Description of two fatal cases of melioidosis in Mexican children with acute pneumonia: case report.

BACKGROUND: Melioidosis is an infectious disease caused by Burkholderia pseudomallei. In Mexico, the disease is rarely diagnosed in humans and there is no evidence of simultaneous environmental isolation of the pathogen. Here, we describe clinical profiles of fatal cases of melioidosis in two children, in a region without history of that disease. CASE PRESENTATION: About 48 h before onset of symptoms, patients swam in a natural body of water, and thereafter they rapidly developed fatal septicemic illness. Upon necropsy, samples from liver, spleen, lung, cerebrospinal fluid, and bronchial aspirate tissues contained Burkholderia pseudomallei. Environmental samples collected from the locations where the children swam also contained B. pseudomallei. All the clinical and environmental strains showed the same BOX-PCR pattern, suggesting that infection originated from the area where the patients were swimming. CONCLUSIONS: The identification of B. pseudomallei confirmed that melioidosis disease exists in Sonora, Mexico. The presence of B. pseudomallei in the environment may suggest endemicity of the pathogen in the region. This study highlights the importance of strengthening laboratory capacity to prevent and control future melioidosis cases.

The treatment of melioidosis: is there a role for repurposed drugs? A proposal and review.

Introduction: Melioidosis is a significant health problem within endemic areas such as Southeast Asia and Northern Australia. The varied presentation of melioidosis and the intrinsic antibiotic resistance of Burkholderia pseudomallei, the causative organism, make melioidosis a difficult infection to manage. Often prolonged courses of antibiotic treatments are required with no guarantee of clinical success.Areas covered: B. pseudomallei is able to enter phagocytic cells, affect immune function, and replicate, via manipulation of the caspase system. An examination of this mechanism, and a look at other factors in the pathogenesis of melioidosis, shows that there are multiple potential points of therapeutic intervention, some of which may be complementary. These include the directed use of antimicrobial compounds, blocking virulence mechanisms, balancing or modulating cytokine responses, and ameliorating sepsis.Expert commentary: There may be therapeutic options derived from drugs in clinical use for unrelated conditions that may have benefit in melioidosis. Key compounds of interest primarily affect the disequilibrium of the cytokine response, and further preclinical work is needed to explore the utility of this approach and encourage the clinical research needed to bring these into beneficial use.

Lipid A Remodeling Is a Pathoadaptive Mechanism That Impacts Lipopolysaccharide Recognition and Intracellular Survival of Burkholderia pseudomallei.

Burkholderia pseudomallei causes the severe disease melioidosis. The bacterium subverts the host immune system and replicates inside cells, and host mortality results primarily from sepsis-related complications. Lipopolysaccharide (LPS) is a major virulence factor and mediator of sepsis that many pathogens capable of intracellular growth modify to reduce their immunological "footprint." The binding strength of B. pseudomallei LPS for human LPS binding protein (hLBP) was measured using surface plasmon resonance. The structures of lipid A isolated from B. pseudomallei under different temperatures were analyzed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and the gene expression of two lipid A remodeling genes, lpxO and pagL, was investigated. The LPS was characterized for its ability to trigger tumor necrosis factor alpha (TNF-α) release and to activate caspase-11-triggered pyroptosis by introduction of LPS into the cytosol. Lipid A from long-term chronic-infection isolates was isolated and characterized by MALDI-TOF MS and also by the ability to trigger caspase-11-mediated cell death. Lipid A from B. pseudomallei 1026b lpxO and pagL mutants were characterized by positive- and negative-mode MALDI-TOF MS to ultimately identify their role in lipid A structural modifications. Replication of lpxO and pagL mutants and their complements within macrophages showed that lipid A remodeling can effect growth in host cells and activation of caspase-11-mediated cytotoxicity.

Emergence of melioidosis in the Indian Ocean region: Two new cases and a literature review.

Melioidosis is a disease caused by bacteria called B. pseudomallei. Infections can develop after contact with standing water. This disease can reach all the organs and especially the lungs. It is associated with a high mortality rate (up to 50%). Melioidosis is endemic in northern Australia and in Southeast Asia. Nevertheless, B. pseudomallei may be endemic in the Indian Ocean region and in Madagascar in particular, so clinicians and microbiologists should consider acute melioidosis as a differential diagnosis in the Indian Ocean region, in particular from Madagascar.

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.

Neuromelioidosis: a series of seven cases in Hainan province, China.

Melioidosis, which is caused by Burkholderia pseudomallei, is predominately a disease of tropical climates and is especially widespread in south-east Asia and northern Australia. Melioidosis affecting the central nervous system has a low incidence but a high mortality. We present seven cases of neuromelioidosis and analyze the disease characteristics and imaging features. Typical clinical features of this disease included high fever and headache. Five patients had an irregular fever with a temperature ≥ 39℃. Peripheral blood leukocytes and the neutrophil ratio were raised in all patients. On computed tomography and magnetic resonance imaging the disease mainly manifested as intracerebral single or multiple nodules, as well as ring and flake-like enhancements with rapid lesion progression. This study demonstrated the importance of imaging examination in the clinical evaluation and diagnosis of neuromelioidosis.

Involvement of L-selectin expression in Burkholderia pseudomallei-infected monocytes invading the brain during murine melioidosis.

The development of neurologic melioidosis was linked to the elicitation of Burkholderia pseudomallei-infected L-selectinhiCD11b+ BALB/c cells in our previous study. However, whether monocytic L-selectin (CD62L, encoded by the sell gene) is a key factor remains uncertain. In the present study, after establishing multi-organ foci via hematogenous routes, we demonstrated that B. pseudomallei GFP steadily persisted in blood, splenic, hepatic and bone marrow (BM) Ly6C monocytes; however, the circulating CD16/32+CD45hiGFP+ brain-infiltrating leukocytes (BILs) derived from the blood Ly6C monocytes were expanded in BALB/c but not in C57BL/6 bacteremic melioidosis. Consistent with these results, 60% of BALB/c mice but only 10% of C57BL/6 mice exhibited neurologic melioidosis. In a time-dependent manner, B. pseudomallei invaded C57BL/6 BM-derived phagocytes and monocytic progenitors by 2 d. The number of Ly6C+CD62L+GFP+ inflamed cells that had expanded in the BM and that were ready for emigration peaked on d 21 post-infection. Hematogenous B. pseudomallei-loaded sell+/+Ly6C monocytes exacerbated the bacterial loads and the proportion of Ly6C+GFP+ BILs in the recipient brains compared to sell-/- infected Ly6C cells when adoptively transferred. Moreover, a neutralizing anti-CD62L antibody significantly depleted the bacterial colonization of the brain following adoptive transfer of B. pseudomallei-loaded C57BL/6 or BALB/c Ly6C cells. Our data thus suggest that Ly6C+CD62L+ infected monocytes served as a Trojan horse across the cerebral endothelium to induce brain infection. Therefore, CD62L should be considered as not only a temporally elicited antigen but also a disease-relevant leukocyte marker during the development of neurologic melioidosis.

An 11-Year Analysis of Emergency Presentations of Melioidosis in Northeastern Malaysia.

A neglected tropical disease, melioidosis is known to have variability in clinical presentations. Here, we described clinical features that should alert the physicians on the possibility of melioidosis. In this review of 86 cases from 2001 to 2011, the common presentations of melioidosis in the Emergency Department (ED), Hospital Universiti Sains Malaysia were; male gender (79.1 %), in working age group (47.8 ± 15.2 year-old), worked in contact with soil (73.3 %), presented with fever (91.9 %), in rainy season (55.8 %), have underlying diabetes mellitus (79.1 %), have leukocytosis (67.4 %) and high blood glucose (62.8 %) during presentation. In 34.9 % of cases, the antimicrobials were initiated at the ED and only 10.5 % include antimelioid drugs. Thirty-one patients (36.0 %) died due to melioidosis and 51.6 % of this were within 48 h of admission. Despite high mortality rate, the clinical awareness on the possibility of melioidosis among emergency physicians is still low and need to be strengthened.

Goodpasture disease as a consequence of melioidosis.

We describe a case of anti-glomerular basement membrane (GBM) antibody-mediated disease in association with concomitant Burkholderia pseudomallei (melioidosis) bacteraemia. The temporal profile of the illness and initial absence of circulating anti-GBM antibodies, in light of the subsequent definitive histological diagnosis of anti-GBM disease, makes this case interesting and unusual. Additionally, there have been no prior case reports suggesting melioidosis as a cause of biopsy-proven glomerulonephritis.

A case of systemic melioidosis: unravelling the etiology of chronic unexplained fever with multiple presentations.

Melioidosis, caused by the environmental saprophyte, Burkholderia pseudomallei, is an important public health problem in Southeast Asia and Northern Australia. It is being increasingly reported from other parts, including India, China, and North and South America expanding the endemic zone of the disease. We report a case of systemic melioidosis in a 58-year-old diabetic, occupationally-unexposed male patient, who presented with chronic fever, sepsis, pneumonia, pleural effusion and subcutaneous abscess, was undiagnosed for long, misidentified as Pseudomonas aeruginosa infection elsewhere, but was saved due to correct identification of the etiologic agent and timely institution of appropriate therapy at our institute. A strong clinical and microbiological suspicion for melioidosis should be considered in the differential diagnosis of acute pyrexia of unknown origin, acute respiratory distress syndrome and acute onset of sepsis, especially in the tropics.

Melioidosis: molecular aspects of pathogenesis.

Burkholderia pseudomallei is a gram-negative bacterium that causes melioidosis, a multifaceted disease that is highly endemic in southeast Asia and northern Australia. This facultative intracellular pathogen possesses a large genome that encodes a wide array of virulence factors that promote survival in vivo by manipulating host cell processes and disarming elements of the host immune system. Antigens and systems that play key roles in B. pseudomallei virulence include capsular polysaccharide, lipopolysaccharide, adhesins, specialized secretion systems, actin-based motility and various secreted factors. This review provides an overview of the current and steadily expanding knowledge regarding the molecular mechanisms used by this organism to survive within a host and their contribution to the pathogenesis of melioidosis.

Short report: Predictors of severe disease in melioidosis patients in Kuala Lumpur, Malaysia.

The predictors of severe disease or death were determined for 85 melioidosis patients in Kuala Lumpur, Malaysia. Most of the patients were male, > 40 years old, and diabetic. Severe disease or death occurred in 28 (32.9%) cases. Lower lymphocyte counts and positive blood cultures were significant independent predictors of severe disease, but age, presentations with pneumonia, inappropriate empirical antibiotics, or flagellin types of the infecting isolates were not. Knowledge of local predictors of severe disease is useful for clinical management.

Endogenous α2-antiplasmin is protective during severe gram-negative sepsis (melioidosis).

RATIONALE: α2-Antiplasmin (A2AP) is a major inhibitor of fibrinolysis by virtue of its capacity to inhibit plasmin. Although the fibrinolytic system is strongly affected by infection, the functional role of A2AP in the host response to sepsis is unknown. OBJECTIVES: To study the role of A2AP in melioidosis, a common form of community-acquired sepsis in Southeast Asia and Northern Australia caused by the gram-negative bacterium Burkholderia pseudomallei. METHODS: In a single-center observational study A2AP was measured in patients with culture-proven septic melioidosis. Wild-type and A2AP-deficient (A2AP(-/-)) mice were intranasally infected with B. pseudomallei to induce severe pneumosepsis (melioidosis). Parameters of inflammation and coagulation were measured, and survival studies were performed. MEASUREMENTS AND MAIN RESULTS: Patients with melioidosis showed elevated A2AP plasma levels. Likewise, A2AP levels in plasma and lung homogenates were elevated in mice infected with B. pseudomallei. A2AP-deficient (A2AP(-/-)) mice had a strongly disturbed host response during experimental melioidosis as reflected by enhanced bacterial growth at the primary site of infection accompanied by increased dissemination to distant organs. In addition, A2AP(-/-) mice showed more severe lung pathology and injury together with an increased accumulation of neutrophils and higher cytokine levels in lung tissue. A2AP deficiency further was associated with exaggerated systemic inflammation and coagulation, increased distant organ injury, and enhanced lethality. CONCLUSIONS: This study is the first to identify A2AP as a protective mediator during gram-negative (pneumo)sepsis by limiting bacterial growth, inflammation, tissue injury, and coagulation.

Uncommon clinical presentations of melioidosis in children: 2 cases with sore throat and 1 case with urticarial rash.

Common clinical presentations of melioidosis in children include suppurative parotitis, lymphadenitis, skin infection and septicemia with pneumonia. Here we describe three cases with uncommon presentations of melioidosis seen among children attending a university hospital in northeastern Thailand. Two patients presented with pharyngitis and subsequently developed cervical lymphadenitis. Another patient presented with high fever and generalized urticarial rash. A pharyngeal culture in each of the first 2 patients and a blood culture and culture of the discharge from the wound of the third patient grew Burkholderia pseudomallei. All patients recovered with treatment. Their clinical presentations, initial diagnosis, treatment, clinical course and outcomes are described. Physicians caring for children living in, or returning from, melioidosis endemic areas should be aware of these uncommon presentations.

Natural history of inhalation melioidosis in rhesus macaques (Macaca mulatta) and African green monkeys (Chlorocebus aethiops).

Burkholderia pseudomallei, the causative agent of melioidosis, is recognized as a serious health threat due to its involvement in septic and pulmonary infections in areas of endemicity and is recognized by the Centers for Disease Control and Prevention as a category B biothreat agent. An animal model is desirable to evaluate the pathogenesis of melioidosis and medical countermeasures. A model system that represents human melioidosis infections is essential in this process. A group of 10 rhesus macaques (RMs) and 10 African green monkeys (AGMs) was exposed to aerosolized B. pseudomallei 1026b. The first clinical signs were fever developing 24 to 40 h postexposure followed by leukocytosis resulting from a high percentage of neutrophils. Dyspnea manifested 2 to 4 days postexposure. In the AGMs, an increase in interleukin 1ß (IL-1ß), IL-6, IL-8, gamma interferon (IFN-γ), and tumor necrosis factor alpha (TNF-α) was observed. In the RMs, IL-1ß, IL-6, and TNF-α increased. All the RMs and AGMs had various degrees of bronchopneumonia, with inflammation consisting of numerous neutrophils and a moderate number of macrophages. Both the RMs and the AGMs appear to develop a melioidosis infection that closely resembles that seen in acute human melioidosis. However, for an evaluation of medical countermeasures, AGMs appear to be a more appropriate model.

Development of an acute model of inhalational melioidosis in the common marmoset (Callithrix jacchus).

Studies of inhalational melioidosis were undertaken in the common marmoset (Callithrix jacchus). Following exposure to an inhaled challenge with aerosolized Burkholderia pseudomallei, lethal infection was observed in marmosets challenged with doses below 10 cfu; a precise LD(50) determination was not possible. The model was further characterized using a target challenge dose of approximately 10(2) cfu. A separate pathogenesis time-course experiment was also conducted. All animals succumbed, between 27 and 78 h postchallenge. The challenge dose received and the time to the humane endpoint (1 °C below normal body temperature postfever) were correlated. The first indicator of disease was an increased core body temperature (T(c) ), at 22 h postchallenge. This coincided with bacteraemia and bacterial dissemination. Overt clinical signs were first observed 3-5 h later. A sharp decrease (typically within 3-6 h) in the T(c) was observed prior to humanely culling the animals in the lethality study. Pathology was noted in the lung, liver and spleen. Disease progression in the common marmoset appears to be consistent with human infection in terms of bacterial spread, pathology and physiology. The common marmoset can therefore be considered a suitable animal model for further studies of inhalational melioidosis.

Diabetes does not influence activation of coagulation, fibrinolysis or anticoagulant pathways in Gram-negative sepsis (melioidosis).

Diabetes is associated with a disturbance of the haemostatic balance and is an important risk factor for sepsis, but the influence of diabetes on the pathogenesis of sepsis remains unclear. Melioidosis ( Burkholderia pseudomallei infection) is a common cause of community-acquired sepsis in Southeast Asia and northern Australia. We sought to investigate the impact of pre-existing diabetes on the coagulation and fibrinolytic systems during sepsis caused by B.pseudomallei . We recruited a cohort of 44 patients (34 with diabetes and 10 without diabetes) with culture-proven melioidosis. Diabetes was defined as a pre-admission diagnosis of diabetes or an HbA1c>7.8% at enrolment. Thirty healthy blood donors and 52 otherwise healthy diabetes patients served as controls. Citrated plasma was collected from all subjects; additionally in melioidosis patients follow-up specimens were collected seven and ≥ 28 days after enrolment where possible. Relative to uninfected healthy controls, diabetes per se (i.e. in the absence of infection) was characterised by a procoagulant effect. Melioidosis was associated with activation of coagulation (thrombin-antithrombin complexes (TAT), prothrombin fragment F1+2 and fibrinogen concentrations were elevated; PT and PTT prolonged), suppression of anti-coagulation (antithrombin, protein C, total and free protein S levels were depressed) and abnormalities of fibrinolysis (D-dimer and plasmin-antiplasmin complex [PAP] were elevated). Remarkably, none of these haemostatic alterations were influenced by pre-existing diabetes. In conclusion, although diabetes is associated with multiple abnormalities of coagulation, anticoagulation and fibrinolysis, these changes are not detectable when superimposed on the background of larger abnormalities attributable to B. pseudomallei sepsis.

Melioidosis: a clinical overview.

INTRODUCTION: Melioidosis, an infection caused by the environmental Gram-negative bacillus Burkholderia pseudomallei, has emerged as an important cause of morbidity and mortality in Southeast Asia and northern Australia. SOURCES OF DATA: a review of the literature using PubMed. AREAS OF AGREEMENT: Approaches to diagnosis and antimicrobial therapy. AREAS OF CONTROVERSY: Whether seroconversion signals the presence of a quiescent bacterial focus and an increase in long-term risk of melioidosis. AREAS TIMELY FOR DEVELOPING RESEARCH: Melioidosis is potentially preventable, but there is a striking lack of evidence on which to base an effective prevention programme. An accurate map defining the global distribution of B. pseudomallei is needed, together with studies on the relative importance of different routes of infection. There is a marked difference in mortality from melioidosis in high-income versus lower income countries, and affordable strategies that reduce death from severe sepsis (from any cause) in resource-restricted settings are needed.