Biological Warfare Agents
Burkholderia cepacia complex
Experimental aerogenic Burkholderia mallei (glanders) infection in the BALB/c mouse. (1/86)The object of this study was to develop and characterize experimental Burkholderia mallei aerosol infection in BALB/c mice. Sixty-five mice were infected with 5000 [approx. 2.5 median lethal doses (MLD)] B. mallei strain ATCC 23344(T) bacteria by the aerosol route. Bacterial counts within lung, liver, spleen, brain, kidney and blood over 14 days were determined and histopathological and immunocytochemical profiles were assessed. Mortality due to B. mallei infection occurred between days 4 and 10 post-infection. Bacterial numbers were consistently higher in the lungs than in other tissues, reaching a maximum of approximately 1.0 x 10(6) c.f.u. ml(-1) at 5 days post-infection. Bacterial counts in liver and spleen tissue remained approximately equal, reaching a maximum of approximately 1.0 x 10(4) c.f.u. ml(-1) at day 4 post-infection. By day 14 post-infection, bacterial counts were in the range 1.0 x 10(3)-1.0 x 10(4) c.f.u. ml(-1) for all tissues. Infection of the lungs by B. mallei resulted in foci of acute inflammation and necrosis. As infection progressed, the inflammatory process became subacute or chronic; this was associated with the development of extensive consolidation. Lesions in liver and spleen tissue were typical of those that might be expected in bacteraemia or bacterial toxaemia. These results suggest that the BALB/c mouse is susceptible to B. mallei when delivered by the aerosol route and that this represents a model system of acute human glanders that is suitable for research into the pathogenesis of and vaccines against this disease. (+info)
Type III secretion: a virulence factor delivery system essential for the pathogenicity of Burkholderia mallei. (2/86)By creating mutations in the Burkholderia mallei ATCC 23344 animal pathogen-like type III secretion system (TTSS), this study analyzes the correlation between type III secretion and the pathogenicity of ATCC 23344 in vivo. Mutagenesis demonstrated that a functional TTSS was required for the full pathogenicity of ATCC 23344 in the BALB/c mouse and Syrian hamster models of infection. However, vaccination with each mutant failed to elicit a protective immunity against challenge with wild-type ATCC 23344. (+info)
Genomic diversity of Burkholderia pseudomallei clinical isolates: subtractive hybridization reveals a Burkholderia mallei-specific prophage in B. pseudomallei 1026b. (3/86)Burkholderia pseudomallei is the etiologic agent of the disease melioidosis and is a category B biological threat agent. The genomic sequence of B. pseudomallei K96243 was recently determined, but little is known about the overall genetic diversity of this species. Suppression subtractive hybridization was employed to assess the genetic variability between two distinct clinical isolates of B. pseudomallei, 1026b and K96243. Numerous mobile genetic elements, including a temperate bacteriophage designated phi1026b, were identified among the 1026b-specific suppression subtractive hybridization products. Bacteriophage phi1026b was spontaneously produced by 1026b, and it had a restricted host range, infecting only Burkholderia mallei. It possessed a noncontractile tail, an isometric head, and a linear 54,865-bp genome. The mosaic nature of the phi1026b genome was revealed by comparison with bacteriophage phiE125, a B. mallei-specific bacteriophage produced by Burkholderia thailandensis. The phi1026b genes for DNA packaging, tail morphogenesis, host lysis, integration, and DNA replication were nearly identical to the corresponding genes in phiE125. On the other hand, phi1026b genes involved in head morphogenesis were similar to head morphogenesis genes encoded by Pseudomonas putida and Pseudomonas aeruginosa bacteriophages. Consistent with this observation, immunogold electron microscopy demonstrated that polyclonal antiserum against phiE125 reacted with the tail of phi1026b but not with the head. The results presented here suggest that B. pseudomallei strains are genetically heterogeneous and that bacteriophages are major contributors to the genomic diversity of this species. The bacteriophage characterized in this study may be a useful diagnostic tool for differentiating B. pseudomallei and B. mallei, two closely related biological threat agents. (+info)
Contribution of gene loss to the pathogenic evolution of Burkholderia pseudomallei and Burkholderia mallei. (4/86)Burkholderia pseudomallei is the causative agent of melioidosis. Burkholderia thailandensis is a closely related species that can readily utilize l-arabinose as a sole carbon source, whereas B. pseudomallei cannot. We used Tn5-OT182 mutagenesis to isolate an arabinose-negative mutant of B. thailandensis. Sequence analysis of regions flanking the transposon insertion revealed the presence of an arabinose assimilation operon consisting of nine genes. Analysis of the B. pseudomallei chromosome showed a deletion of the operon from this organism. This deletion was detected in all B. pseudomallei and Burkholderia mallei strains investigated. We cloned the B. thailandensis E264 arabinose assimilation operon and introduced the entire operon into the chromosome of B. pseudomallei 406e via homologous recombination. The resultant strain, B. pseudomallei SZ5028, was able to utilize l-arabinose as a sole carbon source. Strain SZ5028 had a significantly higher 50% lethal dose for Syrian hamsters compared to the parent strain 406e. Microarray analysis revealed that a number of genes in a type III secretion system were down-regulated in strain SZ5028 when cells were grown in l-arabinose, suggesting a regulatory role for l-arabinose or a metabolite of l-arabinose. These results suggest that the ability to metabolize l-arabinose reduces the virulence of B. pseudomallei and that the genes encoding arabinose assimilation may be considered antivirulence genes. The increase in virulence associated with the loss of these genes may have provided a selective advantage for B. pseudomallei as these organisms adapted to survival in animal hosts. (+info)
Structural flexibility in the Burkholderia mallei genome. (5/86)The complete genome sequence of Burkholderia mallei ATCC 23344 provides insight into this highly infectious bacterium's pathogenicity and evolutionary history. B. mallei, the etiologic agent of glanders, has come under renewed scientific investigation as a result of recent concerns about its past and potential future use as a biological weapon. Genome analysis identified a number of putative virulence factors whose function was supported by comparative genome hybridization and expression profiling of the bacterium in hamster liver in vivo. The genome contains numerous insertion sequence elements that have mediated extensive deletions and rearrangements of the genome relative to Burkholderia pseudomallei. The genome also contains a vast number (>12,000) of simple sequence repeats. Variation in simple sequence repeats in key genes can provide a mechanism for generating antigenic variation that may account for the mammalian host's inability to mount a durable adaptive immune response to a B. mallei infection. (+info)
Quorum sensing: a transcriptional regulatory system involved in the pathogenicity of Burkholderia mallei. (6/86)Numerous gram-negative bacterial pathogens regulate virulence factor expression by using a cell density mechanism termed quorum sensing (QS). An in silico analysis of the Burkholderia mallei ATCC 23344 genome revealed that it encodes at least two luxI and four luxR homologues. Using mass spectrometry, we showed that wild-type B. mallei produces the signaling molecules N-octanoyl-homoserine lactone and N-decanoyl-homoserine lactone. To determine if QS is involved in the virulence of B. mallei, we generated mutations in each putative luxIR homologue and tested the pathogenicities of the derivative strains in aerosol BALB/c mouse and intraperitoneal hamster models. Disruption of the B. mallei QS alleles, especially in RJ16 (bmaII) and RJ17 (bmaI3), which are luxI mutants, significantly reduced virulence, as indicated by the survival of mice who were aerosolized with 10(4) CFU (10 50% lethal doses [LD50s]). For the B. mallei transcriptional regulator mutants (luxR homologues), mutation of the bmaR5 allele resulted in the most pronounced decrease in virulence, with 100% of the challenged animals surviving a dose of 10 LD50s. Using a Syrian hamster intraperitoneal model of infection, we determined the LD50s for wild-type B. mallei and each QS mutant. An increase in the relative LD50 was found for RJ16 (bmaI1) (>967 CFU), RJ17 (bmaI3) (115 CFU), and RJ20 (bmaR5) (151 CFU) compared to wild-type B. mallei (<13 CFU). These findings demonstrate that B. mallei carries multiple luxIR homologues that either directly or indirectly regulate the biosynthesis of an essential virulence factor(s) that contributes to the pathogenicity of B. mallei in vivo. (+info)
Antibiotic susceptibility of 65 isolates of Burkholderia pseudomallei and Burkholderia mallei to 35 antimicrobial agents. (7/86)OBJECTIVES: Fifty isolates of Burkholderia pseudomallei and 15 isolates of Burkholderia mallei were tested for their susceptibilities to 35 antimicrobial agents, including agents not previously tested against these bacteria. METHODS: MICs were determined by agar dilution in Mueller-Hinton medium. RESULTS: Among the antibiotics tested, lower MICs were obtained with imipenem, ceftazidime, piperacillin, piperacillin/tazobactam, doxycycline and minocycline. Fluoroquinolones and aminoglycosides had poor activities. A single clinical isolate of B. pseudomallei was resistant to ceftazidime, co-amoxiclav and doxycycline but remained susceptible to imipenem. CONCLUSIONS: Although B. mallei MICs are often lower, the overall results underline the importance of resistance in both species. The susceptibilities measured are consistent with the current recommendations for the treatment of B. pseudomallei and B. mallei infections. (+info)
Identification and discrimination of Burkholderia pseudomallei, B. mallei, and B. thailandensis by real-time PCR targeting type III secretion system genes. (8/86)Burkholderia pseudomallei and B. mallei are two highly pathogenic bacteria, responsible for melioidosis and glanders, respectively. The two are closely related and can also be mistaken for B. thailandensis, a nonpathogenic species. To improve their differential identification, we describe a hydrolysis probe-based real-time PCR method using the uneven distribution of type III secretion system genes among these three species. (+info)
Glanders is transmitted through direct contact with infected animals, contaminated soil or animal products, or through insect vectors such as biting flies or ticks. The bacteria enter the body through small wounds or abrasions on the skin or mucous membranes and multiply in the lymph nodes and glands.
Clinical signs of glanders include fever, loss of appetite, depression, enlarged glands, and abscessation of the lymph nodes and other organs. The disease can progress rapidly, with death occurring within a few days to weeks after the onset of symptoms.
Diagnosis of glanders is based on clinical signs, laboratory tests such as blood cultures, and the presence of the bacteria in samples from infected animals or contaminated environments. Treatment involves antibiotics, supportive care, and isolation of affected animals to prevent further spread of the disease.
Prevention of glanders primarily involves vaccination of equines, strict sanitation and biosecurity measures, and control of insect vectors. Control programs for glanders are important in areas where the disease is common or where there is a high risk of outbreaks due to factors such as poor animal husbandry practices or movement of infected animals.
Glanders has significant economic importance as it can be a major cause of morbidity and mortality in equines, particularly in areas where the disease is endemic. In addition, the control of glanders is important for public health as the bacteria can be transmitted to humans through contact with infected animals or contaminated environments, although this is rare.
Burkholderia Infections can affect various parts of the body, including the lungs, skin, and bloodstream. Symptoms may include fever, chills, fatigue, and pain in the affected area. Burkholderia infections are often difficult to diagnose, as the symptoms can be similar to those caused by other types of bacterial infections.
Treatment of Burkholderia infections typically involves the use of antibiotics, but the effectiveness of these treatments can vary depending on the severity and location of the infection. In some cases, surgical intervention may be necessary to remove infected tissue or to repair damaged organs.
Preventing Burkholderia infections is challenging, as the bacterium can be found in a variety of environments, including soil, water, and the gastrointestinal tracts of animals. However, practicing good hygiene, avoiding contact with individuals who are infected, and following proper infection control procedures can help reduce the risk of transmission.
In conclusion, Burkholderia infections are a serious medical condition that can affect individuals with compromised immune systems. While treatment options are available, early diagnosis and prevention measures are crucial to reducing the risk of complications and improving patient outcomes.
Melioidosis is typically acquired through contact with contaminated soil or water in tropical and subtropical regions of Asia and Africa. The bacteria can enter the body through open wounds, cuts, or through the eyes, nose, or mouth. Once inside the body, the bacteria can multiply and cause a wide range of symptoms including fever, chills, headache, muscle and joint pain, and skin lesions.
If left untreated, melioidosis can lead to serious complications such as sepsis, meningitis, and pneumonia, which can be fatal. The disease is diagnosed through a combination of physical examination, laboratory tests, and imaging studies. Treatment typically involves antibiotics, and early treatment is essential for effective management of the disease.
In addition to being an important medical condition, melioidosis is also of interest to researchers studying the bacteria that cause the disease. Burkholderia pseudomallei has been found to have a unique ability to survive in a variety of environments, including soil and water, and has been studied for its potential as a bioterrorism agent.
In summary, melioidosis is a serious bacterial infection caused by Burkholderia pseudomallei that can affect multiple organ systems and cause severe illness if left untreated. It is typically acquired through contact with contaminated soil or water in tropical and subtropical regions of Asia and Africa and is diagnosed through a combination of physical examination, laboratory tests, and imaging studies. Early treatment is essential for effective management of the disease.
Although the concept of dourine has been largely discredited by modern medicine, the term is still occasionally used to describe a condition that is characterized by intense feelings of sadness and hopelessness. However, it should be noted that this usage is not widely accepted in mainstream medical practice.