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Genomic fingerprinting of Burkholderia pseudomallei and B. mallei pathogens with DNA array based on interspecies sequence differences obtained by subtractive hybridization.

The ability to rapidly and efficiently identify causative agents of dangerous human and animal diseases is a prerequisite to diagnosis, prophylaxis and therapy. Such identification systems can be developed based on DNA markers enabling differentiation between various bacterial strains. One source of these markers is genetic polymorphism. An efficient method for detecting the most stable polymorphisms without knowledge of genomic sequences is subtractive hybridization. In this work we report an approach to typing of Burkholderia pseudomallei and B. mallei that cause melioidosis and glanders, respectively. Typing is based on hybridization of bacterial genomes with a DNA array of genomic markers obtained using subtractive hybridization. The array comprised 55 DNA fragments which distinguished the genomes of B. pseudomallei C-141 and B. mallei C-5 strains, and it was used to test 28 radioactively labeled B. pseudomallei strains and 8 B. mallei strains. Each strain was characterized by a specific hybridization pattern, and the results were analyzed using cluster analysis. 18 patterns specific to B. pseudomallei and 6 patterns specific to B. mallei were found to be unique. The data allowed us to differentiate most studied B. pseudomallei variants from one another and from B. mallei strains. It was concluded that DNA markers obtained by subtractive hybridization can be potentially useful for molecular typing of B. pseudomallei and B. mallei strains, as well as for their molecular diagnosis. The method reported can be easily adapted for use both with DNA arrays and DNA microarrays with fluorescent probes.

Animals↗

Histofarcin test for the diagnosis of epizootic lymphangitis in Ethiopia: development, optimisation, and validation in the field.

Histofarcin, a skin test antigen for the diagnosis of epizootic lymphangitis, was locally produced from the mycelial form of Histoplasma capsulatum var. farciminosum (HCF) in disease-endemic districts of Ethiopia and tested for its application in the field between April 2002 and May 2003. The test was evaluated using 108 mules, 84 in endemic and 24 in disease-free districts. Microscopic and mycological examinations of clinical lesions were used as the "gold standard" for the validation of the test. The concentration of histofarcin that caused an optimum reaction was 0.2-0.4 mg/mL in a 0.1 mL dose and this was attained 24-48 h post-injection. The sensitivity and specificity of the histofarcin test were 90.3% (CI = 73.1, 97.5) and 69% (95%, CI = 48.1, 84.9%) in disease-endemic districts. On the other hand, specificity was 100% (CI=94.8, 100) in disease-free districts. Positive and negative predictive values of the histofarcin test were 77.78% (95% CI = 60.4, 89.3) and 85.71% (95% CI = 62.6, 96.2), respectively. A marginal substantial agreement (kappa = 0.61, P = 0.0000) was observed between the clinical status and the result of the histofarcin test. A large proportion (31%) of 'false positives' was recorded in endemic districts, which could be due to the pre-clinical stage of the disease. The latter ended in lower specificity and positive predictive value of the test since the true infection status of a 'false positive' could not be known on the basis of clinical features. Therefore, standard test validation procedures including slaughtering and isolation of HCF is required. After proper validation, we conclude that the histofarcin test could play a significant role in detecting early infection, and differentiating of EL from glanders, ulcerative lymphangitis, and sporotrichosis.

Animals↗

[Dermatological aspects in the risk of biological warfare].

The possible cutaneous manifestations of infectious biological warfare are multiple and vary depending on the agent used. An ulcerous and/or necrotic syndrome and/or regional lymphadenitis syndrome are possible with anthrax, tularaemia, bubonic plague and emission of trichotecene mycotoxins. A vesiculo-pustular syndrome with fever is provoked by smallpox, melioidosis and glanders. A purpural and/or haemorrhagic syndrome is seen during haemorrhagic fever viruses and septicaemic plague. These cutaneous manifestations are excellent markers that orient and alert when they occur in a context of a situation at risk, when several cases are observed in a usually non-exposed population and with extra-dermatological syndromes. They permit the early initiation of treatment.

Biological Warfare↗

[Notification according to the law for protection against infections].

Since January 1st 2001, the Law for Protection Against Infections decrees the duty of notification along two tracks, on the one hand by notification of infectious diseases and on the other hand by reporting the pathogens. However, the names of pathogens change due to scientific progress. Furthermore, these names include in some cases not only harmful agents of infectious diseases but also inoffensive organisms, i. e. Giardia lamblia. There are also problems in the notification of other pathogens such as Brucella sp., Campylobacter sp., Chlamydia psittaci,Clostridium botulinum, Cryptosporidium parvum, Leptospira interrogans, Listeria monocytogenes, Mycobacterium tuberculosis and similar agents, Norwalk-like viruses, Salmonella Paratyphi, Treponema pallidum, Trichinella spiralis and pathogenic serovars of Yersinia enterocolitica. Finally, the abandonment of notification for glanders, lymphogranuloma venereum, ulcus molle and variola appears to be risky, the reasons being partly unconvincing and contradictory.

Communicable Disease Control↗

[An acute septic course of melioidosis after a stay in Thailand].

HISTORY AND CLINICAL FINDINGS: Two weeks after returning from a trip to Thailand a 79-year-old man developed a higher fever, pain in the right flank and progressive clouding of consciousness. She had meningism on admission. INVESTIGATIONS: There was a marked leukocytosis (WBC count 17,700/microliter) and raised C-reactive protein (6.5 mg/dl). Cerebrospinal fluid was clear, containing 119 cells/mm3 and elevated protein (90 mg/dl). Abdominal sonography demonstrated segmental pyelonephritis, and blood culture grew Pseudomonas pseudomallei. TREATMENT AND COURSE: On the basis of sensitivity tests imipenem was chosen as the antibiotic and was given for 6 weeks. Because of an inadequate response and a right renal abscess a right nephrectomy was performed. After marked improvement the septicaemia recurred one week after antibiotic treatment had been discontinued, and the patient died. CONCLUSION: Efficacious treatment of melioidosis (a glanders-like disease) presupposes diagnosis of the causative microorganism and testing of its antibiotic sensitivity. As Pseud. pseudomallei may encapsulate and persist intracellularly, the selection of antibiotic and the duration of treatment are crucial.

Abscess↗

Experience in the medical management of potential laboratory exposures to agents of bioterrorism on the basis of risk assessment at the United States Army Medical Research Institute of Infectious Diseases (USAMRIID).

Experience in managing laboratory exposures to potential agents of bioterrorism is limited. The United States Army Medical Research Institute of Infectious Diseases reviewed laboratory exposures involving these agents (1989 to 2002) to assess the effectiveness of medical management. The evaluation of 234 persons (78% vaccinated) for exposure to 289 infectious agents revealed 5 confirmed infections (glanders, Q fever, vaccinia, chikungunya, and Venezuelan equine encephalitis). Postexposure antibiotic prophylaxis was given for most moderate- or high-risk bacterial exposures (41/46; 89%); most unvaccinated minimal-risk (7/10; 70%), and subsets of vaccinated minimal-risk exposures (18/53; 34%) but generally not negligible-risk exposures (6/38; 16%). Vaccine "breakthroughs" were not unexpected (enzootic Venezuelan equine encephalitis, localized vaccinia) or presented with mild symptoms (Q fever). A multifaceted policy of personal protective measures, vaccination, early assessment, and postexposure antibiotic prophylaxis was effective in minimizing morbidity and mortality in at-risk laboratory workers.

Alphavirus Infections↗

Antigenic relatedness between Burkholderia pseudomallei and Burkholderia mallei.

Burkholderia pseudomallei and Burkholderia mallei are causative agents of distinct diseases, namely, melioidosis and glanders, respectively. The two species are very closely related, based on DNA-DNA homology, base sequence of the 16S rRNA, and phenotypic characteristics. Based on the use of polyclonal antisera, B. pseudomallei and B. mallei are also found to be antigenically closely related to one another. We previously reported the production of monoclonal antibodies (MAbs) against B. pseudomallei antigens; one group was specific for the 200-kDa exopolysaccharide present on the surface of all B. pseudomallei isolates, and the other was specific for the lipopolysaccharide (LPS) structure present on more than 95% of the B. pseudomallei tested. In the present study, we showed that the MAbs against 200-kDa antigen of B. pseudomallei cross-reacted with a component present also in some B. mallei isolates (3/6), but the positive immunoblot reaction was noted below the 200-kDa position. On the other hand, none of the six B. mallei isolates reacted with the MAb specific for B. pseudomallei LPS. It was of interest to observe that only the 3 exopolysaccharide-positive B. mallei isolates reacted with a commercial MAb against B. mallei LPS. The data presented suggest that B. mallei can be classified antigenically into two types based on their reactivities with different MAbs, i.e., the presence or absence of exopolysaccharide and the types of lipopolysaccharide. The heterogeneity of the LPS from these two closely related organisms is most likely related to the differences in its O-polysaccharide side chain.

Antigens, Bacterial↗

Burkholderia mallei expresses a unique lipopolysaccharide mixture that is a potent activator of human Toll-like receptor 4 complexes.

Burkholderia mallei, the aetiologic agent of glanders, causes a variety of illnesses in animals and humans ranging from occult infections to acute fulminating septicaemias. To better understand the role of lipopolysaccharide (LPS) in the pathogenesis of these diseases, studies were initiated to characterize the structural and biological properties of lipid A moieties expressed by this organism. Using a combination of chemical analyses and MALDI-TOF mass spectrometry, B. mallei was shown to express a heterogeneous mixture of tetra- and penta-acylated lipid A species that were non-stoichiometrically substituted with 4-amino-4-deoxy-arabinose residues. The major penta-acylated species consisted of bisphosphorylated d-glucosamine disaccharide backbones possessing two amide linked 3-hydroxyhexadecanoic acids, two ester linked 3-hydroxytetradecanoic acids [C14:0(3-OH)] and an acyloxyacyl linked tetradecanoic acid, whereas, the major tetra-acylated species possessed all but the 3'-linked C14:0(3-OH) residues. In addition, although devoid of hexa-acylated species, B. mallei LPS was shown to be a potent activator of human Toll-like receptor 4 complexes and stimulated human macrophage-like cells (THP-1 and U-937), monocyte-derived macrophages and dendritic cells to produce high levels of TNF-alpha, IL-6 and RANTES. Based upon these results, it appears that B. mallei LPS is likely to play a significant role in the pathogenesis of human disease.

Burkholderia mallei↗

Serodiagnosis of Burkholderia mallei infections in horses: state-of-the-art and perspectives.

Burkholderia mallei causes glanders or farcy in solipeds, a disease that must be reported to the OIE (Office International des Epizooties, Paris, France). The number of reported outbreaks has increased steadily during the last decade. Serodiagnosis is hampered by the considerable number of false-positives and -negatives of the internationally prescribed tests. The major problem leading to low sensitivity and specificity of complement fixation test (CFT) and enzyme-linked immunosorbent assay (ELISA) has been linked to the test antigens currently used, i.e. crude preparations of whole cells. Future perspectives for the development and evaluation of serological test kits using well-characterized single antigens are discussed in the light of recent molecular research on B. mallei and the closely related saprozoonotic agent B. pseudomallei.

Animals↗

A possible pitfall in the identification of Burkholderia mallei using molecular identification systems based on the sequence of the flagellin fliC gene.

Amotile Burkholderia mallei and motile Burkholderia pseudomallei display a high similarity with regard to phenotype and clinical syndromes, glanders and melioidosis. The aim of this study was to establish a fast and reliable molecular method for identification and differentiation. Despite amotility, the gene of the filament forming flagellin (fliC) could be completely sequenced in two B. mallei strains. Only one mutation was identified discriminating between B. mallei and B. pseudomallei. A polymerase chain reaction-restriction fragment length polymorphism assay was designed making use of the absence of an AvaII recognition site in B. mallei. All seven B. mallei, 12 out of 15 B. pseudomallei and 36 closely related apathogenic Burkholderia thailandensis strains were identified correctly. However, in three B. pseudomallei strains a point mutation at gene position 798 (G to C) disrupted the AvaII site. Therefore, molecular systems based on the fliC sequence can be used for a reliable proof of strains of the three species but not for the differentiation of B. mallei and B. pseudomallei isolates.

Base Sequence↗

In vitro susceptibilities of Burkholderia mallei in comparison to those of other pathogenic Burkholderia spp.

The in vitro antimicrobial susceptibilities of isolates of Burkholderia mallei to 16 antibiotics were assessed and compared with the susceptibilities of Burkholderia pseudomallei and Burkholderia cepacia. The antibiotic susceptibility profile of B. mallei resembled that of B. pseudomallei more closely than that of B. cepacia, which corresponds to their similarities in terms of biochemistry, antigenicity, and pathogenicity. Ceftazidime, imipenem, doxycycline, and ciprofloxacin were active against both B. mallei and B. pseudomallei. Gentamicin was active against B. mallei but not against B. pseudomallei. Antibiotics clinically proven to be effective in the treatment of melioidosis may therefore be effective for treating glanders.

Anti-Bacterial Agents↗

The animal pathogen-like type III secretion system is required for the intracellular survival of Burkholderia mallei within J774.2 macrophages.

Burkholderia mallei is a highly infectious gram-negative pathogen and is the causative agent of human and animal glanders. By generating polar mutations (disruption of bsaQ and bsaZ) in the B. mallei ATCC 23344 animal pathogen-like type III secretion system (TTS), we demonstrate that this bacterial protein delivery system is required for intracellular growth of B. mallei in J774.2 cells, formation of macrophage membrane protrusions, actin polymerization, and phagosomal escape. These findings suggest that TTS plays a role in the intracellular trafficking of B. mallei and may facilitate cell-to-cell spread via actin-based motility.

Animals↗

Use of 16S rRNA gene sequencing for rapid identification and differentiation of Burkholderia pseudomallei and B. mallei.

Burkholderia pseudomallei and B. mallei, the causative agents of melioidosis and glanders, respectively, are designated category B biothreat agents. Current methods for identifying these organisms rely on their phenotypic characteristics and an extensive set of biochemical reactions. We evaluated the use of 16S rRNA gene sequencing to rapidly identify these two species and differentiate them from each other as well as from closely related species and genera such as Pandoraea spp., Ralstonia spp., Burkholderia gladioli, Burkholderia cepacia, Burkholderia thailandensis, and Pseudomonas aeruginosa. We sequenced the 1.5-kb 16S rRNA gene of 56 B. pseudomallei and 23 B. mallei isolates selected to represent a wide range of temporal, geographic, and origin diversity. Among all 79 isolates, a total of 11 16S types were found based on eight positions of difference. Nine 16S types were identified in B. pseudomallei isolates based on six positions of difference, with differences ranging from 0.5 to 1.5 bp. Twenty-two of 23 B. mallei isolates showed 16S rRNA gene sequence identity and were designated 16S type 10, whereas the remaining isolate was designated type 11. This report provides a basis for rapidly identifying and differentiating B. pseudomallei and B. mallei by molecular methods.

Animals↗

Purification and characterization of a protease from Pseudomonas pseudomallei.

Pseudomonas pseudomallei is the causative agent of melioidosis, a glanders-like disease of humans and animals. The pathogenesis of melioidosis is not well understood, and the role of various extracellular enzymes produced by P. pseudomallei in the development of this disease is not known. The present studies were designed to purify and characterize an extracellular protease produced by P. pseudomallei isolates and to test the hypothesis that this protease may play a role in melioidosis. The protease was present in culture supernatants as an enzyme with a molecular weight of 36,000 that was optimally active at 60 degrees C and at pH 8.0. The P. pseudomallei protease was shown to be a metalloenzyme requiring iron for maximal activity, and activity was inhibited in the presence of ethylenediaminetetraacetic acid (150 mM). Antibodies directed against an alkaline protease produced by Pseudomonas aeruginosa cross-reacted with the P. pseudomallei protease. These data indicate that the P. pseudomallei protease belongs to the family of alkaline proteases sensitive to metal chelators. Purified P. pseudomallei protease was capable of digesting a variety of eucaryotic protein substrates including immunoglobulins. A P. pseudomallei strain deficient in protease production was shown to be less virulent than the parental strain in an animal model of lung infection. These data suggest that this protease may be a significant pathogenic determinant in infections caused by P. pseudomallei.

Amino Acid Sequence↗

Fate of bioterrorism-relevant viruses and bacteria, including spores, aerosolized into an indoor air environment.

An aerosol physics test facility was used in a series of eight experiments to gather an integrated comprehensive broad base of data on the fate of surrogates of microorganisms that cause smallpox, plague, glanders, anthrax, and viral hemorrhagic fevers. The results are directly relevant to the public health issue of how to protect the occupants of buildings against bioterrorism. The test conditions were directly relevant to the indoor air environment situation, and the results can be generalized to buildings that are now occupied. The reductions in concentrations of relevant viruses and bacteria--including gram-negative fermenters and nonfermenters, gram-positive cocci and bacilli, and spores--were substantial and statistically robust. The data show that the bioterrorism-relevant aerosolized viruses and bacteria, including spores, respond like small particulates to the primary (electrical) forces that control the distribution of small particulates in a room. Further, these relevant microorganisms respond like small particulates to means designed to control airborne particulates. The results could be used to anticipate the effects of a bioterrorist attack on the public health, provide information on means that can be used to minimize such effects, and used to make decisions on how best to protect occupants of specific buildings at minimal cost and with assurance of success.

Aerosols↗

Molecular epidemiology of Burkholderia species.

Although most species in the genus Burkholderia are not pathogenic for healthy persons, a few are capable of causing severe, life threatening infection. B. mallei and B. pseudomallei are the causative agents of glanders and melioidosis, respectively. Interest in these species has increased recently owing to their potential for use as agents of bioterrorism. B. cepacia emerged during the past two decades as an important opportunistic pathogen among persons with certain underlying diseases. Persons with chronic granulomatous disease, a primary immunodeficiency, or cystic fibrosis (CF), the most common lethal inherited disorder in Caucasians, are at particular risk. In CF, respiratory tract infection may be chronic or associated with a rapid deterioration in pulmonary function. Studies in the early 1990s utilized a variety of genotyping techniques to provide compelling evidence of person-to-person transmission of B. cepacia among CF patients. This prompted the institution of rigorous infection control measures that have placed a heavy burden on persons with CF. More recent work has demonstrated that several distinct bacterial species actually exist among bacteria previously identified merely as B. cepacia. How these species, collectively referred to as the B. cepacia complex, differ with respect to their epidemiology, natural history, and pathology in CF is the subject of ongoing investigation.

Animals↗

[Brief review of the history of zoonoses].

By studying the surviving documents describing surveillance and methods of control of zoonoses in the distant past, the history of the fight against these diseases can be retraced. Prior to the 20th Century, the best known zoonoses were, amongst others, rabies, anthrax, glanders, tuberculosis, plague, yellow fever, influenza, and certain zoonotic parasitic diseases. An analysis of historical events yields a number of lessons as to the positive and negative influences of past theories regarding the aetiology, contagiousness and control of these diseases. These lessons serve as a reminder, to all those involved in the fight against emerging zoonoses, of the urgent need for extensive research on the aetiology and mode of transmission of these zoonoses, in addition to the need for timely application of the findings of such research to disease control activities.

Animals↗

A history of the traceability of animals and animal products.

The author presents a review of the history of traceability as applied to live animals and animal products from antiquity to the 19th Century. The evidence shows that livestock farmers, owners, and those in charge of animal production and health were concerned with traceability from a very early stage. With regard to live animals, individual identification by means of body markings has been practised for over 3,800 years (Code of Hammurabi). Branding with a red-hot iron, with or without a written record of animal characteristics, was employed in most ancient civilisations. This branding technique was principally used on valuable animals, in particular horses, in which case a written record was kept. Individual indelible branding was used on other species over the following centuries, for example, on swans belonging to the Kings of England as early as the 13th Century. Branding for disease control purposes commenced later, prompted by the major epizootics (rinderpest, contagious bovine pleuropneumonia, glanders and rabies). Marking of animals formed part of a series of very pragmatic measures, and the penalties in the event of violation were much more severe than is currently the case. Although modern traceability techniques were not available, our ancestors, as early as the 17th Century, practised indelible branding and strict health certification. Animal products were likewise closely monitored, particularly during the epidemics of human plague during the 14th Century. Some animal products could not be traded internationally unless accompanied by a certificate of origin guaranteeing safety. During the major epizootics of the 18th Century, some contaminated products (meat, hides) were cut up, slashed or covered with lime to indicate that the product was unfit for trade or consumption.

Animal Diseases↗