Global burden of melioidosis in 2015: a systematic review and data synthesis

Comprehensive approaches for the detection of Burkholderia pseudomallei and diagnosis of melioidosis in human and environmental samples

Melioidosis is endemic in Southeast Asia and northern Australia. The causative agent of melioidosis is a Gram-negative bacterium, Burkholderia pseudomallei. Its invasion can be fatal if melioidosis is not treated promptly. It is intrinsically resistant to a variety of antibiotics. In this paper, we present a comprehensive overview of the current trends on melioidosis cases, treatments, B. pseudomallei virulence factors, and molecular techniques to detect the bacterium from different samples. The clinical and microbial diagnosis methods of identification and detection of B. pseudomallei are commonly used for the rapid diagnosis and typing of strains, such as polymerase chain reaction or multi-locus sequence typing. The genotyping strategies and techniques have been constantly evolving to identify genomic loci linked to or associated with this human disease. More research strategies for detecting and controlling melioidosis should be encouraged and conducted to understand the current situation. In conclusion, we review existing diagnostic methodologies for melioidosis detection and provide insights on prospective diagnostic methods for the bacterium.

Drivers of melioidosis endemicity: epidemiological transition, zoonosis, and climate change

PURPOSE OF REVIEW

Melioidosis, caused by the soil-dwelling bacterium Burkholderia pseudomallei, is a tropical infection associated with high morbidity and mortality. This review summarizes current insights into melioidosis' endemicity, focusing on epidemiological transitions, zoonosis, and climate change.

RECENT FINDINGS

Estimates of the global burden of melioidosis affirm the significance of hot-spots in Australia and Thailand. However, it also highlights the paucity of systematic data from South Asia, The Americas, and Africa. Globally, the growing incidence of diabetes, chronic renal and (alcoholic) liver diseases further increase the susceptibility of individuals to B. pseudomallei infection. Recent outbreaks in nonendemic regions have further exposed the hazard from the trade of animals and products as potential reservoirs for B. pseudomallei. Lastly, global warming will increase precipitation, severe weather events, soil salinity and anthrosol, all associated with the occurrence of B. pseudomallei.

SUMMARY

Epidemiological transitions, zoonotic hazards, and climate change are all contributing to the emergence of novel melioidosis-endemic areas. The adoption of the One Health approach involving multidisciplinary collaboration is important in unraveling the real incidence of B. pseudomallei, as well as reducing the spread and associated mortality.

Distribution of Burkholderia pseudomallei within a 300-cm deep soil profile: implications for environmental sampling

The environmental distribution of Burkholderia pseudomallei, the causative agent of melioidosis, remains poorly understood. B. pseudomallei is known to have the ability to occupy a variety of environmental niches, particularly in soil. This paper provides novel information about a putative association of soil biogeochemical heterogeneity and the vertical distribution of B. pseudomallei. We investigated (1) the distribution of B. pseudomallei along a 300-cm deep soil profile together with the variation of a range of soil physico-chemical properties; (2) whether correlations between the distribution of B. pseudomallei and soil physico-chemical properties exist and (3) when they exist, what such correlations indicate with regards to the environmental conditions conducive to the occurrence of B. pseudomallei in soils. Unexpectedly, the highest concentrations of B. pseudomallei were observed between 100 and 200 cm below the soil surface. Our results indicate that unravelling the environmental conditions favorable to B. pseudomallei entails considering many aspects of the actual complexity of soil. Important recommendations regarding environmental sampling for B. pseudomallei can be drawn from this work, in particular that collecting samples down to the water table is of foremost importance, as groundwater persistence appears to be a controlling factor of the occurrence of B. pseudomallei in soil.

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

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

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

Comparative evaluation of Panther Fusion and real-time PCR for detection of Burkholderia pseudomallei in spiked human blood

Introduction. Melioidosis is an infection that most commonly presents with bacteraemia. Culture-based laboratory methods can result in a significant delay to organism identification. Molecular diagnostic techniques have a high sensitivity and rapid time to diagnosis. A decreased time to diagnosis is likely to improve patient outcomes.

Aim. To compare the Panther Fusion automated molecular instrument to an in-house method for the detection of Burkholderia pseudomallei directly from spiked human whole-blood samples.

Results. The in-house method detected 11/12 (92 %) samples with a B. pseudomallei concentration of 2.5–4.5×10² c.f.u. ml⁻¹. The Panther was less reliable, detecting only 8/14 (75 %) samples with a similar bacterial concentration. The Panther was able to detect 12/12 (100 %) spiked blood culture-positive samples.

Conclusion. The direct detection of B. pseudomallei from patient blood on presentation to a healthcare facility will significantly decrease time to diagnosis. We describe an in-house real-time PCR method with the lowest reported limit of detection to date. Due to lower sensitivity, the Panther Fusion would be best used as a diagnostic method directly from a positive blood culture.

Role of Extracellular Trap Release During Bacterial and Viral Infection

Neutrophils are innate immune cells that play an essential role during the clearance of pathogens that can release chromatin structures coated by several cytoplasmatic and granular antibacterial proteins, called neutrophil extracellular traps (NETs). These supra-molecular structures are produced to kill or immobilize several types of microorganisms, including bacteria and viruses. The contribution of the NET release process (or NETosis) to acute inflammation or the prevention of pathogen spreading depends on the specific microorganism involved in triggering this response. Furthermore, studies highlight the role of innate cells different from neutrophils in triggering the release of extracellular traps during bacterial infection. This review summarizes the contribution of NETs during bacterial and viral infections, explaining the molecular mechanisms involved in their formation and the relationship with different components of such pathogens.

Melioidosis in Africa: Time to Raise Awareness and Build Capacity for Its Detection, Diagnosis, and Treatment

Melioidosis is a tropical infectious disease caused by the soil-dwelling bacterium Burkholderia pseudomallei with a mortality of up to 50% in low resource settings. Only a few cases have been reported from African countries. However, studies on the global burden of melioidosis showed that Africa holds a significant unrecognized disease burden, with Nigeria being at the top of the list. The first World Health Organization African Melioidosis Workshop was organized in Lagos, Nigeria, with representatives of health authorities, microbiology laboratories, and clinical centers from across the continent. Dedicated hands-on training was given on laboratory diagnostics of B. pseudomallei. This report summarises the meeting objectives, including raising awareness of melioidosis and building capacity for the detection, diagnosis, biosafety, treatment, and prevention across Africa. Further, collaboration with regional and international experts provided a platform for sharing ideas on best practices.

Risk factors for melioidosis in Udupi District, Karnataka, India, January 2017-July 2018

We initiated an epidemiological investigation following the death of a previously healthy 17 year-old boy with neuro-melioidosis. A case was defined as a culture-confirmed melioidosis patient from Udupi district admitted to hospital A from January 2013-July 2018. For the case control study, we enrolled a subset of cases admitted to hospital A from January 2017- July 2018. A control was resident of Udupi district admitted to hospital A in July 2018 with a non-infectious condition. Using a matched case-control design, we compared each case to 3 controls using age and sex groups. We assessed for risk factors related to water storage, activities of daily living, injuries and environmental exposures (three months prior to hospitalization), using conditional regression analysis. We identified 50 cases with case fatality rate 16%. Uncontrolled diabetes mellitus was present in 84% cases and 66% of cases occurred between May and October (rainy season). Percutaneous inoculation through exposure to stagnant water and injury leading to breakage in the skin were identified as an important mode of transmission. We used these findings to develop a surveillance case definition and initiated training of the district laboratory for melioidosis diagnosis.

Hyponatremia in melioidosis: Analysis of 10-year data from a hospital-based registry

Introduction:

Methods:

Results:

Conclusion:

In vitro susceptibility of Burkholderia pseudomallei isolates from Thai patients to ceftolozane/tazobactam and ceftazidime/avibactam

Treatment options are limited for melioidosis patients who develop nosocomial infection from extensively drug-resistant (XDR) gram-negative bacilli. Ceftolozane/tazobactam (C/T) and ceftazidime/avibactam (CZA), which have activity against XDR gram-negative bacteria, are two potential options. Data regarding the susceptibility of B. pseudomallei to these agents are limited, especially from Thailand, which is an endemic area for melioidosis. A total of 28 B. pseudomallei isolates from melioidosis patients in northeast Thailand were tested for susceptibility to C/T and CZA using the E-test and disk diffusion test. Minimal inhibitory concentrations (MICs) for other antibiotics commonly used in melioidosis, including trimethoprim/sulfamethoxazole (SXT), ceftazidime (CAZ), imipenem (IPM), and meropenem, were also ascertained. The MIC of C/T was very low in all isolates, ranging from 0.75 to 1.0 µg/mL. For CZA, wide inhibitory zones ranging from 34 to 35 mm and MICs at 0.5 µg/mL were found. All isolates were also susceptible to SXT, CAZ, and IPM based on CLSI breakpoints. C/T and CZA exhibited excellent in vitro activity against B. pseudomallei. Further studies are required to prove efficacy in human subjects.

BpOmpW Antigen Stimulates the Necessary Protective T-Cell Responses Against Melioidosis

Melioidosis is a potentially fatal bacterial disease caused by Burkholderia pseudomallei and is estimated to cause 89,000 deaths per year in endemic areas of Southeast Asia and Northern Australia. People with diabetes mellitus are most at risk of melioidosis, with a 12-fold increased susceptibility for severe disease. Interferon gamma (IFN-γ) responses from CD4 and CD8 T cells, but also from natural killer (NK) and natural killer T (NKT) cells, are necessary to eliminate the pathogen. We previously reported that immunization with B. pseudomallei OmpW (BpOmpW antigen) protected mice from lethal B. pseudomallei challenge for up to 81 days. Elucidating the immune correlates of protection of the protective BpOmpW vaccine is an essential step prior to clinical trials. Thus, we immunized either non-insulin-resistant C57BL/6J mice or an insulin-resistant C57BL/6J mouse model of type 2 diabetes (T2D) with a single dose of BpOmpW. BpOmpW induced strong antibody responses, stimulated effector CD4+ and CD8+ T cells and CD4+ CD25+ Foxp3+ regulatory T cells, and produced higher IFN-γ responses in CD4+, CD8+, NK, and NKT cells in non-insulin-resistant mice. The T-cell responses of insulin-resistant mice to BpOmpW were comparable to those of non-insulin-resistant mice. In addition, as a precursor to its evaluation in human studies, humanized HLA-DR and HLA-DQ (human leukocyte antigen DR and DQ isotypes, respectively) transgenic mice elicited IFN-γ recall responses in an enzyme-linked immune absorbent spot (ELISpot)-based study. Moreover, human donor peripheral blood mononuclear cells (PBMCs) exposed to BpOmpW for 7 days showed T-cell proliferation. Finally, plasma from melioidosis survivors with diabetes recognized our BpOmpW vaccine antigen. Overall, the range of approaches used strongly indicated that BpOmpW elicits the necessary immune responses to combat melioidosis and bring this vaccine closer to clinical trials.

Acute kidney injury and its outcomes in melioidosis

BACKGROUND

Melioidosis is a potentially fatal tropical infection caused by Burkholderia pseudomallei. Kidney involvement is possible, but has not been well described.

AIM

This study aimed to assess the risk of acute kidney injury (AKI) and its outcomes in melioidosis.

METHODS

A retrospective observational cohort study was performed. Case records of consecutive patients with culture-confirmed melioidosis, observed from January 1st, 2012 through December 31st, 2019 were analysed for demographics, presence of comorbidities, including chronic kidney disease (CKD), diabetes mellitus (DM), and presence of bacteraemia, sepsis, shock, AKI, and urinary abnormalities. The outcomes we studied were: mortality, need for hospitalisation in an intensive care unit (ICU), duration of hospitalization. We then compared the outcomes between patients with and without AKI.

RESULTS

Of 164 patients, AKI was observed in 59 (35.98%), and haemodialysis was required in eight (13.56%). In the univariate analysis, AKI was associated with CKD (OR 5.83; CI 1.140-29.90, P = 0.03), bacteraemia (OR 8.82; CI 3.67-21.22, P < 0.001) and shock (OR 3.75; CI 1.63-8.65, P = 0.04). In the multivariate analysis, CKD (adjusted OR 10.68; 95% CI 1.66-68.77; P = 0.013) and bacteraemia (adjusted OR 8.22; 95% CI 3.15-21.47, P < 0.001) predicted AKI. AKI was associated with a greater need for ICU care (37.3% vs. 13.3%, P = 0.001), and mortality (32.2% vs. 5.7%, P < 0.001). Mortality increased with increasing AKI stage, i.e. stage 1 (OR 3.52, CI 0.9-13.7, P = 0.07), stage 2 (OR 6.79, CI 1.92-24, P = 0.002) and stage 3 (OR 17.8, CI 5.05-62.8, P < 0.001), however kidney function recovered in survivors. Hyponatremia was observed in 138 patients (84.15%) and isolated urinary abnormalities were seen in 31(18.9%).

CONCLUSIONS

AKI is frequent in melioidosis and occurred in 35.9% of our cases. Hyponatremia is likewise common. AKI was predicted by bacteraemia and CKD, and was associated with higher mortality and need for ICU care; however kidney function recovery was observed in survivors.

Predictive and Experimental Immunogenicity of Burkholderia Collagen-like Protein 8-Derived Antigens

Burkholderia pseudomallei is an infectious bacterium of clinical and biodefense concern, and is the causative agent of melioidosis. The mortality rate can reach up to 50% and affects 165,000 people per year; however, there is currently no vaccine available. In this study, we examine the antigen-specific immune response to a vaccine formulated with antigens derived from an outer membrane protein in B. pseudomallei, Bucl8. Here, we employed a number of bioinformatic tools to predict Bucl8-derived epitopes that are non-allergenic and non-toxic, but would elicit an immune response. From these data, we formulated a vaccine based on two extracellular components of Bucl8, the β-barrel loops and extended collagen and non-collagen domains. Outbred CD-1 mice were immunized with vaccine formulations—composed of recombinant proteins or conjugated synthetic peptides with adjuvant—to assess the antigen-specific immune responses in mouse sera and lymphoid organs. We found that mice vaccinated with either Bucl8-derived components generated a robust TH2-skewed antibody response when antigen was combined with the adjuvant AddaVax, while the TH1 response was limited. Mice immunized with synthetic loop peptides had a stronger, more consistent antibody response than recombinant protein antigens, based on higher IgG titers and recognition of bacteria. We then compared peptide-based vaccines in an established C57BL/6 inbred mouse model and observed a similar TH2-skewed response. The resulting formulations will be applied in future studies examining the protection of Bucl8-derived vaccines.

Observational study of adult respiratory infections in primary care clinics in Myanmar: understanding the burden of melioidosis, tuberculosis and other infections not covered by empirical treatment regimes

BACKGROUND

Lower respiratory infections constitute a major disease burden worldwide. Treatment is usually empiric and targeted towards typical bacterial pathogens. Understanding the prevalence of pathogens not covered by empirical treatment is important to improve diagnostic and treatment algorithms.

METHODS

A prospective observational study in peri-urban communities of Yangon, Myanmar was conducted between July 2018 and April 2019. Sputum specimens of 299 adults presenting with fever and productive cough were tested for Mycobacterium tuberculosis (microscopy and GeneXpert MTB/RIF [Mycobacterium tuberculosis/resistance to rifampicin]) and Burkholderia pseudomallei (Active Melioidosis Detect Lateral Flow Assay and culture). Nasopharyngeal swabs underwent respiratory virus (influenza A, B, respiratory syncytial virus) polymerase chain reaction testing.

RESULTS

Among 299 patients, 32% (95% confidence interval [CI] 26 to 37) were diagnosed with tuberculosis (TB), including 9 rifampicin-resistant cases. TB patients presented with a longer duration of fever (median 14 d) and productive cough (median 30 d) than non-TB patients (median fever duration 6 d, cough 7 d). One case of melioidosis pneumonia was detected by rapid test and confirmed by culture. Respiratory viruses were detected in 16% (95% CI 12 to 21) of patients.

CONCLUSIONS

TB was very common in this population, suggesting that microscopy and GeneXpert MTB/RIF on all sputum samples should be routinely included in diagnostic algorithms for fever and cough. Melioidosis was uncommon in this population.

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

BACKGROUND

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

METHODS

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

FINDINGS

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

INTERPRETATION

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

FUNDING

The Australian National Health and Medical Research Council.

A, Surendran S, Pradeep M, Rajendran A, Suju G, Ashok A. Risk Factors for Mortality in Melioidosis: A Single-Centre, 10-Year Retrospective Cohort Study

Melioidosis is a tropical infectious disease with diverse clinical presentations. We aimed to investigate the characteristics and mortality risk factors of patients diagnosed with melioidosis in the past 10 years. This was a retrospective cohort study conducted at a quaternary care centre in South India. Clinical, demographic, and biochemical data in patients diagnosed with melioidosis with cultures were collected between January 2011 and December 2020 from medical records. Logistic regression analysis was performed to screen mortality risk factors of melioidosis in addition to descriptive statistics and chi-square analysis. Seventy-three melioidosis patients' records were analysed, and the most common comorbidity was type 2 diabetes mellitus (n = 53, 72.6%). The patients showed diverse presentations: pulmonary involvement, 30 (41.1%); splenomegaly, 29 (39.7%); abscesses and cutaneous involvement, 18 (24.7%); lymph node, 10 (13.7%); arthritis and osteomyelitis, 9 (12.3%); and genitourinary infection, 4 (5.4%). The mortality was noted to be 15 (20.5%). Logistic regression analysis indicated that chronic kidney disease (OR = 14.0), CRP >100 IU/L (OR = 6.964), and S. albumin <3 gm/dl (OR = 8.0) were risk factors associated with mortality and can guide in risk stratification. Hypoalbuminemia is a novel mortality risk factor, detected in this study, and requires further investigation to validate its utility as a prognostic marker and reveal possible therapeutic benefits in clinical correction.

Ending the Neglect of Treatable Bacterial Zoonoses Responsible for Non-Malaria Fevers

Bacterial zoonotic diseases such as leptospirosis, Q fever, melioidosis, spotted fever group rickettsioses, and brucellosis are increasingly recognized causes of non-malaria acute fevers. However, though readily treatable with antibiotics, these diseases are commonly misdiagnosed resulting in poor outcomes in patients. There is a considerable deficit in the understanding of basic aspects of the epidemiology of these neglected diseases and diagnostic tests for these zoonotic bacterial pathogens are not always available in resource-poor settings. Raising awareness about these emerging bacterial zoonoses is directly beneficial to the patients by allowing a test-and-treat approach and is essential to control these life-threatening diseases.

Enhanced melioidosis surveillance in patients attending four tertiary hospitals in Yangon, Myanmar

To investigate the current epidemiology of melioidosis in Yangon, Myanmar, between June 2017 and May 2019 we conducted enhanced surveillance for melioidosis in four tertiary hospitals in Yangon, where the disease was first discovered in 1911. Oxidase-positive Gram-negative rods were obtained from the microbiology laboratories and further analysed at the Department of Medical Research. Analysis included culture on Ashdown agar, the three disc sensitivity test (gentamicin, colistin and co-amoxiclav), latex agglutination, API 20 NE, antibiotic susceptibility testing, and a subset underwent molecular confirmation with a Burkholderia pseudomallei specific assay. Twenty one of 364 isolates (5.7%) were confirmed as B. pseudomallei and were mostly susceptible to the antibiotics used in standard therapy for melioidosis. Ten patients were from Yangon Region, nine were from Ayeyarwaddy region, and one each was from Kayin and Rakhine States. A history of soil contact was given by seven patients, five had diabetes mellitus and one had renal insufficiency. The patients presented with septicaemia (12 cases), pneumonia (three cases), urinary tract infection (two cases) and wound infection (four cases). Eighteen patients survived to hospital discharge. This study highlights the likelihood that melioidosis may be far more common, but underdiagnosed, in more rural parts of Myanmar as in other countries in SE Asia.

The Clinical Efficiency and the Mechanism of Sanzi Yangqin Decoction for Chronic Obstructive Pulmonary Disease

This work is carried out to evaluate the clinical efficacy of Sanzi Yangqin decoction (SZYQD) treating chronic obstructive pulmonary disease (COPD) and to analyze its mechanism. The clinical efficacy of SZYQD treating COPD was evaluated by meta-analysis, and its mechanism was analyzed by network pharmacology. Molecular docking validation of the main active compounds and the core targets was performed by AutoDock vina software. A cigarette smoke (CS) and LPS-induced COPD model in ICR mice was constructed to confirm the effects of luteolin on COPD. Results showed that SZYQD has a greater benefit on the total effect (OR = 3.85, 95% CI [3.07, 4.83], P=1) in the trial group compared with the control group. The percentage of forced expiratory volume in one second (FEV1%) (MD = 0.5, 95% CI [0.41, 0.59], P < 0.00001) and first seconds breathing volume percentage of forced vital capacity (FEV1%/FVC) were improved (MD = 5.97, 95% CI [3.23, 8.71], P < 0.00001). There are 27 compounds in SZYQD targeting 104 disease targets related to COPD. PPI network analysis indicated that EGFR, MMP9, PTGS2, MMP2, APP, and ERBB2 may be the core targets for the treatment of COPD. Molecular docking demonstrated that luteolin in SZYQD showed the strongest binding activity to core targets. Experimental results revealed that the expression of COPD-related targets in lung tissue was significantly increased in the COPD group and was improved in the luteolin group. Our data indicated that SZYQD has a curative effect on COPD and luteolin is a candidate compound for COPD treatment by regulating EGFR, MMP9, PTGS2, MMP2, APP, and ERBB2.

Geographical distribution of Burkholderia pseudomallei in soil in Myanmar

BACKGROUND

Burkholderia pseudomallei is a Gram-negative bacterium found in soil and water in many tropical countries. It causes melioidosis, a potentially fatal infection first described in 1911 in Myanmar. Melioidosis is a common cause of sepsis and death in South and South-east Asia, but it is rarely diagnosed in Myanmar. We conducted a nationwide soil study to identify areas where B. pseudomallei is present.

METHODOLOGY/PRINCIPAL FINDINGS

We collected soil samples from 387 locations in all 15 states and regions of Myanmar between September 2017 and June 2019. At each site, three samples were taken at each of three different depths (30, 60 and 90 cm) and were cultured for B. pseudomallei separately, along with a pooled sample from each site (i.e. 10 cultures per site). We used a negative binomial regression model to assess associations between isolation of B. pseudomallei and environmental factors (season, soil depth, soil type, land use and climate zones). B. pseudomallei was isolated in 7 of 15 states and regions. Of the 387 sites, 31 (8%) had one or more positive samples and of the 3,870 samples cultured, 103 (2.7%) tested positive for B. pseudomallei. B. pseudomallei was isolated more frequently during the monsoon season [RR-2.28 (95% CI: 0.70-7.38)] and less in the hot dry season [RR-0.70 (95% CI: 0.19-2.56)] compared to the cool dry season, and in the tropical monsoon climate zone [RR-2.26; 95% CI (0.21-6.21)] compared to the tropical dry winter climate zone. However, these associations were not statistically significant. B. pseudomallei was detected at all three depths and from various soil types (clay, silt and sand). Isolation was higher in agricultural land (2.2%), pasture land (8.5%) and disused land (5.8%) than in residential land (0.4%), but these differences were also not significant.

CONCLUSION/SIGNIFICANCE

This study confirms a widespread distribution of B. pseudomallei in Myanmar. Clinical studies should follow to obtain a better picture of the burden of melioidosis in Myanmar.

Thinking Outside the Bug: Targeting Outer Membrane Proteins for Burkholderia Vaccines

Increasing antimicrobial resistance due to misuse and overuse of antimicrobials, as well as a lack of new and innovative antibiotics in development has become an alarming global threat. Preventative therapeutics, like vaccines, are combative measures that aim to stop infections at the source, thereby decreasing the overall use of antibiotics. Infections due to Gram-negative pathogens pose a significant treatment challenge because of substantial multidrug resistance that is acquired and spread throughout the bacterial population. Burkholderia spp. are Gram-negative intrinsically resistant bacteria that are responsible for environmental and nosocomial infections. The Burkholderia cepacia complex are respiratory pathogens that primarily infect immunocompromised and cystic fibrosis patients, and are acquired through contaminated products and equipment, or via patient-to-patient transmission. The Burkholderia pseudomallei complex causes percutaneous wound, cardiovascular, and respiratory infections. Transmission occurs through direct exposure to contaminated water, water-vapors, or soil, leading to the human disease melioidosis, or the equine disease glanders. Currently there is no licensed vaccine against any Burkholderia pathogen. This review will discuss Burkholderia vaccine candidates derived from outer membrane proteins, OmpA, OmpW, Omp85, and Bucl8, encompassing their structures, conservation, and vaccine formulation.

Listeriosis Cases and Genetic Diversity of Their L. monocytogenes Isolates in China, 2008-2019

Listeriosis, caused by Listeria monocytogenes, is a severe food-borne infection. The nationwide surveillance in China concerning listeriosis is urgently needed. In the present study, 144 L. monocytogenes isolates were collected from the samples of blood, cerebrospinal fluid (CSF), and fetal membrane/placenta in China for 12 years from 2008 to 2019. We summarized these listeriosis patients’ demographical and clinical features and outcomes. The susceptibility profile for 12 antibiotics was also determined by the broth microdilution method. Multilocus sequence typing (MLST) and serogroups of these listeria isolates were analyzed to designate epidemiological types. We enrolled 144 cases from 29 healthcare centers, including 96 maternal-neonatal infections, 33 cases of bacteremia, 13 cases of neurolisteriosis, and two cutaneous listeriosis. There were 31 (59.6%) fetal loss in 52 pregnant women and four (9.8%) neonatal death in 41 newborns. Among the 48 nonmaternal-neonatal cases, 12.5% (6/48) died, 41.7% (20/48) were female, and 64.6% (31/48) occurred in those with significant comorbidities. By MLST, the strains were distinguished into 23 individual sequence types (STs). The most prevalent ST was ST87 (49 isolates, 34.0%), followed by ST1 (18, 12.5%), ST8 (10, 6.9%), ST619 (9, 6.3%), ST7 (7, 4.9%) and ST3 (7, 4.9%). Furthermore, all L. monocytogenes isolates were uniformly susceptible to penicillin, ampicillin, and meropenem. In summary, our study highlights a high genotypic diversity of L. monocytogenes strains causing clinical listeriosis in China. Furthermore, a high prevalence of ST87 and ST1 in the listeriosis should be noted.

Diagnosis of melioidosis: the role of molecular techniques

Melioidosis is an emerging infectious disease with an estimated global burden of 4.64 million disability-adjusted life years per year. A major determinant related to poor disease outcomes is delay to diagnosis due to the fact that identification of the causative agent Burkholderia pseudomallei may be challenging. Over the last 25 years, advances in molecular diagnostic techniques have resulted in the potential for rapid and accurate organism detection and identification direct from clinical samples. While these methods are not yet routine in clinical practice, laboratory diagnosis of infectious diseases is transitioning to culture-independent techniques. This review article aims to evaluate molecular methods for melioidosis diagnosis direct from clinical samples and discuss current and future utility and limitations.

Systematic review and meta-analysis of diagnostic tests for diagnosis of melioidosis

OBJECTIVES

Melioidosis is an emerging tropical disease caused by B. pseudomallei that can rapidly prove fatal and require prompt and appropriate antibiotic treatment. Diagnosis currently relies on culture; however, this delays appropriate antibiotics and contributes to mortality as results can take up to one week or more. Several non-culture based diagnostic tests are available; however, their role remains a point of contention. This review was performed to characterise the accuracy of various diagnostic tests.

METHODS

Medline/Pubmed, CINAHL, Informit, Scopus, The Cochrane Library, Web of Science and Embase databases were searched from inception to April 2020. Clinical trials investigating diagnostic tests capable of providing results in ≤48 hours using samples from suspected human cases; with bacterial culture as the reference test, and reporting sensitivity and specificity were eligible for inclusion. Data was pooled using bivariate analysis for diagnostic tests reported in ≥4 studies.

RESULTS

22 publications comprising 10963 individual tests were included. Meta-analysis was able to be performed for immunofluorescence assay (sensitivity 63.8% [95% CI, 45.6-78.7%]; specificity 99.4% [95% CI, 97.2-99.9%]), polymerase chain reaction (sensitivity 77.1 [95% CI, 20.8%-97.8%]; specificity 99.8 [95% CI, 91.6%-100.0%]) and lateral flow immunoassay (sensitivity 58.2% [95% CI, 34.1%-78.9%]; specificity 95.0% [95% CI, 93.3%-96.3%]). Measures of sensitivity were overall similar although specificity of immunofluorescence assay was statistically superior to lateral flow immunoassay. There was a trend for reduced sensitivity of direct detection methods applied to blood samples compared to other sample types, although statistically insignificant. Serological methods were unable to be meta-analysed due to an insufficient number of studies, but their sensitivities were generally higher than direct detection methods (median 84% [IQR 71.5-88%] vs 51% [IQR 39-79%]), however they lacked specificity compared to direct detection (median 82% [IQR 70-86%] vs 98% [IQR 95-100%]).

CONCLUSIONS

Overall, no method showed sensitivity and specificity which would allow it to substitute culture. Serological tests may play a role in ruling out infection in endemic regions given their higher sensitivity, with direct detection methods being used for diagnostic confirmation. Further research into cost-effectiveness and implementation studies are required before diagnostic tests can be introduced clinically in the detection of melioidosis.

Melioidosis: A Fulminant Infection in a Patient with Uncontrolled Diabetes

Melioidosis is an endemic infection in Southeast Asia and Northern Australia commonly manifesting with pneumonia and localized skin infection. Though most exposures do not lead to severe illness, a fulminant infection can occur among patients with risk factors. A 59-year-old male presented with cough with expectoration and fever for 1 week. He had diabetes for 10 years with poorly controlled blood sugars. Contrast-enhanced computerized tomography (CECT) of thorax showed right upper lobe consolidation with diffuse ground-glass opacities in right upper lobe along with microabscesses in liver and spleen. Sputum culture and Xpert mycobacterium tuberculosis complex and resistance to rifampin (MTB/RIF) for tuberculosis were negative. Bronchoalveolar lavage culture grew Burkholderia pseudomallei. He was treated with initial intensive therapy with injection amoxicillin-clavulanic acid for 2 weeks and subsequently started on eradication therapy with tablet trimethoprim-sulfamethoxazole. Diagnosis of melioidosis should be considered in a patient of pneumonia with multiorgan involvement in an endemic area, especially with underlying risk factors.

Prioritising pathogens for the management of severe febrile patients to improve clinical care in low- and middle-income countries

Background

Severe febrile illness without a known source (SFWS) is a challenge for clinicians when deciding how to manage a patient, particularly given the wide spectrum of potential aetiologies that contribute to fever. These infections are difficult to distinguish clinically, and accurate diagnosis requires a plethora of diagnostics including blood cultures, imaging techniques, molecular or serological tests, and more. When laboratory services are available, a limited test menu hinders clinical decision-making and antimicrobial stewardship, leading to empiric treatment and suboptimal patient outcomes. To specifically address SFWS, this work aimed to identify priority pathogens for a globally applicable panel for fever causing pathogens.

Method

A pragmatic two-pronged approach combining currently available scientific data in an analytical hierarchy process and systematically gathered expert input, was designed to address the lack of comprehensive global aetiology data. The expert re-ranked list was then further adapted for a specific use case to focus on community acquired infections in whole blood specimens. The resulting list was further analysed to address different geographical regions (Asia, Africa, and Latin America), and Cohen kappa scores of agreement were calculated.

Results

The expert ranked prioritized pathogen list generated as part of this two-pronged approach included typhoidal Salmonella, Plasmodium species and Mycobacterium tuberculosis as the top 3 pathogens. This pathogen list was then further adapted for the SFWS use case to develop a final pathogen list to inform product development. Subsequent analysis comparing the relevance of the SFWS pathogen list to multiple populations and geographical regions showed that the SFWS prioritized list had considerable utility across Africa and Asia, but less so for Latin America. In addition, the list showed high levels of agreement across different patient sub-populations, but lower relevance for neonates and symptomatic HIV patients.

Conclusion

This work highlighted once again the challenges of prioritising in global health, but it also shows that taking a two-pronged approach, combining available prevalence data with expert input, can result in a broadly applicable priority list. This comprehensive utility is particularly important in the context of product development, where a sufficient market size is essential to achieve a sustainable commercialized diagnostic product to address SFWS.

Burkholderia collagen-like protein 8, Bucl8, is a unique outer membrane component of a putative tetrapartite efflux pump in Burkholderia pseudomallei and Burkholderia mallei

Bacterial efflux pumps are an important pathogenicity trait because they extrude a variety of xenobiotics. Our laboratory previously identified in silico Burkholderia collagen-like protein 8 (Bucl8) in the hazardous pathogens Burkholderia pseudomallei and Burkholderia mallei. We hypothesize that Bucl8, which contains two predicted tandem outer membrane efflux pump domains, is a component of a putative efflux pump. Unique to Bucl8, as compared to other outer membrane proteins, is the presence of an extended extracellular region containing a collagen-like (CL) domain and a non-collagenous C-terminus (Ct). Molecular modeling and circular dichroism spectroscopy with a recombinant protein, corresponding to this extracellular CL-Ct portion of Bucl8, demonstrated that it adopts a collagen triple helix, whereas functional assays screening for Bucl8 ligands identified binding to fibrinogen. Bioinformatic analysis of the bucl8 gene locus revealed it resembles a classical efflux-pump operon. The bucl8 gene is co-localized with downstream fusCDE genes encoding fusaric acid (FA) resistance, and with an upstream gene, designated as fusR, encoding a LysR-type transcriptional regulator. Using reverse transcriptase (RT)-qPCR, we defined the boundaries and transcriptional organization of the fusR-bucl8-fusCDE operon. We found exogenous FA induced bucl8 transcription over 80-fold in B. pseudomallei, while deletion of the entire bucl8 locus decreased the minimum inhibitory concentration of FA 4-fold in its isogenic mutant. We furthermore showed that the putative Bucl8-associated pump expressed in the heterologous Escherichia coli host confers FA resistance. On the contrary, the Bucl8-associated pump did not confer resistance to a panel of clinically-relevant antimicrobials in Burkholderia and E. coli. We finally demonstrated that deletion of the bucl8-locus drastically affects the growth of the mutant in L-broth. We determined that Bucl8 is a component of a novel tetrapartite efflux pump, which confers FA resistance, fibrinogen binding, and optimal growth.

3-in-1: bilateral subcutaneous leg abscesses and liver abscess from Klebsiella pneumoniae

Hypervirulent strains of Klebsiella pneumoniae are known to cause liver abscesses and other metastatic infections. Being Asian and having diabetes are known host risk factors. Here we present an unusual case of a Filipino ballet dancer-choreographer with diabetes presenting with bilateral leg pains initially thought to be cellulitis, but was eventually diagnosed as bilateral subcutaneous leg abscesses. He also had a liver abscess, thankfully asymptomatic, which was only discovered on imaging. The occurrence of three distant abscesses in one patient, hence '3-in-1,' makes this case worth reporting. Bilateral subcutaneous leg abscesses as the presenting manifestation of this infection have not been reported yet. We hypothesise that his occupation which makes use of frequent contractions of leg muscles led to increased blood flow and preferentially directed blood-borne bacteria to localise in both legs. We have also characterised the pathogen with regards to its hypermucoviscous phenotype, capsular type, virulence genes and phylogeny.

[Infections of the lungs in returning travellers]

Auf Auslandsreisen kann es zu Infektionen mit Erregern kommen, die in Deutschland nicht endemisch sind. Vor dem Hintergrund einer stetig zunehmenden Reiseaktivität der Bevölkerung gewinnen diese Infektionen bei Reiserückkehrern an Bedeutung. Ältere und vorerkrankte Reisende stellen dabei eine besondere Risikogruppe dar. Die Kenntnis von im Ausland vorkommenden Erregern und typischen Krankheitsbildern ist essenziell, um eine entsprechende Verdachtsdiagnose stellen zu können, insbesondere bei Patienten, bei denen eine erste kalkulierte antibakterielle Therapie ohne Effekt bleibt. Die Erhebung einer detaillierten Reiseanamnese ist entscheidend, um Aufschluss über eine mögliche Exposition gegenüber spezifischen Erregern zu gewinnen und die korrekte Diagnostik in die Wege leiten zu können. Neben Erregern, die primär zu einer Infektion der Lunge führen, müssen differenzialdiagnostisch auch immer nichtpulmonale Infektionen mit einer pulmonalen Begleitsymptomatik, wie beispielsweise Schistosomiasis oder Malaria, in Betracht gezogen werden. Zwei Beispiele von pulmonalen Infektionen, die ausschließlich im Ausland erworben werden können, sind die Melioidose und die Kokzidioidomykose. Während eine pulmonale Manifestation der Melioidose akut und fulminant verlaufen und mit einer hohen Letalität assoziiert sein kann, ist die Kokzidioidomykose primär meist oligosymptomatisch, mit erheblicher Latenz können jedoch pulmonale Manifestationen auftreten, die in ihrer Vielfalt der Tuberkulose oder Malignomen ähneln können.

Melioidosis DS rapid test: A standardized serological dipstick assay with increased sensitivity and reliability due to multiplex detection

BACKGROUND

Melioidosis, caused by Burkholderia pseudomallei, is a severe infectious disease with high mortality rates, but is under-recognized worldwide. In endemic areas, there is a great need for simple, low-cost and rapid diagnostic tools. In a previous study we showed, that a protein multiplex array with 20 B. pseudomallei-specific antigens detects antibodies in melioidosis patients with high sensitivity and specificity. In a subsequent study the high potential of anti-B. pseudomallei antibody detection was confirmed using a rapid Hcp1 single protein-based assay. Our protein array also showed that the antibody profile varies between patients, possibly due to a combination of host factors but also antigen variations in the infecting B. pseudomallei strains. The aim of this study was to develop a rapid test, combining Hcp1 and the best performing antigens BPSL2096, BPSL2697 and BPSS0477 from our previous study, to take advantage of simultaneous antibody detection.

METHODS AND PRINCIPAL FINDINGS

The 4-plex dipstick was validated with sera from 75 patients on admission plus control groups, achieving 92% sensitivity and 97-100% specificity. We then re-evaluated melioidosis sera with the 4-plex assay that were previously misclassified by the monoplex Hcp1 rapid test. 12 out of 55 (21.8%) false-negative samples were positive in our new dipstick assay. Among those, 4 sera (7.3%) were Hcp1 positive, whereas 8 (14.5%) sera remained Hcp1 negative but gave a positive reaction with our additional antigens.

CONCLUSIONS

Our dipstick rapid test represents an inexpensive, standardized and simple diagnostic tool with an improved serodiagnostic performance due to multiplex detection. Each additional band on the test strip makes a false-positive result more unlikely, contributing to its reliability. Future prospective studies will seek to validate the gain in sensitivity and specificity of our multiplex rapid test approach in different melioidosis patient cohorts.

Point-of-Care Ultrasound in the Diagnosis of Melioidosis in Laos

Melioidosis is endemic in many rural areas in Southeast Asia where facilities for culture and identification of Burkholderia pseudomallei are often limited. We performed a prospective observational study in patients presenting with fever to Mahosot Hospital, the primary referral hospital in Laos, to establish whether the detection of abscesses on ultrasound could support a presumptive diagnosis of melioidosis. All patients underwent ultrasound examination to detect abscesses in the liver, spleen, prostate, or, if indicated, subcutaneous tissue. We enrolled 153 patients, including 18 patients with melioidosis. Of these, 11 (61%) had an abscess at one or more sites, including five (28%) with splenic and/or liver abscesses. Absence of abscesses cannot rule out melioidosis, but the positive predictive value of abscesses for melioidosis was high at 93% (88–96%). Therefore, in endemic areas, the presence of abscesses in febrile patients should prompt empiric antibiotic therapy for melioidosis even in the absence of culture confirmation.

Burkholderia pseudomallei Detection among Hospitalized Patients, Sarawak

Burkholderia pseudomallei infections are prevalent in Southeast Asia and northern Australia and often misdiagnosed. Diagnostics are often neither sensitive nor rapid, contributing up to 50% mortality rate. In this 2018 pilot study, we enrolled 100 patients aged 6 months-79 years from Kapit Hospital in Sarawak, Malaysia, with symptoms of B. pseudomallei infection. We used three different methods for the detection of B. pseudomallei: a real-time polymerase chain reaction (PCR) assay, a rapid lateral flow immunoassay, and the standard-of-care bacterial culture-the gold standard. Among the 100 participants, 24 (24%) were positive for B. pseudomallei by one or more of the detection methods. Comparing the two individual diagnostic methods against the gold standard-bacterial culture-of any positive test, there was low sensitivity for each test (25-44%) but high specificity (93-98%). It seems clear that more sensitive diagnostics or a sensitive screening diagnostic followed by specific confirmatory diagnostic is needed for this disease.

Burkholderia pseudomallei peri-prosthetic infection following medial malleolar internal fixation: a case report

Background

Melioidosis-associated peri-prosthetic infection is extremely rare. To date, melioidosis associated septic arthritis of the ankle joint following a medial malleolar internal fixation has not been reported.

Case presentation

We describe a 49-year-old male with a history of long standing diabetes who presented with fever, constitutional symptoms and right ankle pain for 1 week. Ten years ago, he underwent a medial malleolar screw fixation following a traumatic closed fracture. His initial right ankle radiographs showed no evidence of osteomyelitis. He underwent a wound debridement and washout of the right ankle joint. The peripheral blood and pus from the ankle joint was culture positive for Burkholderia pseudomallei with very high antibody titres. His subsequent radiographs showed features of chronic osteomyelitis. He was treated with a prolonged course of antibiotics and repeated wound debridement. At follow up after 6 months, he had no clinical features of recurrent infection.

Conclusions

Melioidosis should be entertained in the differential diagnosis of peri-prosthetic infections in high risk patients.

Melioidosis in travelers: An analysis of Dutch melioidosis registry data 1985-2018

BACKGROUND

Melioidosis, caused by the Gram-negative bacterium Burkholderia pseudomallei, is an opportunistic infection across the tropics. Here, we provide a systematic overview of imported human cases in a non-endemic country over a 25-year period.

METHODS

All 55 Dutch microbiology laboratories were contacted in order to identify all B. pseudomallei positive cultures from 1990 to 2018. A response rate of 100% was achieved. Additionally, a systematic literature search was performed, medical-charts reviewed, and tissue/autopsy specimens were re-assessed.

RESULTS

Thirty-three travelers with melioidosis were identified: 70% male with a median-age of 54 years. Risk factors were present in most patients (n = 23, 70%), most notably diabetes (n = 8, 24%) and cystic fibrosis (n = 3, 9%). Countries of acquisition included Thailand, Brazil, Indonesia, Panama, and The Gambia. Disease manifestations included pneumonia, intra-abdominal abscesses, otitis externa, genitourinary, skin-, CNS-, and thyroid gland infections. Twelve (36%) patients developed sepsis and/or septic shock. Repeat episodes of active infection were observed in five (15%) and mortality in four (12%) patients. Post-mortem analysis showed extensive metastatic (micro)abscesses amongst other sites in the adrenal gland and bone marrow.

CONCLUSIONS

The number of imported melioidosis is likely to increase, given rising numbers of (immunocompromised) travelers, and increased vigilance of the condition. This first systematic retrospective surveillance study in a non-endemic melioidosis country shows that imported cases can serve as sentinels to provide information about disease activity in areas visited and inform pre-travel advice and post-travel clinical management.