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Autotransporters and Their Role in the Virulence of Burkholderia pseudomallei and Burkholderia mallei  [PDF]
Joanne M. Stevens,Edouard E. Galyov
Frontiers in Microbiology , 2011, DOI: 10.3389/fmicb.2011.00151
Abstract: Burkholderia pseudomallei and Burkholderia mallei are closely related Gram-negative bacteria responsible for the infectious diseases melioidosis and glanders, respectively. Autotransporters (ATs) comprise a large and diverse family of secreted and outer membrane proteins that includes virulence-associated invasins, adhesins, proteases, and actin-nucleating factors. The B. pseudomallei K96243 genome contains 11 predicted ATs, eight of which share homologs in the B. mallei ATCC 23344 genome. This review distils key findings from in silico, in vitro, and in vivo studies on the ATs of B. pseudomallei and B. mallei. To date, the best characterized of the predicted ATs of B. pseudomallei and B. mallei is BimA, a predicted trimeric AT mediating actin-based motility which varies in sequence and mode of action between Burkholderia species. Of the remaining eight predicted B. pseudomallei trimeric autotransporters, five of which are also present in B. mallei, two (BoaA and BoaB), have been implicated in bacterial adhesion to epithelial cells. Several predicted Burkholderia ATs are recognized by human humoral and cell-mediated immunity, indicating that they are expressed during infection and may be useful for diagnosis and vaccine-mediated protection. Further studies on the mode of secretion and functions of Burkholderia ATs will facilitate the rational design of control strategies.
Survival of Burkholderia pseudomallei in Water
Richard A Moore, Apichai Tuanyok, Donald E Woods
BMC Research Notes , 2008, DOI: 10.1186/1756-0500-1-11
Abstract: Increased expression of a gene encoding for a putative membrane protein (BPSL0721) was confirmed using a lux-based transcriptional reporter system, and maximal expression was noted at approximately 6 hrs after shifting cells from LB to water. A BPSL0721 deficient mutant of B. pseudomallei was able to survive in water for at least 90 days indicating that although involved, BPSL0721 was not essential for survival. BPSL2961, a gene encoding a putative phosphatidylglycerol phosphatase (PGP), was also induced when cells were shifted to water. This gene is likely involved in cell membrane biosynthesis. We were unable to construct a PGP mutant suggesting that the gene is not only involved in survival in water but is essential for cell viability. We also examined mutants of polyhydroxybutyrate synthase (phbC), lipopolysaccharide (LPS) oligosaccharide and capsule synthesis, and these mutations did not affect survival in water. LPS mutants lacking outer core were found to lose viability in water by 200 days indicating that an intact LPS core provides an outer membrane architecture which allows prolonged survival in water.The results from these studies suggest that B. pseudomallei survival in water is a complex process that requires an LPS molecule which contains an intact core region.Burkholderia pseudomallei is the causative agent of melioidosis, a disease endemic to southeast Asia, northern Australia and temperate areas that lie near the equator[1]. The disease is classified by acute, subacute and chronic illnesses and often mistaken for malaria, plague, pneumonia and miliary tuberculosis [2]. The acute form of the disease is a septicemic illness and is often fatal despite antibiotic treatment. Subacute meliodosis often results in multi-organ involvement, systemic abscess formation and bacteremia [3]. Chronic meliodosis often is detected only after post mortem examination or by activation of other forms of the disease as a result of a traumatic event [4]. Infection most lik
Development of Burkholderia mallei and pseudomallei vaccines  [PDF]
Ediane B. Silva,Steven W. Dow
Frontiers in Cellular and Infection Microbiology , 2013, DOI: 10.3389/fcimb.2013.00010
Abstract: Burkholderia mallei and Burkholderia pseudomallei are Gram-negative bacteria that cause glanders and melioidosis, respectively. Inhalational infection with either organism can result in severe and rapidly fatal pneumonia. Inoculation by the oral and cutaneous routes can also produce infection. Chronic infection may develop after recovery from acute infection with both agents, and control of infection with antibiotics requires prolonged treatment. Symptoms for both meliodosis and glanders are non-specific, making diagnosis difficult. B. pseudomallei can be located in the environment, but in the host, B. mallei and B. psedomallei are intracellular organisms, and infection results in similar immune responses to both agents. Effective early innate immune responses are critical to controlling the early phase of the infection. Innate immune signaling molecules such as TLR, NOD, MyD88, and pro-inflammatory cytokines such as IFN-γ and TNF-α play key roles in regulating control of infection. Neutrophils and monocytes are critical cells in the early infection for both microorganisms. Both monocytes and macrophages are necessary for limiting dissemination of B. pseudomallei. In contrast, the role of adaptive immune responses in controlling Burkholderia infection is less well understood. However, T cell responses are critical for vaccine protection from Burkholderia infection. At present, effective vaccines for prevention of glanders or meliodosis have not been developed, although recently development of Burkholderia vaccines has received renewed attention. This review will summarize current and past approaches to develop B. mallei and B. pseudomalllei vaccines, with emphasis on immune mechanisms of protection and the challenges facing the field. At present, immunization with live attenuated bacteria provides the most effective and durable immunity, and it is important therefore to understand the immune correlates of protection induced by live attenuated vaccines. Subunit vaccines have typically provided less robust immunity, but are safer to administer to a wider variety of people, including immune compromised individuals because they do not reactivate or cause disease. The challenges facing B. mallei and B. pseudomalllei vaccine development include identification of broadly protective antigens, design of efficient vaccine delivery and adjuvant systems, and a better understanding of the correlates of protection from both acute and chronic infection.
Development of Vaccines Against Burkholderia Pseudomallei  [PDF]
Natasha Patel,Melanie De Reynal
Frontiers in Microbiology , 2011, DOI: 10.3389/fmicb.2011.00198
Abstract: Burkholderia pseudomallei is a Gram-negative bacterium which is the causative agent of melioidosis, a disease which carries a high mortality and morbidity rate in endemic areas of South East Asia and Northern Australia. At present there is no available human vaccine that protects against B. pseudomallei, and with the current limitations of antibiotic treatment, the development of new preventative and therapeutic interventions is crucial. This review considers the multiple elements of melioidosis vaccine research including: (i) the immune responses required for protective immunity, (ii) animal models available for preclinical testing of potential candidates, (iii) the different experimental vaccine strategies which are being pursued, and (iv) the obstacles and opportunities for eventual registration of a licensed vaccine in humans.
Burkholderia pseudomallei transcriptional adaptation in macrophages  [cached]
Chieng Sylvia,Carreto Laura,Nathan Sheila
BMC Genomics , 2012, DOI: 10.1186/1471-2164-13-328
Abstract: Background Burkholderia pseudomallei is a facultative intracellular pathogen of phagocytic and non-phagocytic cells. How the bacterium interacts with host macrophage cells is still not well understood and is critical to appreciate the strategies used by this bacterium to survive and how intracellular survival leads to disease manifestation. Results Here we report the expression profile of intracellular B. pseudomallei following infection of human macrophage-like U937 cells. During intracellular growth over the 6 h infection period, approximately 22 % of the B. pseudomallei genome showed significant transcriptional adaptation. B. pseudomallei adapted rapidly to the intracellular environment by down-regulating numerous genes involved in metabolism, cell envelope, motility, replication, amino acid and ion transport system and regulatory function pathways. Reduced expression in catabolic and housekeeping genes suggested lower energy requirement and growth arrest during macrophage infection, while expression of genes encoding anaerobic metabolism functions were up regulated. However, whilst the type VI secretion system was up regulated, expression of many known virulence factors was not significantly modulated over the 6hours of infection. Conclusions The transcriptome profile described here provides the first comprehensive view of how B. pseudomallei survives within host cells and will help identify potential virulence factors and proteins that are important for the survival and growth of B. pseudomallei within human cells.
Burkholderia pseudomallei: abscess in an unusual site.  [cached]
Kiertiburanakul S,Sungkanuparph S,Kositchiwat S,Vorachit M
Journal of Postgraduate Medicine , 2002,
Abstract: Melioidosis is an infection caused by Burkholderia pseudomallei. It is an important human pathogen in tropical area. The clinical manifestations are protean and multisystem involvement. We report an unusual case of melioidosis with abscess at root of mesentery in an elderly, non-insulin dependent diabetic Thai women. She presented with prolonged fever and chronic abdominal pain. The early clinical diagnosis was carcinomatous mass with peritonitis. Diagnosis of melioidosis arose from the surgical finding and pus culture. Treatment with surgical drainage and ceftazidime followed by co-trimoxazole plus doxycycline had a good clinical outcome.
Evolution of Burkholderia pseudomallei in Recurrent Melioidosis  [PDF]
Hillary S. Hayden, Regina Lim, Mitchell J. Brittnacher, Elizabeth H. Sims, Elizabeth R. Ramage, Christine Fong, Zaining Wu, Eva Crist, Jean Chang, Yang Zhou, Matthew Radey, Laurence Rohmer, Eric Haugen, Will Gillett, Vanaporn Wuthiekanun, Sharon J. Peacock, Rajinder Kaul, Samuel I. Miller, Colin Manoil, Michael A. Jacobs
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0036507
Abstract: Burkholderia pseudomallei, the etiologic agent of human melioidosis, is capable of causing severe acute infection with overwhelming septicemia leading to death. A high rate of recurrent disease occurs in adult patients, most often due to recrudescence of the initial infecting strain. Pathogen persistence and evolution during such relapsing infections are not well understood. Bacterial cells present in the primary inoculum and in late infections may differ greatly, as has been observed in chronic disease, or they may be genetically similar. To test these alternative models, we conducted whole-genome comparisons of clonal primary and relapse B. pseudomallei isolates recovered six months to six years apart from four adult Thai patients. We found differences within each of the four pairs, and some, including a 330 Kb deletion, affected substantial portions of the genome. Many of the changes were associated with increased antibiotic resistance. We also found evidence of positive selection for deleterious mutations in a TetR family transcriptional regulator from a set of 107 additional B. pseudomallei strains. As part of the study, we sequenced to base-pair accuracy the genome of B. pseudomallei strain 1026b, the model used for genetic studies of B. pseudomallei pathogenesis and antibiotic resistance. Our findings provide new insights into pathogen evolution during long-term infections and have important implications for the development of intervention strategies to combat recurrent melioidosis.
Strategies for Intracellular Survival of Burkholderia pseudomallei  [PDF]
Ben Adler
Frontiers in Microbiology , 2011, DOI: 10.3389/fmicb.2011.00170
Abstract: Burkholderia pseudomallei is the causative agent of melioidosis, a disease with high mortality that is prevalent in tropical regions of the world. A key component of the pathogenesis of melioidosis is the ability of B. pseudomallei to enter, survive, and replicate within mammalian host cells. For non-phagocytic cells, bacterial adhesins have been identified both on the bacterial surface and associated with Type 4 pili. Cell invasion involves components of one or more of the three Type 3 Secretion System clusters, which also mediate, at least in part, the escape of bacteria from the endosome into the cytoplasm, where bacteria move by actin-based motility. The mechanism of actin-based motility is not clearly understood, but appears to differ from characterized mechanisms in other bacterial species. A small proportion of intracellular bacteria is targeted by host cell autophagy, involving direct recruitment of LC3 to endosomes rather than through uptake by canonical autophagosomes. However, the majority of bacterial cells are able to circumvent autophagy and other intracellular defense mechanisms such as the induction of inducible nitric oxide synthase, and then replicate in the cytoplasm and spread to adjacent cells via membrane fusion, resulting in the formation of multi-nucleated giant cells. A potential role for host cell ubiquitin in the autophagic response to bacterial infection has recently been proposed.
Molecular Procedure for Detection of Burkholderia pseudomallei
Lai L. Suang,Zamberi Sekawi,Nagi A. Al-Haj,Mariana N. Shamsudin,Rasedee Abdullah,Rahmah Mohamed
Research Journal of Applied Sciences , 2012,
Abstract: Recently several cases of melioidosis have been reported in the tropical climates, especially in Southeast Asia where, it is endemic, it also occurs sporadically throughout the world. The diagnosis of the acute or chronic infection remains challenging. The present study highlight on the optimized and reliable technique based DNA preparation for use in Polymerase Chain Reaction (PCR) assay. PCR amplification with specific pair of primer for each putative gene was proving specific for amplification of genes in Burkholderia pseudomallei strain D286. The PCR mixture with addition of DMSO, formamide and glycerol could ease the PCR optimization where different pairs of primers were involved. The findings of this study have contributed to some information on the molecular bases of the LPS biosynthesis genes in B. seudomallei specifically for strain D286. The specific primer pairs with the PCR mixture could be used in developing a PCR diagnosis of melioidosis.
Burkholderia pseudomallei septicaemia - A case report  [cached]
Dias M,Antony B,Aithala S,Hanumanthappa B
Indian Journal of Medical Microbiology , 2004,
Abstract: Burkholderia pseudomallei, a natural saprophyte widely distributed in soil, stagnant waters of endemic areas, is said to infect humans through breaks in the skin or through inhalation causing protean clinical manifestations including fatal septicaemia. A case of septicaemia in a elderly female diabetic due to B. pseudomallei following a history of fall is being reported with complete details.
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