Category B Potential Bioterrorism Agents: Bacteria, Viruses, Toxins, and Foodborne and Waterborne Pathogens

Characterization of BPSS1521 (bprD), a regulator of Burkholderia pseudomallei virulence gene expression in the mouse model

The Gram-negative saprophytic bacterium Burkholderia pseudomallei is the causative agent of melioidosis, a severe infectious disease of both humans and animals. Severity of the disease is thought to be dependent on both the health status of the host, including diabetes mellitus and kidney disease, and bacterial-derived factors. To identify the bacterial factors important during an acute infection, gene expression profiles in the spleen, lung, and liver of BALB/c (Th2 prototype) and C57BL/6 mice (Th1 prototype) were determined using DNA microarrays. This analysis identified BPSS1521 (bprD), a predicted transcriptional regulator located in the type III secretion system (T3SS-3) operon, to be up regulated, specifically in C57BL/6 mice. BALB/c mice infected with a bprD mutant showed a shorter time to death and increased inflammation, as determined by histopathological analysis and enumeration of bacteria in the spleen. Elevated numbers of multinucleated giant cells (MNGCs), which is the hallmark of melioidosis, were detected in both the wild-type and the bprD mutants; a similar elevation occurs in melioidosis patients. One striking observation was the increased expression of BPSS1520 (bprC), located downstream of bprD, in the bprD mutant. BprC is a regulator of T6SS-1 that is required for the virulence of B. pseudomallei in murine infection models. Deletion of bprD led to the overexpression of bprC and a decreased time to death. bprD expression was elevated in C57BL/6--as compared to BALB/c--mice, suggesting a role for BprD in the natural resistance of C57BL/6 mice to B. pseudomallei. Ultimately, this analysis using mice with different immune backgrounds may enhance our understanding of the outcomes of infection in a variety of models.

A single DNA aptamer functions as a biosensor for ricin

The use of microorganisms or toxins as weapons of death and fear is not a novel concept; however, the modes by which these agents of bioterrorism are deployed are increasingly clever and insidious. One mechanism by which biothreats are readily disseminated is through a nation's food supply. Ricin, a toxin derived from the castor bean plant, displays a strong thermostability and remains active at acidic and alkaline pHs. Therefore, the CDC has assigned ricin as a category B reagent since it may be easily amendable as a deliberate food biocontaminate. Current tools for ricin detection utilize enzymatic activity, immunointeractions and presence of castor bean DNA. Many of these tools are confounded by complex food matrices, display a limited dynamic range of detection and/or lack specificity. Aptamers, short RNA and single stranded DNA sequences, have increased affinity to their selected receptors, experience little cross-reactivity to other homologous compounds and are currently being sought after as biosensors for bacterial contaminants in food. This paper describes the selection and characterization of a single, dominant aptamer, designated as SSRA1, against the B-chain of ricin. SSRA1 displays one folding conformation that is stable across 4-63 °C (ΔG = -5.05). SSRA1 is able to concentrate at least 30 ng mL(-1) of ricin B chain from several liquid food matrices and outcompetes a currently available ELISA kit and ricin aptamer. Furthermore, we show detection of 25 ng mL(-1) of intact ricin A-B complex using SSRA1 combined with surface enhanced Raman scattering technique. Thus, SSRA1 would serve well as pre-analytical tool for processing of ricin from liquid foods to aid current diagnostics as well as a sensor for direct ricin detection.

The global burden of bacterial and viral zoonotic infections

Bacterial and viral zoonotic infections comprise a practically endless, ever-expanding list of pathogens that have the potential to induce human disease of varying severity, with varying means of transmission to humans (including vector-borne and foodborne agents) and of varying epidemiology. Not all theoretically zoonotic pathogens are truly zoonotic in practice, the prime example being influenza viruses; aviann H5N1 influenza remains strictly zoonotic, whereas novel H1N1 influenza displays an anthropocentric cycle that led to a pandemic, despite being of zoonotic origin. The burden of disease induced by zoonotic and viral pathogens is enormous: there are more than ten bacterial zoonoses, each of which affects hundreds of thousands patients annually, often leading to chronic infections and causing significant economic losses of a medical and livestock-related nature. Viral zoonotic agents are constantly emerging or re-emerging, and are associated with outbreaks of limited or expanded geographical spread: the typical trends of viral zoonotic infections, however, is to extend their ecological horizon, sometimes in an unexpected but successful manner, as in the case of West Nile virus, and in other instances less effectively, as was the case, fortunately, in the case of avian influenza. The majority of bacterial and viral zoonotic infections attract disproportionately low scientific and public health interest. Understanding their burden may allow for improved surveillance and prevention measures.

[Agroterrorism as a current challenge]

nema

Environmental Health and Bioterrorism

Biological warfare has complex and permanent impact on the environment in comparison to other war types (conventional, nuclear, or chemical). However, changes in the environment interfere with many of the major determinants of biological warfare (bioterrorism - biological attack). Four components are required for a biological attack: perpetrators, agents, mediums/means of delivery, and targets. Environmental changes caused by humans (auto-bioterrorism) and bioterrorism-related diseases they may impact are urbanization, agricultural intensification, de(re)forestation, water projects, and climate changes. Agroterrorism implies deliberate attack against commercial crops or livestock population. Agroterrorism is a multidimensional threat, involving a wide range of motives and perpetrators, and encompassing a wide range of actions, from single act of sabotage to strategic wartime programs with potentially disastrous spill-over' effects on susceptible wildlife and endangered species population. The threat of an agroterrorist attack depends on motivations and technical requirements of agroterrorism. Technical barriers to agroterrorism are lower than these to human-targeted bioterrorism. Terrorists' motives vary widely. The two most common are the profit motive and the anti-GMO (genetically modified organism) motive. The threat of an agroterrorist attack can be countered at four levels: (1) at the organism level, through animal or plant disease resistance; (2) at the farm level, through facility management techniques designed to prevent disease introduction or transmission; (3) at the agricultural sector level, through disease detection and response procedures; (4) at the national level, through policies designed to minimize the social and economic costs of a catastrophic disease outbreak.

A new model of bioterrorism risk assessment

There has been an abundance of different bioterrorist attack scenarios and consequently an unclear biodefense strategy so far. We present a framework for bioterrorism risk assessment that we believe would be useful for policymakers and understandable without needing to be an expert in this field. We retrieved the Medline database via PubMed (from January 1987 to January 2009) and cross-referenced and reviewed the terms biological weapons, biological attacks, bioterror, bio(defense), bio(strategy) and epidemiologic models, and risk assessment. Additionally, we conducted an internet search with the same terms and strategy. We divided bioterrorist attacks into 3 categories: strategical (large-scale), operational (middle-scale), and tactical (small-scale). A bioterrorist attack is presented as a 4-component chain model, including perpetrators, agents, means of delivery, and targets. For any of these 4 components, we propose quantitative and qualitative risk assessment parameters. Here we present a simple scoring system within our model applied to the 2001 U.S. anthrax attacks.

Expression and characterization of soluble 4-diphosphocytidyl-2-C-methyl-D-erythritol kinase from bacterial pathogens

Many bacterial pathogens utilize the 2-C-methyl-D-erythritol 4-phosphate pathway for biosynthesizing isoprenoid precursors, a pathway that is vital for bacterial survival and absent from human cells, providing a potential source of drug targets. However, the characterization of 4-diphosphocytidyl-2-C-methyl-D-erythritol (CDP-ME) kinase (IspE) has been hindered due to a lack of enantiopure CDP-ME and difficulty in obtaining pure IspE. Here, enantiopure CDP-ME was chemically synthesized and recombinant IspE from bacterial pathogens were purified and characterized. Although gene disruption was not possible in Mycobacterium tuberculosis, IspE is essential in Mycobacterium smegmatis. The biochemical and kinetic characteristics of IspE provide the basis for development of a high throughput screen and structural characterization.

Evaluation of automated and manual commercial DNA extraction methods for recovery of Brucella DNA from suspensions and spiked swabs

This study evaluated automated and manual commercial DNA extraction methods for their ability to recover DNA from Brucella species in phosphate-buffered saline (PBS) suspension and from spiked swab specimens. Six extraction methods, representing several of the methodologies which are commercially available for DNA extraction, as well as representing various throughput capacities, were evaluated: the MagNA Pure Compact and the MagNA Pure LC instruments, the IT 1-2-3 DNA sample purification kit, the MasterPure Complete DNA and RNA purification kit, the QIAamp DNA blood mini kit, and the UltraClean microbial DNA isolation kit. These six extraction methods were performed upon three pathogenic Brucella species: B. abortus, B. melitensis, and B. suis. Viability testing of the DNA extracts indicated that all six extraction methods were efficient at inactivating virulent Brucella spp. Real-time PCR analysis using Brucella genus- and species-specific TaqMan assays revealed that use of the MasterPure kit resulted in superior levels of detection from bacterial suspensions, while the MasterPure kit and MagNA Pure Compact performed equally well for extraction of spiked swab samples. This study demonstrated that DNA extraction methodologies differ in their ability to recover Brucella DNA from PBS bacterial suspensions and from swab specimens and, thus, that the extraction method used for a given type of sample matrix can influence the sensitivity of real-time PCR assays for Brucella.

Melioidosis masquerading as community-acquired pneumonia: a case report demonstrating efficacy of intrapleural fibrinolytic therapy

Burkholderia pseudomallei, a soil saprophyte typically associated with the highly fatal disease melioidosis in Southeast Asia, is an increasing global concern as worldwide travel proliferates in our increasingly cosmopolitan society. Emergence of this disease in locations where it was not previously described underscores the importance of understanding the basic microbiology, pathogenesis, and epidemiology of infectious diseases on a global scale rather than the myopic view of the usual microbiological culprits of community-acquired pneumonia (CAP) in developed nations. We report a case of melioidosis originally diagnosed as CAP complicated by empyema successfully cured with combination of antibiotics and intrapleural fibrinolytic therapy, averting operative intervention.

World Wide Web resources on zoonotic infections: a subjective overview

Zoonoses are a diverse group of infections whose significance is underestimated and understudied. The prevalence of zoonoses is higher in the developing world, where health professionals are often deprived of the rapid and free availability of related scientific information; however, continuous evolution of the World Wide Web (WWW) may offer such an option. This review sought to evaluate the content of available WWW resources on zoonoses. Two authors independently identified relevant websites. The selected websites were considered of merit upon consensus of all the authors. Only websites with freely available content were included. Websites on individual zoonoses were excluded. Through the numerous sites encountered on the WWW on zoonoses, there are certain ones that offer adequate information for the public and others that can serve as useful initiators for the non-specialist. Most sites approach zoonoses one-dimensionally, either as a public health, medical or veterinarian problem. The few sites that offer updates on zoonoses unfortunately focus on regional news. Ample information for the public and non-specialists on zoonoses can be traced on the WWW. However, what is missing is a site that will continuously update health professionals who deal with zoonoses in all their medical, veterinary and public health aspects.

Fever of unknown origin in the returning traveler

The returning traveler with fever presents a diagnostic challenge for the health care provider. When evaluating such a patient, the highest priority should be given to diseases that are potentially fatal or may represent public health threats. A good history is paramount and needs to include destination, time and duration of travel, type of activity, onset of fever in relation to travel, associated comorbidities, and any associated symptoms. Pretravel immunizations and chemoprophylaxis may alter the natural course of disease and should be inquired about specifically. The fever pattern, presence of a rash or eschar, organomegaly, or neurologic findings are helpful physical findings. Laboratory abnormalities are nonspecific but when corroborated with clinical and epidemiologic data may offer a clue to diagnosis.

Challenges in Brucella bacteraemia

Brucella possesses unique historical, epidemiological, phylogenetic and pathogenetic characteristics that constantly reinforce the pathogen's place at the epicentre of scientific interest. One such unique characteristic is the significance of bacteraemia in the course of the disease. Bacteraemia in brucellosis may be periodically present, of limited practical diagnostic importance, and of doubtful significance as an index of bacteriological cure. On the other hand, recognition of bacteraemia augments prognosis, typing and biotyping (and thus further research). Recent advances in molecular diagnosis with the help of real time polymerase chain reaction (rtPCR) have shown that bacteraemia in brucellosis may persist, at culture non-detectable levels, for protracted periods even after apparent clinical cure. This raises important issues for future research, implying that the pathogen may actually be non-eradicable.