Phylogeography of Burkholderia pseudomallei Isolates, Western Hemisphere

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 systematic review and meta-analysis of the global prevalence and relationships among Burkholderia pseudomallei sequence types isolated from humans, animals, and the environment

Background and Aim

Burkholderia pseudomallei, a highly pathogenic bacterium responsible for melioidosis, exhibits ecological ubiquity and thrives within soil and water reservoirs, posing significant infection risks to humans and animals through direct contact. The aim of this study was to elucidate the genetic diversity and prevalence patterns of B. pseudomallei sequence types (STs) across a global spectrum and to understand the relationships between strains isolated from different sources.

Materials and Methods

We performed a systematic review and meta-analysis in this study. Extensive research was carried out across three comprehensive databases, including PubMed, Scopus, and ScienceDirect with data collected from 1924 to 2023.

Results

A total of 40 carefully selected articles contributed 2737 B. pseudomallei isolates attributed to 729 distinct STs and were incorporated into the systematic review. Among these, ST46 emerged as the most prominent, featuring in 35% of the articles and demonstrating a dominant prevalence, particularly within Southeast Asia. Moreover, ST51 consistently appeared across human, animal, and environmental studies. Subsequently, we performed a meta-analysis, focusing on nine specific STs: ST46, ST51, ST54, ST70, ST84, ST109, ST289, ST325, and ST376. Surprisingly, no statistically significant differences in their pooled prevalence proportions were observed across these compartments for ST46, ST70, ST289, ST325, and ST376 (all p > 0.69). Conversely, the remaining STs, including ST51, ST54, ST84, and ST109, displayed notable variations in their prevalence among the three domains (all p < 0.04). Notably, the pooled prevalence of ST51 in animals and environmental samples surpassed that found in human isolates (p < 0.01).

Conclusion

To the best of our knowledge, this study is the first systematic review and meta-analysis to investigate the intricate relationships between STs and their sources and contributes significantly to our understanding of B. pseudomallei diversity within the One Health framework.

Melioidosis in Cynomolgus Macaques ( Macaca Fascicularis ) Imported to the United States from Cambodia

Melioidosis, a potentially fatal infectious disease of humans and animals, including nonhuman primates (NHPs), is caused by the high-consequence pathogen Burkholderia pseudomallei. This environmental bacterium is found in the soil and water of tropical regions, such as Southeast Asia, where melioidosis is endemic. The global movement of humans and animals can introduce B. pseudomallei into nonendemic regions of the United States, where environmental conditions could allow establishment of the organism. Approximately 60% of NHPs imported into the United States originate in countries considered endemic for melioidosis. To prevent the introduction of infectious agents to the United States, the Centers for Disease Control and Prevention (CDC) requires newly imported NHPs to be quarantined for at least 31 d, during which time their health is closely monitored. Most diseases of public health concern that are transmissible from imported NHPs have relatively short incubation periods that fall within the 31-d quarantine period. However, animals infected with B. pseudomallei may appear healthy for months to years before showing signs of illness, during which time they can shed the organism into the environment. Melioidosis presents diagnostic challenges because it causes nonspecific clinical signs, serologic screening can produce unreliable results, and culture isolates are often misidentified on rapid commercial testing systems. Here, we present a case of melioidosis in a cynomolgus macaque (Macaca fascicularis) that developed a subcutaneous abscess after importation from Cambodia to the United States. The bacterial isolate from the abscess was initially misidentified on a commercial test. This case emphasizes the possibility of melioidosis in NHPs imported from endemic countries and its associated diagnostic challenges. If melioidosis is suspected, diagnostic samples and culture isolates should be submitted to a laboratory in the CDC Laboratory Response Network for conclusive identification and characterization of the pathogen.

Low risk of acquiring melioidosis from the environment in the continental United States

Melioidosis is an underreported human disease of tropical and sub-tropical regions caused by the saprophyte Burkholderia pseudomallei. Although most global melioidosis cases are reported from tropical regions in Southeast Asia and northern Australia, there are multiple occurrences from sub-tropical regions, including the United States (U.S.). Most melioidosis cases reported from the continental U.S. are the result of acquiring the disease during travel to endemic regions or from contaminated imported materials. Only two human melioidosis cases from the continental U.S. have likely acquired B. pseudomallei directly from local environments and these cases lived only ~7 km from each other in rural Texas. In this study, we assessed the risk of acquiring melioidosis from the environment within the continental U.S. by surveying for B. pseudomallei in the environment in Texas where these two human melioidosis cases likely acquired their infections. We sampled the environment near the homes of the two cases and at additional sampling locations in surrounding counties in Texas that were selected based on ecological niche modeling. B. pseudomallei was not detected at the residences of these two cases or in the surrounding region. These negative data are important to demonstrate that B. pseudomallei is rare in the environment in the U.S. even at locations where locally acquired human cases likely have occurred, documenting the low risk of acquiring B. pseudomallei infection from the environment in the continental U.S.

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.

In silico analyses of penicillin binding proteins in Burkholderia pseudomallei uncovers SNPs with utility for phylogeography, species differentiation, and sequence typing

Burkholderia pseudomallei causes melioidosis. Sequence typing this pathogen can reveal geographical origin and uncover epidemiological associations. Here, we describe B. pseudomallei genes encoding putative penicillin binding proteins (PBPs) and investigate their utility for determining phylogeography and differentiating closely related species. We performed in silico analysis to characterize 10 PBP homologs in B. pseudomallei 1026b. As PBP active site mutations can confer β-lactam resistance in Gram-negative bacteria, PBP sequences in two resistant B. pseudomallei strains were examined for similar alterations. Sequence alignments revealed single amino acid polymorphisms (SAAPs) unique to the multidrug resistant strain Bp1651 in the transpeptidase domains of two PBPs, but not directly within the active sites. Using BLASTn analyses of complete assembled genomes in the NCBI database, we determined genes encoding PBPs were conserved among B. pseudomallei (n = 101) and Burkholderia mallei (n = 26) strains. Within these genes, single nucleotide polymorphisms (SNPs) useful for predicting geographic origin of B. pseudomallei were uncovered. SNPs unique to B. mallei were also identified. Based on 11 SNPs identified in two genes encoding predicted PBP-3s, a dual-locus sequence typing (DLST) scheme was developed. The robustness of this typing scheme was assessed using 1,523 RefSeq genomes from B. pseudomallei (n = 1,442) and B. mallei (n = 81) strains, resulting in 32 sequence types (STs). Compared to multi-locus sequence typing (MLST), the DLST scheme demonstrated less resolution to support the continental separation of Australian B. pseudomallei strains. However, several STs were unique to strains originating from a specific country or region. The phylogeography of Western Hemisphere B. pseudomallei strains was more highly resolved by DLST compared to internal transcribed spacer (ITS) typing, and all B. mallei strains formed a single ST. Conserved genes encoding PBPs in B. pseudomallei are useful for strain typing, can enhance predictions of geographic origin, and differentiate strains of closely related Burkholderia species.

Burkholderia pseudomallei causes the life-threatening disease melioidosis and is considered a biological threat and select agent by the United States government. This soil-dwelling bacterium is commonly found in regions of southeast Asia and northern Australia, but it is also detected in other tropical and sub-tropical areas around the world. With a predicted global burden of 165,000 annual cases and mortality rate that can exceed 40% without prompt and appropriate antibiotic treatment, understanding the epidemiology of melioidosis and mechanisms of antibiotic resistance in B. pseudomallei can benefit public health and safety. Recently, we identified ten conserved genes encoding putative penicillin binding proteins (PBPs) in B. pseudomallei. Here, we examined B. pseudomallei PBP sequences for amino acid mutations that may contribute to β-lactam resistance. We also uncovered nucleotide mutations with utility to predict the geographical origin of B. pseudomallei strains and to differentiate closely related Burkholderia species. Based on 11 informative single nucleotide polymorphisms in two genes each encoding a PBP-3, we developed a simple, targeted dual-locus typing approach.

Multistate Outbreak of Melioidosis Associated with Imported Aromatherapy Spray

Melioidosis, caused by the bacterium Burkholderia pseudomallei, is an uncommon infection that is typically associated with exposure to soil and water in tropical and subtropical environments. It is rarely diagnosed in the continental United States. Patients with melioidosis in the United States commonly report travel to regions where melioidosis is endemic. We report a cluster of four non-travel-associated cases of melioidosis in Georgia, Kansas, Minnesota, and Texas. These cases were caused by the same strain of B. pseudomallei that was linked to an aromatherapy spray product imported from a melioidosis-endemic area.

Genomic epidemiology links Burkholderia pseudomallei from individual human cases to B. pseudomallei from targeted environmental sampling in Northern Australia

Each case of melioidosis results from a single event when a human is infected by the environmental bacterium Burkholderia pseudomallei. Darwin in tropical northern Australia has the highest incidences of melioidosis globally and the Darwin Prospective Melioidosis Study (DPMS) commenced in 1989, documenting all culture confirmed melioidosis cases. From 2000-2019 we sampled DPMS patient's environments for B. pseudomallei when a specific location was considered to have been where infection occurred. With the aim to use genomic epidemiology to understand B. pseudomallei transmission and infecting scenarios. Environmental sampling was performed at 98 DPMS patient sites, where we collected 975 environmental samples (742 soil; 233 water). Genotyping matched the clinical and epidemiologically linked environmental B. pseudomallei for 19 patients (19%), with the environmental isolates cultured from soil (n=11) or water (n=8) sources. B. pseudomallei isolates from patients and their local environments that matched on genotyping were whole genome sequenced (WGS). Of the 19 patients with a clinical-environmental genotype match, 17 pairs clustered on a Darwin core genome single-nucleotide polymorphism (SNP) phylogeny, later confirmed by single ST phylogenies and pairwise comparative genomics. When related back to patient clinical scenarios, the matched clinical and environmental B. pseudomallei pairs informed likely modes of infection: percutaneous inoculation, inhalation, and ingestion. Targeted environmental sampling for B. pseudomallei can inform infecting scenarios for melioidosis and dangerous occupational and recreational activities and identify hot spots of B. pseudomallei presence. However, WGS and careful genomics are required to avoid overcalling the relatedness between clinical and environmental isolates of B. pseudomallei.

Subclinical Burkholderia pseudomallei Infection Associated with Travel to the British Virgin Islands

Phylogenetic analysis of a clinical isolate associated with subclinical Burkholderia pseudomallei infection revealed probable exposure in the British Virgin Islands, where reported infections are limited. Clinicians should consider this geographic distribution when evaluating possible infection among persons with compatible travel history.

Antimicrobial Susceptibility of Western Hemisphere Isolates of Burkholderia pseudomallei: Phenotypic and Genomic Analyses

Current antimicrobial treatment recommendations for melioidosis, the disease caused by Burkholderia pseudomallei, are largely based on studies of strains isolated from the Eastern Hemisphere (EH), where most human cases are identified and reported. In this study, we evaluated the antimicrobial susceptibility of 26 strains in the CDC (Centers for Diseases Control and Prevention) collection from the Western Hemisphere (WH) isolated from 1960 to 2015. Minimal inhibitory concentration (MIC) values were measured by standard broth microdilution for 16 antimicrobials following Clinical and Laboratory Standards Institute (CLSI) guidelines. Twenty-four of the 26 WH strains were susceptible to the six antimicrobials with CLSI-defined MIC susceptibility interpretive criteria for B. pseudomallei: amoxicillin/clavulanate, ceftazidime, imipenem, doxycycline, tetracycline, and trimethoprim/sulfamethoxazole. One WH strain demonstrated intermediate amoxicillin/clavulanate resistance and another strain had intermediate resistance to tetracycline. For all antimicrobials tested, the susceptibility profiles of WH isolates were comparable with previously reported MIC results of EH strains. The overall similarities suggest that the same antimicrobials are useful for melioidosis treatment in both the WH and EH. Using in silico analyses of WH genomes, we identified a novel amino acid substitution P258S in the beta-lactamase PenA, which may contribute to decreased susceptibility to amoxicillin/clavulanate in B. pseudomallei.

The Darwin Prospective Melioidosis Study: a 30-year prospective, observational investigation

BACKGROUND

The global distribution of melioidosis is under considerable scrutiny, with both unmasking of endemic disease in African and Pacific nations and evidence of more recent dispersal in the Americas. Because of the high incidence of disease in tropical northern Australia, The Darwin Prospective Melioidosis Study commenced in October, 1989. We present epidemiology, clinical features, outcomes, and bacterial genomics from this 30-year study, highlighting changes in the past decade.

METHODS

The present study was a prospective analysis of epidemiological, clinical, and laboratory data for all culture-confirmed melioidosis cases from the tropical Northern Territory of Australia from Oct 1, 1989, until Sept 30, 2019. Cases were identified on the basis of culture-confirmed melioidosis, a laboratory-notifiable disease in the Northern Territory of Australia. Patients who were culture-positive were included in the study. Multivariable analysis determined predictors of clinical presentations and outcome. Incidence, survival, and cluster analyses were facilitated by population and rainfall data and genotyping of Burkholderia pseudomallei, including multilocus sequence typing and whole-genome sequencing.

FINDINGS

There were 1148 individuals with culture-confirmed melioidosis, of whom 133 (12%) died. Median age was 50 years (IQR 38-60), 48 (4%) study participants were children younger than 15 years of age, 721 (63%) were male individuals, and 600 (52%) Indigenous Australians. All but 186 (16%) had clinical risk factors, 513 (45%) had diabetes, and 455 (40%) hazardous alcohol use. Only three (2%) of 133 fatalities had no identified risk. Pneumonia was the most common presentation occurring in 595 (52%) patients. Bacteraemia occurred in 633 (56%) of 1135 patients, septic shock in 240 (21%) patients, and 180 (16%) patients required mechanical ventilation. Cases correlated with rainfall, with 80% of infections occurring during the wet season (November to April). Median annual incidence was 20·5 cases per 100 000 people; the highest annual incidence in Indigenous Australians was 103·6 per 100 000 in 2011-12. Over the 30 years, annual incidences increased, as did the proportion of patients with diabetes, although mortality decreased to 17 (6%) of 278 patients over the past 5 years. Genotyping of B pseudomallei confirmed case clusters linked to environmental sources and defined evolving and new sequence types.

INTERPRETATION

Melioidosis is an opportunistic infection with a diverse spectrum of clinical presentations and severity. With early diagnosis, specific antimicrobial therapy, and state-of-the-art intensive care, mortality can be reduced to less than 10%. However, mortality remains much higher in the many endemic regions where health resources remain scarce. Genotyping of B pseudomallei informs evolving local and global epidemiology.

FUNDING

The Australian National Health and Medical Research Council.

Burkholderia species in human infections in Mexico: Identification of B. cepacia, B. contaminans, B. multivorans, B. vietnamiensis,B. pseudomallei and a new Burkholderia species

BACKGROUND

Burkholderia sensu stricto is comprised mainly of opportunistic pathogens. This group is widely distributed in the environment but is especially important in clinical settings. In Mexico, few species have been correctly identified among patients, most often B. cepacia is described.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, approximately 90 strains identified as B. cepacia with the VITEK2 system were isolated from two medical centers in Mexico City and analyzed by MLSA, BOX-PCR and genome analysis. The initial identification of B. cepacia was confirmed for many strains, but B. contaminans, B. multivorans and B. vietnamiensis were also identified among clinical strains for the first time in hospitals in Mexico. Additionally, the presence of B. pseudomallei was confirmed, and a novel species within the B. cepacia complex was documented. Several strains misidentified as B. cepacia actually belong to the genera Pseudomonas, Stenotrophomonas and Providencia.

CONCLUSIONS/SIGNIFICANCE

The presence of different Burkholderia species in Mexico was confirmed. Correct identification of Burkholderia species is important to provide accurate treatment for immunosuppressed patients.

Genomic Diversity of Burkholderia pseudomallei Isolates, Colombia

We report an analysis of the genomic diversity of isolates of Burkholderia pseudomallei, the cause of melioidosis, recovered in Colombia from routine surveillance during 2016–2017. B. pseudomallei appears genetically diverse, suggesting it is well established and has spread across the region.

Melioidosis in a Resident of Texas with No Recent Travel History, United States

To our knowledge, environmental isolation of Burkholderia pseudomallei, the causative agent of melioidosis, from the continental United States has not been reported. We report a case of melioidosis in a Texas resident. Genomic analysis indicated that the isolate groups with B. pseudomallei isolates from patients in the same region, suggesting possible endemicity to this region.

Genomic Diversity of Burkholderia pseudomallei in Ceara, Brazil

B. pseudomallei causes significant morbidity and mortality, but its geographic prevalence and genetic diversity are not well characterized, especially in the Western Hemisphere. A better understanding of the genetic relationships among clinical and environmental isolates will improve knowledge of the population structure of this bacterium as well as the ability to conduct epidemiological investigations of cases of melioidosis.

Burkholderia pseudomallei is a Gram-negative bacterium that causes the sapronotic disease melioidosis. An outbreak in 2003 in the state of Ceara, Brazil, resulted in subsequent surveillance and environmental sampling which led to the recognition of B. pseudomallei as an endemic pathogen in that area. From 2003 to 2015, 24 clinical and 12 environmental isolates were collected across Ceara along with one from the state of Alagoas. Using next-generation sequencing, multilocus sequence typing, and single nucleotide polymorphism analysis, we characterized the genomic diversity of this collection to better understand the population structure of B. pseudomallei associated with Ceara. We found that the isolates in this collection form a distinct subclade compared to other examples from the Western Hemisphere. Substantial genetic diversity among the clinical and environmental isolates was observed, with 14 sequence types (STs) identified among the 37 isolates. Of the 31,594 core single-nucleotide polymorphisms (SNPs) identified, a high proportion (59%) were due to recombination. Because recombination events do not follow a molecular clock, the observation of high occurrence underscores the importance of identifying and removing recombination SNPs prior to evolutionary reconstructions and inferences in public health responses to B. pseudomallei outbreaks. Our results suggest long-term B. pseudomallei prevalence in this recently recognized region of melioidosis endemicity.

IMPORTANCEB. pseudomallei causes significant morbidity and mortality, but its geographic prevalence and genetic diversity are not well characterized, especially in the Western Hemisphere. A better understanding of the genetic relationships among clinical and environmental isolates will improve knowledge of the population structure of this bacterium as well as the ability to conduct epidemiological investigations of cases of melioidosis.

An increase in p62/NBR1 levels in melioidosis patients of Sri Lanka exhibit a characteristic of potential host biomarker

Introduction. Melioidosis, caused by Burkholderia pseudomallei, in endemic areas, poses a challenge for treating the diseased populations without accurate diagnosis, and the disease-specific biomarkers linked with the infection have yet to be reported. Due to the invasive nature of the causative agent, Burkholderia pseudomallei, host innate effector mechanisms, including autophagy are known to be activated, resulting in differential expression of cellular proteins and immune markers. Identification of a disease-specific biomarker associated with B. pseudomallei infection will be helpful to facilitate rapid confirmation of melioidosis, which would enable early treatment and therapeutic success.Aim. We aimed to assess the levels of a host autophagy component, p62/NBR1, which function as a cargo-receptor in the process of autophagy activation leading to the degradation of ubiquitin-coated intracellular bacteria in which p62/NBR1 itself is degraded in the clearance of the pathogen. We further probed the extent of intracellular p62/NBR1 degradation and assessed its potential as a melioidosis biomarker.Methodology. We analysed peripheral blood mononuclear cell (PBMC) lysates using an ELISA-based assay for detecting cytosolic autophagy-related proteins p62/NBR1. We measured p62/NBR1 levels in diseased (confirmed B. pseudomallei infection) and non -diseased populations and utilized receiver operating characteristic (ROC) curve and max Youden index analysis for evaluating potential disease biomarker characteristics.Results. Our results revealed a three to fivefold increase in p62/NBR1 levels confirmed melioidosis cases compared to uninfected healthy donors. Comparable to p62/NBR1, levels of cytosolic LC3-I levels also increased, whereas the levels of degraded membrane bound form LC3-II was low, suggesting autophagy deficiency. Proinflammatory serum cytokine response, particularly IL-6, was consistently higher alongside B. pseudomallei infection in comparison to healthy controls.Conclusions. ROC curve and max Youden index analysis suggest that increased p62/NBR1 levels in diseased populations display characteristics of a potential disease biomarker in melioidosis and illustrates that an elevated p62/NBR1 level, in conjunction with B. pseudomallei infection associated with autophagy deficiency.

MELIOIDOSIS IN A BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS) AFTER A HURRICANE IN THE CARIBBEAN ISLANDS

Melioidosis is an emerging infectious disease of humans and animals caused by the bacterium Burkholderia pseudomallei and endemic in tropical regions, principally Southeast Asia and northern Australia. In September 2017, after Hurricane Maria impacted the Dolphin Discovery facility in the Federation of St. Kitts and Nevis, a juvenile male bottlenose dolphin (Tursiops truncatus) died within 96 hr of presenting with acute anorexia, lethargy, and respiratory distress. Histopathology demonstrated necrohemorrhagic bronchopneumonia, necrotizing hepatitis, splenitis, and lymphadenitis, with intralesional Gram-negative bacilli. B. pseudomallei was confirmed by bacteriological culture and DNA sequencing. This case emphasizes the challenges of melioidosis diagnosis, the importance of awareness for both early detection and efficacious treatment, and recognition in tropical regions where it has been either not reported or underreported. To the authors' knowledge, this is the first case of cetacean melioidosis in the Caribbean Islands, an often severe and fatal disease with increasing prevalence on the American continent.

Molecular Characteristics of Burkholderia pseudomallei Collected From Humans in Hainan, China

Melioidosis is a common infectious disease in Southeast Asia and Northern Australia. In Hainan, several cases have been reported, but no systematic study has yet been done on the molecular epidemiology profiles of the organism. An investigation of the molecular epidemiology links and population structure of Burkholderia pseudomallei would help to better understand the clonally of the isolates and differences among them. In this study, multilocus variable-number tandem repeat analysis (MLVA), and multilocus sequence typing (MLST) were applied to examine the epidemiological relatedness and population structure of 166 B. pseudomallei isolates obtained during 2002–2014 in Hainan, China. Both the MLVA_4 and MLST approaches had high discriminatory power for this population, with diversity indices of 0.9899 and 0.9457, respectively. However, the MLVA_4 assay showed a higher discriminatory power than the MLST approach, and a variable-number tandem repeat (VNTR3 933) found by the MLVA approach was the most useful in discriminating strains from this province. A total of 166 strains yielded 99 MLVA_4 genotypes, of which 34 genotypes were shared by 101 isolates, for a clustering rate of 60.8% (101/166), which suggested that some cases may have a common source. Additionally, 65 isolates showed distinct genotypes, indicating that more than 39.2% (65/166) of melioidosis cases in Hainan had epidemiologically unrelated or sporadic characteristics. The 166 isolates were resolved into 48 STs, of which five STs (ST55, -70, -46, -50, and -58) were here found to be predominant. Phylogenetic analysis of 116 isolates conducted using the eBURST v3 segregated the 48 STs into eight groups with ST50 as predicted founder, and 21 STs were found to be singletons, which suggest that the strains in the Hainan region represent a high diversity of ST clones, indicating that many B. pseudomallei clone groups are endemic to this region. Moreover, ST50 had 5 SLV, 7 DLV, 6 TLV, and 29 satellite STs and formed a radial expansion pattern, suggesting that the melioidosis epidemic in this study was mainly caused by the clonal expansion of ST 50. Phylogenetic analysis on global scale suggests that China’s isolates are closely related to isolates from Southeast Asia, particularly from Thailand and Malaysia.

Human Melioidosis

The causative agent of melioidosis, Burkholderia pseudomallei, a tier 1 select agent, is endemic in Southeast Asia and northern Australia, with increased incidence associated with high levels of rainfall. Increasing reports of this condition have occurred worldwide, with estimates of up to 165,000 cases and 89,000 deaths per year. The ecological niche of the organism has yet to be clearly defined, although the organism is associated with soil and water. The culture of appropriate clinical material remains the mainstay of laboratory diagnosis. Identification is best done by phenotypic methods, although mass spectrometric methods have been described. Serology has a limited diagnostic role. Direct molecular and antigen detection methods have limited availability and sensitivity. Clinical presentations of melioidosis range from acute bacteremic pneumonia to disseminated visceral abscesses and localized infections. Transmission is by direct inoculation, inhalation, or ingestion. Risk factors for melioidosis include male sex, diabetes mellitus, alcohol abuse, and immunosuppression. The organism is well adapted to intracellular survival, with numerous virulence mechanisms. Immunity likely requires innate and adaptive responses. The principles of management of this condition are drainage and debridement of infected material and appropriate antimicrobial therapy. Global mortality rates vary between 9% and 70%. Research into vaccine development is ongoing.

Case Report: Imported Melioidosis from Goa, India to Israel, 2018

A previously healthy young man presented with a chronic cavitary pulmonary infection that began while in Goa, India. Burkholderia pseudomallei was cultured from sputum samples. The infection fully resolved after prolonged antibiotic treatment. Other than traveling during the monsoon season, extensive use of well-water for water-pipe smoking of cannabis was identified as a possible risk factor for infection. This is one of the first reports of travel-associated melioidosis from India. Genomic and immunological characterization suggested that the B. pseudomallei isolate collected from the reported case exhibited limited similarity to other B. pseudomallei strains.

Melioidosis after Hurricanes Irma and Maria, St. Thomas/St. John District, US Virgin Islands, October 2017

We report 2 cases of melioidosis in women with diabetes admitted to an emergency department in the US Virgin Islands during October 2017. These cases emerged after Hurricanes Irma and Maria and did not have a definitively identified source. Poor outcomes were observed when septicemia and pulmonary involvement were present.

Burkholderia pseudomallei, the causative agent of melioidosis, is rare but ecologically established and widely dispersed in the environment in Puerto Rico

BACKGROUND

Burkholderia pseudomallei is a soil-dwelling bacterium and the causative agent of melioidosis. The global burden and distribution of melioidosis is poorly understood, including in the Caribbean. B. pseudomallei was previously isolated from humans and soil in eastern Puerto Rico but the abundance and distribution of B. pseudomallei in Puerto Rico as a whole has not been thoroughly investigated.

METHODOLOGY/PRINCIPAL FINDINGS

We collected 600 environmental samples (500 soil and 100 water) from 60 sites around Puerto Rico. We identified B. pseudomallei by isolating it via culturing and/or using PCR to detect its DNA within complex DNA extracts. Only three adjacent soil samples from one site were positive for B. pseudomallei with PCR; we obtained 55 isolates from two of these samples. The 55 B. pseudomallei isolates exhibited fine-scale variation in the core genome and contained four novel genomic islands. Phylogenetic analyses grouped Puerto Rico B. pseudomallei isolates into a monophyletic clade containing other Caribbean isolates, which was nested inside a larger clade containing all isolates from Central/South America. Other Burkholderia species were commonly observed in Puerto Rico; we cultured 129 isolates from multiple soil and water samples collected at numerous sites around Puerto Rico, including representatives of B. anthina, B. cenocepacia, B. cepacia, B. contaminans, B. glumae, B. seminalis, B. stagnalis, B. ubonensis, and several unidentified novel Burkholderia spp.

CONCLUSIONS/SIGNIFICANCE

B. pseudomallei was only detected in three soil samples collected at one site in north central Puerto Rico with only two of those samples yielding isolates. All previous human and environmental B. pseudomallei isolates were obtained from eastern Puerto Rico. These findings suggest B. pseudomallei is ecologically established and widely dispersed in the environment in Puerto Rico but rare. Phylogeographic patterns suggest the source of B. pseudomallei populations in Puerto Rico and elsewhere in the Caribbean may have been Central or South America.

Isolation of Burkholderia pseudomallei from a Pet Green Iguana, Belgium

We isolated Burkholderia pseudomallei, the causative agent of melioidosis, from liver granulomas of a pet green iguana (Iguana iguana) in Belgium. This case highlights a risk for imported green iguanas acting as a reservoir for introduction of this high-threat, zoonotic pathogen into nonendemic regions.

Burkholderia thailandensis Isolated from Infected Wound, Arkansas, USA

The bacterium Burkholderia thailandensis, a member of the Burkholderia pseudomallei complex, is generally considered nonpathogenic; however, on rare occasions, B. thailandensis infections have been reported. We describe a clinical isolate of B. thailandensis, BtAR2017, recovered from a patient with an infected wound in Arkansas, USA, in 2017.

Draft Genome Sequence of a Rare Israeli Clinical Isolate of Burkholderia pseudomallei

We report here the draft genome sequence of Burkholderia pseudomallei MAA2018. This highly virulent strain was isolated in 2018 from the first melioidosis case in Israel associated with recreational travel to Goa, India.

We report here the draft genome sequence of Burkholderia pseudomallei MAA2018. This highly virulent strain was isolated in 2018 from the first melioidosis case in Israel associated with recreational travel to Goa, India.

Novel multi-component vaccine approaches for Burkholderia pseudomallei

Burkholderia pseudomallei is the causative agent of melioidosis. Historically believed to be a relatively rare human disease in tropical countries, a recent study estimated that, worldwide, there are approximately 165 000 human melioidosis cases per year, more than half of whom die. The bacterium is inherently resistant to many antibiotics and treatment of the disease is often protracted and ineffective. There is no licensed vaccine against melioidosis, but a vaccine is predicted to be of value if used in high-risk populations. There has been progress over the last decade in the pursuit of an effective vaccine against melioidosis. Animal models of disease including mouse and non-human primates have been developed, and these models show that antibody responses play a key role in protection against melioidosis. Surprisingly, although B. pseudomallei is an intracellular pathogen there is limited evidence that CD8⁺  T cells play a role in protection. It is evident that a multi-component vaccine, incorporating one or more protective antigens, will probably be essential for protection because of the pathogen's sophisticated virulence mechanisms as well as strain heterogeneity. Multi-component vaccines in development include glycoconjugates, multivalent subunit preparations, outer membrane vesicles and other nano/microparticle platforms and live-attenuated or inactivated bacteria. A consistent finding with vaccine candidates tested in mice is the ability to induce sterilizing immunity at low challenge doses and extended time to death at higher challenge doses. Further research to identify ways of eliciting more potent immune responses might provide a path for licensing an effective vaccine.

CNS Melioidosis in a Traveler Returning from Cabo, Mexico

Melioidosis is caused by the gram-negative bacillus Burkholderia pseudomallei, endemic to northern Australia and Southeast Asia. We present a patient who traveled to Mexico, returned to the United States, and developed progressive manifestations of melioidosis, culminating as central nervous system disease. Standard therapy was contraindicated, and a prolonged intensive phase was employed.

Melioidosis in the Western Indian Ocean and the Importance of Improving Diagnosis, Surveillance, and Molecular Typing

Melioidosis, caused by the bacterium Burkholderia pseudomallei, is an infectious disease of humans or animals, and the specific environmental conditions that are present in western Indian Ocean islands are particularly suitable for the establishment/survival of B. pseudomallei. Indeed, an increasing number of new cases have been reported in this region (Madagascar, Mauritius, Réunion (France), and Seychelles, except Comoros and Mayotte (France)), and are described in this review. Our review clearly points out that further studies are needed in order to investigate the real incidence and burden of melioidosis in the western Indian Ocean and especially Madagascar, since it is likely to be higher than currently reported. Thus, research and surveillance priorities were recommended (i) to improve awareness of melioidosis in the population and among clinicians; (ii) to improve diagnostics, in order to provide rapid and effective treatment; (iii) to implement a surveillance and reporting system in the western Indian Ocean; and (iv) to investigate the presence of B. pseudomallei in environmental samples, since we have demonstrated its presence in soil samples originating from the yard of a Madagascan case.

Melioidosis in Mexico, Central America, and the Caribbean

Burkholderia pseudomallei is the causative agent of melioidosis, an endemic disease in tropical areas around the world. Cumulative human cases have demonstrated that melioidosis is prevalent and increasingly recognized in the American continent. Even though the first reports of melioidosis in Mexico, Central America, and the Caribbean Islands date back to the late 1940s, the potential of the disease as a public health concern in the region has not been fully appreciated. Unfortunately, recent studies predicting the global distribution of the disease and the demonstration of melioidosis endemicity in Puerto Rico have not increased recognition of the disease by health professionals in this region. Furthermore, a lack of both diagnostic capacity and awareness of the disease has resulted in a limited number of studies that have attempted to accurately determine its prevalence and geographical distribution. In this review, a summary of reported cases in the countries of this region are presented, as well as recommendations to increase the diagnosis and awareness of the disease as an important public health problem in Mexico, Central America, and the Caribbean islands.

Melioidosis

Burkholderia pseudomallei is a Gram-negative environmental bacterium and the aetiological agent of melioidosis, a life-threatening infection that is estimated to account for ∼89,000 deaths per year worldwide. Diabetes mellitus is a major risk factor for melioidosis, and the global diabetes pandemic could increase the number of fatalities caused by melioidosis. Melioidosis is endemic across tropical areas, especially in southeast Asia and northern Australia. Disease manifestations can range from acute septicaemia to chronic infection, as the facultative intracellular lifestyle and virulence factors of B. pseudomallei promote survival and persistence of the pathogen within a broad range of cells, and the bacteria can manipulate the host's immune responses and signalling pathways to escape surveillance. The majority of patients present with sepsis, but specific clinical presentations and their severity vary depending on the route of bacterial entry (skin penetration, inhalation or ingestion), host immune function and bacterial strain and load. Diagnosis is based on clinical and epidemiological features as well as bacterial culture. Treatment requires long-term intravenous and oral antibiotic courses. Delays in treatment due to difficulties in clinical recognition and laboratory diagnosis often lead to poor outcomes and mortality can exceed 40% in some regions. Research into B. pseudomallei is increasing, owing to the biothreat potential of this pathogen and increasing awareness of the disease and its burden; however, better diagnostic tests are needed to improve early confirmation of diagnosis, which would enable better therapeutic efficacy and survival.