Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Grupo DASA / Melioidose à uma doenÃa infecciosa grave causada por Burkholderia pseudomallei, um bacilo Gram-negativo encontrado no solo e na Ãgua. A doenÃa à endÃmica no sudeste asiÃtico e hiperendÃmica no norte da AustrÃlia, onde a letalidade permanece com uma taxa de 21%. No Brasil, à considerada uma doenÃa emergente desde marÃo de 2003. Nos Ãltimos oito anos, 12 casos ocorreram no Estado do Cearà e um notificado pelo Governo holandÃs, por se tratar de um turista que morreu de melioidose, apÃs visita ao CearÃ. Em razÃo da ocorrÃncia clÃnica de melioidose e do isolamento de B. pseudomallei no ambiente do Estado do CearÃ, este trabalho objetivou estudar as cepas clÃnicas e ambientais de B. pseudomallei isoladas no Estado no perÃodo de 2003 a 2011, visando a identificar as cepas por mÃtodos fenotÃpicos e moleculares, determinar o perfil de sensibilidade contra cinco agentes antimicrobianos (amoxicilina/clavulanato, ceftazidima, imipenem, doxicilina e sulfametoxazol/trimetoprim), realizar a genotipagem das cepas pela amplificaÃÃo aleatÃria de DNA polimÃrfico - Random Amplified Polymorphic DNA (RAPD), detectar o gene de virulÃncia Type Three Secretion System (TTSS), alÃm de avaliar os aspectos clÃnico-epidemiolÃgicos que caracterizaram a emergÃncia desta doenÃa no Brasil. Todas as 20 cepas (dez clÃnicas e dez ambientais) de B. pseudomallei foram precisamente identificadas tanto pela metodologia VITEK2 quanto pelo sequenciamento da regiÃo 16S do DNA, mostraram resultado negativo no teste de assimilaÃÃo de L-arabinose, e exibiram-se positivas para a detecÃÃo do gene de virulÃncia TTSS. As concentraÃÃes inibitÃrias mÃnimas (CIMs), obtidas por microdiluiÃÃo em caldo MÃeller-Hinton, demonstraram que todos os isolados (100%) foram sensÃveis ao imipenem, à doxicilina e ao sulfametoxazol- trimetoprim, no entanto, para amoxicilina/clavulanato e ceftazidima, a sensibilidade foi de 80 e 90%, respectivamente. A tÃcnica de RAPD evidenciou uma variabilidade genÃtica de 63% entre as cepas de B. pseudomallei oriundas do Estado do CearÃ, as quais foram agrupadas em trÃs clusters diferentes. Este trabalho decerto contribuirà para o conhecimento das caracterÃsticas fenotÃpicas e genotÃpicas das cepas de B. pseudomallei isoladas no Cearà e da atualizaÃÃo da vigilÃncia epidemiolÃgica dos casos de melioidose ocorridos no Estado, alÃm de contribuir para a conscientizaÃÃo dos ÃrgÃos de saÃde competentes para a inclusÃo do Cearà como zona endÃmica para esta enfermidade. / Melioidosis is a serious infectious disease caused by Burkholderia pseudomallei, a Gram negative rod, commonly found in soil and water. The disease is endemic in Southeastern Asia and hyperendemic in Northern Australia. Despite the initiation of empiric therapy, mortality remains at 21% in patients with melioidosis in Australia. In Brazil, it is considered an emerging disease, since April 2003, when it was first diagnosed in Ceara, Northeastern Brazil. In the last eight years, thirteen cases were reported, twelve local cases and one case reported by the Dutch government because of a tourist who died of melioidosis after a visit to Ceara. Considering the occurrence of melioidosis in CearÃ, this work aimed at studying these clinical and environmental strains of Burkholderia pseudomallei isolated from Cearà from 2003 to 2011, focusing on the bacterial and molecular identification; determining the susceptibility profile against five antimicrobial agents (amoxicillin/clavulanate, ceftazidime, imipenem, doxycycline and trimethoprim/sulfamethoxazole); genotyping through Random Amplified Polymorphic DNA (RAPD), detecting the virulence gene Type Three Secretion System (TTSS); and analyzing epidemiological and clinical aspects that characterized the emergence of this disease in Brazil. All 20 strains (10 clinical and 10 environment) from B. pseudomallei were accurately identified by both VITEK2  and sequencing of the 16S DNA, showed to be negative for the assimilation of L-arabinose and were positive results for the detection of the virulence gene TTSS. The minimum inhibitory concentrations (MICs) obtained through microdilution in MÃeller-Hinton broth, showed that all (100%) isolates were sensitive to imipenem, doxycycline and trimethoprim-sulfamethoxazole, however, the susceptibility rate to amoxicillin/clavulanate and ceftazidime was of 80 and 90%, respectively, with no differences between clinical and environmental strains. RAPD-PCR showed a genetic relatedness of 63% among the B. pseudomallei strains from the State of CearÃ, which were grouped in two different clusters. This work will contribute to the knowledge of phenotypic and genotypic characteristics of B. pseudomallei strains isolated in Cearà and the update of epidemiological surveillance of melioidosis cases in the state, also contribute to the awareness of agencies health authority for inclusion of Cearà State as an endemic area for this disease.

The trimethoprim and sulfamethoxazole combination, co-trimoxazole, plays a vital role in the treatment of Burkholderia pseudomallei infections. Previous studies demonstrated that the B. pseudomallei BpeEF-OprC efflux pump confers widespread trimethoprim resistance in clinical and environmental isolates, but this is not accompanied by significant resistance to co-trimoxazole. Using the excluded select-agent strain B. pseudomallei Bp82, we now show that in vitro acquired trimethoprim versus cotrimoxazole resistance is mainly mediated by constitutive BpeEF-OprC expression due to bpeT mutations or by BpeEF-OprC overexpression due to bpeS mutations. Mutations in bpeT affect the carboxy-terminal effector-binding domain of the BpeT LysR-type activator protein. Trimethoprim resistance can also be mediated by dihydrofolate reductase (FolA) target mutations, but this occurs rarely unless BpeEF-OprC is absent. BpeS is a transcriptional regulator that is 62% identical to BpeT. Mutations affecting the BpeS DNA-binding or carboxy-terminal effector-binding domains result in constitutive BpeEF-OprC overexpression, leading to trimethoprim and sulfamethoxazole efflux and thus to cotrimoxazole resistance. The majority of laboratory-selected co-trimoxazole-resistant mutants often also contain mutations in folM, encoding a pterin reductase. Genetic analyses of these mutants established that both bpeS mutations and folM mutations contribute to co-trimoxazole resistance, although the exact role of folM remains to be determined. Mutations affecting bpeT, bpeS, and folM are common in co-trimoxazole-resistant clinical isolates, indicating that mutations affecting these genes are clinically significant. Cotrimoxazole resistance in B. pseudomallei is a complex phenomenon, which may explain why resistance to this drug is rare in this bacterium. IMPORTANCE Burkholderia pseudomallei causes melioidosis, a tropical disease that is difficult to treat. The bacterium's resistance to antibiotics limits therapeutic options. The paucity of orally available drugs further complicates therapy. The oral drug of choice is co-trimoxazole, a combination of trimethoprim and sulfamethoxazole. These antibiotics target two distinct enzymes, FolA (dihydrofolate reductase) and FolP (dihydropteroate synthase), in the bacterial tetrahydrofolate biosynthetic pathway. Although co-trimoxazole resistance is minimized due to two-target inhibition, bacterial resistance due to folA and folP mutations does occur. Co-trimoxazole resistance in B. pseudomallei is rare and has not yet been studied. Co-trimoxazole resistance in this bacterium employs a novel strategy involving differential regulation of BpeEF-OprC efflux pump expression that determines the drug resistance profile. Contributing are mutations affecting folA, but not folP, and folM, a folate pathway-associated gene whose function is not yet well understood and which has not been previously implicated in folate inhibitor resistance in clinical isolates.

Melioidosis is an important cause of community-acquired sepsis, endemic to Southeast Asia and Northern Australia. Melioidosis is caused by the soil saprophyte, Burkholderia pseudomallei, a motile Gram-negative bacillus, and is associated with a mortality rate that approaches 50% in Northeast Thailand. The most important risk factor for melioidosis is diabetes mellitus, and two-thirds of all adult patients with melioidosis have diabetes as a risk factor. It has been noted previously, however, that patients with diabetes have lower mortality than patients without diabetes. In this dissertation, we look at a cohort of 1160 consecutive adult melioidosis patients presenting to Sappasithiprasong Hospital in Ubon Ratchathani, Thailand, 410 (35%) of whom were diagnosed with diabetes prior to admission. We confirmed previous findings that diabetes protected from mortality in melioidosis, but also found that this protective effect was confined to a smaller subset of patients (208 patients) who were treated with glibenclamide prior to admission. Patients with hyperglycaemia (but no diagnosis of diabetes prior to admission) had the same mortality rate as patients without diabetes. In vitro experiments found no inhibitory effect of glibenclamide on bacterial growth, and we therefore looked for evidence of an effect of glibenclamide on the host. We conducted a gene expression study of circulating blood leukocytes in melioidosis patients and compared them to uninfected controls. In this study, we found that glibenclamide was associated with an anti-inflammatory effect on the host response to melioidosis. To further elucidate a mechanism for the action of glibenclamide, we studied the effect of glibenclamide therapy in a mouse model of melioidosis and found that the effect of glibenclamide was specific to interleukin-1β secretion. This reduction in interleukin-1β secretion was associated with reduced cellular influx into the lungs as well as lower bacterial loads in blood, liver and spleen.

Burkholderia pseudomallei is a gram-negative opportunistic soil pathogen that causes the life-threatening disease melioidosis. It is endemic in Northern Australia and Southeast Asia but can be found throughout many other regions in the world. Diabetes mellitus is a predisposing risk factor for infection with this organism and it has been demonstrated that diabetic males are particularly susceptible to severe infection. Previous research suggested that monocytes isolated from the whole blood of diabetic males demonstrated a decreased ability to produce the proinflammatory cytokines IL-1β and IL-8. We hypothesized that monocyte-derived macrophages from diabetic males would also secrete lower levels of pro-inflammatory cytokines and that this difference between gender and diabetic state would be more pronounced compared to those seen previously with monocytes. Twenty volunteer with type I diabetes mellitus (ten males and ten females), along with twenty healthy age- and gender-matched controls donated blood for this study. Monocytes were collected from whole blood and allowed to differentiate into macrophages with the use of human recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF). Macrophages were then divided into groups and infected with B. pseudomallei, B. thailandensis (a closely related by non-pathogenic bacterium that inhabits similar niches), and E. coli. An uninfected control was used as well. At six hours post-infection, mRNA was collected from all cells and qPCR was performed to determine cytokine expression levels. All mRNA values collected from cells which had been infected with bacterial agents were normalized against the corresponding concentrations of mRNA from mock-infected cells. Mean log fold increases in both IL-1β and IL-8 were computed and compared. Preliminary testing showed decreased levels of both IL-1β and IL-8 from B. pseudomallei-infected macrophages isolated from a diabetic male compared to the healthy, age-matched male control. Surprisingly, results from all forty donors demonstrated that gender and diabetic state were not significant factors in the proinflammatory responses of macrophages infected with B. pseudomallei, although further testing is needed to determine if these results were influenced by experimental parameters.

The aim of this study was to identify and characterise type II toxin-antitoxin (TA) systems in Burkholderia pseudomallei, the causative agent of the human disease melioidosis. 8 putative TA systems were identified within the genome of B. pseudomallei K96243. 5 of these were located witihn genome islands. Of the candidate toxins, BPSL0175 (RelE1) or BPSS1060 (RelE2) caused growth to cease when expressed in Escherichia coli, whereas expression of BPSS0390 (HicA) or BPSS1584 (HipA) (in an E. coli ΔhipBA background) caused a reduction in the number of culturable bacteria. HicA also caused growth arrest in B. pseudomallei K96243 ΔhicAB. These toxin induced phenotypes were enhanced by an <3kDa extracellular factor that accumulated in the spent medium during growth. Expression of the cognate antitoxins could restore growth and culturability of cells. Expression of hicA in E. coli gave an increased number of persister cells in response to ciprofloxacin or ceftazidime. Site directed mutagenesis studies identified two key residues within the HicA toxin that were essential for both the reduced culturability and increased persistence phenotypes. Deletion of hicAB from B. pseudomallei K96243 did not affect persister cell or survival frequencies compared to the wild type following treatment with a variety of stress conditions. Deletion of the ΔhipBA locus from B. pseudomallei K96243 also had no affect on bacterial persistence or survival under the conditions tested.

The causative agents of plague (Y. pestis), glanders (B. mallei) and melioidosis (B. pseudomallei) are included in critical agents of bioterrorisim. They belong to the most intensively studied agents during cold war, specially in the former Soviet Union (FSU). Mostly what is known about these agents, particularly (Y. pestis ) is not available in English language publications. Many of the studies are written in Russian language and published in Russian scientific journals. Thus, the work is designed to evaluate, published and unpublished Russian language written data obtained, in comparisions to the current state of global knowledge on the pathogens in concern.

Burkholderia pseudomallei is an opportunistic soil pathogen that causes melioidosis, a life-threatening human disease prevalent in Southeast Asia, northern Australia, the Middle East, Africa, and South America. The organism also causes disease in plants and animals. Persons with severe melioidosis usually die of septicemia. Relatively little is known regarding the virulence mechanisms of B. pseudomallei; however, several putative virulence determinants have been identified. The organism is able to invade and replicate within phagocytic cells and is particularly pathogenic in males with diabetes mellitus. B. thailandensis is closely related to B. pseudomallei, but is not pathogenic. This study examines various in vitro monocyte / macrophage infection models used to study innate immune responses to B. pseudomallei. Several monocyte and macrophage models showed little or no significant differences between proinflammatory cytokines secreted in response to infection with B. pseudomallei and B. thailandensis. Peripheral blood monocytes from diabetic males produced lower normalized levels of proinflammatory cytokines IL-1α, IL-1β, IL-6, and IL-8 than monocytes from healthy males in response to infection with B. pseudomallei, B. thailandensis, and E. coli. Surprisingly, normalized levels of secreted IL-1β from B. pseudomallei-infected monocytes from diabetic females were higher than levels from healthy females. The results revealed a significant interactive effect of gender and diabetic state on peripheral blood monocyte secretion of IL-1β (p = 0.0370) and IL-8 (p = 0.0390), as well as a significant interactive effect of diabetic state and type of infectious agent on peripheral blood monocyte secretion of IL-1α (p=0.0210) and IL-6 (p=0.0204). These results may help explain why diabetic males are unusually susceptible to infection with B. pseudomallei.

Burkholderia pseudomallei est l’agent causal de la mélioïdose, une maladie tropicale endémique dans le Nord de l’Australie et en Asie du Sud-Est. Nous avons analysé le système d’efflux, mécanisme majoritairement impliqué la multi-résistance aux antibiotiques. Nous avons chercher à identifier des mutations dans les pompes d’efflux et des modulation de l’expression de ces dernières afin d’expliquer ces phénotypes de résistance. Les techniques de séquençage de l’ADN et de transcriptomique par RT-qPCR nous ont permis d’identifier deux mécanismes chez des souches cliniques. Un mécanisme transitoire responsable d'une résistance croisée du Cotrimoxazole, avec les quinolones, et le chloramphénicol, pour lequel nous suspectons une modulation de l’expression de l’efflux. Le second, impliqué dans la résistance au méropénème, par surexpression de l'efflux suite à une mutation dans le régulateur de la pompe AmrAB-OprA.Dans un second axe de recherche, nous avons également criblé plusieurs molécules afin d'identifier des candidats inhibiteurs de l'efflux, dérivant de la famille des phénothiazines et capables de restaurer une sensibilité aux antibiotiques. Nous avons analysé l’impact de ces molécules sur des souches modèles de multi-résistance (Burkholderia thailandensis) et sur des souches cliniques et environnementales de B. pseudomallei. Ces molécules sont capables d’impacter l’expression de l’efflux, mais nous pensons que le mécanisme majeur d’inhibition de cette famille de molécules reste l’entrée en compétition avec les antibiotiques efflués. Nous avons identifié une molécule, AST17, capable de restaurer la sensibilité au Cotrimoxazole, ainsi qu'aux quinolones. / Burkholderia pseudomallei is thecausal agent of melioidosis, a tropical disease, endemic in Notrhern Australia and South-East Asia. We have analyzed efflux systeme, known to be one of the main mecanism implicated in antibiotic resistance phenotypes. We have looked for mutations in efflux pumps and for transient modulations of the efflux pumps expression, that could explain resistance phenotypes. Whole genome sequencing and a the targeted method of RT-qPCR allowed us to identified two mecanisms in clinical strains. A transient mecanism, responsible of a cross-resistance to Cotrimoxazole, quinolones and chloramphenicol, and we suspect an implication of modulation of efflux. The second one is implicated in meropenem resistance by an overexpression of the AmrAB-OprA efflux pumps, due to a mutation of its regulator. In a second time, we also have screened several compounds, all derivated from phenothiazines, in order to identify efflux pump inhibitors for a restoration of the antibiotic susceptibility. We have analyzed the impact of these molecules in multi-resistant strain models, and on several clinical and environnemental strains. These molecules are able to modulate efflux pumps expression, however, we think that the main inhibition mecanism of these derivatives is about a competition between the molecule and the antibiotics. We have identified one molecule, AST17, that is able to restore Cotrimoxazole and quinolones susceptibilities.

In under a century, melioidosis, the infection due to Burkholderia pseudomallei, has emerged from Whitmore’s series of glanders-like infections amongst the morphia addicts in Burma to a major cause of mortality in northeastern Thailand and northern Australia. Also endemic in other parts of south-east Asia, melioidosis may have varied presentations ranging from severe, overwhelming infection to chronic, low grade disease. Observational evidence had suggested that granulocyte colony stimulating factor (G-CSF), a naturally occurring substance produced by the body in response to infection, may have been useful in reducing the high mortality associated with the more severe forms of this infection. Other observations linked the occurrence of this disease to various environmental factors, such as contamination of drinking water and the annual rainfall. This thesis explores and attempts to quantify these associations. There are three parts to this thesis. In the first part, I reviewed the epidemiology and management of patients with melioidosis. The use of G-CSF and meropenem was associated with a fall in mortality, although other factors may have at least partially contributed to this effect. In the second part, I progressed towards a clinical trial of G-CSF. There was no other evidence supporting the use of G-CSF in severe sepsis and ethical issues precluded a trial in Darwin. There was not evidence from laboratory models of G-CSF action in melioidosis to support the use of G-CSF in patients, although there remained some doubt regarding the applicability of such models to human disease. I examined clinical methods to identify patients at high risk of death from melioidosis. A simple scoring system based on clinical and laboratory parameters was developed and externally validated. However, clinical definitions of severe sepsis appeared to be better predictors of mortality. A clinical trial based on clinical definitions was commenced in Thailand. In the final part, I explored the question of whether different strains or B. pseudomallei or different environmental conditions caused different patterns of infection. There was no evidence that strain types of this bacterium determine the pattern or severity of disease, but weather conditions appeared to influence the distribution of disease in northern Australia.

No description available.