The genetic diversity and evolution analysis of the Hainan melioidosis outbreak strains.

Melioidosis is a zoonotic disease, with its outbreaks being rare and indicative of an unusual concurrence of extreme climate and natural environmental factors. An outbreak of melioidosis cases emerged in Hainan following Typhoon "Dianmu" from October to December 2021, presenting an opportunity to identify the environmental sources of infection for these cases due to its nature as a well-defined point-source cluster. To investigate the relationship between the occurrence of these melioidosis cases and the environment, we extracted the entire genome of 25 clinical strains and conducted MLST typing, followed by whole genome sequencing and analysis of molecular genetic information for four ST46 genotypes from these strains. Phylogenetic and evolutionary relationships between Hainan sequence types (STs) and those found in other endemic regions were analyzed using IslandPath-DIMO, PHASTER, e-BURST, PHYLOViZ, and the maximum likelihood method. Notably, a total of 25 clinical strains were identified, encompassing 12 STs (ST46, ST1105, ST1991, ST30, ST1992, ST50, ST164, ST55, ST70, ST1993, ST1545, and ST58), with ST1991, ST1992, and ST1993 being newly discovered subtypes. PHYLOViZ clustering analysis divided the strains into two groups (A and B), both closely related to the Asian region. Phylogenetic tree analysis further revealed that most of the strains in this study were closely related to those found in Australia and Thailand. Analysis of patient information and visits to their residences suggested that contaminated water sources might be the primary source of infection during this outbreak. Our findings underscore that extreme weather events, such as typhoons, significantly increase the infection rate of B. pseudomallei, along with its genetic diversity, necessitating additional prevention strategies to control these B. pseudomallei infections.

Multiple liver, splenic and psoas abscesses due to melioidosis: A case report.

Melioidosis is caused by community-acquired gram-negative bacillus Burkholderia pseudomallei which resides in soil and water. It was first described in 1912 in Burma and 1927 in Sri Lanka. Melioidosis presents with non-specific clinical and biochemical findings. Diagnosis is confirmed by the isolation of bacteria in cultures or demonstrating antibody response. Once the diagnosis is made, patients are managed with a course of intravenous antibiotics followed by a long course of oral antibiotics. Even with antibiotic treatments, most patients do not achieve complete recovery which results in chronic disease. Prolonged antibiotic therapy makes patients less compliant with treatment. Here we present a 50-year-old Sri Lankan male with diabetes mellitus presented with low-grade fever and back pain. He was found to have multiple abscesses involving the liver, spleen and left psoas muscle. Initially, he was evaluated for tuberculosis and later only melioidosis was diagnosed. The patient was managed with guided aspiration of abscesses and intravenous antibiotics. Subsequently, the patient defaulted on all treatments. It is important to consider melioidosis as a differential diagnosis in immunocompromised patients presented with multiple abscesses. It is important to maintain a registry for follow-up melioidosis patients to prevent becoming chronic melioidosis patients and to save healthcare costs.

Pyrexia of Unknown Origin in a Young Male: Unmasking Melioidosis in a Tuberculosis-Endemic Setting.

A young male, plantation worker from Southeast Asia, presented with a non-productive cough, intermittent high-grade fever with chills, and significant weight loss over two months. Prior investigations were non-contributory, despite various antibiotics, his symptoms persisted. Physical examination and routine investigations, including an extensive microbiological workup for fever were non-contributory. A positron emission tomography-computed tomography (PET-CT) scan performed for pyrexia of unknown origin (PUO) revealed pulmonary consolidation, mediastinal lymphadenopathy, and splenic microabscesses. Material aspirated via endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) from the left interlobar lymph node was positive for Burkholderia pseudomallei on conventional nested polymerase chain reaction (PCR), confirming a diagnosis of melioidosis. Following appropriate antibiotic therapy, there was a complete resolution of symptoms. This case underscores the diagnostic challenges and the need for advanced techniques in identifying melioidosis, which can mimic tuberculosis.

Predictors of mortality in culture-proven Burkholderia pseudomallei infections in a Singapore Tertiary Hospital.

Burkholderia pseudomallei is a pathogen expanding in geographic range. We performed a retrospective study analyzing the clinical, microbiologic features of culture-proven melioidosis, and predictors of mortality based on data from a Singapore tertiary hospital between 2006- 2016. We found ICU admission, bacteremia, and mechanical ventilation to be associated with mortality.

Medical imaging in melioidosis - 20-year experience in a non-endemic Australian city.

INTRODUCTION: Melioidosis may occasionally be encountered in non-endemic areas and medical imaging is frequently used to identify and characterise sites of disease. The purpose of this study is to describe the spectrum of imaging findings encountered in melioidosis patients treated in the tertiary public hospitals of Perth, Western Australia, between 2002 and 2022. METHODS: A database search and electronic medical record review was used to identify cases. Cases were included if they had Burkholderia pseudomallei isolated on culture and if they had at least one diagnostic imaging study performed at a Perth public tertiary hospital. The relevant imaging studies were reviewed, and imaging findings were recorded. RESULTS: Thirty-six cases were identified. The most common disease manifestation was bacteraemia (72%, 26 cases), followed by pulmonary infection (58%, 21 cases), skin and soft tissue infection (22%, eight cases), prostate abscess (14%, five cases) and septic arthritis (6%, two cases). A previously unreported case of isolated melioid pleural effusion was identified, as was a case of reactivated chronic latent pulmonary melioidosis with an apparent delay of over 20 years between the onset of symptoms and the time of infection. In cases with pulmonary melioidosis, the major lung abnormalities on CT chest could be categorised into one of two distinct patterns: nodular-predominant (78%) or consolidation-predominant (22%). CONCLUSION: Further research is required to assess the utility of the pattern-based categorisation of lung abnormalities on CT chest seen in the pulmonary melioidosis cases of this series.

Clinical and microbiological features of positive blood culture episodes caused by non-fermenting gram-negative bacilli other than Pseudomonas and Acinetobacter species (2020-2023).

INTRODUCTION: Non-fermenting Gram-negative bacilli (NFGNB) other than Pseudomonas aeruginosa and Acinetobacter baumannii complex are pathogens of interest due to their ability to cause health-care associated infections and display complex drug resistance phenotypes. However, their clinical and microbiological landscape is still poorly characterized. METHODS: Observational retrospective study including all hospitalized patients presenting with a positive positive blood culture (BC) episode caused by less common NFGNB over a four-year period (January 2020-December 2023). Clinical-microbiological features and factors associated with mortality were investigated. RESULTS: Sixty-six less common NFGNB isolates other than Pseudomonas and Acinetobacter species causing 63 positive BC episodes were recovered from 60 patients. Positive BC episodes were predominantly sustained by Stenotrophomonas maltophilia (49.2%) followed by Achromobacter species (15.9%) that exhibited the most complex resistance phenotype. Positive BC episodes had bloodstream infection criteria in 95.2% of cases (60 out 63), being intravascular device (30.2%) and respiratory tract (19.1%) the main sources of infection. Fourteen-day, 30-day, and in-hospital mortality rates were 6.4%, 9.5%, and 15.9%, respectively. The longer time from admission to the positive BC episode, older age, diabetes, admission due to sepsis, and higher Charlson Comorbidity Index were identified as the main predictors of in-hospital mortality. CONCLUSIONS: Positive BC episodes sustained by NFGNB other than Pseudomonas and Acinetobacter species were predominantly sustained by Stenotrophomonas maltophilia and Achromobacter species, having bloodstream infection criteria in the vast majority of cases. Factors that have emerged to be associated with mortality highlighted how these species may have more room in prolonged hospitalisation and at the end of life for patients with chronic organ diseases.

Melioidosis in a returned traveler: Case report and review of the imported cases in Oman.

Melioidosis is an emerging tropical infectious disease in travelers. We present a case of travel related melioidosis in a 65-year-old man with chronic obstructive pulmonary disease and end stage renal disease following a two-week business trip to Thailand and attendance of the Songkran festival. This case emphasizes that vigilance, heightened clinical suspicion, and use of appropriate microbiology diagnostic tools are of paramount importance for a timely diagnosis and successful management. With the ever-increasing global travel, infectious diseases specialists, microbiologists, and public health professionals are constantly challenged by unfamiliar infections in returned travelers.

The Genomic Epidemiology of Clinical Burkholderia pseudomallei Isolates in North Queensland, Australia.

Background:Burkholderia pseudomallei, the causative agent of melioidosis, is highly genetically recombinant, resulting in significant genomic diversity. Multiple virulence factors have been associated with specific disease presentations. To date, there are limited data relating to genomic diversity and virulence factors associated with melioidosis cases in North Queensland, Australia. Aim: To describe the genetic diversity of B. pseudomallei and identify virulence factors associated with clinical risk factors and patient outcomes. Methods: Whole genome sequencing of clinical isolates was performed and analysed with clinical data obtained from a retrospective melioidosis cohort study. Results: Fifty-nine distinct sequence types (STs) were identified from the 128 clinical isolates. Six STs comprised 64/128 (50%) isolates. Novel STs accounted for 38/59 (64%) STs, with ST TSV-13 as the most prevalent (n = 7), and were less likely to possess an LPS A genotype or YLF gene cluster (p < 0.001). These isolates were most likely to be found outside the inner city (aOR: 4.0, 95% CI: 1.7-9.0, p = 0.001). ST TSV-13 was associated with increased mortality (aOR: 6.1, 95% CI: 1.2-30.9, p = 0.03). Patients with a history of alcohol excess were less likely to be infected by fhaB3 (aOR 0.2, 95% CI: 0.1-0.7, p = 0.01) or YLF (aOR: 0.4, 95% CI: 0.2-0.9, p = 0.04) positive isolates. Conclusions: There are a significant number of novel sequence types in Townsville, Australia. An emerging novel ST appears to have an association with geographic location and mortality. Ongoing investigation is required to further understand the impact of this ST on the Townsville region.

Clinical Prediction Rules for In-Hospital Mortality Outcome in Melioidosis Patients.

BACKGROUND: Melioidosis, a disease induced by Burkholderia pseudomallei, poses a significant health threat in tropical areas where it is endemic. Despite the availability of effective treatments, mortality rates remain notably elevated. Many risk factors are associated with mortality. This study aims to develop a scoring system for predicting the in-hospital mortality from melioidosis using readily available clinical data. METHODS: The data were collected from Surin Hospital, Surin, Thailand, during the period from April 2014 to March 2017. We included patients aged 15 years and above who had cultures that tested positive for Burkholderia pseudomallei. The clinical prediction rules were developed using significant risk factors from the multivariable analysis. RESULTS: A total of 282 patients with melioidosis were included in this study. In the final analysis model, 251 patients were used for identifying the significant risk factors of in-hospital fatal melioidosis. Five factors were identified and used for developing the clinical prediction rules, and the factors were as follows: qSOFA ≥ 2 (odds ratio [OR] = 2.39, p= 0.025), abnormal chest X-ray findings (OR = 5.86, p < 0.001), creatinine ≥ 1.5 mg/dL (OR = 2.80, p = 0.004), aspartate aminotransferase ≥50 U/L (OR = 4.032, p < 0.001), and bicarbonate ≤ 20 mEq/L (OR = 2.96, p = 0.002). The prediction scores ranged from 0 to 7. Patients with high scores (4-7) exhibited a significantly elevated mortality rate exceeding 65.0% (likelihood ratio [LR+] 2.18, p < 0.001) compared to the low-risk group (scores 0-3) with a lower mortality rate (LR + 0.18, p < 0.001). The area under the receiver operating characteristic curve (AUC) was 0.84, indicating good model performance. CONCLUSIONS: This study presents a simple scoring system based on easily obtainable clinical parameters to predict in-hospital mortality in melioidosis patients. This tool may facilitate the early identification of high-risk patients who could benefit from more aggressive treatment strategies, potentially improving clinical decision-making and patient outcomes.

Dysfunctional host cellular immune responses are associated with mortality in melioidosis.

Melioidosis is a tropical infection caused by the intracellular pathogen Burkholderia pseudomallei, an underreported and emerging global threat. As melioidosis-associated mortality is frequently high despite antibiotics, novel management strategies are critically needed. Therefore, we sought to determine whether functional changes in the host innate and adaptive immune responses are induced during acute melioidosis and are associated with outcome. Using a unique whole blood stimulation assay developed for use in resource-limited settings, we examined induced cellular functional and phenotypic changes in a cohort of patients with bacteremic melioidosis prospectively enrolled within 24 h of positive blood culture and followed for 28 days. Compared to healthy controls, melioidosis survivors generated an IL-17 response mediated by Th17 cells and terminally-differentiated effector memory CD8+ T cells (P < .05, both), persisting to 28 days after enrolment. Furthermore, melioidosis survivors developed polyfunctional cytokine production in CD8+ T cells (P < .01). Conversely, a reduction in CCR6+ CD4+ T cells was associated with higher mortality, even after adjustments for severity of illness (P = 0.004). Acute melioidosis was also associated with a profound acute impairment in monocyte function as stimulated cytokine responses were reduced in classical, intermediate and non-classical monocytes. Impaired monocyte cytokine function improved by 28-days after enrolment. These data suggest that IL-17 mediated cellular responses may be contributors to host defense during acute melioidosis, and that innate immune function may be impaired. These insights could provide novel targets for the development of therapies and vaccine targets in this frequently lethal disease.

Metabolic requirements of CD160 expressing memory-like NK cells in Gram-negative bacterial infection.

Objective: Unique metabolic requirements accompany the development and functional fates of immune cells. How cellular metabolism is important in natural killer (NK) cells and their memory-like differentiation in bacterial infections remains elusive. Methods: Here, we utilise our established NK cell memory assay to investigate the metabolic requirement for memory-like NK cell formation and function in response to the Gram-negative intracellular bacteria Burkholderia pseudomallei (BP), the causative agent of melioidosis. Results: We demonstrate that CD160+ memory-like NK cells upon BP stimulation upregulate glucose and amino acid transporters in a cohort of recovered melioidosis patients which is maintained at least 3-month post-hospital admission. Using an in vitro assay, human BP-specific CD160+ memory-like NK cells show metabolic priming including increased expression of glucose and amino acid transporters with elevated glucose uptake, increased mTOR activation and mitochondrial membrane potential upon BP re-stimulation. Antigen-specific and cytokine-induced IFN-γ production of this memory-like NK cell subset are highly dependent on oxidative phosphorylation (OXPHOS) with some dependency on glycolysis, whereas the formation of CD160+ memory-like NK cells in vitro is dependent on fatty acid oxidation and OXPHOS and further increased by metformin. Conclusion: This study reveals the link between metabolism and cellular function of memory-like NK cells, which can be exploited for vaccine design and for monitoring protection against Gram-negative bacterial infection.

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.

Phylogenetic and phenotypic characterization of Burkholderia pseudomallei isolates from Ghana reveals a novel sequence type and common phenotypes.

Melioidosis is a potentially severe disease caused by the gram-negative soil-dwelling bacterium called Burkholderia pseudomallei. The true breadth of the distribution of this tropical pathogen is starting to emerge with environmental and clinical isolates frequently characterized in new countries and regions. Even so, isolates, clinical cases, and genetic data from the continent of Africa remain scant. We previously confirmed the presence of B. pseudomallei in the environment of Ghana, unmasking a new area of endemicity for this pathogen. Here, we describe the genetic characteristics of isolates obtained from that environmental survey. Twenty-one isolates were subjected to whole genome sequencing and found to represent three discrete sequence types (ST), one of which was novel, and designated ST2058. Phylogenetic analysis places this novel isolate within a B. pseudomallei clade that includes genomes derived from the Americas, although it is closely related to a sub-clade that includes isolates from Africa. Importantly, phenotypic characterization demonstrates common features including API 20NE profiles and B. pseudomallei CPS to support existing diagnostics, and susceptibility to standard of care antibiotics often used in the clinical management of melioidosis. These findings add to our knowledge about the presence and distribution of B. pseudomallei in Africa and represent the first published genomes out of Ghana.

Enhancing Diagnosis and Treatment Adjustments for Travelers Infected with Burkholderia pseudomallei: A Case Report - Beijing Municipality, China, June 2023.

What is already known about this topic?: Burkholderia pseudomallei (BP) infection leads to melioidosis, a tropical disease endemic to coastal provinces of southern China. Physicians in non-endemic areas, do not commonly consider this disease as a primary differential diagnosis for febrile patients. What is added by this report?: This article discusses a case of melioidosis in Northern China. The patient, who had recently visited a Southeast Asian region with high melioidosis prevalence, fell ill after exposure to contaminated water. The disease progressed quickly and with severity. What are the implications for public health practice?: Healthcare workers need to remain vigilant regarding travel-related diseases for accurate differential diagnosis and to provide timely and effective treatment, especially for patients with recent travel history or symptoms during travel.

First Case Report of Cystic Echinococcosis Caused by G7 Genotype Echinococcus intermedius Confirmed by Genetic Sequencing - Southern China, December 2023.

What is already known about this topic?: Echinococcosis exhibits a global distribution. In China, the primary endemic area is the northwest region. In December 2023, we documented a case of echinococcosis in an individual lacking any travel or residential history in endemic regions. What is added by this report?: This is the first laboratory-confirmed case of hepatic echinococcosis reported in Guangdong Province, associated with the G7 genotype of Echinococcus granulosus (E. granulosus). The most probable mode of transmission is a local infection resulting from E. granulosus introduced from endemic regions. What are the implications for public health practice?: As the circulation of agricultural products increases, it is essential to enhance the quarantine and management of livestock from epidemic areas to prevent and control the spread of echinococcosis to non-epidemic regions.

γδ T Cells Mediate Protection Against Neutrophil-associated Lung Inflammation in Pulmonary Melioidosis.

Pulmonary melioidosis is a severe tropical infection caused by Burkholderia pseudomallei and is associated with high mortality despite early antibiotic treatment. γδ T cells have been increasingly implicated as drivers of the host neutrophil response during bacterial pneumonia, but their role in pulmonary melioidosis is unknown. Here, we report that in patients with melioidosis, a lower peripheral blood γδ T cell concentration is associated with higher mortality even when adjusting for severity of illness. γδ T cells were also enriched in the lung and protected against mortality in a mouse model of pulmonary melioidosis. γδ T cell deficiency in infected mice induced an early recruitment of neutrophils to the lung, independent of bacterial burden. Subsequently, γδ T cell deficiency resulted in increased neutrophil-associated inflammation in the lung as well as impaired bacterial clearance. Additionally, γδ T cells influenced neutrophil function and subset diversity in the lung after infection. Our results indicate that γδ T cells serve a novel protective role in the lung during a severe bacterial pneumonia by regulating excessive neutrophil-associated inflammation.

A new computed tomography score-based staging for melioidosis pneumonia to predict progression.

Background: Melioidosis pneumonia, caused by the bacterium Burkholderia pseudomallei, is a serious infectious disease prevalent in tropical regions. Chest computed tomography (CT) has emerged as a valuable tool for assessing the severity and progression of lung involvement in melioidosis pneumonia. However, there persists a need for the quantitative assessment of CT characteristics and staging methodologies to precisely anticipate disease progression. This study aimed to quantitatively extract CT features and evaluate a CT score-based staging system in predicting the progression of melioidosis pneumonia. Methods: This study included 97 patients with culture-confirmed melioidosis pneumonia who presented between January 2002 and December 2021. Lung segmentation and annotation of lesions (consolidation, nodules, and cavity) were used for feature extraction. The features, including the involved area, amount, and intensity, were extracted. The CT scores of the lesion features were defined by the feature importance weight and qualitative stage of melioidosis pneumonia. Gaussian process regression (GPR) was used to predict patients with severe or critical melioidosis pneumonia according to CT scores. Results: The melioidosis pneumonia stages included acute stage (0-7 days), subacute stage (8-28 days), and chronic stage (>28 days). In the acute stage, the CT scores of all patients ranged from 2.5 to 6.5. In the subacute stage, the CT scores for the severe and mild patients were 3.0-7.0 and 2.0-5.0, respectively. In the chronic stage, the CT score of the mild patients fluctuated approximately between 2.5 and 3.5 in a linear distribution. Consolidation was the most common type of lung lesion in those with melioidosis pneumonia. Between stages I and II, the percentage of severe scans with nodules dropped from 72.22% to 47.62% (P<0.05), and the percentage of severe scans with cavities significantly increased from 16.67% to 57.14% (P<0.05). The GPR optimization function yielded area under the receiver operating characteristic curves of 0.71 for stage I, 0.92 for stage II, and 0.87 for all stages. Conclusions: In patients with melioidosis pneumonia, it is reasonable to divide the period (the whole progression of melioidosis pneumonia) into three stages to determine the prognosis.

EBUS-TBNA diagnosis of mediastinal melioidosis in patient presented with lymphadenopathy and SVC thrombosis: A rare manifestation in non-diabetic patient.

Melioidosis is a tropical infectious disease that ranks as northeastern Thailand's third most common infectious cause of death. The manifestations of melioidosis vary depending on the organs involved and often resemble malignancy and tuberculosis. We present a case of an atypical melioidosis presentation in a patient with low-grade fever and facial swelling without any risk factors. Chest CT revealed a 3.3-cm heterogeneous enhancing right lower paratracheal lymph nodes with thrombosis of the superior vena cava and azygos vein. Endobronchial ultrasound-guided transbronchial needle aspiration of lymph node was performed, and Burkholderia pseudomallei was identified through lymph node culture. The patient underwent a three-week intravenous course of ceftazidime and a 12-week oral course of trimethoprim-sulfamethoxazole. Oral anticoagulation was also administered. Follow-up computed tomography of the thorax after completion of treatment revealed no residual lymphadenopathy and thrombosis.

Tracking melioidosis in Iran: Utilizing abattoir-based surveillance as a One Health approach.

BACKGROUND: Burkholderia pseudomallei, an environmental saprophyte bacterium, causes melioidosis in humans and animals. It was first discovered in Iran between 1967 and 1976 in small ruminants, equines, environments and humans. No subsequent studies have been conducted to determine the existence and prevalence of this pathogen in the country. OBJECTIVES: The present study aims to monitor the presence of B. pseudomallei in the ruminant population of the Golestan province of Iran, which largely depends on pastures. The ruminants can serve as sentinels to indicate the presence of the bacteria in the environment and its potential impact on human health in the One Health triad. METHODS: Liver and lung abscesses from domestic sheep, cattle and goats in three industrial and three conventional slaughterhouses were sampled and analysed using 23S ribosomal DNA polymerase chain reaction (rDNA PCR) with primers CVMP 23-1 and CVP-23-2 for B. pseudomallei, Burkholderia cepacia and Burkholderia vietnamiensis, as well as B. pseudomallei-specific TTS1 real-time PCR, along with microbiological and biochemical assays. RESULTS: Out of the 97 animals sampled, only 14 (15%) tested positive for 23S rDNA PCR. However, the follow-up evaluation using TTS1 real-time PCR and microbiological and biochemical assays did not confirm the presence of B. pseudomallei in the samples. CONCLUSIONS: Although B. pseudomallei was not detected in the current survey, conducting abattoir-based surveillance of ruminants is a cost-effective One Health approach to monitor pathogenic Burkholderia. Developing standards of clinical and laboratory good practices for Burkholderia infections is crucial for One Health surveillance.