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The American Journal of Tropical... Nov 2015The resilience of Burkholderia pseudomallei, the causative agent of melioidosis, was evaluated in control soil microcosms and in soil microcosms containing NaCl or FeSO4...
The resilience of Burkholderia pseudomallei, the causative agent of melioidosis, was evaluated in control soil microcosms and in soil microcosms containing NaCl or FeSO4 at 30°C. Iron (Fe(II)) promoted the growth of B. pseudomallei during the 30-day observation, contrary to the presence of 1.5% and 3% NaCl. Scanning electron micrographs of B. pseudomallei in soil revealed their morphological alteration from rod to coccoid and the formation of microcolonies. The smallest B. pseudomallei cells were found in soil with 100 μM FeSO4 compared with in the control soil or soil with 0.6% NaCl (P < 0.05). The colony count on Ashdown's agar and bacterial viability assay using the LIVE/DEAD(®) BacLight(™) stain combined with flow cytometry showed that B. pseudomallei remained culturable and viable in the control soil microcosms for at least 120 days. In contrast, soil with 1.5% NaCl affected their culturability at day 90 and their viability at day 120. Our results suggested that a low salinity and iron may influence the survival of B. pseudomallei and its ability to change from a rod-like to coccoid form. The morphological changes of B. pseudomallei cells may be advantageous for their persistence in the environment and may increase the risk of their transmission to humans.
Topics: Burkholderia pseudomallei; Environment; Ferric Compounds; Humans; Melioidosis; Microbial Viability; Microscopy, Electron, Scanning; Salinity; Sodium Chloride; Soil; Soil Microbiology
PubMed: 26324731
DOI: 10.4269/ajtmh.15-0177 -
PloS One 2014Burkholderia mallei and Burkholderia pseudomallei are potentially lethal pathogens categorized as biothreat agents due, in part, to their ability to be disseminated via...
Burkholderia mallei and Burkholderia pseudomallei are potentially lethal pathogens categorized as biothreat agents due, in part, to their ability to be disseminated via aerosol. There are no protective vaccines against these pathogens and treatment options are limited and cumbersome. Since disease severity is greatest when these agents are inhaled, efforts to develop pre- or post-exposure prophylaxis focus largely on inhalation models of infection. Here, we demonstrate a non-invasive and technically simple method for affecting the inhalational challenge of BALB/c mice with B. pseudomallei and B. mallei. In this model, two investigators utilized common laboratory tools such as forceps and a micropipette to conduct and characterize an effective and reproducible inhalational challenge of BALB/c mice with B. mallei and B. pseudomallei. Challenge by oropharyngeal aspiration resulted in acute disease. Additionally, 50% endpoints for B. pseudomallei K96243 and B. mallei ATCC 23344 were nearly identical to published aerosol challenge methods. Furthermore, the pathogens disseminated to all major organs typically targeted by these agents where they proliferated. The pro-inflammatory cytokine production in the proximal and peripheral fluids demonstrated a rapid and robust immune response comparable to previously described murine and human studies. These observations demonstrate that OA is a viable alternative to aerosol exposure.
Topics: Acute Disease; Animals; Bacterial Infections; Burkholderia mallei; Burkholderia pseudomallei; Disease Models, Animal; Female; Host-Pathogen Interactions; Humans; Immunity, Innate; Mice; Mice, Inbred BALB C; Post-Exposure Prophylaxis
PubMed: 25503969
DOI: 10.1371/journal.pone.0115066 -
Frontiers in Immunology 2021() causes melioidosis, a potentially fatal disease for which no licensed vaccine is available thus far. The host-pathogen interactions in infection largely remain the... (Review)
Review
() causes melioidosis, a potentially fatal disease for which no licensed vaccine is available thus far. The host-pathogen interactions in infection largely remain the tip of the iceberg. The pathological manifestations are protean ranging from acute to chronic involving one or more visceral organs leading to septic shock, especially in individuals with underlying conditions similar to COVID-19. Pathogenesis is attributed to the intracellular ability of the bacterium to 'step into' the host cell's cytoplasm from the endocytotic vacuole, where it appears to polymerize actin filaments to spread across cells in the closer vicinity. effectively evades the host's surveillance armory to remain latent for prolonged duration also causing relapses despite antimicrobial therapy. Therefore, eradication of intracellular is highly dependent on robust cellular immune responses. However, it remains ambiguous why certain individuals in endemic areas experience asymptomatic seroconversion, whereas others succumb to sepsis-associated sequelae. Here, we propose key insights on how the host's surveillance radars get commandeered by .
Topics: Animals; Burkholderia pseudomallei; Host Microbial Interactions; Humans; Immunologic Surveillance; Melioidosis; Virulence
PubMed: 34456925
DOI: 10.3389/fimmu.2021.718719 -
Microbial Genomics Feb 2021, a soil-dwelling Gram-negative bacterium, is the causative agent of the endemic tropical disease melioidosis. Clinical manifestations of infection range from acute or...
, a soil-dwelling Gram-negative bacterium, is the causative agent of the endemic tropical disease melioidosis. Clinical manifestations of infection range from acute or chronic localized infection in a single organ to fulminant septicaemia in multiple organs. The diverse clinical manifestations are attributed to various factors, including the genome plasticity across strains. We previously characterized strains isolated in Malaysia and noted different levels of virulence in model hosts. We hypothesized that the difference in virulence might be a result of variance at the genome level. In this study, we sequenced and assembled four Malaysian clinical isolates, UKMR15, UKMPMC2000, UKMD286 and UKMH10. Phylogenomic analysis showed that Malaysian subclades emerged from the Asian subclade, suggesting that the Malaysian strains originated from the Asian region. Interestingly, the low-virulence strain, UKMH10, was the most distantly related compared to the other Malaysian isolates. Genomic island (GI) prediction analysis identified a new island of 23 kb, GI9c, which is present in and , but not . Genes encoding known virulence factors were present across all four genomes, but comparative analysis of the total gene content across the Malaysian strains identified 104 genes that are absent in UKMH10. We propose that these genes may encode novel virulence factors, which may explain the reduced virulence of this strain. Further investigation on the identity and role of these 104 proteins may aid in understanding pathogenicity to guide the design of new therapeutics for treating melioidosis.
Topics: Bacterial Typing Techniques; Burkholderia pseudomallei; Genome Size; Genome, Bacterial; Genomic Islands; Genomics; High-Throughput Nucleotide Sequencing; Humans; Malaysia; Melioidosis; Multilocus Sequence Typing; Phylogeny; Virulence Factors; Whole Genome Sequencing
PubMed: 33565959
DOI: 10.1099/mgen.0.000527 -
Current Opinion in Microbiology Feb 2016The Burkholderia genus contains a group of soil-dwelling Gram-negative organisms that are prevalent in warm and humid climates. Two species in particular are able to... (Review)
Review
The Burkholderia genus contains a group of soil-dwelling Gram-negative organisms that are prevalent in warm and humid climates. Two species in particular are able to cause disease in animals, B. mallei primarily infects Equus spp. and B. pseudomallei (BPS), that is able to cause potentially life-threatening disease in humans. BPS is naturally resistant to many antibiotics and there is no vaccine available. Although not a specialised human pathogen, BPS possesses a large genome and many virulence traits that allow it to adapt and survive very successfully in the human host. Key to this survival is the ability of BPS to replicate intracellularly. In this review we highlight recent advances in our understanding of the intracellular survival of BPS, including how it overcomes host immune defenses and other challenges to establish its niche and then spread the infection. Knowledge of these mechanisms increases our capacity for therapeutic interventions against a well-armed foe.
Topics: Actins; Animals; Burkholderia pseudomallei; Cytoplasm; DNA Replication; Giant Cells; Host-Pathogen Interactions; Humans; Melioidosis; Type VI Secretion Systems; Virulence; Virulence Factors
PubMed: 26803404
DOI: 10.1016/j.mib.2015.11.007 -
Journal of Clinical Microbiology Sep 2017Clinical outcomes of melioidosis patients improve when the infecting agent, , is rapidly detected and identified by laboratory testing. Detection of DNA or recovery of...
Clinical outcomes of melioidosis patients improve when the infecting agent, , is rapidly detected and identified by laboratory testing. Detection of DNA or recovery of the pathogen by culture from urine can support a diagnosis of melioidosis and guide patient care. Two new methods, designated filter-capture DNA isolation (FCDI) and filter cellular recovery (FCR), were developed to increase the sensitivity of detection and recovery of viable cells from small volumes (0.45 ml) of urine. DNA from eight strains of that were spiked into synthetic urine at low concentrations (1 × 10 CFU/ml) was detected in FCDI cell lysates using real-time PCR with greater consistency than with preparations from a QIAamp DNA Blood minikit. The FCR method showed greater detection sensitivity than conventional urine culture methods and resulted in typical colony growth at 24 h from as few as 1 × 10 CFU/ml. In addition, the FCR method does not rely on precipitation of a urine pellet by centrifugation and requires a smaller volume of urine. The FCDI and FCR methods described here could improve time-to-results and decrease the number of negative reports that are currently observed from urine culture as a consequence of samples containing low or variable bacterial cell concentrations.
Topics: Burkholderia pseudomallei; DNA, Bacterial; Humans; Melioidosis; Real-Time Polymerase Chain Reaction; Sensitivity and Specificity; Urinalysis
PubMed: 28637908
DOI: 10.1128/JCM.00764-17 -
MSphere Jan 2019is a Gram-negative facultative intracellular bacterium and the causative agent of melioidosis, a severe infectious disease found throughout the tropics. This organism...
is a Gram-negative facultative intracellular bacterium and the causative agent of melioidosis, a severe infectious disease found throughout the tropics. This organism is closely related to , the etiological agent of glanders disease which primarily affects equines. These two pathogenic bacteria are classified as Tier 1 select agents due to their amenability to aerosolization, limited treatment options, and lack of an effective vaccine. We have previously successfully demonstrated the immunogenicity and protective efficacy of a live attenuated vaccine strain, (CLH001). Thus, we applied this successful approach to the development of a similar vaccine against melioidosis by constructing the (PBK001) strain. C57BL/6 mice were vaccinated intranasally with the live attenuated PBK001 strain and then challenged with wild-type K96243 by the aerosol route. Immunization with strain PBK001 resulted in full protection (100% survival) against acute aerosolized melioidosis with very low bacterial burden as observed in the lungs, livers, and spleens of immunized mice. PBK001 vaccination induced strong production of -specific serum IgG antibodies and both Th1 and Th17 CD4 T cell responses. Further, humoral immunity appeared to be essential for vaccine-induced protection, whereas CD4 and CD8 T cells played a less direct immune role. Overall, PBK001 was shown to be an effective attenuated vaccine strain that activates a robust immune response and offers full protection against aerosol infection with In recent years, an increasing number of melioidosis cases have been reported in several regions where melioidosis is endemic and in areas where melioidosis had not commonly been diagnosed. Currently, the estimated burden of disease is around 165,000 new cases annually, including 89,000 cases that have fatal outcomes. This life-threatening infectious disease is caused by , which is classified as a Tier 1 select agent. Due to the high case fatality rate, intrinsic resistance to multiple antibiotic treatments, susceptibility to infection via the aerosol route, and potential use as a bioweapon, we have developed an effective live attenuated PBK001 vaccine capable of protecting against aerosolized melioidosis.
Topics: Animals; Antibodies, Bacterial; Bacterial Vaccines; Burkholderia pseudomallei; Disease Models, Animal; Female; Melioidosis; Mice, Inbred C57BL; Vaccines, Attenuated
PubMed: 30602524
DOI: 10.1128/mSphere.00570-18 -
Scientific Reports Jan 2022Burkholderia pseudomallei is a saprophytic bacterium endemic throughout the tropics causing severe disease in humans and animals. Environmental signals such as the...
Burkholderia pseudomallei is a saprophytic bacterium endemic throughout the tropics causing severe disease in humans and animals. Environmental signals such as the accumulation of inorganic ions mediates the biofilm forming capabilities and survival of B. pseudomallei. We have previously shown that B. pseudomallei responds to nitrate and nitrite by inhibiting biofilm formation and altering cyclic di-GMP signaling. To better understand the roles of nitrate-sensing in the biofilm inhibitory phenotype of B. pseudomallei, we created in-frame deletions of narX (Bp1026b_I1014) and narL (Bp1026b_I1013), which are adjacent components of a conserved nitrate-sensing two-component system. We observed transcriptional downregulation in key components of the biofilm matrix in response to nitrate and nitrite. Some of the most differentially expressed genes were nonribosomal peptide synthases (NRPS) and/or polyketide synthases (PKS) encoding the proteins for the biosynthesis of bactobolin, malleilactone, and syrbactin, and an uncharacterized cryptic NRPS biosynthetic cluster. RNA expression patterns were reversed in ∆narX and ∆narL mutants, suggesting that nitrate sensing is an important checkpoint for regulating the diverse metabolic changes occurring in the biofilm inhibitory phenotype. Moreover, in a macrophage model of infection, ∆narX and ∆narL mutants were attenuated in intracellular replication, suggesting that nitrate sensing contributes to survival in the host.
Topics: Bacterial Proteins; Benzopyrans; Biofilms; Biological Products; Burkholderia pseudomallei; Gene Expression Regulation, Bacterial; Host-Pathogen Interactions; Lactones; Microbial Viability; Mutation; Nitrates; Nitrites; Transcription, Genetic
PubMed: 34997073
DOI: 10.1038/s41598-021-04053-6 -
Microbiology Spectrum Sep 2021Burkholderia pseudomallei is an opportunistic pathogen that is responsible for the disease melioidosis in humans and animals. The microbe is a tier 1 select agent...
Burkholderia pseudomallei is an opportunistic pathogen that is responsible for the disease melioidosis in humans and animals. The microbe is a tier 1 select agent because it is highly infectious by the aerosol route, it is inherently resistant to multiple antibiotics, and no licensed vaccine currently exists. Naturally acquired infections result from contact with contaminated soil or water sources in regions of endemicity. There have been few reports investigating the molecular mechanism(s) utilized by B. pseudomallei to survive and persist in ecological niches harboring microbial competitors. Here, we report the isolation of Gram-positive bacteria from multiple environmental sources and show that ∼45% of these isolates are inhibited by B. pseudomallei in head-to-head competition assays. Two competition-deficient B. pseudomallei transposon mutants were identified that contained insertion mutations in the operon. This large biosynthetic gene cluster encodes the enzymes that produce a family of secondary metabolites called 4-hydroxy-3-methyl-2-alkylquinolines (HMAQs). Liquid chromatography and mass spectrometry conducted on filter-sterilized culture supernatants revealed five HMAQs and -oxide derivatives that were produced by the parental strain but were absent in an isogenic deletion mutant. The results demonstrate that B. pseudomallei inhibits the growth of environmental Gram-positive bacteria in a contact-independent manner via the production of HMAQs by the operon. Burkholderia pseudomallei naturally resides in water, soil, and the rhizosphere and its success as an opportunistic pathogen is dependent on the ability to persist in these harsh habitats long enough to come into contact with a susceptible host. In addition to adapting to limiting nutrients and diverse chemical and physical challenges, B. pseudomallei also has to interact with a variety of microbial competitors. Our research shows that one of the ways in which B. pseudomallei competes with Gram-positive environmental bacteria is by exporting a diverse array of closely related antimicrobial secondary metabolites.
Topics: Anti-Bacterial Agents; Bacterial Proteins; Burkholderia pseudomallei; Gram-Positive Bacteria; Microbial Interactions; Mutagenesis, Insertional; Operon; Secondary Metabolism
PubMed: 34160272
DOI: 10.1128/Spectrum.00102-21 -
Infection and Immunity Sep 2012Burkholderia pseudomallei is a Gram-negative soil bacterium and the causative agent of melioidosis, a disease of humans and animals. It is also listed as a category B...
Burkholderia pseudomallei is a Gram-negative soil bacterium and the causative agent of melioidosis, a disease of humans and animals. It is also listed as a category B bioterrorism threat agent by the U.S. Centers for Disease Control and Prevention, and there is currently no melioidosis vaccine available. Small modified nucleotides such as the hyperphosphorylated guanosine molecules ppGpp and pppGpp play an important role as signaling molecules in prokaryotes. They mediate a global stress response under starvation conditions and have been implicated in the regulation of virulence and survival factors in many bacterial species. In this study, we created a relA spoT double mutant in B. pseudomallei strain K96243, which lacks (p)ppGpp-synthesizing enzymes, and investigated its phenotype in vitro and in vivo. The B. pseudomallei ΔrelA ΔspoT mutant displayed a defect in stationary-phase survival and intracellular replication in murine macrophages. Moreover, the mutant was attenuated in the Galleria mellonella insect model and in both acute and chronic mouse models of melioidosis. Vaccination of mice with the ΔrelA ΔspoT mutant resulted in partial protection against infection with wild-type B. pseudomallei. In summary, (p)ppGpp signaling appears to represent an essential component of the regulatory network governing virulence gene expression and stress adaptation in B. pseudomallei, and the ΔrelA ΔspoT mutant may be a promising live-attenuated vaccine candidate.
Topics: Animals; Bacterial Vaccines; Burkholderia pseudomallei; Disease Models, Animal; Female; Gene Deletion; Humans; Lepidoptera; Ligases; Macrophages; Melioidosis; Mice; Mice, Inbred C57BL; Microbial Viability; Pyrophosphatases; Survival Analysis; Vaccines, Attenuated; Virulence; Virulence Factors
PubMed: 22778096
DOI: 10.1128/IAI.00178-12