquired the infection in the Americas-Caribbean area (6%), Africa (5%) and Oceania (2%). The most frequent comorbidity was diabetes mellitus (25%) followed by underlying pulmonary, liver or renal disease (8, 5 and 3%, respectively). Alcohol/tobacco use were noted for seven and six patients, respectively (5%). Five patients (4%) had associated non-human immunodeficiency virus (HIV)-related immunosuppression, and three patients (2%) had HIV infection. One patient (0.8%) had concomitant coronavirus disease 19. A proportion (27%) had no underlying diseases. The most frequent clinical presentations included pneumonia (35%), sepsis (30%) and skin/soft tissue infections (14%). Most developed symptoms <1 week after return (55%), and 29% developed symptoms >12 weeks after. Ceftazidime and meropenem were the main treatments used during the intensive intravenous phase (52 and 41% of patients, respectively) and the majority (82%) received co-trimoxazole alone/combination, for the eradication phase. Most patients had a favourable outcome/survived (87%). The search also retrieved cases in imported animals or cases secondary to imported commercial products.

CONCLUSIONS

As post-pandemic travel soars, health professionals should be aware of the possibility of imported melioidosis with its diverse presentations. Currently, no licensed vaccine is available, so prevention in travellers should focus on protective measures (avoiding contact with soil/stagnant water in endemic areas). Biological samples from suspected cases require processing in biosafety level 3 facilities.

Case Report: Burkholderia pseudomallei-Caused Sclerokeratitis

This report is on a 45-year-old male patient without underlying disease who presented with a Burkholderia pseudomallei-caused keratoscleritis in his right eye. Slit-lamp examination revealed multiple, indistinct corneal infiltrations with subconjunctival/scleral abscesses. Corneal tissue culture was positive for B. pseudomallei and confirmed by mass spectrometry. The patient was treated with fortified ceftazidime, fortified gentamicin eyedrops, and intravenous ceftazidime injection. Penetrating keratoplasty, including intracameral ceftazidime injections, was undertaken due to corneal lesion worsening. Scleral debridement with subconjunctival ceftazidime injections were undertaken due to the progression of the scleral abscess. After 2 months, the corneal and scleral lesions were inactive, and the systemic and topical antibiotics were tapered. This is the first case report of B. pseudomallei-caused keratoscleritis with photography. The patient was seen in an endemic geographical area with multiple corneal infiltrations and subconjunctival/scleral abscess. Systemic and topical antibiotics accompanied with surgery should be considered.

Melioidosis and Burkholderia pseudomallei : progress in epidemiology, diagnosis, treatment and vaccination

PURPOSE OF REVIEW

Melioidosis and its causative bacterium Burkholderia pseudomallei are being found in unexpected locations and bacterial genotyping is providing new insights into global spread and where and how individuals are being infected. This review summarizes recent studies covering the epidemiology, diagnosis, treatment, and prevention of melioidosis.

RECENT FINDINGS

Whole-genome sequencing of B. pseudomallei from patients and environmental sampling is informing the phylogeography of B. pseudomallei at regional, continental, and global levels, while also defining the epidemiology for individual cases. The situation in Africa remains the most unresolved, while the evolving story of B. pseudomallei in the Americas may establish that B. pseudomallei is endemic in parts of southern USA. Guidelines for diagnosis and treatment of melioidosis are well established, and published mortality has decreased from 50% or higher to 10% or lower in some countries but access to laboratory and therapeutic resources are not available or are extremely limited in many melioidosis-endemic regions.

SUMMARY

The enormous clinical diversity of melioidosis and the complexities of laboratory diagnosis and of treatment make it a sentinel disease for highlighting the continuing global disparities in access to and provision of healthcare.