Isolation, identification and characterization of Burkholderia pseudomallei from soil of coastal region of India

MALDI-TOF MS analysis of Burkholderia pseudomallei and closely related species isolated from soils and water in Khon Kaen, Thailand

Melioidosis is caused by Burkholderia pseudomallei (Bp) acquired from the environment. Conventional identification methods for environmental Bp are challenging due to the presence of closely related species. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is accurate for bacterial identification, but has been little used to identify Bp from environmental samples. This study aims to evaluate MALDI-TOF MS for the identification of Bp and closely related species isolated from environmental samples in Thailand using whole-genome sequencing (WGS) as the gold standard, including determining the best sample preparation method for this purpose. We identified Bp (n = 22), Burkholderia spp. (n = 28), and other bacterial species (n = 32) using WGS. MALDI-TOF analysis of all Bp isolates yielded results consistent with WGS. A decision-tree algorithm identified 16 important variable peaks, using the protein extraction method (PEM), demonstrating distinct MALDI-TOF profiles for the three categories (Bp, Burkholderia spp. and "other bacterial species"). Three biomarker peaks (4060, 5196, and 6553 Da) could discriminate Bp from other Burkholderia and closely related species with 100% sensitivity and specificity. Hence, the MALDI-TOF technique has shown its potential as a species discriminatory tool, providing results comparable to WGS for classification and surveillance of environmental Bp.

A rare and fatal case of tubo-ovarian abscess due to Burkholderia pseudomallei presenting as puerperal sepsis

Introduction

Melioidosis is an emerging life-threatening infectious disease caused by the Gram-negative Burkholderia pseudomallei found in contaminated soil and surface ground water. It often presents with varied clinical manifestations and has a high mortality if left untreated due to lack of clinical suspicion. Here we report a rare and fatal case of tubo-ovarian abscess presenting as puerperal sepsis due to B. pseudomallei in a young woman.

Case report

A 25-year-old female presented for medical consultation at day 43 postpartum complaining of fever on and off for the past 40 days associated with vomiting. On per speculum examination, greenish discharge from the cervix was seen and a right adnexal mass was felt which was cystic in consistency, non-tender and pushing the cervix to the left side. An exploratory laparotomy was carried out and pus was drained from below the rectus sheath, and from the right tubo-ovarian mass. Peripheral blood and the pus samples collected intraoperatively grew B. pseudomallei . The patient died on the fifth post-operative day due to septic shock with disseminated intravascular coagulation secondary to puerperal sepsis.

Conclusion

Melioidosis is a fatal but treatable disease when it is promptly diagnosed. In countries such as India, where tuberculosis is highly endemic, underdiagnosis of melioidosis can be common. Clinicians and microbiologists should have a high index of suspicion of melioidosis especially in individuals with underlying illness.

Burkholderia pseudomallei in soil and natural water bodies in rural Sri Lanka: A hidden threat to public health

Burkholderia pseudomallei is the causative agent of the potentially fatal infection, melioidosis. This study provides the first evidence for the presence of B. pseudomallei in soil and water in Sri Lanka. Targeted sampling of soil and natural water sources was done between November 2019 and October 2020 over eight field visits encompassing the neighborhood of 28 culture and/or antibody-positive melioidosis patients in northwestern, western and southern Sri Lanka. A total of eight environmental isolates of B. pseudomallei (BPs-env1 to BPs-env8) were cultured from 116 soil and 117 natural water samples collected from 72 locations. The presence of B. pseudomallei in soil and natural water in these areas poses a risk of melioidosis for populations cultivating crops in such soils and using untreated water from these sources for drinking, bathing, and other domestic purposes. Identifying sites positive for B. pseudomallei may help to mitigate risk by raising public awareness of contaminated environmental sources and allowing soil and water remediation.

Environmental Factors Associated With Soil Prevalence of the Melioidosis Pathogen Burkholderia pseudomallei: A Longitudinal Seasonal Study From South West India

Melioidosis is a seasonal infectious disease in tropical and subtropical areas caused by the soil bacterium Burkholderia pseudomallei. In many parts of the world, including South West India, most cases of human infections are reported during times of heavy rainfall, but the underlying causes of this phenomenon are not fully understood. India is among the countries with the highest predicted melioidosis burden globally, but there is very little information on the environmental distribution of B. pseudomallei and its determining factors. The present study aimed (i) to investigate the prevalence of B. pseudomallei in soil in South West India, (ii) determine geochemical factors associated with B. pseudomallei presence and (iii) look for potential seasonal patterns of B. pseudomallei soil abundance. Environmental samplings were performed in two regions during the monsoon and post-monsoon season and summer from July 2016 to November 2018. We applied direct quantitative real time PCR (qPCR) together with culture protocols to overcome the insufficient sensitivity of solely culture-based B. pseudomallei detection from soil. A total of 1,704 soil samples from 20 different agricultural sites were screened for the presence of B. pseudomallei. Direct qPCR detected B. pseudomallei in all 20 sites and in 30.2% (517/1,704) of all soil samples, whereas only two samples from two sites were culture-positive. B. pseudomallei DNA-positive samples were negatively associated with the concentration of iron, manganese and nitrogen in a binomial logistic regression model. The highest number of B. pseudomallei-positive samples (42.6%, p < 0.0001) and the highest B. pseudomallei loads in positive samples [median 4.45 × 103 genome equivalents (GE)/g, p < 0.0001] were observed during the monsoon season and eventually declined to 18.9% and a median of 1.47 × 103 GE/g in summer. In conclusion, our study from South West India shows a wide environmental distribution of B. pseudomallei, but also considerable differences in the abundance between sites and within single sites. Our results support the hypothesis that nutrient-depleted habitats promote the presence of B. pseudomallei. Most importantly, the highest B. pseudomallei abundance in soil is seen during the rainy season, when melioidosis cases occur.

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.

Estimation of seroprevalence of melioidosis among adult high risk groups in Southeastern India by indirect Hemagglutination assay

Burkholderia pseudomallei is an environmental saprophyte known to cause melioidosis, a disease endemic in northern Australia and Southeast Asia. With the increasing number of melioidosis cases, there is a lack of data on seroprevalence rates and extent of exposure in high risk population of melioidosis from different endemic regions in India. The present cross sectional study was undertaken to estimate the seroprevalence of melioidosis in high risk populations in and around Puducherry, a coastal town in Southeastern India. Blood samples were collected from 275 diabetic individuals attending a tertiary care centre in Southern India and 275 farmers residing under the rural field practice area of our hospital. The antibody levels were estimated using an Indirect Hemagglutination Assay. The overall seropositivity was found to be 19.8% with a titer ≥1:20. Farmers were 2.8 times more likely to be seropositive than non-farmers. Rates of seroprevalence among diabetic subjects were less compared to the non-diabetic individuals. The seropositivity rates in non-diabetic farmers were higher (56/203, 27.6%) compared to diabetic farmers (34/164, 20.7%). The lowest seropositivity was seen among diabetic non-farmers at 10.4%. Multivariable logistic regression analysis revealed domicile (adjusted odds ratio-aOR: 2.32, 95% Confidence interval-CI: 1.05, 5.13) and contact with animals (aOR: 1.89, 95% CI:1.04, 3.44) as significant predictors of seropositivity. None of the other socio-demographic factors including gender and age were significantly associated with seropositivity. This study demonstrates widespread exposure to B. pseudomallei among adults residing in and around Puducherry, including those engaged in non-farming occupations.

Molecular Characteristics of Burkholderia pseudomallei Collected From Humans in Hainan, China

Melioidosis is a common infectious disease in Southeast Asia and Northern Australia. In Hainan, several cases have been reported, but no systematic study has yet been done on the molecular epidemiology profiles of the organism. An investigation of the molecular epidemiology links and population structure of Burkholderia pseudomallei would help to better understand the clonally of the isolates and differences among them. In this study, multilocus variable-number tandem repeat analysis (MLVA), and multilocus sequence typing (MLST) were applied to examine the epidemiological relatedness and population structure of 166 B. pseudomallei isolates obtained during 2002–2014 in Hainan, China. Both the MLVA_4 and MLST approaches had high discriminatory power for this population, with diversity indices of 0.9899 and 0.9457, respectively. However, the MLVA_4 assay showed a higher discriminatory power than the MLST approach, and a variable-number tandem repeat (VNTR3 933) found by the MLVA approach was the most useful in discriminating strains from this province. A total of 166 strains yielded 99 MLVA_4 genotypes, of which 34 genotypes were shared by 101 isolates, for a clustering rate of 60.8% (101/166), which suggested that some cases may have a common source. Additionally, 65 isolates showed distinct genotypes, indicating that more than 39.2% (65/166) of melioidosis cases in Hainan had epidemiologically unrelated or sporadic characteristics. The 166 isolates were resolved into 48 STs, of which five STs (ST55, -70, -46, -50, and -58) were here found to be predominant. Phylogenetic analysis of 116 isolates conducted using the eBURST v3 segregated the 48 STs into eight groups with ST50 as predicted founder, and 21 STs were found to be singletons, which suggest that the strains in the Hainan region represent a high diversity of ST clones, indicating that many B. pseudomallei clone groups are endemic to this region. Moreover, ST50 had 5 SLV, 7 DLV, 6 TLV, and 29 satellite STs and formed a radial expansion pattern, suggesting that the melioidosis epidemic in this study was mainly caused by the clonal expansion of ST 50. Phylogenetic analysis on global scale suggests that China’s isolates are closely related to isolates from Southeast Asia, particularly from Thailand and Malaysia.

Human Melioidosis

The causative agent of melioidosis, Burkholderia pseudomallei, a tier 1 select agent, is endemic in Southeast Asia and northern Australia, with increased incidence associated with high levels of rainfall. Increasing reports of this condition have occurred worldwide, with estimates of up to 165,000 cases and 89,000 deaths per year. The ecological niche of the organism has yet to be clearly defined, although the organism is associated with soil and water. The culture of appropriate clinical material remains the mainstay of laboratory diagnosis. Identification is best done by phenotypic methods, although mass spectrometric methods have been described. Serology has a limited diagnostic role. Direct molecular and antigen detection methods have limited availability and sensitivity. Clinical presentations of melioidosis range from acute bacteremic pneumonia to disseminated visceral abscesses and localized infections. Transmission is by direct inoculation, inhalation, or ingestion. Risk factors for melioidosis include male sex, diabetes mellitus, alcohol abuse, and immunosuppression. The organism is well adapted to intracellular survival, with numerous virulence mechanisms. Immunity likely requires innate and adaptive responses. The principles of management of this condition are drainage and debridement of infected material and appropriate antimicrobial therapy. Global mortality rates vary between 9% and 70%. Research into vaccine development is ongoing.

Presence of Burkholderia pseudomallei in the 'Granary of Myanmar'

Melioidosis is a frequently fatal infectious disease caused by the Gram negative bacillus Burkholderia pseudomallei. Although it was originally discovered in Myanmar, the disease disappeared from sight for many decades. This study focuses on detection of B. pseudomallei in soil in selected sampling sites in an attempt to start to fill the gaps in the current status of our knowledge of the geographical distribution of B. pseudomallei in soil in Myanmar. This cross-sectional study consists of 400 soil samples from 10 selected study townships from two major paddy growing regions. Bacterial isolation was done using a simplified method for the isolation of Burkholderia pseudomallei from soil. In this study, only 1% (4/400) of soil samples were found to be positive; two of four were found at 90 cm depth and another two positive samples were found at 30 cm and 60 cm. This survey has confirmed the presence of environmental B. pseudomallei in Myanmar indicating that the conditions are in place for melioidosis acquisition.

Evaluation of consensus method for the culture of Burkholderia pseudomallei in soil samples from Laos

Background: We have previously shown that PCR following enrichment culture is the most sensitive method to detect Burkholderia pseudomallei in environmental samples. Here we report an evaluation of the published consensus method for the culture of B. pseudomallei from Lao soil in comparison with our conventional culture method and with PCR with or without prior broth enrichment. Methods: One hundred soil samples were collected from a field known to contain B. pseudomallei and processed by: (i) the conventional method, (ii-iii) the consensus method using media prepared in either Laos or Thailand, and (iv) the consensus method performed in Thailand, as well as by (v) PCR following direct extraction of DNA from soil and (vi) PCR following broth pre-enrichment. Results: The numbers of samples in which B. pseudomallei was detected were 42, 10, 7, 6, 6 and 84, respectively. However, two samples were positive by the consensus method but negative by conventional culture, and one sample was negative by PCR following enrichment although B. pseudomallei was isolated by the conventional culture method. Conclusions/Discussion: The results show that no single method will detect all environmental samples that contain B. pseudomallei. People conducting environmental surveys for this organism should be aware of the possibility of false-negative results using the consensus culture method. An approach that entails screening using PCR after enrichment, followed by the evaluation of a range of different culture methods on PCR-positive samples to determine which works best in each setting, is recommended.

The prevalence and distribution of Burkholderia pseudomallei in rice paddy within Hainan, China

Melioidosis is an infectious disease caused by Burkholderia pseudomallei, mainly found in Southeast Asia and northern Australia. In Hainan, sporadic cases were first described in 1990; since then, more cases have been identified. No systematic study has yet been done to detect the environmental source of the organism and its true extent in Hainan. This study is aimed to confirm the prevalence of B. pseudomallei in soil samples in Hainan. 1080 soil samples from 18 different counties were collected from 3 sampling points of 360 sites. They were screened for the presence of B. pseudomallei by Ashdown selective media. Suspected colonies of B. pseudomallei were confirmed by biochemical test and a specific PCR assay. 48 of 360 sites (13.3%) were positive for B. pseudomallei, including all coastal counties in Hainan Island. This study revealed the prevalence and distribution of B. pseudomallei in the soil environment in Hainan Island of southern China and may be helpful to understand the distribution of B. pseudomallei and to access its epidemiological importance.

Evaluation of consensus method for the culture of Burkholderia pseudomallei in soil samples from Laos

Background: We have previously shown that PCR following enrichment culture is the most sensitive method to detect Burkholderia pseudomallei in environmental samples. Here we report an evaluation of the published consensus method for the culture of B. pseudomallei from Lao soil in comparison with our conventional culture method and with PCR with or without prior broth enrichment. Methods: One hundred soil samples were collected from a field known to contain B. pseudomallei and processed by: (i) the conventional method, (ii-iii) the consensus method using media prepared in either Laos or Thailand, and (iv) the consensus method performed in Thailand, as well as by (v) PCR following direct extraction of DNA from soil and (vi) PCR following broth pre-enrichment. Results: The numbers of samples in which B. pseudomallei was detected were 42, 10, 7, 6, 6 and 84, respectively. However, two samples were positive by the consensus method but negative by conventional culture, and one sample was negative by PCR following enrichment although B. pseudomallei was isolated by the conventional culture method. Conclusions/Discussion: The results show that no single method will detect all environmental samples that contain B. pseudomallei. People conducting environmental surveys for this organism should be aware of the possibility of false-negative results using the consensus culture method. An approach that entails screening using PCR after enrichment, followed by the evaluation of a range of different culture methods on PCR-positive samples to determine which works best in each setting, is recommended.

Melioidosis in South Asia (India, Nepal, Pakistan, Bhutan and Afghanistan)

Despite the fact that South Asia is predicted to have the highest number of cases worldwide, melioidosis is a little-known entity in South Asian countries. It has never been heard of by the majority of doctors and has as yet failed to gain the attention of national Ministries of Health and country offices of the World Health Organization (WHO). Although a few centers are diagnosing increasing numbers of cases, and the mortality documented from these institutions is relatively high (nearly 20%), the true burden of the disease remains unknown. In India, most cases have been reported from southwestern coastal Karnataka and northeastern Tamil Nadu, although this probably simply reflects the presence of centers of excellence and researchers with an interest in the disease. As elsewhere, the majority of cases have type 2 diabetes mellitus and occupational exposure to the environment. Most present with community-acquired pneumonia and/or bacteremia, especially during heavy rainfall. The high seropositivity rate (29%) in Karnataka and isolation of B. pseudomallei from the environment in Tamil Nadu and Kerala confirm India as melioidosis-endemic, although the full extent of the distribution of the organism across the country is unknown. There are limited molecular epidemiological data, but, thus far, the majority of Indian isolates have appeared distinct from those from South East Asia and Australia. Among other South Asian countries, Sri Lanka and Bangladesh are known to be melioidosis-endemic, but there are no cases that have conclusively proved to have been acquired in Nepal, Bhutan, Afghanistan or Pakistan. There are no surveillance systems in place for melioidosis in South Asian countries. However, over the past two years, researchers at the Center for Emerging and Tropical Diseases of Kasturba Medical College, University of Manipal, have established the Indian Melioidosis Research Forum (IMRF), held the first South Asian Melioidosis Congress, and have been working to connect researchers, microbiologists and physicians in India and elsewhere in South Asia to raise awareness through training initiatives, the media, workshops, and conferences, with the hope that more patients with melioidosis will be diagnosed and treated appropriately. However, much more work needs to be done before we will know the true burden and distribution of melioidosis across South Asia.

Isolation & characterization of Brucella melitensis isolated from patients suspected for human brucellosis in India

Background & objectives:

Brucellosis is endemic in the southern part of India. A combination of biochemical, serological and molecular methods is required for identification and biotyping of Brucella. The present study describes the isolation and biochemical, molecular characterization of Brucella melitensis from patients suspected for human brucellosis.

Methods:

The blood samples were collected from febrile patients suspected to have brucellosis. A total of 18 isolates were obtained from 102 blood samples subjected to culture. The characterization of these 18 isolates was done by growth on Brucella specific medium, biochemical reactions, CO₂ requirement, H₂S production, agglutination with A and M mono-specific antiserum, dye sensitivity to basic fuchsin and thionin. Further, molecular characterization of the isolates was done by amplification of B. melitensis species specific IS711 repetitive DNA fragment and 16S (rRNA) sequence analysis. PCR-restriction fragment length polymorphism (RFLP) analysis of omp2 locus and IS711 gene was also done for molecular characterization.

Results:

All 102 suspected samples were subjected to bacteria isolation and of these, 18 isolates could be recovered on blood culture. The biochemical, PCR and PCR-RFLP and 16s rRNA sequencing revealed that all isolates were of B. melitensis and matched exactly with reference strain B. melitensis 16M.

Interpretation & conclusions:

The present study showed an overall isolation rate of 17.64 per cent for B. melitensis. There is a need to establish facilities for isolation and characterization of Brucella species for effective clinical management of the disease among patients as well as surveillance and control of infection in domestic animals. Further studies are needed from different geographical areas of the country with different level of endemicity to plan and execute control strategies against human brucellosis.

Gastrointestinal manifestations of melioidosis: A single center experience

Melioidosis, being increasing, is reported from India. Gastrointestinal manifestations are typically reported as unusual cause of liver and/or splenic abscess. We aimed to describe various gastrointestinal manifestation of melioidosis in the present study. We retrospectively collected data of culture positive melioidosis cases from hospital database during August 2014-October 2016 at Asian Institute of Gastroenterology, Hyderabad. A total of nine culture positive cases (8 male) of melioidosis with median age of 40 years (range 23-66) were analyzed. Median duration of symptoms was 45 days. Two patients were being treated as tuberculosis. Three patients presented with liver abscess with two of them having simultaneous splenic abscess, and one had prostatic abscess. Three patients (43%) with history of acute pancreatitis had infected pancreatic collection, and one patient had left empyema with splenic abscess. One patient had wound infection with left lower limb cellulitis, presented as acute in chronic liver failure and another as spontaneous bacterial peritonitis (SBP). Diabetes and/or alcoholism was present in all patients. Seven patients had disseminated organ involvement. Seven patients underwent percutaneous intervention for drainage of abscess. Induction therapy as ceftazidime (n=4) or meropenem (n=5) followed by continuation therapy as oral cotrimoxazole (n=6) and doxycycline (n=1) was given. Six patients completed therapy and asymptomatic at end of follow up. Two patients died in the study period. One patient died due to acute-on-chronic liver failure (ACLF) with acute kidney injury and the other due to cardiac failure. One patient with SBP had lost to follow up. Apart from being unusual cause of liver/splenic abscess, melioidosis can present with infection of pancreatic collection, SBP, and infection in a compensated cirrhosis which can precipitate ACLF. Early recognition and specific therapy can improve prognosis.

Prevalence and Identification of Burkholderia pseudomallei and Near-Neighbor Species in the Malabar Coastal Region of India

Accurate identification of pathogens with biowarfare importance requires detection tools that specifically differentiate them from near-neighbor species. Burkholderia pseudomallei, the causative agent of a fatal disease melioidosis, is one such biothreat agent whose differentiation from its near-neighbor species is always a challenge. This is because of its phenotypic similarity with other Burkholderia species which have a wide spread geographical distribution with shared environmental niches. Melioidosis is a major public health concern in endemic regions including Southeast Asia and northern Australia. In India, the disease is still considered to be emerging. Prevalence surveys of this saprophytic bacterium in environment are under-reported in the country. A major challenge in this case is the specific identification and differentiation of B. pseudomallei from the growing list of species of Burkholderia genus. The objectives of this study included examining the prevalence of B. pseudomallei and near-neighbor species in coastal region of South India and development of a novel detection tool for specific identification and differentiation of Burkholderia species. Briefly, we analyzed soil and water samples collected from Malabar coastal region of Kerala, South India for prevalence of B. pseudomallei. The presumptive Burkholderia isolates were identified using recA PCR assay. The recA PCR assay identified 22 of the total 40 presumptive isolates as Burkholderia strains (22.72% and 77.27% B. pseudomallei and non-pseudomallei Burkholderia respectively). In order to identify each isolate screened, we performed recA and 16S rDNA sequencing. This two genes sequencing revealed that the presumptive isolates included B. pseudomallei, non-pseudomallei Burkholderia as well as non-Burkholderia strains. Furthermore, a gene termed D-beta hydroxybutyrate dehydrogenase (bdha) was studied both in silico and in vitro for accurate detection of Burkholderia genus. The optimized bdha based PCR assay when evaluated on the Burkholderia isolates of this study, it was found to be highly specific (100%) in its detection feature and a clear detection sensitivity of 10 pg/μl of purified gDNA was recorded. Nucleotide sequence variations of bdha among interspecies, as per in silico analysis, ranged from 8 to 29% within the target stretch of 730 bp highlighting the potential utility of bdha sequencing method in specific detection of Burkholderia species. Further, sequencing of the 730 bp bdha PCR amplicon of each Burkholderia strain isolated could differentiate the species and the data was comparable with recA sequence data of the strains. All sequencing results obtained were submitted to NCBI database. Bayesian phylogenetic analysis of bdha in comparison with recA and 16S rDNA showed that the bdha gene provided comparable identification of Burkholderia species.

Burkholderia pseudomallei: Its Detection in Soil and Seroprevalence in Bangladesh

Background

Melioidosis, caused by Burkholderia pseudomallei, is an endemic disease in Bangladesh. No systematic study has yet been done to detect the environmental source of the organism and its true extent in Bangladesh. The present study attempted to isolate B. pseudomallei in soil samples and to determine its seroprevalence in several districts in Bangladesh.

Methodology and Results

Soil samples were collected from rural areas of four districts of Bangladesh from where culture confirmed melioidosis cases were detected earlier. Multiple soil samples, collected from 5–7 sampling points of 3–5 sites of each district, were cultured in Ashdown selective media. Suspected colonies of B. pseudomallei were identified by biochemical and serological test, and by polymerase chain reaction (PCR) using 16s rRNA specific primers. Blood samples were collected from 940 healthy individuals of four districts to determine anti- B. pseudomallei IgG antibody levels by indirect enzyme linked immunosorbent assay (ELISA) using sonicated crude antigen. Out of 179 soil samples, B. pseudomallei was isolated from two samples of Gazipur district which is located 58 km north of capital Dhaka city. Both the isolates were phenotypically identical, arabinose negative and showed specific 550bp band in PCR. Out of 940 blood samples, anti- B. pseudomallei IgG antibody, higher than the cut-off value (>0.8), was detected in 21.5% individuals. Seropositivity rate was 22.6%-30.8% in three districts from where melioidosis cases were detected earlier, compared to 9.8% in a district where no melioidosis case was either detected or reported (p<0.01). Seropositivity increased with the advancement of age from 5.3% to 30.4% among individuals aged 1–10 years and > 50 years respectively. The seropositivity rates were 26.0% and 20.6% in male and female respectively, while it was 20–27% among different occupational groups. No significant association was observed with gender (χ2 = 3.441, p = 0.064) or any occupational group (χ² = 3.835, p = 0.280).

Conclusion

This is the first study demonstrating the presence of B. pseudomallei in the environmental (soil) samples of Bangladesh. It also suggested that a large proportion of people, residing in these districts, were exposed to the organism.

Melioidosis, caused by B. pseudomallei, can be a fatal disease if not treated with appropriate antibiotics. The organism is mainly present in soil and water in endemic areas, and people become infected through skin inoculation, inhalation or ingestion. The disease has been sporadically detected in Bangladesh over last several decades. However, its actual prevalence in Bangladesh is largely unknown due to the lack of systematic study and awareness of the medical community about the disease and the organism. In order to address the issue, we have undertaken this study to assess the presence of the organism in the soil as well as its magnitude of exposure among the people of selected areas of the country. The study revealed the presence of B. pseudomallei in the soil and its exposure among the people of different areas. The information would increase the awareness of the medical community for prevention and correct diagnosis of the disease.

Laboratory diagnosis of melioidosis: past, present and future

Melioidosis is an emerging, potentially fatal disease caused by Burkholderia pseudomallei, which requires prolonged antibiotic treatment to prevent disease relapse. However, difficulties in laboratory diagnosis of melioidosis may delay treatment and affect disease outcomes. Isolation of B. pseudomallei from clinical specimens has been improved with the use of selective media. However, even with positive cultures, identification of B. pseudomallei can be difficult in clinical microbiology laboratories, especially in non-endemic areas where clinical suspicion is low. Commercial identification systems may fail to distinguish between B. pseudomallei and closely related species such as Burkholderia thailandensis. Genotypic identification of suspected isolates can be achieved by sequencing of gene targets such as groEL which offer higher discriminative power than 16S rRNA. Specific PCR-based identification of B. pseudomallei has also been developed using B. pseudomallei-specific gene targets such as Type III secretion system and Tat-domain protein. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry, a revolutionary technique for pathogen identification, has been shown to be potentially useful for rapid identification of B. pseudomallei, although existing databases require optimization by adding reference spectra for B. pseudomallei. Despite these advances in bacterial identification, diagnostic problems encountered in culture-negative cases remain largely unresolved. Although various serological tests have been developed, they are generally unstandardized "in house" assays and have low sensitivities and specificities. Although specific PCR assays have been applied to direct clinical and environmental specimens, the sensitivities for diagnosis remain to be evaluated. Metabolomics is an uprising tool for studying infectious diseases and may offer a novel approach for exploring potential diagnostic biomarkers. The metabolomics profiles of B. pseudomallei culture supernatants can be potentially distinguished from those of related bacterial species including B. thailandensis . Further studies using bacterial cultures and direct patient samples are required to evaluate the potential of metabolomics for improving diagnosis of melioidosis.

Biodegradation of PAHs by Burkholderia sp. VITRSB1 Isolated from Marine Sediments

The polycyclic aromatic hydrocarbons (PAHs) pollution to the environment is a major threat to the living organisms, and hence the degradation of these PAHs is necessary. Studies on PAHs degrading bacteria have focussed on terrestrial microbes and the potential of marine derived microbes is undermined. Herein we report the isolation and characterization of PAHs degrading Burkholderia sp. from lagoon sediments collected at the Southern coast of India. The strain was Gram negative, rod-shaped, motile, and ∼2-5 μm in length. Based on the phylogenetic data the strain was identified as Burkholderia and designated as VITRSB1. Initial PAHs degradation ability of the strain was assessed using basal salt medium supplemented with diesel, kerosene, toluene, aniline, naphthalene, and phenol. The strain was found to be effectively degrading kerosene, diesel, toluene, and aniline even at higher concentration (1%). However, naphthalene and aniline were degraded only at lower concentration (0.1%) and phenol, camphor, and DAP inhibited the growth of the strain. Furthermore, the degraded end products of the PAHs were determined using FTIR. Notably, none of the end products were found to be toxic to the biosphere. Our results indicate that the isolated Burkholderia sp. could be a prospective candidate for the effective degradation of selective PAHs.