Melioidosis: the great mimicker

A case report from non-endemic Australia on systemic melioidosis presenting with septic arthritis

Clinical spectrum of melioidosis can vary from a simple skin infection and pneumonia to severe septicaemia with multiorgan failure. Bone involvement in melioidosis is generally low, and the major risk factor is the delay in diagnosing the primary site infection. We present a case of septic arthritis with primary lung melioidosis, whose diagnosis of pulmonary melioidosis was delayed for 5 weeks leading to a septicaemia and septic arthritis. This case highlights the importance of improved clinical awareness among health practitioners and a low threshold for radiological screening of high-risk patients, even in non-endemic areas. It also highlights the fact that having adjunctive open arthrotomy in managing joint infection in melioidosis improves the clinical response to treatment.

Melioidosis - An under-recognized dreaded disease in Southeast Asia

Melioidosis is a disease endemic to India but often goes unrecognized, leading to considerable illness and death. We present the case of a 31-year-old man who had a fever of unknown origin, abnormal renal and liver function tests, and negative tests for dengue, typhoid, leptospirosis, and scrub typhus. Imaging revealed multiple splenic infarcts. Initially suspected to be malaria due to its prevalence in South India, further investigation uncovered pneumonia along with several liver and splenic abscesses, raising the possibility of melioidosis. Blood culture eventually identified Burkholderia pseudomallei, confirming the diagnosis. As malaria cases decline in Southeast Asia, emergency physicians should consider melioidosis in their differential diagnosis of acute febrile illnesses, especially in endemic areas. Early detection and prompt antibiotic treatment are vital for managing this often under-recognized disease with a high fatality rate. Thus, melioidosis should be considered in patients with unexplained fever in endemic regions, as early diagnosis and intervention can be life-saving.

Clinicopathological findings of melioidosis in captive red-legged pademelons (Thylogale stigmatica) in northern Queensland, Australia

BACKGROUND

Melioidosis, caused by Burkholderia pseudomallei, is an important disease that is endemic in areas of northern Australia and can cause a wide range of clinical signs in people and animals. There is limited published data on the disease in marsupials.

CASE REPORT

Two captive red-legged pademelons (Thylogale stigmatica) with collective signs of lethargy, dysphagia and bloody oral discharge were submitted for necropsy and showed variations in pathology findings ranging from multifocal abscessation in various tissues to evidence of fulminant septicaemia. In both cases Burkholderia pseudomallei was confirmed by bacterial culture and qPCR.

CONCLUSION

This report details the first report of melioidosis in captive red-legged pademelons (Thylogale stigmatica) and describes the variations in clinical signs and pathological findings that were encountered with the disease. More research is needed to better understand melioidosis in marsupials to aid clinicians in making a prompt diagnosis.

A molecular epidemiological analysis of Burkholderia pseudomallei in southern Thailand

Melioidosis, a severe bacterial illness caused by Burkholderia pseudomallei, is prevalent in most parts of Thailand, including its southern region situated within the Malay Peninsula. Despite a lower reported incidence rate of melioidosis in the South compared to the Northeast, the mortality rate remains persistently high. This study aimed to better understand the epidemiology and investigate the presence of B. pseudomallei in the natural environment of southern Thailand. Using multi-locus sequence typing (MLST), we characterized B. pseudomallei isolates derived from human cases and compared them with previously reported sequence types (STs) from the same region. A total of 263 clinical isolates retrieved from 156 melioidosis patients between 2014 and 2020 were analyzed, revealing 72 distinct STs, with 25 (35%) matching STs from Finkelstein's environmental isolates collected in southern Thailand during 1964-1967. Notably, strains bearing STs 288, 84, 54, 289, and 46 were frequently found among patients. Additionally, we observed strain diversity with multiple STs in 13 of 59 patients, indicating exposure to various B. pseudomallei genotypes in the environmental sources of the infection. Environmental surveys were conducted in Songkhla Province to detect B. pseudomallei in soil and water samples where local patients lived. Of the 2737 soil samples from 208 locations and 244 water samples from diverse sources, 52 (25%) soil sampling locations and 63 (26%) water sources were cultured positive for B. pseudomallei. Positive soil samples were predominantly found in animal farming area and non-agricultural zones like mountains and grasslands, while water samples were frequently positive in waterfalls, streams, and surface runoffs, with only 9% of rice paddies testing positive. Collectively, a significant proportion of recent melioidosis cases in Songkhla Province can be attributed to known B. pseudomallei STs persisting in the environment for at least the past six decades. Further characterization of B. pseudomallei isolates from recent environment surveys is warranted. These findings illuminate the contemporary landscape of B. pseudomallei infections and their environmental prevalence in southern Thailand, contributing to the regional threat assessment in Thailand and Southeast Asia.

Understanding The Mimicker: Epidemiological Pattern and Determinant of Melioidosis Mortality in Negeri Sembilan, Malaysia

BACKGROUND

Melioidosis, a tropical infectious disease caused by Burkholderia pseudomallei, is epidemic in most region in Southeast Asia with high case fatality. However, there is scanty information regarding the disease's epidemiological pattern, demographics, and underlying risk factors.

METHOD

This 5-year retrospective study of 185 confirmed cases which were taken from the Negeri Sembilan Melioidosis Registry between 2018 and 2022. We aim to describe the incidence, mortality rate, case fatality, relationship with meteorology, and factors that influence mortality in this central region of Peninsular Malaysia.

RESULTS

Incidence rate (IR) of melioidosis in Negeri Sembilan is varied at 1.9 to 5.1 with mean of 3.1 in 100,000 population per year. IR varied between districts in the state from zero to 22.01 in 100,000 population per year. Mortality rate were ranged from 0.17 to 0.74 cases with mean of 0.44 cases in 100,000 population per year. The case fatality rate of this state scattered from 8.70% to 16.67%. There were no significant linear associations between cases and deaths with monthly rainfall and humidity. The mean age of patients was 52.8 years, predominated with age around 41-60 years old. Males (77.8%) predominated, and the majority of cases were Malays (88.9%) and had exposed to soil related activities (74.6%). Mortality from melioidosis was more likely in Bumiputera and non-Malaysians (p<0.05). Patients who had at least one comorbidity were at a higher risk of death from melioidosis (p<0.05). Diabetes mellitus was found in 41.1% of all identified cases, making it a major underlying risk factor for both developing and dying from melioidosis (aOR:19.32, 95%CI:1.91-195.59, p<0.05). Hypertension and mortality status in melioidosis are also significantly correlated (aOR: 7.75, 95% CI: 2.26-26.61, p<0.05).

CONCLUSION

The epidemiological patterns of cases reported from Negeri Sembilan are consistent for the most part from previous studies in other states in Malaysia and global with regard to its incidence, case fatality, demographic and predisposing chronic diseases. Diabetes mellitus and hypertension were significantly linked to increased mortality among all determinants.

Burkholderia pseudomallei Complex Subunit and Glycoconjugate Vaccines and Their Potential to Elicit Cross-Protection to Burkholderia cepacia Complex

Burkholderia are a group of Gram-negative bacteria that can cause a variety of diseases in at-risk populations. B. pseudomallei and B. mallei, the etiological agents of melioidosis and glanders, respectively, are the two clinically relevant members of the B. pseudomallei complex (Bpc). The development of vaccines against Bpc species has been accelerated in recent years, resulting in numerous promising subunits and glycoconjugate vaccines incorporating a variety of antigens. However, a second group of pathogenic Burkholderia species exists known as the Burkholderia cepacia complex (Bcc), a group of opportunistic bacteria which tend to affect individuals with weakened immunity or cystic fibrosis. To date, there have been few attempts to develop vaccines to Bcc species. Therefore, the primary goal of this review is to provide a broad overview of the various subunit antigens that have been tested in Bpc species, their protective efficacy, study limitations, and known or suspected mechanisms of protection. Then, we assess the reviewed Bpc antigens for their amino acid sequence conservation to homologous proteins found in Bcc species. We propose that protective Bpc antigens with a high degree of Bpc-to-Bcc sequence conservation could serve as components of a pan-Burkholderia vaccine capable of protecting against both disease-causing groups.

Synchronous detection of Burkholderia pseudomallei and its ceftazidime resistance mutation based on RNase-HII hydrolysis combined with lateral flow strip assay

IMPORTANCE

This study focused on the development of a reaction system using rhPCR to amplify a specific gene, ORF2, of B. pseudomallei and to identify the P174L mutation associated with increased drug resistance to ceftazidime (CAZ). The system incorporated universal primer probes and a simple temperature cycle reaction. The amplified products were then analyzed using lateral flow strip assay (LFSA) for strain identification and mutation interpretation. The developed system provides a reliable basis for diagnosing melioidosis and selecting appropriate drugs. Its potential impact is particularly significant in resource-limited settings where access to advanced diagnostic techniques is limited. This platform stands out for its simplicity, convenience, sensitivity, specificity, and portability. It shows promise as a point-of-care testing method for detecting single nucleotide polymorphism in genes associated with other diseases. By leveraging the advantages of this platform, researchers and healthcare professionals can potentially expand its use beyond melioidosis and apply it to the rapid detection of genetic variations in other disease-related genes.

Travel-associated melioidosis: a narrative review

BACKGROUND

Melioidosis, caused by Burkholderia pseudomallei, may be considered a neglected tropical disease that remains underdiagnosed in many geographical areas. Travellers can act as the sentinels of disease activity, and data from imported cases may help complete the global map of melioidosis.

METHODS

A literature search for imported melioidosis for the period 2016-22 was performed in PubMed and Google Scholar.

RESULTS

In total, 137 reports of melioidosis associated with travel were identified. The majority were males (71%) and associated with exposure in Asia (77%) (mainly Thailand, 41%, and India, 9%). A minority acquired the infection in the Americas-Caribbean area (6%), Africa (5%) and Oceania (2%). The most frequent comorbidity was diabetes mellitus (25%) followed by underlying pulmonary, liver or renal disease (8, 5 and 3%, respectively). Alcohol/tobacco use were noted for seven and six patients, respectively (5%). Five patients (4%) had associated non-human immunodeficiency virus (HIV)-related immunosuppression, and three patients (2%) had HIV infection. One patient (0.8%) had concomitant coronavirus disease 19. A proportion (27%) had no underlying diseases. The most frequent clinical presentations included pneumonia (35%), sepsis (30%) and skin/soft tissue infections (14%). Most developed symptoms <1 week after return (55%), and 29% developed symptoms >12 weeks after. Ceftazidime and meropenem were the main treatments used during the intensive intravenous phase (52 and 41% of patients, respectively) and the majority (82%) received co-trimoxazole alone/combination, for the eradication phase. Most patients had a favourable outcome/survived (87%). The search also retrieved cases in imported animals or cases secondary to imported commercial products.

CONCLUSIONS

As post-pandemic travel soars, health professionals should be aware of the possibility of imported melioidosis with its diverse presentations. Currently, no licensed vaccine is available, so prevention in travellers should focus on protective measures (avoiding contact with soil/stagnant water in endemic areas). Biological samples from suspected cases require processing in biosafety level 3 facilities.

Acute Pneumonia Like Illness and Sepsis in India: Is it Time to Suspect Pulmonary Melioidosis?

This article describes a case of melioidosis, a severe and potentially fatal disease caused by the Gram-negative bacillus Burkholderia pseudomallei, in a 55-year-old female in India. The disease is endemic in Southeast Asia and Northern Australia. Recently there has been an increased number of cases reported in India. The source of B. pseudomallei in India is thought to be soil and water, with the most common mode of infection being through skin contact. The clinical presentation of melioidosis in India varies greatly, making diagnosis difficult. The case presented here with a history of acute febrile illness and progressive dyspnoea, with clinical worsening leading to intensive care unit (ICU) care. We managed this acute pneumonia-like melioidosis with antibiotics and supportive care which showed rapid recovery at follow-up. This case highlights the need for a high index of suspicion and increased awareness of early diagnosis of melioidosis in the Indian subcontinent to improve the patient.

A mathematical model analysis of the human melioidosis transmission dynamics with an asymptomatic case

In this paper, we develop and examine a mathematical model of human melioidosis transmission with asymptomatic cases to describe the dynamics of the epidemic. The basic reproduction number ( R 0 ) of the model is obtained. Disease-free equilibrium of the model is proven to be globally asymptotically stable whenR 0 is less than the unity, while the endemic equilibrium of the model is shown to be locally asymptotically stable ifR 0 is greater than unity. Sensitivity analysis is performed to illustrate the effect of the model parameters influencing on the disease dynamics. Furthermore, numerical experiments of the model are conducted to validate the theoretical findings.

A novel lytic phage potentially effective for phage therapy against Burkholderia pseudomallei in the tropics

Background

Burkholderia pseudomallei is a tropical pathogen that causes melioidosis. Its intrinsic drug-resistance is a leading cause of treatment failure, and the few available antibiotics require prolonged use to be effective. This study aimed to assess the clinical potential of B. pseudomallei phages isolated from Hainan, China.

Methods

Burkholderia pseudomallei strain (HNBP001) was used as the isolation host, and phages were recovered from domestic environmental sources, which were submitted to the host range determination, lytic property assays, and stability tests. The best candidate was examined via the transmission electron microscope for classification. With its genome sequenced and analyzed, its protective efficacy against B. pseudomallei infection in A549 cells and Caenorhabditis elegans was evaluated, in which cell viability and survival rates were compared using the one-way ANOVA method and the log-rank test.

Results

A phage able to lyse 24/25 clinical isolates was recovered. It was classified in the Podoviridae family and was found to be amenable to propagation. Under the optimal multiplicity of infection (MOI) of 0.1, an eclipse period of around 20 min and a high titer (10¹² PFU/ml) produced within 1 h were demonstrated. This phage was found stabile at a wide range of temperatures (24, 37, 40, 50, and 60 °C) and pH values (3–12). After being designated as vB_BpP_HN01, it was fully sequenced, and the 71,398 bp linear genome, containing 93 open reading frames and a tRNA-Asn, displayed a low sequence similarity with known viruses. Additionally, protective effects of applications of vB_BpP_HN01 (MOI = 0.1 and MOI = 1) alone or in combination with antibiotics were found to improve viability of infected cells (70.6 ± 6.8%, 85.8 ± 5.7%, 91.9 ± 1.8%, and 96.8 ± 1.8%, respectively). A significantly reduced mortality (10%) and a decreased pathogen load were demonstrated in infected C. elegans following the addition of this phage.

Conclusions

As the first B. pseudomallei phage was isolated in Hainan, China, phage vB_BpP_HN01 was characterized by promising lytic property, stability, and efficiency of bacterial elimination during the in vitro/vivo experiments. Therefore, we can conclude that it is a potential alternative agent for combating melioidosis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s40249-022-01012-9.

Andrographolide stabilized-silver nanoparticles overcome ceftazidime-resistant Burkholderia pseudomallei: study of antimicrobial activity and mode of action

Burkholderia pseudomallei (B. pseudomallei) is a Gram-negative pathogen that causes melioidosis, a deadly but neglected tropical disease. B. pseudomallei is intrinsically resistant to a growing list of antibiotics, and alternative antimicrobial agents are being sought with urgency. In this study, we synthesize andrographolide-stabilized silver nanoparticles (andro-AgNPs, spherically shaped with 16 nm average diameter) that show excellent antimicrobial activity against B. pseudomallei, including ceftazidime-resistant strains, being 1-3 orders of magnitude more effective than ceftazidime and 1-2 orders of magnitude more effective than other green-synthesized AgNPs. The andro-AgNPs are meanwhile non-toxic to mammalian cell lines. The mode of action of Andro-AgNPs toward B. pseudomallei is unraveled by killing kinetics, membrane neutralization, silver ions (Ag+) release, reactive oxygen species (ROS) induction, membrane integrity, and cell morphology change studies. The antimicrobial activity and mode of action of andro-AgNPs against B. pseudomallei reported here may pave the way to alternative treatments for melioidosis.

Clinical, Epidemiological and Microbiological Profile of A Potentially Pathogenic Environmental Saprophyte, Burkholderia pseudomallei; at A Tertiary Care Hospital in Coastal India

Melioidosis is a severe systemic infectious disease caused by Burkholderia pseudomallei, a gram-negative bacillus with bipolar staining. It is an environmental saprophyte endemic to Southeast Asia and Northern Australia. The disease can have varying manifestations. This is a retrospective study of the clinical and microbiological profile of culture-proven cases of melioidosis who presented to a tertiary care hospital in Coastal Karnataka between January 2018 and December 2020. The epidemiological, demographic, clinical and laboratory characteristics were studied and analyzed. A total of 27 cases were seen during the study period. All patients were from the western coastal areas of India. Fever was the most common presenting complaint. Analysis of the clinical manifestations showed 11 (40.74%) with bacteremia. Pneumonia was the most common primary clinical presentation with 11 cases (40.74%). 9 (33.3%) patients had an abscess in some part of the body on presentation. Secondary foci were seen in 5 (18.5%) patients. The prominent risk factors seen were history of type 2 diabetes mellitus, age >40 years, alcoholism and smoking. 13 (48.15%) were started with the treatment regimen for melioidosis. Only 8 (29.63%) were prescribed the eradication treatment regimen. One case which was inadequately treated came back with reactivation of melioidosis. Varied clinical presentation of melioidosis makes the specific clinical diagnosis difficult. Due to the high mortality and morbidity rate, early diagnosis and prompt management is warranted, this requires clinical vigilance and an intensive microbiological workup. Lack of adherence to the treatment protocol can lead to reactivation.

Monoclonal Antibodies Opsonize Burkholderia spp. and Reduce Intracellular Actin Tail Formation in a Macrophage Infection Assay

Melioidosis is a neglected tropical disease caused by the bacterium Burkholderia pseudomallei. The bacterium is intrinsically resistant to various antibiotics, and melioidosis is therefore difficult to treat successfully without a relapse in infection. B. pseudomallei is an intracellular pathogen and therefore, to eradicate the infection, antimicrobials must be able to access bacteria in an intracellular niche. This study assessed the ability of a panel of monoclonal antibodies (MAbs) to opsonize Burkholderia species and determine the effect that each antibody has on bacterial virulence in vitro. Murine macrophage infection assays demonstrated that monoclonal antibodies against the capsule of B. pseudomallei are opsonizing. Furthermore, one of these monoclonal antibodies reduced bacterial actin tail formation in our in vitro assays, indicating that antibodies could reduce the intracellular spread of Burkholderia thailandensis. The data presented in this paper demonstrate that monoclonal antibodies are opsonizing and can decrease bacterial actin tail formation, thus decreasing their intracellular spread. These data have informed selection of an antibody for development of an antibody-antibiotic conjugate (AAC) for melioidosis.

IMPORTANCE Melioidosis is difficult to treat successfully due to the causal bacterium being resistant to many classes of antibiotics, therefore limiting available therapeutic options. New and improved therapies are urgently required to treat this disease. Here, we have investigated the potential of monoclonal antibodies to target this intracellular pathogen. We have demonstrated that monoclonal antibodies can target the bacterium, increase uptake into macrophages, and reduce actin tail formation required by the bacterium for spread between cells. Through targeting the bacterium with antibodies, we hope to disarm the pathogen, reducing the spread of infection. Ultimately, we aim to use an opsonizing antibody to deliver antibiotics intracellularly by developing an antibody-antibiotic conjugate therapeutic for melioidosis.

Evaluation of four sampling devices for Burkholderia pseudomallei laboratory aerosol studies

Previous field and laboratory studies investigating airborne Burkholderia pseudomallei have used a variety of different aerosol samplers to detect and quantify concentrations of the bacteria in aerosols. However, the performance of aerosol samplers can vary in their ability to preserve the viability of collected microorganisms, depending on the resistance of the organisms to impaction, desiccation, or other stresses associated with the sampling process. Consequently, sampler selection is critical to maximizing the probability of detecting viable microorganisms in collected air samples in field studies and for accurate determination of aerosol concentrations in laboratory studies. To inform such decisions, the present study assessed the performance of four laboratory aerosol samplers, specifically the all-glass impinger (AGI), gelatin filter, midget impinger, and Mercer cascade impactor, for collecting aerosols containing B. pseudomallei generated from suspensions in two types of culture media. The results suggest that the relative performance of the sampling devices is dependent on the suspension medium utilized for aerosolization. Performance across the four samplers was similar for aerosols generated from suspensions supplemented with 4% glycerol. However, for aerosols generated from suspensions without glycerol, use of the filter sampler or an impactor resulted in significantly lower estimates of the viable aerosol concentration than those obtained with either the AGI or midget impinger. These results demonstrate that sampler selection has the potential to affect estimation of doses in inhalational animal models of melioidosis, as well as the likelihood of detection of viable B. pseudomallei in the environment, and will be useful to inform design of future laboratory and field studies.

A Young Diabetic Patient With Sepsis After Gardening

We report a case of soft tissue infection, sepsis, and bacteremia due to Burkholderia pseudomallei (melioidosis) in a diabetic young patient and the genomic characterization of Burkholderia pseudomallei isolate (COL-5428).

Melioidosis in the Philippines

The first documented case of melioidosis in the Philippines occurred in 1948. Since then, there have been sporadic reports in the literature about travelers diagnosed with melioidosis after returning from the Philippines. Indigenous cases, however, have been documented rarely, and under-reporting is highly likely. This review collated all Philippine cases of melioidosis published internationally and locally, as well as unpublished case series and reports from different tertiary hospitals in the Philippines. In total, 25 papers and 41 cases were identified. Among these, 23 were indigenous cases (of which 20 have not been previously reported in the literature). The most common co-morbidity present was diabetes mellitus, and the most common presentations were pulmonary and soft tissue infections. Most of the cases received ceftazidime during the intensive phase, while trimethoprim-sulfamethoxazole was given during the eradication phase. The known mortality rate was 14.6%, while 4.9% of all cases were reported to have had recurrence. The true burden of melioidosis in the country is not well defined. A lack of awareness among clinicians, a dearth of adequate laboratories, and the absence of a surveillance system for the disease are major challenges in determining the magnitude of the problem.

A case report: Splenic abscess caused by Burkholderia pseudomallei

RATIONALE

Melioidosis is an emerging infectious disease caused by Burkholderia pseudomallei. To our knowledge, there have been very few cases of splenic abscesses due to melioidosis in Hainan, China.

PATIENT CONCERNS

The patient was a 55-year-old male farmer, who was admitted in our hospital with persistent left epigastric dull pain accompanied by chills and febrile. One month before, the patient presented with persistent abdominal pain. After received anti-infection therapy, the subjective symptoms eased slightly, but recently he suffered from intermittent abdominal pain again.

DIAGNOSES

Bacteria isolated from splenic pus were identified as B. pseudomallei by the Phoenix-100 system and indirect immunofluorescence.

INTERVENTIONS

The patient was treated by surgical excision and anti-infection therapy.

OUTCOMES

The patient was then treated with intravenous ceftazidime and oral trimethoprim-sulfamethoxazole for 2 weeks and his clinical symptoms improved.

LESSONS

In endemic areas, B. pseudomallei should be considered as a causative organism of splenic abscess in patients with established risk factors. The isolation of B. pseudomallei from abscess sites is crucial to improve clinical outcomes by appropriate antimicrobial therapy coupled with surgical drainage.