Brain abscesses caused by Burkholderia pseudomallei

Massive calvarial melioidosis abscess following minor trauma in rural areas of Thailand

Background

Melioidosis is uncommon but endemic in Southeast Asia and parts of Northern Australia. Cerebral melioidosis is rare but can be spread through several routes, such as hematogenous spreading or the direct inoculation of organisms from wound contamination with soil. It can cause devastating sequelae if the treatment is delayed. However, with early and adequate treatment, patients can recover and have a good quality of life.

Case Description

A 62-year-old diabetic male presented with epilepsy 2 months after a head injury. A computed tomography scan revealed an abscess extending from the subgaleal layer to the subdural with osteomyelitis. A craniotomy was performed to remove the abscess. Melioidosis was identified from pus culture. Intravenous meropenem with Bactrim was started, followed by oral doxycycline and bactrim. The patient recovered with no seizure episodes. This patient showed a rare but straightforward infection from direct inoculation in a wound contaminated with soil. Incubation time could be up to 2 months. The infection originates from previously lacerated scalp tissue and invades the skull, causing osteomyelitis and epidural abscess. Prompt treatment brings a good outcome. In patients with risk factors and a suspicious history, broad-spectrum antibiotics should be initiated after removal of the abscess.

Conclusion

Melioidosis is still endemic in Thailand. Doctors should be aware of this organism in patients with high-risk factors or travelers who have just returned from an endemic area. Patients should be treated early with an adequate dose and duration of anti-melioidosis.

Critical approach to atypical spectrum of melioidosis: a case-series based literature review

Melioidosis is an emerging infectious disease with highest predominance in Southeast Asia, but it has a significantly lower incidence across other parts of the globe. The most common systemic involvement seen in melioidosis is pulmonary, followed by multiple visceral and cutaneous abscesses. Infrequently, melioidosis manifests with atypical presentations such as spontaneous bacterial peritonitis (SBP), acute pyogenic meningitis or septic arthritis. Our primary case discusses an extremely rare presentation of melioidosis with SBP. There have not been any cases of SBP reported secondary to melioidosis infection. The second case exhibits development of acute pyogenic meningitis from haematogenous dissemination of this organism, while the final case demonstrates musculoskeletal melioidosis as an uncommon presentation. Of note, this case series also discusses the guidelines of management of melioidosis and illustrates the tremendous impact of appropriate and timely antibiotic therapy on mortality and morbidity secondary to melioidosis.

Neuromelioidosis: A Single-Center Experience with Emphasis on Imaging

Introduction  Infection with Burkholderia pseudomallei , a gram-negative bacterium found in soil and surface water, is termed melioidosis and is commonly reported to occur in Southeast Asia and Northern Australia, where it is endemic. It is being increasingly reported in India, and transmission occurs through inhalation, inoculation, and ingestion. The neuroparenchyma, the adjacent soft tissue, and bone are known to be affected in both the acute and chronic disease forms. Involvement of these structures is rare but causes significant mortality and morbidity.

Material and Methods  Eighteen culture-proven cases of neuromelioidosis were identified between January 2008 and December 2019. The patients were retrospectively identified via search of the hospital’s electronic database.

Results  Cranial disease was in the form of parenchymal abscesses ( n = 4), cerebritis/encephalitis ( n = 5), and extradural ( n = 4) and dural disease ( n = 1). Acute myelitis ( n = 1) and spondylodiscitis ( n = 3) were seen in the spinal disease form. Neuroparenchymal involvement ranged from cerebritis/encephalitis to early and mature parenchymal abscesses. Extradural involvement was in the form of extradural abscesses and/or thick irregular enhancement in the extradural region. Early diagnosis and initiation of appropriate therapy had favorable outcomes in 15 out of 18 patients. Two patients with parenchymal abscesses and one with myelitis succumbed to the illness.

Conclusion  Neuromelioidosis is a rare manifestation of melioidosis with significant morbidity and mortality, necessitating a high index of clinical suspicion, especially if there has been travel to endemic regions. Imaging plays a key role in facilitating early diagnosis and initiation of therapy.

Persistent infection due to a small-colony variant of Burkholderia pseudomallei leads to PD-1 upregulation on circulating immune cells and mononuclear infiltration in viscera of experimental BALB/c mice

Background

Melioidosis is a neglected tropical disease endemic across South East Asia and Northern Australia. The etiological agent, Burkholderia pseudomallei (B.pseudomallei), is a Gram-negative, rod-shaped, motile bacterium residing in the soil and muddy water across endemic regions of the tropical world. The bacterium is known to cause persistent infections by remaining latent within host cells for prolonged duration. Reactivation of the recrudescent disease often occurs in elders whose immunity wanes. Moreover, recurrence rates in melioidosis patients can be up to ~13% despite appropriate antibiotic therapy, suggestive of bacterial persistence and inefficacy of antibiotic regimens. The mechanisms behind bacterial persistence in the host remain unclear, and hence understanding host immunity during persistent B. pseudomallei infections may help designing potential immunotherapy.

Methodology/Principal findings

A persistent infection was generated using a small-colony variant (SCV) and a wild-type (WT) B. pseudomallei in BALB/c mice via intranasal administration. Infected mice that survived for >60 days were sacrificed. Lungs, livers, spleens, and peripheral blood mononuclear cells were harvested for experimental investigations. Histopathological changes of organs were observed in the infected mice, suggestive of successful establishment of persistent infections. Moreover, natural killer (NK) cell frequency was increased in SCV- and WT-infected mice. We observed programmed death-1 (PD-1) upregulation on B cells of SCV- and WT-infected mice. Interestingly, PD-1 upregulation was only observed on NK cells and monocytes of SCV-infected mice. In contrast, cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) downregulation was seen on NK cells of WT-infected mice, and on monocytes of SCV- and WT-infected mice.

Conclusions/Significance

The SCV and the WT of B. pseudomallei distinctly upregulated PD-1 expression on B cells, NK cells, and monocytes to dampen host immunity, which likely facilitates bacterial persistence. PD-1/PD-L1 pathway appears to play an important role in the persistence of B. pseudomallei in the host.

B. pseudomallei is a bacterium that causes melioidosis, a disease endemic in Southeastern Asia and Northern Australia. It is estimated that melioidosis leads to 89,000 deaths worldwide each year. Nevertheless, melioidosis continues to remain a neglected tropical disease that is not even on the list of neglected tropical diseases of the World Health Organization. Furthermore, the disease has a high mortality and recurrence rate, which can be up to 40% and 13%, respectively. It has also been well documented that B. pseudomallei causes latent/persistent infections for a prolonged period without showing apparent symptoms in the infected individual. The mechanisms that are responsible for bacterial persistence in the host remain unclear. Our results demonstrated that B. pseudomallei were able to upregulate PD-1 expression on B cells, NK cells, and/or monocytes during persistent diseases, which likely diminish optimal host immunity. The weakened host immunity in turns facilitates persistence of the bacterium. Interestingly, the SCV had a higher PD-1 expression on distinct immune cells compared to the WT, which might explain its frequent association with persistent infections. Immunotherapies by targeting PD-1/PD-L1 pathway could serve as a better treatment than the conventional antibiotic regimens, which cause a high rate of recurrence in melioidosis patients.

Central nervous system melioidosis in the pediatric age group: review

PURPOSE

Melioidosis is a potentially fatal infectious disease caused by Burkholderia pseudomallei. Neurologic involvement in pediatric age group is very rare, and only a handful of cases have been reported in literature. We sought to provide a systematic review of pediatric neurologic melioidosis.

METHODS

Literature review was performed to analyze reported cases of pediatric neurologic melioidosis (≤16 years) by searching online database (PubMed/MEDLINE).

RESULTS

Twenty-seven cases were analyzed. Mean age was 6.7 years (range 2 days-14 years) and around 50% were older children (>5 years). Cranial nerve palsies and fever were most common presenting features. Major manifestations were meningoencephalitis in 16 (59%) and cerebral abscesses in eight (29%) cases. Abscesses were mostly located in parietal lobe. Among older children, abscesses were common than meningeal disease, while being converse for neonates. Mean follow-up duration was 11.5 months. Ten cases showed good to excellent outcome, while eight cases had fair (incomplete recovery) outcomes. The overall mortality rate was 18.5% (5/27) and tends to decrease with age. Among the five deaths, 4 (80%) had septicemia or pneumonia.

CONCLUSIONS

Pediatric neurologic melioidosis is very rare. Meningoencephalitis is the most common presentation. Mortality is the highest in neonates. Ceftazidime appears to be the drug of choice in intensive phase, although the best drug in maintenance phase cannot be commented upon, especially in very young children.

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.

Melioidosis in Travelers: Review of the Literature

BACKGROUND

Melioidosis is a bacterial infection endemic essentially in Southeast Asia and northern Australia. In temperate areas, the infection is extremely rare and is almost always imported by travelers or immigrants. The infection may affect almost any organ in the body, with various degrees of severity.

METHODS

We reviewed the literature on melioidosis in travelers. For this purpose we searched PubMed and Google for relevant articles up to July 2015.

RESULTS

We have identified 72 cases of melioidosis in travelers published in the literature. Melioidosis in travelers was acquired mostly in Thailand (46% of cases). The mean duration of stay in the endemic area was 36 days (range 7-330 days). Symptoms usually started at 23 days (range 1-360 days) after leaving the endemic area. The clinical presentation was varied, sepsis being the most common (34%) followed by pneumonia (29%) and abscess formation (25%). Melioidosis in travelers was less often associated with predisposing risk factors (37.5%), diabetes mellitus being the most common (21%), and had lower mortality (17%) than had the infection in autochthonous cases in Southeast Asia.

CONCLUSIONS

Melioidosis in travelers has its own characteristics, which distinguish it from other autochthonous diseases in indigenous populations. The possibility of melioidosis should be considered not only in patients originating from endemic areas, but also in patients returning from travel in those regions.

Neuromelioidosis: Craniospinal MRI Findings in Burkholderia pseudomallei Infection

PURPOSE

To investigate magnetic resonance imaging (MRI) findings of central nervous system (CNS) infection with Burkholderia pseudomallei.

METHODS

Retrospective analysis of 10 patients (5 male and 5 female, age range from 13 to 69 years) with CNS melioidosis confirmed on culture of blood, sputum, cerebrospinal fluid, brain biopsy, and postmortem brain tissue. Clinical data were collected and MRI brain and/or spine were independently reviewed.

RESULTS

Seven patients with brain parenchymal or intramedullary spinal cord lesions demonstrated rim-enhancing microabscesses with propensity for white matter tracts including the corticospinal tracts, corpus callosum, and cerebellar peduncles. Three of these 7 patients also showed thickening and enhancement of the trigeminal nerves with contiguous spread to brain stem trigeminal nuclei. Three patients had isolated extraaxial disease with findings including meningeal enhancement, extradural abscess, skull osteomyelitis, and scalp abscess.

CONCLUSION

Spread of microabscesses along white matter tracts and frequent trigeminal nerve involvement are unique imaging characteristics of CNS melioidosis. These findings may provide insight into potential mechanisms for B. pseuodomallei entry into the CNS through direct axonal transport in cranial nerves bypassing the blood brain barrier. Prompt recognition of the neuroimaging features of this potentially fatal infection may allow for early microbiological culture and treatment.

Cerebral melioidosis for the first time in the western hemisphere

This report is the first published case of cerebral melioidosis in the western hemisphere. In this paper the authors review the literature on neurological melioidosis and its presentation and treatment in endemic areas, describe the clinical course of this unique case of a presentation of the disease with cranial abscess in the US, review the pathological and radiological findings associated with this seminal case, and put forth recommendations for recognizing and treating possible future instances of the disease within the western hemisphere.

Particle-size dependent effects in the Balb/c murine model of inhalational melioidosis

Deposition of Burkholderia pseudomallei within either the lungs or nasal passages of the Balb/c murine model resulted in different infection kinetics. The infection resulting from the inhalation of B. pseudomallei within a 12 μm particle aerosol was prolonged compared to a 1 μm particle aerosol with a mean time-to-death (MTD) of 174.7 ± 14.9 h and 73.8 ± 11.3 h, respectively. Inhalation of B. pseudomallei within 1 μm or 12 μm particle aerosols resulted in a median lethal dose (MLD) of 4 and 12 cfu, respectively. The 12 μm particle inhalational infection was characterized by a marked involvement of the nasal mucosa and extension of bacterial colonization and inflammatory lesions from the olfactory epithelium through the olfactory nerves (or tracts) to the olfactory bulb (100%), culminating in abscessation of the brain (33%). Initial involvement of the upper respiratory tract lymphoid tissues (nasal-associated lymphoid tissue (NALT) and cervical lymph nodes) was observed in both the 1 and 12 μm particle inhalational infections (80-85%). Necrotising alveolitis and bronchiolitis were evident in both inhalational infections, however, lung pathology was greater after inhalation of the 1 μm particle aerosol with pronounced involvement of the mediastinal lymph node (50%). Terminal disease was characterized by bacteraemia in both inhalational infections with dissemination to the spleen, liver, kidneys, and thymus. Treatment with co-trimoxazole was more effective than treatment with doxycycline irrespective of the size of the particles inhaled. Doxycycline was more effective against the 12 μm particle inhalational infection as evidenced by increased time to death. However, both treatment regimes exhibited significant relapse when therapy was discontinued with massive enlargement and abscessation of the lungs, spleen, and cervical lymph nodes observed.

Cranial melioidosis presenting as a mass lesion or osteomyelitis

Object

Melioidosis is caused by Burkholderia pseudomallei and causes multiple abscesses in different organs of the body. Cranial melioidosis, although uncommon, is sometimes confused with tuberculosis and is therefore underecognized. The authors report on 6 cases of cranial infections caused by Burkholderia pseudomalleii, presenting as mass lesions or cranial osteomyelitis, and review the literature.

Methods

The authors performed a retrospective review of the records of patients with cranial melioidosis treated at their institution between 1998 and 2005 to determine the presentation, management, and outcome of patients with this infection.

Results

Of the 6 patients diagnosed with cranial melioidosis during this period, 4 had brain abscesses and 2 had cranial osteomyelitis. All patients were treated surgically, and a diagnosis was made on the basis of histopathological studies. All patients were started on antibiotic therapy following surgery and this was continued for 6 months. One patient died soon after stereotactic aspiration of a brain abscess, and the other 5 patients had good outcomes.

Conclusions

Cranial melioidosis is probably more prevalent than has been previously reported. A high index of suspicion, early diagnosis, initiation of appropriate antibiotic therapy and treatment for an adequate period are essential for assuring good outcome in patients with cranial melioidosis. The authors recommend surgery followed by intravenous ceftazidime treatment for 6 weeks and oral cotrimoxazole for 6 months thereafter in patients with cranial melioidosis.

Cerebral melioidosis in Singapore: a review of five cases

A variety of neurological manifestations of infection with Burkholderia pseudomallei have been described including cerebral abscesses, which are a well-recognized form of neurological melioidosis. The optimal antibiotic therapy for this condition has not been defined; however, combinations of intravenous antibiotics are frequently used in the early stages. Five cases of melioidosis involving brain abscesses are described which presented in Singapore over the past 3 years (1997-2000), 4 of which cases had evidence of disseminated infection. Despite profound neurological deficits and low Glasgow Coma Scale scores at presentation in 3 of these cases, all survived after surgical drainage and prolonged courses of intravenous ceftazidime or imipenem, and only 2 of whom had residual neurological impairment. One incidental finding on computed tomography (CT) or magnetic resonance imaging (MRI) scans not described before as an association with cerebral melioidosis was sinusitis in 4 out of the 5 cases.