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Clinical Microbiology Reviews Apr 2005Melioidosis, caused by the gram-negative saprophyte Burkholderia pseudomallei, is a disease of public health importance in southeast Asia and northern Australia that is... (Review)
Review
Melioidosis, caused by the gram-negative saprophyte Burkholderia pseudomallei, is a disease of public health importance in southeast Asia and northern Australia that is associated with high case-fatality rates in animals and humans. It has the potential for epidemic spread to areas where it is not endemic, and sporadic case reports elsewhere in the world suggest that as-yet-unrecognized foci of infection may exist. Environmental determinants of this infection, apart from a close association with rainfall, are yet to be elucidated. The sequencing of the genome of a strain of B. pseudomallei has recently been completed and will help in the further identification of virulence factors. The presence of specific risk factors for infection, such as diabetes, suggests that functional neutrophil defects are important in the pathogenesis of melioidosis; other studies have defined virulence factors (including a type III secretion system) that allow evasion of killing mechanisms by phagocytes. There is a possible role for cell-mediated immunity, but repeated environmental exposure does not elicit protective humoral or cellular immunity. A vaccine is under development, but economic constraints may make vaccination an unrealistic option for many regions of endemicity. Disease manifestations are protean, and no inexpensive, practical, and accurate rapid diagnostic tests are commercially available; diagnosis relies on culture of the organism. Despite the introduction of ceftazidime- and carbapenem-based intravenous treatments, melioidosis is still associated with a significant mortality attributable to severe sepsis and its complications. A long course of oral eradication therapy is required to prevent relapse. Studies exploring the role of preventative measures, earlier clinical identification, and better management of severe sepsis are required to reduce the burden of this disease.
Topics: Animals; Anti-Bacterial Agents; Burkholderia pseudomallei; Humans; Melioidosis
PubMed: 15831829
DOI: 10.1128/CMR.18.2.383-416.2005 -
BMC Microbiology May 2019Burkholderia pseudomallei is a human pathogen causing severe infections in tropical and subtropical regions and is classified as a bio-threat agent. B. thailandensis...
BACKGROUND
Burkholderia pseudomallei is a human pathogen causing severe infections in tropical and subtropical regions and is classified as a bio-threat agent. B. thailandensis strain E264 has been proposed as less pathogenic surrogate for understanding the interactions of B. pseudomallei with host cells.
RESULTS
We show that, unlike B. thailandensis strain E264, the pattern of growth of B. thailandensis strain E555 in macrophages is similar to that of B. pseudomallei. We have genome sequenced B. thailandensis strain E555 and using the annotated sequence identified genes and proteins up-regulated during infection. Changes in gene expression identified more of the known B. pseudomallei virulence factors than changes in protein levels and used together we identified 16% of the currently known B. pseudomallei virulence factors. These findings demonstrate the utility of B. thailandensis strain E555 to study virulence of B. pseudomallei.
CONCLUSIONS
A weakness of studies using B. thailandensis as a surrogate for B. pseudomallei is that the strains used replicate at a slower rate in infected cells. We show that the pattern of growth of B. thailandensis strain E555 in macrophages closely mirrors that of B. pseudomallei. Using this infection model we have shown that virulence factors of B. pseudomallei can be identified as genes or proteins whose expression is elevated on the infection of macrophages. This finding confirms the utility of B. thailandensis strain E555 as a surrogate for B. pseudomallei and this strain should be used for future studies on virulence mechanisms.
Topics: Animals; Burkholderia; Burkholderia pseudomallei; Cell Line; Gene Expression Profiling; Genome, Bacterial; Host-Pathogen Interactions; Macrophages; Mice; Microbial Viability; Virulence; Virulence Factors; Whole Genome Sequencing
PubMed: 31092204
DOI: 10.1186/s12866-019-1469-8 -
Infection and Immunity May 2015Burkholderia pseudomallei is a CDC tier 1 select agent that causes melioidosis, a severe disease in humans and animals. Persistent infections are common, and there is...
Burkholderia pseudomallei is a CDC tier 1 select agent that causes melioidosis, a severe disease in humans and animals. Persistent infections are common, and there is currently no vaccine available. Lipopolysaccharide (LPS) is a potential vaccine candidate. B. pseudomallei expresses three serologically distinct LPS types. The predominant O-polysaccharide (OPS) is an unbranched heteropolymer with repeating d-glucose and 6-deoxy-l-talose residues in which the 6-deoxy-l-talose residues are variably replaced with O-acetyl and O-methyl modifications. We observed that primary clinical B. pseudomallei isolates with mucoid and nonmucoid colony morphologies from the same sample expressed different antigenic types distinguishable using an LPS-specific monoclonal antibody (MAb). MAb-reactive (nonmucoid) and nonreactive (mucoid) strains from the same patient exhibited identical LPS banding patterns by silver staining and indistinguishable genotypes. We hypothesized that LPS antigenic variation reflected modification of the OPS moieties. Mutagenesis of three genes involved in LPS synthesis was performed in B. pseudomallei K96243. Loss of MAb reactivity was observed in both wbiA (encoding a 2-O-acetyltransferase) and wbiD (putative methyl transferase) mutants. The structural characteristics of the OPS moieties from isogenic nonmucoid strain 4095a and mucoid strain 4095c were further investigated. Utilizing nuclear magnetic resonance (NMR) spectroscopy, we found that B. pseudomallei 4095a and 4095c OPS antigens exhibited substitution patterns that differed from the prototypic OPS structure. Specifically, 4095a lacked 4-O-acetylation, while 4095c lacked both 4-O-acetylation and 2-O-methylation. Our studies indicate that B. pseudomallei OPS undergoes antigenic variation and suggest that the 9D5 MAb recognizes a conformational epitope that is influenced by both O-acetyl and O-methyl substitution patterns.
Topics: Antibodies, Bacterial; Antibodies, Monoclonal; Antigenic Variation; Burkholderia pseudomallei; Electrophoresis, Polyacrylamide Gel; Humans; Magnetic Resonance Spectroscopy; Melioidosis; O Antigens; Protein Binding
PubMed: 25776750
DOI: 10.1128/IAI.02785-14 -
Infection and Immunity Oct 2017The human pathogen and the related species are facultative intracellular bacteria characterized by the ability to escape into the cytosol of the host cell and to...
The human pathogen and the related species are facultative intracellular bacteria characterized by the ability to escape into the cytosol of the host cell and to stimulate the formation of multinucleated giant cells (MNGCs). MNGC formation is induced via an unknown mechanism by bacterial type VI secretion system 5 (T6SS-5), which is an essential virulence factor in both species. Despite the vital role of the intracellular life cycle in the pathogenesis of the bacteria, the range of host cell types permissive for initiation and completion of the intracellular cycle is poorly defined. In the present study, we used several different types of human primary cells to evaluate bacterial entry, intracellular survival, and MNGC formation. We report the capacity of to enter, efficiently replicate in, and mediate MNGC formation of vein endothelial and bronchial epithelial cells, indicating that the T6SS-5 is important in the host-pathogen interaction in these cells. Furthermore, we show that invades fibroblasts and keratinocytes and survives inside these cells as well as in monocyte-derived macrophages and neutrophils for at least 17 h postinfection; however, MNGC formation is not induced in these cells. In contrast, infection of mixed neutrophils and RAW264.7 macrophages with stimulated the formation of heterotypic MNGCs in a T6SS-5-dependent manner. In summary, the ability of the bacteria to enter and survive as well as induce MNGC formation in certain host cells may contribute to the pathogenesis observed in infection.
Topics: Animals; Bronchi; Burkholderia pseudomallei; Cell Line; Cells, Cultured; Cytosol; Endothelial Cells; Epithelial Cells; Fibroblasts; Giant Cells; Host-Pathogen Interactions; Humans; Keratinocytes; Macrophages; Mice; Neutrophils; Phagocytes; Type VI Secretion Systems; Virulence
PubMed: 28760929
DOI: 10.1128/IAI.00468-17 -
Microbiological Research Sep 2019The Burkholderia pseudomallei complex consists of six phylogenetically related Gram-negative bacterial species that include environmental saprophytes and mammalian... (Review)
Review
The Burkholderia pseudomallei complex consists of six phylogenetically related Gram-negative bacterial species that include environmental saprophytes and mammalian pathogens. These microbes possess multiple type VI secretion systems (T6SS) that provide a fitness advantage in diverse niches by translocating effector molecules into prokaryotic and eukaryotic cells in a contact-dependent manner. Several recent studies have elucidated the regulation and function of T6SS-2, a novel contact-independent member of the T6SS family. Expression of the T6SS-2 gene cluster is repressed by OxyR, Zur and TctR and is activated by GvmR and reactive oxygen species (ROS). The last two genes of the T6SS-2 gene cluster encode a zincophore (TseZ) and a manganeseophore (TseM) that are exported into the extracellular milieu in a contact-independent fashion when microbes encounter oxidative stress. TseZ and TseM bind Zn and Mn, respectively, and deliver them to bacteria where they provide protection against the lethal effects of ROS. The TonB-dependent transporters that interact with TseZ and TseM, and actively transport Zn and Mn across the outer membrane, have also been identified. Finally, T6SS-2 provides a contact-independent growth advantage in nutrient limited environments and is critical for virulence in Galleria mellonella larvae, but is dispensable for virulence in rodent models of infection.
Topics: Animals; Bacterial Proteins; Burkholderia pseudomallei; Gene Expression Regulation, Bacterial; Genes, Regulator; Homeostasis; Larva; Manganese; Membrane Transport Proteins; Methyltransferases; Multigene Family; Oxidation-Reduction; Oxidative Stress; Reactive Oxygen Species; Type VI Secretion Systems; Virulence; Zinc
PubMed: 31284944
DOI: 10.1016/j.micres.2019.05.007 -
Emerging Infectious Diseases 2021A melioidosis case cluster of 10 blood culture-positive patients occurred in eastern Sri Lanka after an extreme weather event. Four infections were caused by...
A melioidosis case cluster of 10 blood culture-positive patients occurred in eastern Sri Lanka after an extreme weather event. Four infections were caused by Burkholderia pseudomallei isolates of sequence type 594. Whole-genome analysis showed that the isolates were genetically diverse and the case cluster was nonclonal.
Topics: Burkholderia pseudomallei; Humans; Melioidosis; Sri Lanka
PubMed: 34379585
DOI: 10.3201/eid2711.210219 -
Journal of Clinical Microbiology Dec 2016Melioidosis is a potentially fatal infection caused by the bacterium Burkholderia pseudomallei Clinical diagnosis of melioidosis can be challenging since there is no... (Review)
Review
Melioidosis is a potentially fatal infection caused by the bacterium Burkholderia pseudomallei Clinical diagnosis of melioidosis can be challenging since there is no pathognomonic clinical syndrome, and the organism is often misidentified by methods used routinely in clinical laboratories. Although the disease is more prevalent in Thailand and northern Australia, sporadic cases may be encountered in areas where it is not endemic, including the United States. Since the organism is considered a tier 1 select agent according to the Centers for Disease Control and Prevention and the U.S. Department of Agriculture Animal and Plant Health Inspection Service, clinical laboratories must be proficient at rapidly recognizing isolates suspicious for B. pseudomallei, be able to safely perform necessary rule-out tests, and to refer suspect isolates to Laboratory Response Network reference laboratories. In this minireview, we report a case of melioidosis encountered at our institution and discuss the laboratory challenges encountered when dealing with clinical isolates suspicious for B. pseudomallei or clinical specimens from suspected melioidosis cases.
Topics: Aged; Aneurysm, Infected; Anti-Bacterial Agents; Bacterial Typing Techniques; Burkholderia pseudomallei; Drug Resistance, Multiple, Bacterial; Female; Humans; Melioidosis; Microbial Sensitivity Tests
PubMed: 27654336
DOI: 10.1128/JCM.01636-16 -
PLoS Neglected Tropical Diseases Dec 2020Melioidosis is a neglected tropical disease with rising global public health and clinical importance. Melioidosis is endemic in Southeast Asia and Northern Australia and...
BACKGROUND
Melioidosis is a neglected tropical disease with rising global public health and clinical importance. Melioidosis is endemic in Southeast Asia and Northern Australia and is of increasing concern in Malaysia. Despite a number of reported studies from Malaysia, these reports are limited to certain parts of the country and do not provide a cohesive link between epidemiology of melioidosis cases and the nation-wide distribution of the causative agent Burkholderia pseudomallei.
METHODOLOGY/PRINCIPLE FINDINGS
Here we report on the distribution of B. pseudomallei sequence types (STs) in Malaysia and how the STs are related to STs globally. We obtained 84 culture-confirmed B. pseudomallei from confirmed septicaemic melioidosis patients from all over Malaysia. Prior to performing Multi Locus Sequence Typing, the isolates were subjected to antimicrobial susceptibility testing and detection of the YLF/BTFC genes and BimA allele. Up to 90.5% of the isolates were sensitive to all antimicrobials tested while resistance was observed for antimicrobials typically administered during the eradication stage of treatment. YLF gene cluster and bimABp allele variant were detected in all the isolates. The epidemiological distribution patterns of the Malaysian B. pseudomallei isolates were analysed in silico using phylogenetic tools and compared to Southeast Asian and world-wide isolates. Genotyping of the 84 Malaysian B. pseudomallei isolates revealed 29 different STs of which 6 (7.1%) were novel. ST50 was identified as the group founder followed by subgroup founders ST376, ST211 and ST84. A low-level diversity is noted for the B. pseudomallei isolates described in this study while phylogenetic analysis associated the Malaysian STs to Southeast Asian isolates especially isolates from Thailand. Further analysis also showed a strong association that implicates agriculture and domestication activities as high-risk routes of infection.
CONCLUSIONS/SIGNIFICANCE
In conclusion, MLST analysis of B. pseudomallei clinical isolates from all states in Malaysia revealed low diversity and a close association to Southeast Asian isolates.
Topics: Bacterial Typing Techniques; Burkholderia pseudomallei; DNA, Bacterial; Humans; Malaysia; Melioidosis; Molecular Epidemiology; Multilocus Sequence Typing; Sequence Analysis, DNA
PubMed: 33370273
DOI: 10.1371/journal.pntd.0008979 -
Applied and Environmental Microbiology May 2021Melioidosis is a life-threatening disease in humans caused by the Gram-negative bacterium Burkholderia pseudomallei. As severe septicemic melioidosis can lead to death...
Melioidosis is a life-threatening disease in humans caused by the Gram-negative bacterium Burkholderia pseudomallei. As severe septicemic melioidosis can lead to death within 24 to 48 h, a rapid diagnosis of melioidosis is critical for ensuring that an optimal antibiotic course is prescribed to patients. Here, we report the development and evaluation of a bacteriophage tail fiber-based latex agglutination assay for rapid detection of B. pseudomallei infection. phage E094 was isolated from rice paddy fields in northeast Thailand, and the whole genome was sequenced to identify its tail fiber (94TF). The 94TF complex was structurally characterized, which involved identification of a tail assembly protein that forms an essential component of the mature fiber. Recombinant 94TF was conjugated to latex beads and developed into an agglutination-based assay (94TF-LAA). 94TF-LAA was initially tested against a large library of and other bacterial strains before a field evaluation was performed during routine clinical testing. The sensitivity and specificity of the 94TF-LAA were assessed alongside standard biochemical analyses on 300 patient specimens collected from an area of melioidosis endemicity over 11 months. The 94TF-LAA took less than 5 min to produce positive agglutination, demonstrating 98% (95% confidence interval [CI] of 94.2% to 99.59%) sensitivity and 83% (95% CI of 75.64% to 88.35%) specificity compared to biochemical-based detection. Overall, we show how a -specific phage tail fiber can be exploited for rapid detection of B. pseudomallei. The 94TF-LAA has the potential for further development as a supplementary diagnostic to assist in clinical identification of this life-threatening pathogen. Rapid diagnosis of melioidosis is essential for ensuring that optimal antibiotic courses are prescribed to patients and thus warrants the development of cost-effective and easy-to-use tests for implementation in underresourced areas such as northeastern Thailand and other tropical regions. Phage tail fibers are an interesting alternative to antibodies for use in various diagnostic assays for different pathogenic bacteria. As exposed appendages of phages, tail fibers are physically robust and easy to manufacture, with many tail fibers (such as 94TF investigated here) capable of targeting a given bacterial species with remarkable specificity. Here, we demonstrate the effectiveness of a latex agglutination assay using a -specific tail fiber 94TF against biochemical-based detection methods that are the standard diagnostic in many areas where melioidosis is endemic.
Topics: Bacteriophages; Burkholderia pseudomallei; Capsid Proteins; Humans; Latex Fixation Tests; Melioidosis; Sensitivity and Specificity
PubMed: 33811022
DOI: 10.1128/AEM.03019-20 -
BMC Infectious Diseases Jan 2018Previous studies on the Burkholderia pseudomallei genetic diversity among clinical isolates from melioidosis-endemic areas have identified genetic factors contributing...
BACKGROUND
Previous studies on the Burkholderia pseudomallei genetic diversity among clinical isolates from melioidosis-endemic areas have identified genetic factors contributing to differential virulence. Although it has been ruled out in Australian and Thai B. pseudomallei populations, it remains unclear whether B. pseudomallei sequence types (STs) correlate with disease in Malaysian patients with melioidosis.
METHODS
In this study, multi-locus sequence typing (MLST) was performed on clinical B. pseudomallei isolates collected from Kelantan state of Malaysia, patients' clinical data were reviewed and then genotype-risk correlations were investigated.
RESULTS
Genotyping of 83 B. pseudomallei isolates revealed 32 different STs, of which 13(40%) were novel. The frequencies of the STs among the 83 isolates ranged from 1 to 12 observations, and ST54, ST371 and ST289 were predominant. All non-novel STs reported in this study have also been identified in other Asian countries. Based on the MLST data analysis, the phylogenetic tree showed clustering of the STs with each other, as well as with the STs from Southeast Asia and China. No evidence for associations between any of B. pseudomallei STs and clinical melioidosis presentation was detected. In addition, the bacterial genotype clusters in relation with each clinical outcome were statistically insignificant, and no risk estimate was reported. This study has expanded the data for B. pseudomallei on MLST database map and provided insights into the molecular epidemiology of melioidosis in Peninsular Malaysia.
CONCLUSION
This study concurs with previous reports concluding that infecting strain type plays no role in determining disease presentation.
Topics: Asia, Southeastern; Bacterial Typing Techniques; Burkholderia pseudomallei; China; Cluster Analysis; Female; Genotype; Humans; Malaysia; Melioidosis; Molecular Epidemiology; Multilocus Sequence Typing; Phylogeny; Polymorphism, Single Nucleotide; Virulence
PubMed: 29291714
DOI: 10.1186/s12879-017-2912-9