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.

Health Outcomes and Cost-effectiveness of Monoclonal SARS-CoV-2 Antibodies as Pre-exposure Prophylaxis.

Importance: Pre-exposure prophylaxis with neutralizing SARS-CoV-2 monoclonal antibodies (mAbs PrEP) prevents infection and reduces hospitalizations and the duration thereof for COVID-19 and death among high-risk individuals. However, reduced effectiveness due to a changing SARS-CoV-2 viral landscape and high drug prices remain substantial implementation barriers. Objective: To assess the cost-effectiveness of mAbs PrEP as COVID-19 PrEP. Design, Setting, and Participants: For this economic evaluation, a decision analytic model was developed and parameterized with health care outcome and utilization data from individuals with high risk for COVID-19. The SARS-CoV-2 infection probability, mAbs PrEP effectiveness, and drug pricing were varied. All costs were collected from a third-party payer perspective. Data were analyzed from September 2021 to December 2022. Main Outcomes and Measures: Health care outcomes including new SARS-CoV-2 infections, hospitalization, and deaths. The cost per death averted and cost-effectiveness ratios using a threshold for prevention interventions of $22 000 or less per quality-adjusted life year (QALY) gained. Results: The clinical cohort consisted of 636 individuals with COVID-19 (mean [SD] age 63 [18] years; 341 [54%] male). Most individuals were at high risk for severe COVID-19, including 137 (21%) with a body mass index of 30 or higher, 60 (9.4%) with hematological malignant neoplasm, 108 (17%) post-transplantation, and 152 (23.9%) who used immunosuppressive medication before COVID-19. Within the context of a high (18%) SARS-CoV-2 infection probability and low (25%) effectiveness the model calculated a short-term reduction of 42% ward admissions, 31% intensive care unit (ICU) admissions, and 34% deaths. Cost-saving scenarios were obtained with drug prices of $275 and 75% or higher effectiveness. With a 100% effectiveness mAbs PrEP can reduce ward admissions by 70%, ICU admissions by 97%, and deaths by 92%. Drug prices, however, need to reduce to $550 for cost-effectiveness ratios less than $22 000 per QALY gained per death averted and to $2200 for ratios between $22 000 and $88 000. Conclusions and Relevance: In this study, use of mAbs PrEP for preventing SARS-CoV-2 infections was cost-saving at the beginning of an epidemic wave (high infection probability) with 75% or higher effectiveness and drug price of $275. These results are timely and relevant for decision-makers involved in mAbs PrEP implementation. When newer mAbs PrEP combinations become available, guidance on implementation should be formulated ensuring a fast rollout. Nevertheless, advocacy for mAbs PrEP use and critical discussion on drug prices are necessary to ensuring cost-effectiveness for different epidemic settings.

Presence of Burkholderia pseudomallei in Soil, Nigeria, 2019.

Melioidosis, caused by the soil-dwelling bacterium Burkholderia pseudomallei, is predicted to be endemic in Nigeria but is only occasionally reported. This report documents the systematic identification of the presence of B. pseudomallei and B. thailandensis in the soil across multiple states in Nigeria.

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

PURPOSE OF REVIEW: Melioidosis, caused by the soil-dwelling bacterium Burkholderia pseudomallei, is a tropical infection associated with high morbidity and mortality. This review summarizes current insights into melioidosis' endemicity, focusing on epidemiological transitions, zoonosis, and climate change. RECENT FINDINGS: Estimates of the global burden of melioidosis affirm the significance of hot-spots in Australia and Thailand. However, it also highlights the paucity of systematic data from South Asia, The Americas, and Africa. Globally, the growing incidence of diabetes, chronic renal and (alcoholic) liver diseases further increase the susceptibility of individuals to B. pseudomallei infection. Recent outbreaks in nonendemic regions have further exposed the hazard from the trade of animals and products as potential reservoirs for B. pseudomallei. Lastly, global warming will increase precipitation, severe weather events, soil salinity and anthrosol, all associated with the occurrence of B. pseudomallei. SUMMARY: Epidemiological transitions, zoonotic hazards, and climate change are all contributing to the emergence of novel melioidosis-endemic areas. The adoption of the One Health approach involving multidisciplinary collaboration is important in unraveling the real incidence of B. pseudomallei, as well as reducing the spread and associated mortality.

Melioidosis in Africa: Time to Raise Awareness and Build Capacity for Its Detection, Diagnosis, and Treatment.

Melioidosis is a tropical infectious disease caused by the soil-dwelling bacterium Burkholderia pseudomallei with a mortality of up to 50% in low resource settings. Only a few cases have been reported from African countries. However, studies on the global burden of melioidosis showed that Africa holds a significant unrecognized disease burden, with Nigeria being at the top of the list. The first World Health Organization African Melioidosis Workshop was organized in Lagos, Nigeria, with representatives of health authorities, microbiology laboratories, and clinical centers from across the continent. Dedicated hands-on training was given on laboratory diagnostics of B. pseudomallei. This report summarises the meeting objectives, including raising awareness of melioidosis and building capacity for the detection, diagnosis, biosafety, treatment, and prevention across Africa. Further, collaboration with regional and international experts provided a platform for sharing ideas on best practices.

Correction: Increased Von Willebrand factor, decreased ADAMTS13 and thrombocytopenia in melioidosis.

[This corrects the article DOI: 10.1371/journal.pntd.0005468.].

Melioidosis in travelers: An analysis of Dutch melioidosis registry data 1985-2018.

BACKGROUND: Melioidosis, caused by the Gram-negative bacterium Burkholderia pseudomallei, is an opportunistic infection across the tropics. Here, we provide a systematic overview of imported human cases in a non-endemic country over a 25-year period. METHODS: All 55 Dutch microbiology laboratories were contacted in order to identify all B. pseudomallei positive cultures from 1990 to 2018. A response rate of 100% was achieved. Additionally, a systematic literature search was performed, medical-charts reviewed, and tissue/autopsy specimens were re-assessed. RESULTS: Thirty-three travelers with melioidosis were identified: 70% male with a median-age of 54 years. Risk factors were present in most patients (n = 23, 70%), most notably diabetes (n = 8, 24%) and cystic fibrosis (n = 3, 9%). Countries of acquisition included Thailand, Brazil, Indonesia, Panama, and The Gambia. Disease manifestations included pneumonia, intra-abdominal abscesses, otitis externa, genitourinary, skin-, CNS-, and thyroid gland infections. Twelve (36%) patients developed sepsis and/or septic shock. Repeat episodes of active infection were observed in five (15%) and mortality in four (12%) patients. Post-mortem analysis showed extensive metastatic (micro)abscesses amongst other sites in the adrenal gland and bone marrow. CONCLUSIONS: The number of imported melioidosis is likely to increase, given rising numbers of (immunocompromised) travelers, and increased vigilance of the condition. This first systematic retrospective surveillance study in a non-endemic melioidosis country shows that imported cases can serve as sentinels to provide information about disease activity in areas visited and inform pre-travel advice and post-travel clinical management.

Global burden of melioidosis in 2015: a systematic review and data synthesis.

BACKGROUND: Melioidosis is an infectious disease caused by the environmental bacterium Burkholderia pseudomallei. It is often fatal, with a high prevalence in tropical areas. Clinical presentation can vary from abscess formation to pneumonia and sepsis. We assessed the global burden of melioidosis, expressed in disability-adjusted life-years (DALYs), for 2015. METHODS: We did a systematic review of the peer-reviewed literature for human melioidosis cases between Jan 1, 1990, and Dec 31, 2015. Quantitative data for cases of melioidosis were extracted, including mortality, age, sex, infectious and post-infectious sequelae, antibiotic treatment, and symptom duration. These data were combined with established disability weights and expert panel discussions to construct an incidence-based disease model. The disease model was integrated with established global incidence and mortality estimates to calculate global melioidosis DALYs. The study is registered with PROSPERO, number CRD42018106372. FINDINGS: 2888 articles were screened, of which 475 eligible studies containing quantitative data were retained. Pneumonia, intra-abdominal abscess, and sepsis were the most common outcomes, with pneumonia occurring in 3633 (35·7%, 95% uncertainty interval [UI] 34·8-36·6) of 10 175 patients, intra-abdominal abscess in 1619 (18·3%, 17·5-19·1) of 8830 patients, and sepsis in 1526 (18·0%, 17·2-18·8) of 8469 patients. We estimate that in 2015, the global burden of melioidosis was 4·6 million DALYs (UI 3·2-6·6) or 84·3 per 100 000 people (57·5-120·0). Years of life lost accounted for 98·9% (UI 97·7-99·5) of the total DALYs, and years lived with disability accounted for 1·1% (0·5-2·3). INTERPRETATION: Melioidosis causes a larger disease burden than many other tropical diseases that are recognised as neglected, and so it should be reconsidered as a major neglected tropical disease. FUNDING: European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Research Grant 2018, AMC PhD Scholarship, The Netherlands Organisation for Scientific Research (NWO), H2020 Marie Sklodowska-Curie Innovative Training Network European Sepsis Academy.

Identification of Burkholderia thailandensis with novel genotypes in the soil of central Sierra Leone.

BACKGROUND: The soil-dwelling bacillus Burkholderia pseudomallei is the etiological-agent of the neglected and life-threatening emerging infection melioidosis. The distribution of B. pseudomallei in West Africa is unknown. In the present study we aimed to determine whether B. pseudomallei and B. thailandensis are present in the environment of central Sierra Leone. METHODOLOGY/PRINCIPAL FINDINGS: In June-July 2017, we conducted an environmental surveillance study-designed in accordance with existing consensus guidelines-in central Sierra Leone. A total of 1,000 soil samples (100 per site) were collected and cultured. B. pseudomallei was not identified in the soil, but we identified seven novel B. thailandensis sequence types with multi-locus sequence typing (MLST) and 16S rRNA gene sequence analyses. CONCLUSIONS/SIGNIFICANCE: The presence of B. pseudomallei was not demonstrated, however, multiple novel B. thailandensis sequence types were identified. More environmental and sequencing studies are needed to further understand the genetic diversity, evolution and virulence of these emerging organisms.

Role of Toll-Like Receptor 5 (TLR5) in Experimental Melioidosis.

The Gram-negative intracellular pathogen Burkholderia pseudomallei is the causative agent of melioidosis, an important cause of sepsis in Southeast Asia. Recognition of pathogen-associated molecular patterns by Toll-like receptors (TLRs) is essential for an appropriate immune response during pathogen invasion. In patients with melioidosis, TLR5 is the most abundantly expressed TLR, and a hypofunctional TLR5 variant has been associated with improved survival. Here, we studied the functional role of TLR5 and its ligand flagellin in experimental melioidosis. First, we observed differential TLR5 expression in the pulmonary and hepatic compartments upon infection with B. pseudomallei Next, we found that B. pseudomallei-challenged TLR5-deficient (Tlr5-/- ) mice were more susceptible to infection than wild-type (WT) mice, as demonstrated by higher systemic bacterial loads, increased organ injury, and impaired survival. Lung bacterial loads were not different between the two groups. The phenotype was flagellin independent; no difference in in vivo virulence was observed for the flagellin-lacking mutant MM36 compared to the wild-type B. pseudomallei strain 1026b. Tlr5-/- mice showed a similar impaired antibacterial defense when infected with MM36 or 1026b. Ex vivo experiments showed that TLR5-deficient macrophages display markedly impaired phagocytosis of B. pseudomallei In conclusion, these data suggest that TLR5 deficiency has a detrimental flagellin-independent effect on the host response against pulmonary B. pseudomallei infection.

Thrombocytopenia Impairs Host Defense Against Burkholderia pseudomallei (Melioidosis).

Background: Infection with the gram-negative bacillus Burkholderia pseudomallei (melioidosis) is an important cause of pneumosepsis in Southeast Asia and has a mortality of up to 40%. We aimed to assess the role of platelets in the host response against B. pseudomallei infection. Methods: Association between platelet counts and mortality was determined in 1160 patients with culture-proven melioidosis. Mice treated with (low- or high-dose) platelet-depleting antibody were inoculated intranasally with B. pseudomallei and killed. Additional studies using functional glycoprotein Ibα-deficient mice were conducted. Results: Thrombocytopenia was present in 31% of patients at admission and predicted mortality in melioidosis patients even after adjustment for confounders. In our murine-melioidosis model, platelet counts decreased, and mice treated with a platelet-depleting antibody showed enhanced mortality and higher bacterial loads compared to mice with normal platelet counts. Low platelet counts had a modest impact on early-pulmonary neutrophil influx. Reminiscent of their role in hemostasis, platelet depletion impaired vascular integrity, resulting in early lung bleeding. Glycoprotein Ibα-deficient mice had reduced platelet counts during B. pseudomallei infection together with an impaired local host defense in the lung. Conclusions: Thrombocytopenia predicts mortality in melioidosis patients and, during experimental melioidosis, platelets play a protective role in both innate immunity and vascular integrity.

Differences in Inflammation Patterns Induced by African and Asian Burkholderia pseudomallei Isolates in Mice.

AbstractBurkholderia pseudomallei is the causative agent of melioidosis, an emerging tropical disease of high mortality. Sub-Saharan Africa represents potential melioidosis "hotspots"; however, to date, only a few cases have been reported. Here in, we compared the inflammatory patterns induced by a B. pseudomallei strain recently isolated from a fatal Gabonese case with the Thai reference strain B. pseudomallei-1026b and Burkholderia thailandensis-E264. Ex vivo, no differences were observed in terms of cellular responsiveness between strains. However, when compared with the B. pseudomallei-1026b strain, the Gabonese isolate was significantly less virulent in terms of bacterial dissemination, inflammatory response, and organ damage in mice. Genomic comparison between strains showed differences in regions containing a fimbriae/adhesion virulence protein. In addition to a lack of microbiology facilities, differences in virulence of Burkholderia strains might contribute to the diverse global clinical occurrence of melioidosis.

The gut microbiota as a modulator of innate immunity during melioidosis.

BACKGROUND: Melioidosis, caused by the Gram-negative bacterium Burkholderia pseudomallei, is an emerging cause of pneumonia-derived sepsis in the tropics. The gut microbiota supports local mucosal immunity and is increasingly recognized as a protective mediator in host defenses against systemic infection. Here, we aimed to characterize the composition and function of the intestinal microbiota during experimental melioidosis. METHODOLOGY/PRINCIPAL FINDINGS: C57BL/6 mice were infected intranasally with B. pseudomallei and sacrificed at different time points to assess bacterial loads and inflammation. In selected experiments, the gut microbiota was disrupted with broad-spectrum antibiotics prior to inoculation. Fecal bacterial composition was analyzed by means of IS-pro, a 16S-23S interspacer region-based profiling method. A marked shift in fecal bacterial composition was seen in all mice during systemic B. pseudomallei infection with a strong increase in Proteobacteria and decrease in Actinobacteria, with an increase in bacterial diversity. We found enhanced early dissemination of B. pseudomallei and systemic inflammation during experimental melioidosis in microbiota-disrupted mice compared with controls. Whole-genome transcriptional profiling of the lung identified several genes that were differentially expressed between mice with a normal or disrupted intestinal microbiota. Genes involved in acute phase signaling, including macrophage-related signaling pathways were significantly elevated in microbiota disrupted mice. Compared with controls, alveolar macrophages derived from antibiotic pretreated mice showed a diminished capacity to phagocytose B. pseudomallei. This might in part explain the observed protective effect of the gut microbiota in the host defense against pneumonia-derived melioidosis. CONCLUSIONS/SIGNIFICANCE: Taken together, these data identify the gut microbiota as a potential modulator of innate immunity during B. pseudomallei infection.

Increased Von Willebrand factor, decreased ADAMTS13 and thrombocytopenia in melioidosis.

BACKGROUND: Melioidosis, caused by bioterror treat agent Burkholderia pseudomallei, is an important cause of community-acquired Gram-negative sepsis in Southeast Asia and Northern Australia. New insights into the pathogenesis of melioidosis may help improve treatment and decrease mortality rates from this dreadful disease. We hypothesized that changes in Von Willebrand factor (VWF) function should occur in melioidosis, based on the presence of endothelial stimulation by endotoxin, pro-inflammatory cytokines and thrombin in melioidosis, and investigated whether this impacted on outcome. METHODS/PRINCIPAL FINDINGS: We recruited 52 controls and 34 culture-confirmed melioidosis patients at Sappasithiprasong Hospital in Ubon Ratchathani, Thailand. All subjects were diabetic. Platelet counts in melioidosis patients were lower compared to controls (p = 0.0001) and correlated with mortality (p = 0.02). VWF antigen levels were higher in patients (geometric mean, 478 U/dl) compared to controls (166 U/dL, p<0.0001). The high levels of VWF in melioidosis appeared to be due to increased endothelial stimulation (VWF propeptide levels were elevated, p<0.0001) and reduced clearance (ADAMTS13 reduction, p<0.0001). However, VWF antigen levels did not correlate with platelet counts implying that thrombocytopenia in acute melioidosis has an alternative cause. CONCLUSIONS/SIGNIFICANCE: Thrombocytopenia is a key feature of melioidosis and is correlated with mortality. Additionally, excess VWF and ADAMTS13 deficiency are features of acute melioidosis, but are not the primary drivers of thrombocytopenia in melioidosis. Further studies on the role of thrombocytopenia in B. pseudomallei infection are needed.

Rapid DNA vaccination against Burkholderia pseudomallei flagellin by tattoo or intranasal application.

Melioidosis is a severe infectious disease with a high mortality that is endemic in South-East Asia and Northern Australia. The causative pathogen, Burkholderia pseudomallei, is listed as potential bioterror weapon due to its high virulence and potential for easy dissemination. Currently, there is no licensed vaccine for prevention of melioidosis. Here, we explore the use of rapid plasmid DNA vaccination against B. pseudomallei flagellin for protection against respiratory challenge. We tested three flagellin DNA vaccines with different subcellular targeting designs. C57BL/6 mice were vaccinated via skin tattoo on day 0, 3 and 6 before intranasal challenge with B. pseudomallei on day 21. Next, the most effective construct was used as single vaccination on day 0 by tattoo or intranasal formulation. Mice were sacrificed 72 hours post-challenge to assess bacterial loads, cytokine responses, inflammation and microscopic lesions. A construct encoding a cellular secretion signal resulted in the most effective protection against melioidosis via tattooing, with a 10-fold reduction in bacterial loads in lungs and distant organs compared to the empty vector. Strikingly, a single intranasal administration of the same vaccine resulted in >1000-fold lower bacterial loads and increased survival. Pro-inflammatory cytokine responses were significantly diminished and strong reductions in markers for distant organ damage were observed. A rapid vaccination scheme using flagellin DNA tattoo provides significant protection against intranasal challenge with B. pseudomallei, markedly improved by a single administration via airway mucosa. Hence intranasal vaccination with flagellin-encoding DNA may be applicable when acute mass vaccination is indicated and warrants further testing.

Tuberculosis patients' pre-hospital delay and non-compliance with a longstanding DOT programme: a mixed methods study in urban Zambia.

BACKGROUND: Tuberculosis (TB) remains a major health problem in Zambia, despite considerable efforts to control and prevent it. With this study, we aim to understand how perceptions and cultural, social, economic, and organisational factors influence TB patients' pre-hospital delay and non-compliance with care provided by the National Tuberculosis Programme (NTP). METHODS: A mixed methods study was conducted with 300 TB patients recruited at Kanyama clinic for structured interviews. Thirty were followed-up for multiple in-depth interviews. Six focus group discussions were organised and participant observation was conducted. Ten biomedical care providers, 10 traditional healers, and 10 faith healers were interviewed. Factors associated with non-compliance (disruption of treatment > one week) were assessed by applying logistic regression analyses; qualitative analysis was used to additionally assess factors influencing pre-hospital delay and for triangulation of study findings. RESULTS: TB treatment non-compliance was low (10 %), no association of outcome with cultural or socio-economic factors was found. Only patients' time constraints and long distance to the clinic indicated a possible association with a higher risk of non-compliance (OR 0.52; 95 % CI 0.25, 1.10, p = 0.086). Qualitative data showed that most TB patients combined understandings of biomedical and traditional TB knowledge, used herbal, traditional and/or faith healing, suffered from stigmatizing attitudes, experienced poverty and food shortages, and faced several organisational obstacles while being on treatment. This led in some cases to pre-hospital delay or treatment non-compliance. CONCLUSIONS: Mixed methods analysis demonstrated the importance of in-depth information ascertained by qualitative approaches to understand how cultural, socio-economic and organisational factors are influencing patients' pre-hospital delay and treatment compliance. To strengthen the Zambian NTP, combating stigma is of utmost priority coupled with programmes addressing poverty. Organisational barriers and co-operation between (private) clinics and traditional/faith healers should be considered.

Melioidosis in Africa: should we be looking more closely?

Melioidosis is a life-threatening infection caused by the Gram-negative bacterium Burkholderia pseudomallei, mainly found in Southeast Asia. Recently, African foci have been identified, although reports remain mostly anecdotal. In Africa, multiple febrile diseases have been erroneously attributed to malaria in the past, and many cases of fever remain mis- or undiagnosed. Vigilance for previously under-recognized pathogens may enhance our understanding of disease epidemiology and facilitate improvement of patient care. Melioidosis may be such a condition. We summarize data on melioidosis in Africa and discuss the future directions for epidemiological, clinical and bacteriological studies. We conclude that searching for old bugs in new places is no academic treasure hunt but a clinically relevant activity to pursue.

Clinical, environmental, and serologic surveillance studies of melioidosis in Gabon, 2012-2013.

Burkholderia pseudomallei, an environmental gram-negative bacillus, is the causative agent of melioidosis and a bio-threat agent. Reports of B. pseudomallei isolation from soil and animals in East and West Africa suggest that melioidosis might be more widely distributed than previously thought. Because it has been found in equatorial areas with tropical climates, we hypothesized that B. pseudomallei could exist in Gabon. During 2012-2013, we conducted a seroprevalance study in which we set up microbiology facilities at a large clinical referral center and prospectively screened all febrile patients by conducting blood cultures and testing for B. pseudomallei and related species; we also determined whether B. pseudomallei could be isolated from soil. We discovered a novel B. pseudomallei sequence type that caused lethal septic shock and identified B. pseudomallei and B. thailandensis in the environment. Our data suggest that melioidosis is emerging in Central Africa but is unrecognized because of the lack of diagnostic microbiology facilities.