Imaging of anthrax intoxication in mice reveals shared and individual functions of surface receptors CMG-2 and TEM-8 in cellular toxin entry.

Bacillus anthracis lethal toxin and edema toxin are binary toxins that consist of a common cell-binding moiety, protective antigen (PA), and the enzymatic moieties, lethal factor (LF) and edema factor (EF). PA binds to either of two receptors, capillary morphogenesis protein-2 (CMG-2) or tumor endothelial marker-8 (TEM-8), which triggers the binding and cytoplasmic translocation of LF and EF. However, the distribution of functional TEM-8 and CMG-2 receptors during anthrax toxin intoxication in animals has not been fully elucidated. Herein, we describe an assay to image anthrax toxin intoxication in animals, and we use it to visualize TEM-8- and CMG-2-dependent intoxication in mice. Specifically, we generated a chimeric protein consisting of the N-terminal domain of LF fused to a nuclear localization signal-tagged Cre recombinase (LFn-NLS-Cre). When PA and LFn-NLS-Cre were coadministered to transgenic mice expressing a red fluorescent protein in the absence of Cre and a green fluorescent protein in the presence of Cre, intoxication could be visualized at single-cell resolution by confocal microscopy or flow cytometry. Using this assay, we found that: (a) CMG-2 is critical for intoxication in the liver and heart, (b) TEM-8 is required for intoxication in the kidney and spleen, (c) CMG-2 and TEM-8 are redundant for intoxication of some organs, (d) combined loss of CMG-2 and TEM-8 completely abolishes intoxication, and (e) CMG-2 is the dominant receptor on leukocytes. The novel assay will be useful for basic and clinical/translational studies of Bacillus anthracis infection and for clinical development of reengineered toxin variants for cancer treatment.

Modeling and detection of respiratory-related outbreak signatures.

BACKGROUND: Time series methods are commonly used to detect disease outbreak signatures (e.g., signals due to influenza outbreaks and anthrax attacks) from varying respiratory-related diagnostic or syndromic data sources. Typically this involves two components: (i) Using time series methods to model the baseline background distribution (the time series process that is assumed to contain no outbreak signatures), (ii) Detecting outbreak signatures using filter-based time series methods. METHODS: We consider time series models for chest radiograph data obtained from Midwest children's emergency departments. These models incorporate available covariate information such as patient visit counts and smoothed ambient temperature series, as well as time series dependencies on daily and weekly seasonal scales. Respiratory-related outbreak signature detection is based on filtering the one-step-ahead prediction errors obtained from the time series models for the respiratory-complaint background. RESULTS: Using simulation experiments based on a stochastic model for an anthrax attack, we illustrate the effect of the choice of filter and the statistical models upon radiograph-attributed outbreak signature detection. CONCLUSION: We demonstrate the importance of using seasonal autoregressive integrated average time series models (SARIMA) with covariates in the modeling of respiratory-related time series data. We find some homogeneity in the time series models for the respiratory-complaint backgrounds across the Midwest emergency departments studied. Our simulations show that the balance between specificity, sensitivity, and timeliness to detect an outbreak signature differs by the emergency department and the choice of filter. The linear and exponential filters provide a good balance.

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.

Inhalational anthrax.

Inhalational anthrax is a lethal infection acquired from the inhalation of Bacillus anthracis, a pathogen classified as a Category A bioterrorist agent by the Centers for Disease Control and Prevention. The recent 2001 attack in which weaponized spores were delivered by mail to several US cities exposed our vulnerability to bioterrorism, and taught us important lessons in the timely diagnosis of this devastating disease. It is clear that patient mortality is significantly decreased by early recognition and immediate administration of antibiotic therapy. Unfortunately, the nonspecific clinical presentation is often misinterpreted as a flu-like illness and confirmatory microbiologic tests may take up to 24 hours. Radiologic manifestations, however, are distinctive and may prove essential in directing appropriate clinical care in the critical early hours of inhalational anthrax.

Acute lung infections in normal and immunocompromised hosts.

Pulmonary infections are among the most common causes of morbidity and mortality worldwide, and contribute substantially to annual medical expenditures in the United States. Despite the availability of antimicrobial agents, pneumonia constitutes the sixth most common cause of death and the number one cause of death from infection. Pneumonia can be particularly life-threatening in the elderly, in individuals who have pre-existing heart and lung conditions, in patients who have suppressed or weakened immunity, and in pregnant women. This article discusses some of the important causes of acute lung infections in normal and immunocompromised hosts. Because there often is considerable overlap, infections are categorized by the host immune status that is most likely to be associated with a particular pathogen.

Screening for inhalational anthrax due to bioterrorism: evaluating proposed screening protocols.

Eleven known cases of bioterrorism-related inhalational anthrax (IA) were treated in the United States during 2001. We retrospectively compared 2 methods that have been proposed to screen for IA. The 2 screening protocols for IA were applied to the emergency department charts of patients who presented with possible signs or symptoms of IA at Inova Fairfax Hospital (Falls Church, Virginia) from 20 October 2001 through 3 November 2001. The Mayer criteria would have screened 4 patients (0.4%; 95% CI, 0.1%-0.9%) and generated charges of 1900 dollars. If 29 patients (2.6%; 95% CI, 1.7%-3.7%) with >or=5 symptoms (but without fever and tachycardia) were screened, charges were 13,325 dollars. The Hupert criteria would have screened 273 patients (24%; 95% CI, 22%-27%) and generated charges of 126,025 dollars. In this outbreak of bioterrorism-related IA, applying the Mayer criteria would have identified both patients with IA and would have generated fewer charges than applying the Hupert criteria.

When bioterrorism strikes: diagnosis and management of inhalational anthrax.

In October and November, 2001, reports of patients with inhalational anthrax reacquainted the public with this ancient disease and introduced the harsh reality of a bioterrorist act. Bacillus anthracis, a rod-shaped, spore-forming bacterium, primarily infects herbivores. Humans traditionally have acquired the disease from occupational or agricultural exposure to infected animals and animal products. Recent events saw the intentional release of anthrax spores, using the U.S. postal system as an unlikely and unwilling agent. Cutaneous disease, pulmonary disease, and gastrointestinal anthrax are the known clinical manifestations of anthrax. Inhalational anthrax has the highest mortality and is the main focus of this report.

Creating a text classifier to detect radiology reports describing mediastinal findings associated with inhalational anthrax and other disorders.

OBJECTIVE: The aim of this study was to create a classifier for automatic detection of chest radiograph reports consistent with the mediastinal findings of inhalational anthrax. DESIGN: The authors used the Identify Patient Sets (IPS) system to create a key word classifier for detecting reports describing mediastinal findings consistent with anthrax and compared their performances on a test set of 79,032 chest radiograph reports. MEASUREMENTS: Area under the ROC curve was the main outcome measure of the IPS classifier. Sensitivity and specificity of an initial IPS model were calculated based on an existing key word search and were compared against a Boolean version of the IPS classifier. RESULTS: The IPS classifier received an area under the ROC curve of 0.677 (90% CI = 0.628 to 0.772) with a specificity of 0.99 and maximum sensitivity of 0.35. The initial IPS model attained a specificity of 1.0 and a sensitivity of 0.04. CONCLUSION: The IPS system is a useful tool for helping domain experts create a statistical key word classifier for textual reports that is a potentially useful component in surveillance of radiographic findings suspicious for anthrax.

Inhalational anthrax after bioterrorism exposure: spectrum of imaging findings in two surviving patients.

The radiographic and computed tomographic (CT) findings in two patients with documented inhalational anthrax resulting from bioterrorism exposure are presented. Chest radiographs demonstrated mediastinal widening, adenopathy, pleural effusions, and air-space disease. Chest CT images revealed enlarged hyperattenuating mediastinal and hilar lymph nodes and edema of mediastinal fat. Chest CT findings are helpful for making the initial diagnosis. To the authors' knowledge, the spectrum and follow-up of CT findings have not been previously described.