Clinical presentation of inhalational anthrax following bioterrorism exposure: report of 2 surviving patients

Knowledge and preparedness of healthcare providers towards bioterrorism

Background

Several emergent circumstances require healthcare providers to recognize the unusual and dangerous and pathogenic agents. An in-depth literature review showed that studies about bioterrorism preparedness amongst healthcare providers are lacking. Therefore, this study aimed to investigate the knowledge and preparedness level of first emergency respondents towards bioterrorism events.

Methods

This study has a cross-sectional design and was carried out at the Emergency departments and poison control centers/clinical laboratories three in major tertiary care hospitals in Riyadh, Saudi Arabia. The subjects were randomly selected to complete the self-administered questionnaire to collect study outcomes.

Results

A total of 1030 participants were included in the final data analysis. The mean knowledge score in the basic concepts of bioterrorism and introductory clinical presentations of bioterrorism-related agents was 4.92 ± 1.86 out of 12 points.

Moreover, the findings showed a mean knowledge score of 22.80 ± 3.92 out of 38 in the bioterrorism preparedness and governing policies and procedures. Respondents who received previous training in bioterrorism preparedness had a significantly higher number of perceived benefits than those not sure and without prior training (z = − 2.67, p = 0.008) and (z = − 4.4, p < 0.0001), respectively. About 79.4% of participants did not have previous training in bioterrorism preparedness, but 68.7% expressed willingness in the institution’s response and control to assist in a bioterrorist attack incident.

Conclusion

Although healthcare professionals have reported their desire to help in bioterrorism events, they need to enhance their knowledge of bioterrorism preparedness.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12913-021-06442-z.

Review: The risk of contracting anthrax from spore-contaminated soil - A military medical perspective

Anthrax is an infectious disease of relevance for military forces. Although spores of Bacillus anthracis obiquitously occur in soil, reports on soil-borne transmission to humans are scarce. In this narrative review, the potential of soil-borne transmission of anthrax to humans is discussed based on pathogen-specific characteristics and reports on anthrax in the course of several centuries of warfare. In theory, anthrax foci can pose a potential risk of infection to animals and humans if sufficient amounts of virulent spores are present in the soil even after an extended period of time. In praxis, however, transmissions are usually due to contacts with animal products and reported events of soil-based transmissions are scarce. In the history of warfare, even in the trenches of World War I, reported anthrax cases due to soil-contaminated wounds are virtually absent. Both the perspectives and the experience of the Western hemisphere and of former Soviet Republics are presented. Based on the accessible data as provided in the review, the transmission risk of anthrax by infections of wounds due to spore-contaminated soil is considered as very low under the most circumstance. Active historic anthrax foci may, however, still pose a risk to the health of deployed soldiers.

Zoonotic Infections and Biowarfare Agents in Critical Care: Anthrax, Plague, and Tularemia

Bacterial zoonotic infections are rare in developed countries in the twenty-first century but may cause major morbidity and mortality in developing regions of the world. In addition, their potential use as biological weapons makes early recognition and effective empiric therapy important for the critical care practitioner. Anthrax, plague, and tularemia share overlapping presenting syndromes, including fulminant respiratory infections and less severe but still highly morbid lymphocutaneous infections. Although all three may be transmitted as infectious aerosols, only plague has a risk of direct human-to-human transmission. Diagnostic testing will require special precautions for laboratory staff and most often involvement of regional and national reference laboratories. Empiric therapy with aminoglycosides may be life-saving for plague and tularemia, while the treatment of anthrax is complex and varies depending on the site of infection. In outbreaks or for post-exposure prophylaxis, treatment with doxycycline or a fluoroquinolone is recommended for all three diseases.

Does Bacillus anthracis Lethal Toxin Directly Depress Myocardial Function? A Review of Clinical Cases and Preclinical Studies

The US outbreak of B.anthracis infection in 2001 and subsequent cases in the US and Europe demonstrate that anthrax is a continuing risk for the developed world. While several bacterial components contribute to the pathogenesis of B. anthracis, production of lethal toxin (LT) is strongly associated with the development of hypotension and lethality. However, the mechanisms underlying the cardiovascular instability LT produces are unclear. Some evidence suggests that LT causes shock by impairing the peripheral vasculature, effects consistent with the substantial extravasation of fluid in patients dying with B. anthracis. Other data suggests that LT directly depresses myocardial function. However a clinical correlate for this latter possibility is less evident since functional studies and post-mortem examination in patients demonstrate absent or minimal cardiac changes. The purposes of this review were to first present clinical studies of cardiac functional and histologic pathology with B. anthracis infection and to then examine in vivo, in vitro, and ex vivo preclinical studies of LT’s myocardial effects. Together, these data suggest that it is unclear whether that LT directly depresses cardiac function. This question is important for the clinical management and development of new therapies for anthrax and efforts should continue to be made to answer it.

Antimicrobial Treatment for Systemic Anthrax: Analysis of Cases from 1945 to 2014 Identified Through a Systematic Literature Review

Systemic anthrax is associated with high mortality. Current national guidelines, developed for the individualized treatment of systemic anthrax, outline the use of combination intravenous antimicrobials for a minimum of 2 weeks, bactericidal and protein synthesis inhibitor antimicrobials for all cases of systemic anthrax, and at least 3 antimicrobials with good blood-brain barrier penetration for anthrax meningitis. However, in an anthrax mass casualty incident, large numbers of anthrax cases may create challenges in meeting antimicrobial needs. To further inform our understanding of the role of antimicrobials in treating systemic anthrax, a systematic review of the English-language literature was conducted to identify cases of systemic anthrax treated with antimicrobials for which a clinical outcome was recorded. A total of 149 cases of systemic anthrax were identified. Among the identified 59 cases of cutaneous anthrax, 33 were complicated by meningitis (76% mortality), while 26 simply had evidence of the systemic inflammatory response syndrome (4% mortality); 21 of 26 (81%) of this latter group received monotherapy. Subsequent analysis regarding combination antimicrobial therapy was restricted to the remaining 123 cases of more severe anthrax (overall 67% mortality). Recipients of combination bactericidal and protein synthesis inhibitor therapy had a 45% survival versus 28% in the absence of combination therapy (p = 0.07). For meningitis cases (n = 77), survival was greater for those receiving 3 or more antimicrobials over the course of treatment (3 of 4; 75%), compared to receipt of 1 or 2 antimicrobials (12 of 73; 16%) (p = 0.02). Median parenteral antimicrobial duration was 14 days. Combination bactericidal and protein synthesis inhibitor therapy may be appropriate in severe anthrax disease, particularly anthrax meningitis, in a mass casualty incident.

Whole Genome-Sequencing and Phylogenetic Analysis of a Historical Collection of Bacillus anthracis Strains from Danish Cattle

Bacillus anthracis, the causative agent of anthrax, is known as one of the most genetically monomorphic species. Canonical single-nucleotide polymorphism (SNP) typing and whole-genome sequencing were used to investigate the molecular diversity of eleven B. anthracis strains isolated from cattle in Denmark between 1935 and 1988. Danish strains were assigned into five canSNP groups or lineages, i.e. A.Br.001/002 (n = 4), A.Br.Ames (n = 2), A.Br.008/011 (n = 2), A.Br.005/006 (n = 2) and A.Br.Aust94 (n = 1). The match with the A.Br.Ames lineage is of particular interest as the occurrence of such lineage in Europe is demonstrated for the first time, filling an historical gap within the phylogeography of the lineage. Comparative genome analyses of these strains with 41 isolates from other parts of the world revealed that the two Danish A.Br.008/011 strains were related to the heroin-associated strains responsible for outbreaks of injection anthrax in drug users in Europe. Eight novel diagnostic SNPs that specifically discriminate the different sub-groups of Danish strains were identified and developed into PCR-based genotyping assays.

In silico analysis suggests interaction between Ebola virus and the extracellular matrix

The worst Ebola virus (EV) outbreak in history has hit Liberia, Sierra Leone and Guinea hardest and the trend lines in this crisis are grave, and now represents a global public health threat concern. Limited therapeutic and/or prophylactic options are available for people suffering from Ebola virus disease (EVD) and further complicate the situation. Previous studies suggested that the EV glycoprotein (GP) is the main determinant causing structural damage of endothelial cells that triggers the hemorrhagic diathesis, but molecular mechanisms underlying this phenomenon remains elusive. Using the informational spectrum method (ISM), a virtual spectroscopy method for analysis of the protein-protein interactions, the interaction of GP with endothelial extracellular matrix (ECM) was investigated. Presented results of this in silico study suggest that Elastin Microfibril Interface Located Proteins (EMILINs) are involved in interaction between GP and ECM. This finding could contribute to a better understanding of EV/endothelium interaction and its role in pathogenesis, prevention and therapy of EVD.

Genetic diversity of Bacillus anthracis in Europe: genotyping methods in forensic and epidemiologic investigations

Bacillus anthracis, the etiological agent of anthrax, a zoonosis relatively common throughout the world, can be used as an agent of bioterrorism. In naturally occurring outbreaks and in criminal release of this pathogen, a fast and accurate diagnosis is crucial to an effective response. Microbiological forensics and epidemiologic investigations increasingly rely on molecular markers, such as polymorphisms in DNA sequence, to obtain reliable information regarding the identification or source of a suspicious strain. Over the past decade, significant research efforts have been undertaken to develop genotyping methods with increased power to differentiate B. anthracis strains. A growing number of DNA signatures have been identified and used to survey B. anthracis diversity in nature, leading to rapid advances in our understanding of the global population of this pathogen. This article provides an overview of the different phylogenetic subgroups distributed across the world, with a particular focus on Europe. Updated information on the anthrax situation in Europe is reported. A brief description of some of the work in progress in the work package 5.1 of the AniBioThreat project is also presented, including (1) the development of a robust typing tool based on a suspension array technology and multiplexed single nucleotide polymorphisms scoring and (2) the typing of a collection of DNA from European isolates exchanged between the partners of the project. The know-how acquired will contribute to improving the EU's ability to react rapidly when the identity and real origin of a strain need to be established.

Microevolution during an Anthrax outbreak leading to clonal heterogeneity and penicillin resistance

Anthrax is a bacterial disease primarily affecting grazing animals but it can also cause severe disease in humans. We have used genomic epidemiology to study microevolution of the bacterium in a confined outbreak in cattle which involved emergence of an antibiotic-resistant phenotype. At the time of death, the animals contained a heterogeneous population of Single Nucleotide Variants (SNVs), some being clonal but most being subclonal. We found that independent isolates from the same carcass had similar levels of SNV differences as isolates from different animals. Furthermore the relative levels of subclonal populations were different in different locations in the same carcass. The heterogeneity appeared to be derived in part from heterogeneity in the infectious dose. The resistance phenotype was linked to clonal mutations in an anti-sigma factor gene and in one case was preceded by an acquisition of a hypermutator phenotype. In another animal, small subclonal populations were observed with counteracting mutations that had turned off the resistance genes. In summary, this study shows the importance of accounting for both acquired and inherited heterogeneity when doing high-resolution infection tracing and when estimating the risks associated with penicillin treatment.

Characterization of AmiBA2446, a novel bacteriolytic enzyme active against Bacillus species

There continues to be a need for developing efficient and environmentally friendly treatments for Bacillus anthracis, the causative agent of anthrax. One emerging approach for inactivation of vegetative B. anthracis is the use of bacteriophage endolysins or lytic enzymes encoded by bacterial genomes (autolysins) with highly evolved specificity toward bacterium-specific peptidoglycan cell walls. In this work, we performed in silico analysis of the genome of Bacillus anthracis strain Ames, using a consensus binding domain amino acid sequence as a probe, and identified a novel lytic enzyme that we termed AmiBA2446. This enzyme exists as a homodimer, as determined by size exclusion studies. It possesses N-acetylmuramoyl-l-alanine amidase activity, as determined from liquid chromatography-mass spectrometry (LC-MS) analysis of muropeptides released due to the enzymatic digestion of peptidoglycan. Phylogenetic analysis suggested that AmiBA2446 was an autolysin of bacterial origin. We characterized the effects of enzyme concentration and phase of bacterial growth on bactericidal activity and observed close to a 5-log reduction in the viability of cells of Bacillus cereus 4342, a surrogate for B. anthracis. We further tested the bactericidal activity of AmiBA2446 against various Bacillus species and demonstrated significant activity against B. anthracis and B. cereus strains. We also demonstrated activity against B. anthracis spores after pretreatment with germinants. AmiBA2446 enzyme was also stable in solution, retaining its activity after 4 months of storage at room temperature.

An Evaluation of Situation Reports and Incident Notices: The DBPR/ESRB Experience

OBJECTIVE

The main objective of this study is to review information within the situation reports (SITREPs) and incident notices (INs) prepared by the Division of Bioterrorism Preparedness and Response/Epidemiology Surveillance and Response Branch, (DBPR/ESRB), Centers for Disease Control and Prevention (CDC). The secondary objective is to evaluate accuracy and completeness of the information provided in these documents.

METHODS

The authors reviewed all SITREPs/INs prepared by DBPR/ESRB from January 2007 to June 2009. Data were abstracted for variables related to the type of incidents, the type of CDC assistance requested, the geographic origin of the calls, and the organization reporting the event or requesting CDC assistance or both. In addition, variables were also created to assess the accuracy and completeness of reports for quality improvement analysis.

RESULTS

The DBPR/ESRB prepared 77 SITREPs and 22 INs. Most of them were related to unknown white powders/suspicious packages or BioWatch Actionable Reports (78%). Most calls (79%), requesting CDC assistance or not, were domestic. Almost all calls requesting CDC assistance were for clinical and/or laboratory consultation and/or request for analysis of samples. Most of the calls requesting CDC assistance came from city, county, state, or federal government agencies and military organizations (82%). However, 14 of the analyzed documents (14.4%) were misclassified, that is, a SITREP was written when it should have been an IN or vice versa. The authors also noted the absence of some relevant information among some of the documents, for example, date/time of update.

CONCLUSIONS

All of the issues/incidents reported in this article to which DBPR/ESRB responded were cause for legitimate concern. However, significant improvement can be made in the preparation of these reports by CDC staff to ensure efficient and effective response from CDC and its partners. Finally, local entities may wish to develop a similar documentation and reporting process to help manage significant incidents.

Unusual bacterial infections and the pleura

Rickettsiosis, Q fever, tularemia, and anthrax are all bacterial diseases that can affect the pleura. Rocky Mountain Spotted Fever (RMSF) and Mediterranean Spotted Fever (MSF) are caused by Rickettsia rickettsii and Rickettsia conorii, respectively. Pleural fluid from a patient with MSF had a neutrophil-predominant exudate. Coxiellaburnetii is the causative agent of Q fever. Of the two cases described in the literature, one was an exudate with a marked eosinophilia while the other case was a transudate due to a constrictive pericarditis. Francisella tularensis is the causative agent of tularemia. Pleural fluid from three tularemia patients showed a lymphocyte predominant exudate. Bacillusanthracis is the causative agent of anthrax. Cases of inhalational anthrax from a recent bioterrorist attack evidenced the presence of a serosanguineous exudative pleural effusion. These four bacterial microorganisms should be suspected in patients presenting with a clinical history, exposure to known risk factors and an unexplained pleural effusion.

Molecular epidemiologic investigation of an anthrax outbreak among heroin users, Europe

In December 2009, two unusual cases of anthrax were diagnosed in heroin users in Scotland. A subsequent anthrax outbreak in heroin users emerged throughout Scotland and expanded into England and Germany, sparking concern of nefarious introduction of anthrax spores into the heroin supply. To better understand the outbreak origin, we used established genetic signatures that provided insights about strain origin. Next, we sequenced the whole genome of a representative Bacillus anthracis strain from a heroin user (Ba4599), developed Ba4599-specific single-nucleotide polymorphism assays, and genotyped all available material from other heroin users with anthrax. Of 34 case-patients with B. anthracis-positive PCR results, all shared the Ba4599 single-nucleotide polymorphism genotype. Phylogeographic analysis demonstrated that Ba4599 was closely related to strains from Turkey and not to previously identified isolates from Scotland or Afghanistan, the presumed origin of the heroin. Our results suggest accidental contamination along the drug trafficking route through a cutting agent or animal hides used to smuggle heroin into Europe.

Hawaii Physician and Nurse Bioterrorism Preparedness Survey

Introduction:

Physicians and nurses are integral components of the public health bioterrorism surveillance system. However, most published bioterrorism preparedness surveys focus on gathering information related to selfassessed knowledge or perceived needs and abilities.

Objective:

A survey of physicians and nurses in Hawaii was conducted to assess objective knowledge regarding bioterrorism agents and diseases and perceived response readiness for a bioterrorism event.

Methods:

During June and July 2004, an anonymous survey was mailed up to three times to a random sample of all licensed physicians and nurses residing in Hawaii.

Results:

The response rate was 45% (115 of 255) for physicians and 53% (146 of 278) for nurses. Previous bioterrorism preparedness training associated significantly with knowledge-based test performance in both groups. Only 20% of physicians or nurses had had previous training in bioterrorism preparedness, and <15% felt able to respond effectively to a bioterrorism event. But, >70% expressed willingness to assist the state in the event of a bioterrorist attack.

Conclusions:

Additional bioterrorism preparedness training should be made available through continuing education and also should become a component of both medical and nursing school curricula. It is important to provide the knowledge necessary for physicians and nurses to improve their ability to perform in the event of a bioterrorist attack.

The EMILIN/Multimerin family

Elastin microfibrillar interface proteins (EMILINs) and Multimerins (EMILIN1, EMILIN2, Multimerin1, and Multimerin2) constitute a four member family that in addition to the shared C-terminus gC1q domain typical of the gC1q/TNF superfamily members contain a N-terminus unique cysteine-rich EMI domain. These glycoproteins are homotrimeric and assemble into high molecular weight multimers. They are predominantly expressed in the extracellular matrix and contribute to several cellular functions in part associated with the gC1q domain and in part not yet assigned nor linked to other specific regions of the sequence. Among the latter is the control of arterial blood pressure, the inhibition of Bacillus anthracis cell cytotoxicity, the promotion of cell death, the proangiogenic function, and a role in platelet hemostasis. The focus of this review is to highlight the multiplicity of functions and domains of the EMILIN/Multimerin family with a particular emphasis on the regulatory role played by the ligand-receptor interactions of the gC1q domain. EMILIN1 is the most extensively studied member both from the structural and functional point of view. The structure of the gC1q of EMILIN1 solved by NMR highlights unique characteristics compared to other gC1q domains: it shows a marked decrease of the contact surface of the trimeric assembly and while conserving the jelly-roll topology with two β-sheets of antiparallel strands it presents a nine-stranded β-sandwich fold instead of the usual 10-stranded fold. This is likely due to the insertion of nine residues that disrupt the ordered strand organization and forma a highly dynamic protruding loop. In this loop the residue E933 is the site of interaction between gC1q and the α4β1 and α9β1 integrins, and contrary to integrin occupancy that usually upregulates cell growth, when gC1q is ligated by the integrin the cells reduce their proliferative activity.

Bacillus anthracis lethal toxin alters regulation of visceral sympathetic nerve discharge

Bacillus anthracis infection is a pathophysiological condition that is complicated by progressive decreases in mean arterial pressure (MAP). Lethal toxin (LeTx) is central to the pathogenesis of B. anthracis infection, and the sympathetic nervous system plays a critical role in physiological regulation of acute stressors. However, the effect of LeTx on sympathetic nerve discharge (SND), a critical link between central sympathetic neural circuits and MAP regulation, remains unknown. We determined visceral (renal, splenic, and adrenal) SND responses to continuous infusion of LeTx [lethal factor (100 μg/kg) + protective antigen (200 μg/kg) infused at 0.5 ml/h for ≤6 h] and vehicle (infused at 0.5 ml/h) in anesthetized, baroreceptor-intact and baroreceptor (sinoaortic)-denervated (SAD) Sprague-Dawley rats. LeTx infusions produced an initial state of cardiovascular and sympathetic nervous system activation in intact and SAD rats. Subsequent to peak LeTx-induced increases in arterial blood pressure, intact rats demonstrated a marked hypotension that was accompanied by significant reductions in SND (renal and splenic) and heart rate (HR) from peak levels. After peak LeTx-induced pressor and sympathoexcitatory responses in SAD rats, MAP, SND (renal, splenic, and adrenal), and HR were progressively and significantly reduced, supporting the hypothesis that LeTx alters the central regulation of sympathetic nerve outflow. These findings demonstrate that the regulation of visceral SND is altered in a complex manner during continuous anthrax LeTx infusions and suggest that sympathetic nervous system dysregulation may contribute to the marked hypotension accompanying B. anthracis infection.

New target for inhibition of bacterial RNA polymerase: 'switch region'

A new drug target - the 'switch region' - has been identified within bacterial RNA polymerase (RNAP), the enzyme that mediates bacterial RNA synthesis. The new target serves as the binding site for compounds that inhibit bacterial RNA synthesis and kill bacteria. Since the new target is present in most bacterial species, compounds that bind to the new target are active against a broad spectrum of bacterial species. Since the new target is different from targets of other antibacterial agents, compounds that bind to the new target are not cross-resistant with other antibacterial agents. Four antibiotics that function through the new target have been identified: myxopyronin, corallopyronin, ripostatin, and lipiarmycin. This review summarizes the switch region, switch-region inhibitors, and implications for antibacterial drug discovery.

Biological terrorism

A biological terrorism event could have a large impact on the general population and health care system. The impact of an infectious disaster will most likely be great to emergency departments, and the collaboration between emergency and infectious disease specialists will be critical in developing an effective response. A bioterrorism event is a disaster that requires specific preparations beyond the usual medical disaster planning. An effective response would include attention to infection control issues and plans for large-scale vaccination or antimicrobial prophylaxis. This article addresses some general issues related to preparing an effective response to a biological terrorism event. It will also review organisms and toxins that could be used in biological terrorism, including clinical features, management, diagnostic testing, and infection control.

EMILINs interact with anthrax protective antigen and inhibit toxin action in vitro

The informational spectrum method (ISM) is a virtual spectroscopy method for the fast analysis of potential protein-protein relationships. By applying the ISM approach to the GeneBank protein database the vascular proteins EMILIN1 (Elastin Microfibril Interface Located ProteIN), EMILIN2, MMN1, and MMN2 were identified as additional anthrax PA antigen interacting molecules. This virtual molecular interaction was formally proven by solid phase assays using recombinant proteins. The interaction is independent of the presence of divalent cations and does not involve PA aspartic residue at 683, a critical residue in receptor binding. In fact, the D683A point mutation fully prevented the cell intoxication ability of PA in the presence of Lethal Factor, but it was fully ineffective on the binding of mutated PA to EMILIN1 and EMILIN2. The ISM approach also led to the identification of the potential interaction sites between PA and EMILINs. A PA mutant with a deletion at residue D425 and solid phase protein-protein interaction studies as well as deletion mutant of EMILIN2 confirmed the hypothesized interaction site. Our findings imply that the PA-cell surface receptor interaction is not likely to provide the full explanation for the vascular lesions and prominent hemorrhages that follow Bacillus anthracis infection and spreading and call into play vascular associated proteins such as EMILINs as potential inhibitory proteins.

In vitro and in vivo characterization of anthrax anti-protective antigen and anti-lethal factor monoclonal antibodies after passive transfer in a mouse lethal toxin challenge model to define correlates of immunity

Passive transfer of antibody may be useful for preexposure prophylaxis against biological agents used as weapons of terror, such as Bacillus anthracis. Studies were performed to evaluate the ability of anthrax antiprotective antigen (anti-PA) and antilethal factor (anti-LF) neutralizing monoclonal antibodies (mAbs) to protect against an anthrax lethal toxin (LeTx) challenge in a mouse model and to identify correlates of immunity to LeTx challenge. Despite having similar affinities for their respective antigens, anti-PA (3F11) and anti-LF (9A11), passive transfer of up to 1.5 mg of anti-PA 3F11 mAb did not provide significant protection when transferred to mice 24 h before LeTx challenge, while passive transfer of as low as 0.375 mg of anti-LF 9A11 did provide significant protection. Serum collected 24 h after passive transfer had LeTx-neutralizing activity when tested using a standard LeTx neutralization assay, but neutralization titers measured using this assay did not correlate with protection against LeTx challenge. However, measurement of LeTx-neutralizing serum responses with an LeTx neutralization assay in vitro employing the addition of LeTx to J774A.1 cells 15 min before the addition of the serum did result in neutralization titers that correlated with protection against LeTx challenge. Our results demonstrate that only the LeTx neutralization titers measured utilizing the addition of LeTx to J774A.1 cells 15 min before the addition of sample correlated with protection in vivo. Thus, this LeTx neutralization assay may be a more biologically relevant neutralization assay to predict the in vivo protective capacity of LeTx-neutralizing antibodies.

Anthrax toxins induce shock in rats by depressed cardiac ventricular function

Anthrax infections are frequently associated with severe and often irreversible hypotensive shock. The isolated toxic proteins of Bacillus anthracis produce a non-cytokine-mediated hypotension in rats by unknown mechanisms. These observations suggest the anthrax toxins have direct cardiovascular effects. Here, we characterize these effects. As a first step, we administered systemically anthrax lethal toxin (LeTx) and edema toxin (EdTx) to cohorts of three to twelve rats at different doses and determined the time of onset, degree of hypotension and mortality. We measured serum concentrations of the protective antigen (PA) toxin component at various time points after infusion. Peak serum levels of PA were in the µg/mL range with half-lives of 10–20 minutes. With doses that produced hypotension with delayed lethality, we then gave bolus intravenous infusions of toxins to groups of four to six instrumented rats and continuously monitored blood pressure by telemetry. Finally, the same doses used in the telemetry experiments were given to additional groups of four rats, and echocardiography was performed pretreatment and one, two, three and twenty-four hours post-treatment. LeTx and EdTx each produced hypotension. We observed a doubling of the velocity of propagation and 20% increases in left ventricular diastolic and systolic areas in LeTx-treated rats, but not in EdTx-treated rats. EdTx-but not LeTx-treated rats showed a significant increase in heart rate. These results indicate that LeTx reduced left ventricular systolic function and EdTx reduced preload. Uptake of toxins occurs readily into tissues with biological effects occurring within minutes to hours of serum toxin concentrations in the µg/mL range. LeTx and EdTx yield an irreversible shock with subsequent death. These findings should provide a basis for the rational design of drug interventions to reduce the dismal prognosis of systemic anthrax infections.

The cost-effectiveness of strategies to reduce mortality from an intentional release of aerosolized anthrax spores

BACKGROUND

Intentional exposures to aerosolized Bacillus anthracis spores have caused fatalities.

OBJECTIVE

To evaluate the cost-effectiveness of strategies to reduce mortality from future inhalational anthrax exposures.

METHODS

Computer cohort simulation of a 100,000-person single-site exposure (worst-case scenario) and a 100-person multiple-site exposure (resembling the recent US attack). For each scenario, universal vaccination and an emergency surveillance and response (ESR) system were compared with a default strategy that assumed eventual discovery of the exposure.

RESULTS

If an exposure was unlikely to occur or was small in scale, neither vaccination nor an ESR system was cost-effective. If an exposure was certain and large in scale, an ESR system was more cost-effective than vaccination ($73 v. $29,600 per life-year saved), and a rapid response saved more lives than improved surveillance.

CONCLUSIONS

Strategies to reduce deaths from anthrax attacks are cost-effective only if large exposures are certain. A faster response is more beneficial than enhanced surveillance.

Discriminating Inhalational Anthrax From Community-Acquired Pneumonia Using Chest Radiograph Findings and a Clinical Algorithm

BACKGROUND

Limiting the effects of a large-scale bioterrorist anthrax attack will require rapid and accurate detection of the earliest victims. We undertook this study to improve physicians' ability to rapidly detect inhalational anthrax victims.

METHODS

We conducted a case-control study to compare chest radiograph findings from 47 patients from historical inhalational anthrax cases and 188 community-acquired pneumonia control subjects. We then used classification tree analyses to derive an algorithm of chest radiograph findings and clinical characteristics that accurately and explicitly discriminated between inhalational anthrax and community-acquired pneumonia.

RESULTS

Twenty-two of the 47 patients from historical inhalational anthrax cases (46.8%) had reported chest radiograph findings. All 22 case patients (100%) had mediastinal widening, pleural effusion, or both. However, 16 case patients (72.7%) also had infiltrates. In comparison, all 188 community-acquired control subjects had reported chest radiographs. Of these, 127 control subjects (67.6%) had infiltrates, 43 control subjects (22.9%) had pleural effusions, and 15 control subjects (8.0%) had mediastinal widening. A derived algorithm with three predictor variables (chest radiograph finding of mediastinal widening, altered mental status, and elevated hematocrit) is 100% sensitive (95% confidence interval [CI], 73.5 to 100) and 98.3% specific (95% CI, 95.1 to 99.6). The derivation process used 12 patients with inhalational anthrax and 177 control subjects with community-acquired pneumonia who had information available for all three variables.

CONCLUSIONS

There are significant chest radiograph differences between inhalational anthrax and community-acquired pneumonia, but none of the chest radiograph findings are both highly sensitive and highly specific. The derived clinical algorithm can improve physicians' ability to discriminate inhalational anthrax from community-acquired pneumonia, but its utility is limited to previously healthy individuals and its accuracy may be limited by missing values.

Contribution of toxins to the pathogenesis of inhalational anthrax

Inhalational anthrax is a life-threatening infectious disease of considerable concern, especially as a potential bioterrorism agent. Progress is gradually being made towards understanding the mechanisms used by Bacillus anthracis to escape the immune system and to induce severe septicaemia associated with toxaemia and leading to death. Recent advances in fundamental research have revealed previously unsuspected roles for toxins in various cell types. We summarize here pathological data for animal models and macroscopic histological examination data from recent clinical records, which we link to the effects of toxins. We describe three major steps in infection: (i) an invasion phase in the lung, during which toxins have short-distance effects on lung phagocytes; (ii) a phase of bacillus proliferation in the mediastinal lymph nodes, with local effects of toxins; and (iii) a terminal, diffusion phase, characterized by a high blood bacterial load and by long-distance effects of toxins, leading to host death. The pathophysiology of inhalational anthrax thus involves interactions between toxins and various cell partners, throughout the course of infection.

Emerging infectious disease outbreaks: old lessons and new challenges for obstetrician-gynecologists

OBJECTIVE

The purpose of this study was to summarize 3 recent high-profile infectious disease threats that have affected the United States: severe acute respiratory syndrome, West Nile virus, and anthrax.

STUDY DESIGN

A systematic review was conducted with the use of Medline searches, searches of the Centers for Disease Control and Prevention website, and review by experts at the Centers for Disease Control and Prevention.

RESULTS

The 3 emerging infectious diseases pose very different threats: Severe acute respiratory syndrome is a newly identified pathogen that caused an international pandemic; the West Nile virus investigation involved an old pathogen that was identified in a new location; and the anthrax attacks involved the intentional introduction of a pathogen.

CONCLUSION

All 3 outbreaks highlight the importance of obstetrician-gynecologists keeping current with new information as it emerges. In this global environment, it is likely that novel disease threats will continue to emerge in the United States.

Genetic polymorphisms and susceptibility to lung disease

Susceptibility to infection by bacterium such as Bacillus anthracis has a genetic basis in mice and may also have a genetic basis in humans. In the limited human cases of inhalation anthrax, studies suggest that not all individuals exposed to anthrax spores were infected, but rather, individuals with underlying lung disease, particularly asthma, sarcoidosis and tuberculosis, might be more susceptible. In this study, we determined if polymorphisms in genes important in innate immunity are associated with increased susceptibility to infectious and non-infectious lung diseases, particularly tuberculosis and sarcoidosis, respectively, and therefore might be a risk factor for inhalation anthrax. Examination of 45 non-synonymous polymorphisms in ten genes: p47phox (NCF1), p67phox (NCF2), p40phox (NCF4), p22phox (CYBA), gp91phox (CYBB), DUOX1, DUOX2, TLR2, TLR9 and alpha 1-antitrypsin (AAT) in a cohort of 95 lung disease individuals and 95 control individuals did not show an association of these polymorphisms with increased susceptibility to lung disease.

Inhibition of platelet aggregation by anthrax edema toxin

Edema toxin is a key virulence determinant in anthrax pathogenesis that causes augmentation of cAMP inside host cells. This exotoxin has been implicated in facilitating bacterial invasion by impairing host defenses. Here, we report for the first time that edema toxin plays an important role in suppression of platelet aggregation; an effect that could be of vital significance in anthrax afflicted subjects. It was found that edema toxin induces a dose dependent and time dependent increase in cAMP inside rabbit platelets. Elevation of cAMP led to suppression of platelet aggregation as demonstrated by in vitro aggregation assays. A 95% suppression of platelet aggregation in response to thrombin and a complete suppression in response to ADP, at toxin concentrations of 7 and 2.2 nM, respectively, were observed. Antibody neutralized wild type edema factor and non-toxic mutants of this binary toxin failed to show any alteration in the normal aggregation pattern. Edema toxin caused the activation of cAMP dependent protein kinase A inside platelets, a phenomenon that could be speculated to initiate the cascade of events responsible for suppressing platelet aggregation. Furthermore, in vivo bleeding time registered a sharp increase in response to edema toxin. These findings can explicate the systemic occurrence of hemorrhage, which is a prominent symptom of anthrax. This study exemplifies how Bacillus anthracis has evolved the ability to use host's physiological processes by mimicking the eukaryotic signal transduction machinery, thus inflicting persistent infection.

Pulmonary Disease from Biological Agents: Anthrax, Plague, Q Fever, and Tularemia

Anthrax, plague, Q fever, and tularemia are all potential inhalational bioterrorism agents. The pulmonary manifestations of these agents can be readily confused with each other as well as other more common diseases such as influenza and atypical pneumonia. This article reviews the threat potential, microbiology, pathogenesis, clinical features, diagnosis, and treatment of each of these agents and highlights the similarities and differences between their pulmonary presentations.

Inter-alpha-inhibitor proteins are endogenous furin inhibitors and provide protection against experimental anthrax intoxication

Inter-alpha-inhibitor protein (IalphaIp) functions as an endogenous serine protease inhibitor in human plasma, and IalphaIp levels diminish rapidly during acute inflammatory states. One potential target for IalphaIp is furin, a cell-associated serine endopeptidase essential for the activation of protective antigen and the formation of anthrax lethal toxin (LT). IalphaIp blocks furin activity in vitro and provides significant protection against cytotoxicity for murine peritoneal macrophages exposed to up to 500 ng/ml LT. A monoclonal antibody (MAb), 69.31, that specifically blocks the enzymatic activity of IalphaIp eliminates its protective effect against LT-induced cytotoxicity. IalphaIp (30 mg/kg of body weight) administered to BALB/c mice 1 hour prior to an intravenous LT challenge resulted in 71% survival after 7 days compared with no survivors among the control animals (P < 0.001). We conclude that human IalphaIp may be an effective preventative or therapeutic agent against anthrax intoxication.

An immuno-diffusion assay to assess the protective antigen content of anthrax vaccine

The UK anthrax vaccine uses the culture supernatant of toxigenic non-encapsulated Bacillus anthracis as a crude source for protective antigen (PA). The precise amount of PA is not known. We developed a single radial immuno-diffusion (SRD) assay and an indirect ELISA to measure PA in desorbed anthrax vaccines. Based on 23 batches, the PA contents varied from 19.1 to 88.8 microgml(-1), with an average of 39.6 microgml(-1). Analysis of four batches by ELISA revealed considerably lower levels of PA. This discrepancy can be explained by competition of other proteins for binding sites, which results in an artificially low amount of bound PA per well. We conclude that the SRD assay is a reproducible method for the measurement of PA and this assay will contribute to quality control and improve the specifications of current anthrax vaccines.

Potential applications of conventional and molecular imaging to biodefense research

Imaging methods that visualize the structure and function of the living body are widely used in patient care and biomedical research, but their full potential has not yet been applied to the study and treatment of the severe illnesses caused by pathogens of biodefense concern. "Conventional" imaging techniques (e.g., radiography, computed tomography, ultrasound, or magnetic resonance imaging) delineate anatomic changes in tissues, whereas "molecular" methods employ magnetic resonance, positron emission tomography, single-photon emission computed tomography, or optical (fluorescence or bioluminescence) imaging to detect biochemical reactions that accompany pathogen replication or host responses. We review the basic principles of these methods, describe the diseases caused by 6 pathogens classified as category A or B bioterror agents (anthrax, plague, tularemia, filoviral hemorrhagic fever, smallpox, and aerosolized equine encephalitis virus infection), and discuss how imaging could be used to study their pathogenesis in laboratory animals and to diagnose and monitor infection in humans.

Bioterrorism: Preparing for the impossible or the improbable

OBJECTIVE

To review the current literature surrounding the history of bioterrorism, the relative risk of a bioterrorist attack, methods of surveillance for biological agents, identification and management of various biological agent casualties, as well as the role of the intensivist in managing a bioterrorist attack.

METHODS

Internet and Medline search (from 1966 to 2004) for articles relating to bioterrorism, biological agents, biological warfare, hospital preparedness, disaster management, and intensive care.

CONCLUSIONS

There are few instances of a successful large-scale biological weapons attack in history. Weaponization of biological agents for aerosol dispersal is difficult and has often proved to be the rate-limiting step for a successful attack. Although a successful biological attack is currently unlikely, it is still feasible. More importantly, the threat of one is likely to cause much panic in the public, while a successful attack would overburden the current healthcare infrastructure. Intensivists will need to have specific knowledge of identifying and managing casualties from various biological agents. In addition, they will need to play an integral part in the preparedness of their institutions and communities for managing a bioterrorist event.

A conceptual framework for evaluating information technologies and decision support systems for bioterrorism preparedness and response

OBJECTIVES

The authors sought to develop a conceptual framework for evaluating whether existing information technologies and decision support systems (IT/DSSs) would assist the key decisions faced by clinicians and public health officials preparing for and responding to bioterrorism.

METHODS

They reviewed reports of natural and bioterrorism related infectious outbreaks, bioterrorism preparedness exercises, and advice from experts to identify the key decisions, tasks, and information needs of clinicians and public health officials during a bioterrorism response. The authors used task decomposition to identify the subtasks and data requirements of IT/DSSs designed to facilitate a bioterrorism response. They used the results of the task decomposition to develop evaluation criteria for IT/DSSs for bioterrorism preparedness. They then applied these evaluation criteria to 341 reports of 217 existing IT/DSSs that could be used to support a bioterrorism response.

MAIN RESULTS

In response to bioterrorism, clinicians must make decisions in 4 critical domains (diagnosis, management, prevention, and reporting to public health), and public health officials must make decisions in 4 other domains (interpretation of bioterrorism surveillance data, outbreak investigation, outbreak control, and communication). The time horizons and utility functions for these decisions differ. From the task decomposition, the authors identified critical subtasks for each of the 8 decisions. For example, interpretation of diagnostic tests is an important subtask of diagnostic decision making that requires an understanding of the tests' sensitivity and specificity. Therefore, an evaluation criterion applied to reports of diagnostic IT/DSSs for bioterrorism asked whether the reports described the systems' sensitivity and specificity. Of the 217 existing IT/DSSs that could be used to respond to bioterrorism, 79 studies evaluated 58 systems for at least 1 performance metric.

CONCLUSIONS

The authors identified 8 key decisions that clinicians and public health officials must make in response to bioterrorism. When applying the evaluation system to 217 currently available IT/DSSs that could potentially support the decisions of clinicians and public health officials, the authors found that the literature provides little information about the accuracy of these systems.

Is it influenza or anthrax? A decision analytic approach to the treatment of patients with influenza-like illnesses

STUDY OBJECTIVE

We analyze the risks and benefits of alternative treatment strategies for non-septic-appearing febrile patients with influenza-like illnesses and possible exposure to anthrax.

METHODS

We used a decision analytic model to evaluate 6 testing and treatment strategies in an emergency department. Patients were non-septic-appearing and had influenza-like illnesses but low likelihood of exposure to anthrax. The following interventions were used: (1) no empiric antibiotics; (2) blood culture and treatment only if the result was positive; (3) rapid testing for influenza and, for those who tested negative, treatment with 60 days of ciprofloxacin; (4) a two-test strategy in which all patients were first tested for influenza; those who tested negative had a blood culture test and were treated empirically with ciprofloxacin for 3 days while waiting for blood culture results; (5) culture test for all patients and treatment with ciprofloxacin for up to 3 days while waiting for blood culture results; and (6) treatment of all patients with ciprofloxacin empirically for 60 days. Main outcome measures were deaths, complications from anthrax, adverse events from ciprofloxacin, and ciprofloxacin patient-days.

RESULTS

For nonzero probabilities of anthrax, patient mortality was always lowest in the strategies in which all patients were treated empirically for anthrax either for 60 days or for 3 days pending blood culture results. These strategies, however, were associated with more morbidity (more ciprofloxacin patient-days and more antibiotic adverse events) than were strategies without empiric treatment. The numbers of adverse events and antibiotic patient-days were reduced substantially with the two-test strategy, in which patients with influenza were identified early and not treated. In general, for probabilities of anthrax equaling or exceeding 2%, treating all patients empirically for 60 days was best, but for probabilities between 0.1% and 2%, the sensitivity of blood culture for anthrax determined the optimal strategy: when the sensitivity exceeded 95%, a short course of empiric ciprofloxacin until blood culture results became available was best, but for sensitivities below 95%, more aggressive empiric antibiotics use was warranted. The proportion of patients with influenza in the community affected the choice of strategy, so that seasonal variation exists.

CONCLUSION

During influenza season, our findings support rapid testing for influenza, followed by empiric treatment for anthrax pending blood culture results for those who test negative for influenza. Our results help to highlight the importance of developing rapid and sensitive tests for anthrax and of developing improved surveillance and methods to calculate the previous probability of attacks.

Lethality during continuous anthrax lethal toxin infusion is associated with circulatory shock but not inflammatory cytokine or nitric oxide release in rats

Although circulatory shock related to lethal toxin (LeTx) may play a primary role in lethality due to Bacillus anthracis infection, its mechanisms are unclear. We investigated whether LeTx-induced shock is associated with inflammatory cytokine and nitric oxide (NO) release. Sprague-Dawley rats with central venous and arterial catheters received 24-h infusions of LeTx (lethal factor 100 microg/kg; protective antigen 200 microg/kg) that produced death beginning at 9 h and a 7-day mortality rate of 53%. By 9 h, mean arterial blood pressure, heart rate, pH, and base excess were decreased and lactate and hemoglobin levels were increased in LeTx nonsurvivors compared with LeTx survivors and controls (diluent only) (P < or = 0.05 for each comparing the 3 groups). Despite these changes, arterial oxygen and circulating leukocytes and platelets were not decreased and TNF-alpha, IL-beta, IL-6, and IL-10 levels were not increased comparing either LeTx nonsurvivors or survivors to controls. Nitrate/nitrite levels and tissue histology also did not differ comparing LeTx animals and controls. In additional experiments, although 24-h infusions of LeTx and Escherichia coli LPS produced similar mortality rates (54 and 56%, respectively) and times to death (13.2 +/- 0.8 vs. 11.0 +/- 1.7 h, respectively) compared with controls, only LPS reduced circulating leukocytes, platelets, and IL-2 levels and increased TNF-alpha, IL-1 alpha and -1 beta, IL-6, IL-10, interferon-gamma, granulocyte macrophage-colony stimulating factor, RANTES, migratory inhibitory protein-1 alpha, -2, and -3, and monocyte chemotactic protein-1, as well as nitrate/nitrite levels (all P < or = 0.05 for the effects of LPS). Thus, in contrast to LPS, excessive inflammatory cytokine and NO release does not appear to contribute to the circulatory shock and lethality occurring with LeTx in this at model. Although therapies to modulate these host mediators may be applicable fo shock caused by LPS or other bacterial toxins, they may not with LeTx.

Syndromic surveillance and bioterrorism-related epidemics

To facilitate rapid detection of a future bioterrorist attack, an increasing number of public health departments are investing in new surveillance systems that target the early manifestations of bioterrorism-related disease. Whether this approach is likely to detect an epidemic sooner than reporting by alert clinicians remains unknown. The detection of a bioterrorism-related epidemic will depend on population characteristics, availability and use of health services, the nature of an attack, epidemiologic features of individual diseases, surveillance methods, and the capacity of health departments to respond to alerts. Predicting how these factors will combine in a bioterrorism attack may be impossible. Nevertheless, understanding their likely effect on epidemic detection should help define the usefulness of syndromic surveillance and identify approaches to increasing the likelihood that clinicians recognize and report an epidemic.

Bacillus anthracis lethal toxin induces TNF-alpha-independent hypoxia-mediated toxicity in mice

Bacillus anthracis lethal toxin (LT) is the major virulence factor of anthrax and reproduces most of the laboratory manifestations of the disease in animals. We studied LT toxicity in BALB/cJ and C57BL/6J mice. BALB/cJ mice became terminally ill earlier and with higher frequency than C57BL/6J mice. Timed histopathological analysis identified bone marrow, spleen, and liver as major affected organs in both mouse strains. LT induced extensive hypoxia. Crisis was due to extensive liver necrosis accompanied by pleural edema. There was no evidence of disseminated intravascular coagulation or renal dysfunction. Instead, analyses revealed hepatic dysfunction, hypoalbuminemia, and vascular/oxygenation insufficiency. Of 50 cytokines analyzed, BALB/cJ mice showed rapid but transitory increases in specific factors including KC, MCP-1/JE, IL-6, MIP-2, G-CSF, GM-CSF, eotaxin, FasL, and IL-1beta. No changes in TNF-alpha occurred. The C57BL/6J mice did not mount a similar cytokine response. These factors were not induced in vitro by LT treatment of toxin-sensitive macrophages. The evidence presented shows that LT kills mice through a TNF-alpha-independent, FasL-independent, noninflammatory mechanism that involves hypoxic tissue injury but does not require macrophage sensitivity to toxin.

Bioterrorism and catastrophe response: a quick-reference guide to resources

BACKGROUND

Dentists' responses to catastrophe have been redefined by bioterrorism. Informed response requires accurate information about agents and diseases that have the potential to be used as weapons.

METHODS

The authors reviewed information about the most probable bioterrorist weapons (those from the Center for Disease Control and Prevention's Category A) from the World Wide Web and print journals and distilled it into a resource list that is current, relevant to dentistry and noncommercial. The Web sites cited include those sponsored by federal agencies, academic institutions and professional organizations. The articles cited include those published in English within the last six years in refereed journals that are available in most higher education institutions.

RESULTS

The authors present the information in a table that provides a quick-reference guide to resources describing agents and diseases with the greatest potential for use as weapons: anthrax, botulism, plague, smallpox, tularemia and viral hemorrhagic fevers. This article presents Web site and journal citations for background and patient-oriented information (fact sheets), signs and symptoms, and prophylactic measures and treatment for each of the agents and diseases. The table facilitates quick access to this information, especially in an emergency. This article also points out guidelines for response should a suspected attack occur.

CONCLUSIONS

Armed with information about biological weapons, dentists can provide faster diagnosis, inform their patients about risks, prophylaxis or treatment and rethink their own role in terrorism response.

CLINICAL IMPLICATIONS

Fast, accurate diagnosis limits the spread of exceptionally contagious diseases. Providing accurate information to patients minimizes misinformation and the associated public fear and panic that, unchecked, could overwhelm health care systems.