Sensitive and Rapid Quantitative Detection of Anthrax Spores Isolated from Soil Samples by Real-Time PCR

Comparative evaluation of in-house developed latex agglutination test (LAT) with World Organisation for Animal Health (WOAH) -recommended methods for the detection of Bacillus anthracis spores from the soil

In-house developed Bacillus anthracis-specific synthetic peptide-based latex agglutination test (LAT) assay was comparatively evaluated with World Organisation for Animal Health (WOAH)-recommended polymerase chain reaction (PCR)/real-time PCR (qPCR) methods for the screening of B. anthracis spores from the soil to provide a simple, rapid, and economical immunodiagnostic test for field application.

Nanotechnology as a Novel Approach in Combating Microbes Providing an Alternative to Antibiotics

The emergence of infectious diseases promises to be one of the leading mortality factors in the healthcare sector. Although several drugs are available on the market, newly found microorganisms carrying multidrug resistance (MDR) against which existing drugs cannot function effectively, giving rise to escalated antibiotic dosage therapies and the need to develop novel drugs, which require time, money, and manpower. Thus, the exploitation of antimicrobials has led to the production of MDR bacteria, and their prevalence and growth are a major concern. Novel approaches to prevent antimicrobial drug resistance are in practice. Nanotechnology-based innovation provides physicians and patients the opportunity to overcome the crisis of drug resistance. Nanoparticles have promising potential in the healthcare sector. Recently, nanoparticles have been designed to address pathogenic microorganisms. A multitude of processes that can vary with various traits, including size, morphology, electrical charge, and surface coatings, allow researchers to develop novel composite antimicrobial substances for use in different applications performing antimicrobial activities. The antimicrobial activity of inorganic and carbon-based nanoparticles can be applied to various research, medical, and industrial uses in the future and offer a solution to the crisis of antimicrobial resistance to traditional approaches. Metal-based nanoparticles have also been extensively studied for many biomedical applications. In addition to reduced size and selectivity for bacteria, metal-based nanoparticles have proven effective against pathogens listed as a priority, according to the World Health Organization (WHO). Moreover, antimicrobial studies of nanoparticles were carried out not only in vitro but in vivo as well in order to investigate their efficacy. In addition, nanomaterials provide numerous opportunities for infection prevention, diagnosis, treatment, and biofilm control. This study emphasizes the antimicrobial effects of nanoparticles and contrasts nanoparticles' with antibiotics' role in the fight against pathogenic microorganisms. Future prospects revolve around developing new strategies and products to prevent, control, and treat microbial infections in humans and other animals, including viral infections seen in the current pandemic scenarios.

No hints for abundance of Bacillus anthracis and Burkholderia pseudomallei in 100 environmental samples from Cameroon

BACKGROUND

Little is known on the abundance of the pathogens Bacillus anthracis and Burkholderia pseudomallei in environmental samples in Cameroon. Therefore, 100 respective samples were assessed in a proof-of-principle assessment.

METHODS

DNA residuals from nucleic acid extractions of 100 environmental samples, which were collected between 2011 and 2013 in the Mapé Basin of Cameroon, were screened for B. anthracis and B. pseudomallei by real-time PCR. The samples comprised soil samples with water contact (n = 88), soil samples without water contact (n = 6), plant material with water contact (n = 3), water (n = 2), and soil from a hospital dressing room (n = 1).

RESULTS

B. anthracis and B. pseudomallei were detected in none of the samples assessed.

CONCLUSION

The results indicate that at least a quantitatively overwhelming, ubiquitous occurrence of B. anthracis and B. pseudomallei in the environment in Cameroon is highly unlikely. However, the number and choice of the assessed samples limit the interpretability of the results.

Acoustofluidic device for acoustic capture of Bacillus anthracis spore analogues at low concentration

A portable device for the rapid concentration of Bacillus subtilis var niger spores, also known as Bacillus globigii (BG), using a thin-reflector acoustofluidic configuration is described. BG spores form an important laboratory analog for the Bacillus anthracis spores, a serious health and bioterrorism risk. Existing systems for spore detection have limitations on detection time and detection that will benefit from the combination with this technology. Thin-reflector acoustofluidic devices can be cheaply and robustly manufactured and provide a more reliable acoustic force than previously explored quarter-wave resonator systems. The system uses the acoustic forces to drive spores carried in sample flows of 30 ml/h toward an antibody functionalized surface, which captures and immobilizes them. In this implementation, spores were fluorescently labeled and imaged. Detection at concentrations of 100 CFU/ml were demonstrated in an assay time of 10 min with 60% capture. We envisage future systems to incorporate more advanced detection of the concentrated spores, leading to rapid, sensitive detection in the presence of significant noise.

Quantification of endospores in ancient permafrost using time-resolved terbium luminescence

We describe herein a simple procedure for quantifying endospore abundances in ancient and organic-rich permafrost. We repeatedly (10x) extracted and fractionated permafrost using a tandem filter assembly composed of 3 and 0.2 μm filters. Then, the 0.2 μm filter was washed (7x), autoclaved, and the contents eluted, including dipicolinic acid (DPA). Time-resolved luminescence using Tb(EDTA) yielded a LOD of 1.46 nM DPA (6.55 × 10³ endospores/mL). In review, DPA/endospore abundances were ~2.2-fold greater in older 33 ky permafrost (258 ± 36 pmol DPA gdw^-1; 1.15 × 10⁶ ± 0.16 × 10⁶ spores gdw^-1) versus younger 19 ky permafrost (p = 0.007297). This suggests that dormancy increases with permafrost age.

Molecular characterization of B. anthracis isolates from the anthrax outbreak among cattle in Karnataka, India

Background

Anthrax, a zoonotic disease is caused by the Gram positive bacterium Bacillus anthracis. During January 2013, an anthrax outbreak among cattle was reported in Gundlupet Taluk, neighboring Bandipur National Park and tiger reserve, India. The present study aims at the molecular identification and characterization of 12 B. anthracis isolates from this outbreak by 16S rRNA gene sequencing, screening B. anthracis specific prophages and chromosomal markers, protective antigen (pag) gene and canonical single nucleotide polymorphism (canSNP) analysis to subtype the isolates into one of the twelve globally identified clonal sub-lineages of B. anthracis.

Results

These isolates had identical 16S rDNA nucleotide sequences with B. anthracis specific dual peaks showing mixed base pair R (G/A) at position 1139 with visual inspection while the automated basecaller software indicated a G. Alternatively the nucleotide A at 1146 position was indicative of the 16S rDNA type 7. Multiple sequence alignment with additional 170 (16S rDNA) sequences of B. cereus sensu lato group from GenBank database revealed 28 new 16S types in addition to eleven 16S types reported earlier. The twelve B. anthracis isolates were found to harbor the four B. anthracis specific prophages (lambdaBa01, lambdaBa02, lambdaBa03, and lambdaBa04) along with its four specific loci markers (dhp 61.183, dhp 77.002, dhp 73.019, and dhp 73.017). The pag gene sequencing identified the isolates as protective antigen (PA) genotype I with phenylalanine-proline-alanine phenotype (FPA phenotype). However, sequence clustering with additional 34 pag sequences from GenBank revealed two additional missense mutations at nucleotide positions 196 bp and 869 bp of the 2294 bp pag sequence among the 5 B. cereus strains with pXO1 like plasmids. The canSNP analysis showed that the isolates belong to A.Br.Aust94 sub-lineage that is distributed geographically in countries of Asia, Africa, Europe and Australia.

Conclusions

The analysis of 16S rDNA sequences reiterated the earlier findings that visual inspection of electropherogram for position 1139 having nucleotide R could be used for B. anthracis identification and not the consensus sequence from base caller. The canSNP results indicated that the anthrax outbreak among cattle was caused by B. anthracis of A.Br.Aust94 sub-lineage.

Rapid and Sensitive Multiplex Assay for the Detection of B. anthracis Spores from Environmental Samples

Prompt and accurate detection of Bacillus anthracis spores is crucial in the event of intentional spore dissemination in order to reduce the number of expected casualties. Specific identification of these spores from environmental samples is both challenging and time-consuming. This is due to the high homology with other Bacillus species as well as the complex composition of environmental samples, which further impedes assay sensitivity. Previously, we showed that a short incubation of B.anthracis spores in a defined growth medium results in rapid germination, bacterial growth, and secretion of toxins, including protective antigen. In this work, we tested whether coupling the incubation process to a newly developed immune-assay will enable the detection of secreted toxins as markers for the presence of spores in environmental samples. The new immune assay is a flow cytometry-based multiplex that simultaneously detects a protective antigen, lethal factor, and edema factor. Our combined assay detects 1 × 10³–1 × 10⁴/mL spores after a 2 h incubation followed by the ~80 min immune-multiplex detection. Extending the incubation step to 5 h increased assay sensitivity to 1 × 10²/mL spore. The protocol was validated in various environmental samples using attenuated or fully virulent B. anthracis spores. There was no substantial influence of contaminants derived from real environmental samples on the performance of the assay compared to clean samples, which allow the unequivocal detection of 3 × 10³/mL and 3 × 10²/mL spores following 2 and 5 hour’s incubation, respectively. Overall, we propose this method as a rapid, sensitive, and specific procedure for the identification of B. anthracis spores in environmental samples.

Gel green fluorescence ssDNA aptasensor based on carbon nanotubes for detection of anthrax protective antigen

Bacillus anthracis, the causative agent of anthrax, is a harmful pathogen with potential ability as a biological weapon which persuades scientists to develop novel methods to detect anthrax from infected resources. In this study, a multi-walled carbon nanotube (MWCNTs)-based fluorescence aptasensor was fabricated to detect the recombinant protective antigen domain 4 (rPAD4) of Bacillus anthracis as the most important key factor in development of anthrax. First, PAD4 was recombinant expressed in E. coli and purified by Ni-NTA column. Second, the affinity of aptamer to rPAD4 was confirmed by ELAA assay. In aptasensor design, the aptamer was labeled with Gel Green and immobilized on MWCNTs. Upon the adsorption of labeled aptamer on MWCNTs, fluorescence emission was quenched. In contrast, by adding rPAD4 to hybridization reaction and incubation for 10 min, the fluorescence emission was significantly recovered to 85% compared to the control. Detection limit for the sensitivity and specificity of the aptasensor was determined 20 ng/ml and 62.5 ng/ml purified and unpurified rPAD4 protein, respectively. Also, applicability of aptasensor was showed in mouse serum sample. Finally, results indicated that nanosensor has the potential to be developed as a high-sensitive, cost-effective and fast-acting system for measuring of PA in anthrax diagnostic tests.

An unusual case of bovine anthrax in the canton of Jura, Switzerland in 2017

Background

Anthrax caused by Bacillus anthracis is a zoonotic disease mainly affecting herbivores. The last Swiss outbreak was over 20 years ago. We describe a recent anthrax outbreak involving two cows from the same herd. One cow was designated as a peracute clinical case with sudden death and typical lung lesions, while the other cow presented with protracted fever and abortion.

Case presentation

On April 29th 2017, a 3.5-year-old Montbéliard dairy cow was found dead while out at pasture with haemorrhage from the nose. The veterinarian suspected pneumonia and performed a necropsy on site. Subsequently, a lung and liver sample were sent to the laboratory. Unexpectedly, Bacillus anthracis was isolated, a pathogen not found in Switzerland for decades. Several days later, a second cow from the same farm showed signs of abortion after protracted fever. Since these symptoms are not typical for anthrax, and the bacteria could not be demonstrated in blood samples from this animal, a necropsy was performed under appropriate biosafety measures. Subsequently, Bacillus anthracis could be isolated from the placenta and the sublumbal lymph nodes but not from the blood, liver, spleen and kidney. The outbreak strain (17OD930) was shown to belong to the lineage B.Br.CNEVA, the same as Swiss strains from previous outbreaks in the region. We speculate that the disease came from a temporarily opened cave system that is connected to an old carcass burial site and was flushed by heavy rainfall preceding the outbreak.

Conclusion

Even in countries like Switzerland, where anthrax is very rare, new cases can occur after unusual weather conditions or ground disturbance. It is important for public officials to be aware of this risk to avoid possible spread.

Pathogenicity, population genetics and dissemination of Bacillus anthracis

Bacillus anthracis, the etiological agent of anthrax, procures its particular virulence by a capsule and two AB type toxins: the lethal factor LF and the edema factor EF. These toxins primarily disable immune cells. Both toxins are translocated to the host cell by the adhesin-internalin subunit called protective antigen PA. PA enables LF to reach intra-luminal vesicles, where it remains active for long periods. Subsequently, LF translocates to non-infected cells, leading to inefficient late therapy of anthrax. B. anthracis undergoes slow evolution because it alternates between vegetative and long spore phases. Full genome sequence analysis of a large number of worldwide strains resulted in a robust evolutionary reconstruction of this bacterium, showing that B. anthracis is split in three main clades: A, B and C. Clade A efficiently disseminated worldwide underpinned by human activities including heavy intercontinental trade of goat and sheep hair. Subclade A.Br.WNA, which is widespread in the Northern American continent, is estimated to have split from clade A reaching the Northern American continent in the late Pleistocene epoch via the former Bering Land Bridge and further spread from Northwest southwards. An alternative hypothesis is that subclade A.Br.WNA. evolved from clade A.Br.TEA tracing it back to strains from Northern France that were assumingly dispatched by European explorers that settled along the St. Lawrence River. Clade B established mostly in Europe along the alpine axis where it evolved in association with local cattle breeds and hence displays specific geographic subclusters. Sequencing technologies are also used for forensic applications to trace unintended or criminal acts of release of B. anthracis. Under natural conditions, B. anthracis generally affects domesticated and wild ruminants in arid ecosystems. The more recently discovered B. cereus biovar anthracis spreads in tropical forests, where it threatens particularly endangered primate populations.

Sensitive and Specific Recombinase Polymerase Amplification Assays for Fast Screening, Detection, and Identification of Bacillus anthracis in a Field Setting

Four isothermal recombinase polymerase amplification (RPA) assays were developed for fast in-field identification of Bacillus anthracis The RPA assays targeted three specific sequences (i.e., the BA_5345 chromosomal marker, the lethal factor lef [from pXO1], and the capsule-biosynthesis-related capA [from pXO2]) and a conserved sequence in the adenylate cyclase gene (adk) for the Bacillus cereus group. B. anthracis-specific RPA assays were tested first with purified genomic DNAs (n = 60), including 11 representatives of B. anthracis, and then with soil (n = 8) and white powder (n = 8) samples spiked with inactivated B. anthracis spores and/or other biological agents. The RPA assays were also tested in another laboratory facility, which blindly provided DNA and lysate samples (n = 30, including 20 B. anthracis strains). RPA assays displayed 100% specificity and sensitivity. The hands-off turnaround times at 42°C ranged from 5 to 6 min for 10² genomic copies. The analytical sensitivity of each RPA assay was ∼10 molecules per reaction. In addition, the BA_5345 and adk RPA assays were assessed under field conditions with a series of surface swabs (n = 13, including 11 swabs contaminated with B. thuringiensis spores) that were blindly brought to the field laboratory by a chemical, biological, radiological, and nuclear (CBRN) sampling team. None of the 13 samples, except the control, tested positive for B. anthracis, and all samples that had been harvested from spore-contaminated surfaces tested positive with the adk RPA assay. All three B. anthracis-specific RPA assays proved suitable for rapid and reliable identification of B. anthracis and therefore could easily be used by first responders under field conditions to quickly discriminate between a deliberate release of B. anthracis spores and a hoax attack involving white powder.IMPORTANCE In recent decades, particularly following the 11 September 2001 and Amerithrax attacks, the world has experienced attempts to sow panic and chaos in society through thousands of white-powder copycats using household powders to mimic real bioterrorism attacks. In such circumstances, field-deployable detection methods are particularly needed to screen samples collected from the scene. The aim is to test the samples directly using a fast and reliable assay for detection of the presence of B. anthracis While this would not preclude further confirmatory tests from being performed in reference laboratories, it would bring useful, timely, and relevant information to local crisis managers and help them make appropriate decisions without having to wait for quantitative PCR results (with turnaround times of a few hours) or phenotypic identification and sequencing (with turnaround times of a few days). In the current investigation, we developed a set of isothermal RPA assays for the rapid screening and identification of B. anthracis in powders and soil samples, with the purpose of discriminating a deliberate release of B. anthracis spores from a hoax attack involving white powder; this would also apply to dispersion by spraying of aerosolized forms of B. anthracis Further work is now ongoing to confirm the first observations and validate the on-site use of these assays by first responders.

Caenorhabditis elegans Predation on Bacillus anthracis: Decontamination of Spore Contaminated Soil with Germinants and Nematodes

Remediation of Bacillus anthracis-contaminated soil is challenging and approaches to reduce overall spore levels in environmentally contaminated soil or after intentional release of the infectious disease agent in a safe, low-cost manner are needed. B. anthracis spores are highly resistant to biocides, but once germinated they become susceptible to traditional biocides or potentially even natural predators such as nematodes in the soil environment. Here, we describe a two-step approach to reducing B. anthracis spore load in soil during laboratory trials, whereby germinants and Caenorhabditis elegans nematodes are applied concurrently. While the application of germinants reduced B. anthracis spore load by up to four logs depending on soil type, the addition of nematodes achieved a further log reduction in spore count. These laboratory based results suggest that the combined use of nematodes and germinants could represent a promising approach for the remediation of B. anthracis spore contaminated soil.

Originality-Significance Statement: This study demonstrates for the first time the successful use of environmentally friendly decontamination methods to inactivate Bacillus anthracis spores in soil using natural predators of the bacterium, nematode worms.

Optimization of a sample processing protocol for recovery of Bacillus anthracis spores from soil

Following a release of Bacillus anthracis spores into the environment, there is a potential for lasting environmental contamination in soils. There is a need for detection protocols for B. anthracis in environmental matrices. However, identification of B. anthracis within a soil is a difficult task. Processing soil samples helps to remove debris, chemical components, and biological impurities that can interfere with microbiological detection. This study aimed to optimize a previously used indirect processing protocol, which included a series of washing and centrifugation steps. Optimization of the protocol included: identifying an ideal extraction diluent, variation in the number of wash steps, variation in the initial centrifugation speed, sonication and shaking mechanisms. The optimized protocol was demonstrated at two laboratories in order to evaluate the recovery of spores from loamy and sandy soils. The new protocol demonstrated an improved limit of detection for loamy and sandy soils over the non-optimized protocol with an approximate matrix limit of detection at 14spores/g of soil. There were no significant differences overall between the two laboratories for either soil type, suggesting that the processing protocol will be robust enough to use at multiple laboratories while achieving comparable recoveries.

Ultrasensitive electrochemical immunoassay for surface array protein, a Bacillus anthracis biomarker using Au-Pd nanocrystals loaded on boron-nitride nanosheets as catalytic labels

Bacillus anthracis, the causative agent of anthrax, is a well known bioterrorism agent. The determination of surface array protein (Sap), a unique biomarker for B. anthracis can offer an opportunity for specific detection of B. anthracis in culture broth. In this study, we designed a new catalytic bionanolabel and fabricated a novel electrochemical immunosensor for ultrasensitive detection of B. anthracis Sap antigen. Bimetallic gold-palladium nanoparticles were in-situ grown on poly (diallyldimethylammonium chloride) functionalized boron nitride nanosheets (Au-Pd NPs@BNNSs) and conjugated with the mouse anti-B. anthracis Sap antibodies (Ab2); named Au-Pd NPs@BNNSs/Ab2. The resulting Au-Pd NPs@BNNSs/Ab2 bionanolabel demonstrated high catalytic activity towards reduction of 4-nitrophenol. The sensitivity of the electrochemical immunosensor along with redox cycling of 4-aminophenol to 4-quinoneimine was improved to a great extent. Under optimal conditions, the proposed immunosensor exhibited a wide working range from 5 pg/mL to 100 ng/mL with a minimum detection limit of 1 pg/mL B. anthracis Sap antigen. The practical applicability of the immunosensor was demonstrated by specific detection of Sap secreted by the B. anthracis in culture broth just after 1h of growth. These labels open a new direction for the ultrasensitive detection of different biological warfare agents and their markers in different matrices.

SERS of meso-droplets supported on superhydrophobic wires allows exquisitely sensitive detection of dipicolinic acid, an anthrax biomarker, considerably below the infective dose

SERS of <1 μL colloid meso-droplets on superhydrophobic supports allowed detection of a total mass of dipicolinic acid equivalent to 18 anthrax spores.

Food Targeting: A Real-Time PCR Assay Targeting 16S rDNA for Direct Quantification of Alicyclobacillus spp. Spores after Aptamer-Based Enrichment

Spore-forming Alicyclobacillus spp. are able to form metabolites that induce even in small amounts an antiseptical or medicinal off-flavor in fruit juices. Microbial contaminations could occur by endospores, which overcame the pasteurization process. The current detection method for Alicyclobacillus spp. can take up to 1 week because of microbiological enrichment. In a previous study, DNA aptamers were selected and characterized for an aptamer-driven rapid enrichment of Alicyclobacillus spp. spores from orange juice by magnetic separation. In the present work, a direct quantification assay for Alicyclobacillus spp. spores was developed to complete the two-step approach of enrichment and detection. After mechanical treatment of the spores, the isolated DNA was quantified in a real-time PCR-assay targeting 16S rDNA. The assay was evaluated by the performance requirements of the European Network of Genetically Modified Organisms Laboratories (ENGL). Hence, the presented method is applicable for direct spore detection from orange juice in connection with an enrichment step.

Multiplex PCR for species-level identification of Bacillus anthracis and detection of pXO1, pXO2, and related plasmids

The Bacillus anthracis virulence plasmids pXO1 and pXO2 have critical implications for biosafety and select agent status. The proper identification and characterization of B. anthracis and its plasmid profile is important to the biodefense research community. Multiplex PCR was used to simultaneously detect a B. anthracis-specific chromosomal mutation, 4 targets distributed across pXO1, 3 targets distributed across pXO2, and highly conserved regions of the 16S gene, allowing an internal positive control for each sample. The multiplex PCR can produce as many as 9 easily separable and distinguishable amplicons, ranging in size from 188 to 555 bp. The PCR results were used to characterize DNA samples extracted from B. anthracis, other Bacillus species, and other bacterial species from many different genera. With the exception of 2 novel putative plasmids discovered, testing against inclusion and extensive exclusion panels showed 100% correlation to previously published and expected results. Upon testing 29 previously unpublished B. anthracis strains, 10 (34.5%) were pXO1(+)/pXO2(+), 9 (31.0%) were pXO1(+)/pXO2(-), 7 (24.1%) were pXO1(-)/pXO2(+), and 3 (10.3%) were pXO1(-)/pXO2(-). The present work presents a novel 9-target multiplex PCR assay capable of species-level identification of B. anthracis via a unique chromosomal marker and the detection of pXO1 and pXO2 via multiply redundant targets on each.

Application of Real-Time PCR for Quantitative Detection ofClostridium botulinumType A Toxin Gene in Food

The TaqMan real-time PCR method for the quantitative detection of C. botulinum type A was developed based on sequence-specific hybridization probes. The validity of this assay was verified by using 10 genera of 20 strains, including reference strains of C. botulinum types A, B, C, D, E and F. The detection limit of this assay was evaluated on C. botulinum type A, using a 10-fold dilution series of DNA and spores . The DNA and spores were detected up to level of 0.1 ng/ml and 10(2)spores/ml, respectively. Spore spiked food sample preparation prior to the real-time PCR was performed by two methods, heat treatment and GuSCN. The detection limits after heat treatment showed 10(2) spores/ml for spiked sausage slurry, and 10(3) spores/ml for spiked canned corn slurry, while detection limits after GuSCN precipitation showed 10(2) spores/ml in both sausage and canned corn. Therefore the real-time PCR assay after GuSCN precipitation is useful for the quantification of C. botulinum type A because it showed identical CT values in both pure spore solutions and food slurries. We suggest that quantitative analysis of C. botulinum type A by TaqMan real-time PCR can be a rapid and accurate assessment method for botulinal risk in food samples.

In silico and in vitro evaluation of PCR-based assays for the detection of Bacillus anthracis chromosomal signature sequences

Bacillus anthracis, the causative agent of anthrax, is a zoonotic pathogen that is relatively common throughout the world and may cause life threatening diseases in animals and humans. There are many PCR-based assays in use for the detection of B. anthracis. While most of the developed assays rely on unique markers present on virulence plasmids pXO1 and pXO2, relatively few assays incorporate chromosomal DNA markers due to the close relatedness of B. anthracis to the B. cereus group strains. For the detection of chromosomal DNA, different genes have been used, such as BA813, rpoB, gyrA, plcR, S-layer, and prophage-lambda. Following a review of the literature, an in silico analysis of all signature sequences reported for identification of B. anthracis was conducted. Published primer and probe sequences were compared for specificity against 134 available Bacillus spp. genomes. Although many of the chromosomal targets evaluated are claimed to be specific to B. anthracis, cross-reactions with closely related B. cereus and B. thuringiensis strains were often observed. Of the 35 investigated PCR assays, only 4 were 100% specific for the B. anthracis chromosome. An interlaboratory ring trial among five European laboratories was then performed to evaluate six assays, including the WHO recommended procedures, using a collection of 90 Bacillus strains. Three assays performed adequately, yielding no false positive or negative results. All three assays target chromosomal markers located within the lambdaBa03 prophage region (PL3, BA5345, and BA5357). Detection limit was further assessed for one of these highly specific assays.

Evaluation of inhibitor-resistant real-time PCR methods for diagnostics in clinical and environmental samples

Polymerase chain reaction (PCR) is commonly used for pathogen detection in clinical and environmental samples. These sample matrices often contain inhibitors of PCR, which is a primary reason for sample processing; however, the purification process is highly inefficient, becoming unacceptable at lower signature concentrations. One potential solution is direct PCR assessment without sample processing. Here, we evaluated nine inhibitor-resistant PCR reagents for direct detection of Francisella tularensis in seven different clinical and environmental samples using an established real-time PCR assay to assess ability to overcome PCR inhibition. While several of these reagents were designed for standard PCR, the described inhibitor resistant properties (ex. Omni Klentaq can amplify target DNA samples of up to 20% whole blood or soil) led to our evaluation with real-time PCR. A preliminary limit of detection (LOD) was determined for each chemistry in whole blood and buffer, and LODs (20 replicates) were determined for the top five chemistries in each matrix (buffer, whole blood, sputum, stool, swab, soil, and sand). Not surprisingly, no single chemistry performed the best across all of the different matrices evaluated. For instance, Phusion Blood Direct PCR Kit, Phire Hot Start DNA polymerase, and Phire Hot Start DNA polymerase with STR Boost performed best for direct detection in whole blood while Phire Hot Start DNA polymerase with STR Boost were the only reagents to yield an LOD in the femtogram range for soil. Although not the best performer across all matrices, KAPA Blood PCR kit produced the most consistent results among the various conditions assessed. Overall, while these inhibitor resistant reagents show promise for direct amplification of complex samples by real-time PCR, the amount of template required for detection would not be in a clinically relevant range for most matrices.

Ground Anthrax Bacillus Refined Isolation (GABRI) method for analyzing environmental samples with low levels of Bacillus anthracis contamination

Background

In this work are reported the results of a qualitative analytical method capable of detecting Bacillus anthracis spores when they are present in very low concentration in the soil. The Ground Anthrax Bacillus Refined Isolation (GABRI) method, assessed in our laboratory, was compared with the classic method. The comparison involved artificially anthrax-contaminated soil samples (500 spores/7.5 grams soil) and naturally contaminated soil samples collected in Bangladesh during a field investigation.

Results

The results indicated that, in contrast to the classic method, the GABRI method was able to detect B.anthracis in all contaminated samples. The GABRI method produces a more sensitive measure of anthrax spore presence significantly different from the standard method. In particular, the latter is more sensitive to the presence of normal soil contaminants.

Conclusion

The main feature of the GABRI method is its ability to strongly reduce the presence of the environmental contaminants, which being much more numerous than B. anthracis tend to inhibit their germination and growth making it extremely difficult to visualize any colonies. The reduction of the microbial environment also allows one to be able to culture and test a larger quantity of potentially contaminated soil and to isolate B. anthracis when the spores are present in very low concentrations in the soil.

Fast spore breaking by superheating

Here we present the results of Bacillus subtilis spores breaking using superheating. The spore sample was pumped through the open-ended capillary tube mounted across the heated zone. We investigated the influence of temperature in the range 120-180 °C. The heat exposure was controlled by the length of the heated zone, the inner diameter of the capillary and the sample flow rate. We found that spore treatment above 120 °C resulted in the release of DNA within 20 s.

Isolation of Bacillus anthracis from soil in selected high-risk areas of Zimbabwe

AIMS

To isolate Bacillus anthracis from cattle carcass burial sites from high-risk districts in Zimbabwe.

METHODS AND RESULTS

Soil samples were collected from carcass burial sites from seven areas, including two national game parks. Samples were collected from top 5-10 cm, and for spore extraction, 25 g of soil was suspended in sterile distilled water overnight. Supernatants were filtered through 0.45-μm pore cellulose nitrate, deposits suspended in 5 ml phosphate-buffered saline, aliquoted and heated at temperature regimen of 65, 70, 75 and 80 °C for 15 min. Samples were plated onto PLET agar. B. anthracis isolates were identified using growth morphology and PCR detecting pXO1 and pXO2 virulence plasmids. From samples heated at 75 °C for 15 min, B. anthracis were isolated from 9 of 81 (11.1%) soil samples representing five of the seven sampled areas.

CONCLUSIONS

We isolated B. anthracis from soil collected from carcass burial sites. PCR targeting virulence plasmids provided a rapid confirmation of B. anthracis.

SIGNIFICANCE AND IMPACT OF THE STUDY

The positive isolation indicated that some carcass burial sites may retain viable spores for at least 12 months after the previous outbreak, which suggests that they may be important sources of B. anthracis and new disease outbreaks.

Comparison of nucleic acid extraction platforms for detection of select biothreat agents for use in clinical resource limited settings

High-quality nucleic acids are critical for optimal PCR-based diagnostics and pathogen detection. Rapid sample processing time is important for the earliest administration of therapeutic and containment measures, especially in the case of biothreat agents. In this context, we compared the Fujifilm QuickGene-Mini80 to Qiagen's QIAamp Mini Purification kits for extraction of DNA and RNA for potential use in austere settings. Qiagen (QIAamp) column-based extraction is the currently recommended purification platform by United States Army Medical Research Institute for Infectious Diseases for both DNA and RNA extraction. However, this sample processing system requires dedicated laboratory equipment including a centrifuge. In this study, we investigated the QuickGene-Mini80, which does not require centrifugation, as a suitable platform for nucleic acid extraction for use in resource-limited locations. Quality of the sample extraction was evaluated using pathogen-specific, real-time PCR assays for nucleic acids extracted from viable and γ-irradiated Bacillus anthracis, Yersinia pestis, vaccinia virus, Venezuelan equine encephalitis virus, or B. anthracis spores in buffer or human whole blood. QuickGene-Mini80 and QIAamp performed similarly for DNA extraction regardless of organism viability. It was noteworthy that γ-irradiation did not have a significant impact on real-time PCR for organism detection. Comparison with QIAamp showed a less than adequate performance of the Fujifilm instrument for RNA extraction. However, QuickGene-Mini80 remains a viable alternative to QIAamp for DNA extraction for use in remote settings due to extraction quality, time efficiency, reduced instrument requirements, and ease of use.

Evaluation of fluorescence in situ hybridization to detect encapsulated Bacillus pumilus SAFR-032 spores released from poly(methylmethacrylate)

Bacillus pumilus SAFR-032 spores originally isolated from the Jet Propulsion Laboratory spacecraft assembly facility clean room are extremely resistant to UV radiation, H(2)O(2), desiccation, chemical disinfection and starvation compared to spores of other Bacillus species. The resistance of B. pumilus SAFR-032 spores to standard industrial clean room sterilization practices is not only a major concern for medical, pharmaceutical and food industries, but also a threat to the extraterrestrial environment during search for life via spacecraft. The objective of the present study was to investigate the potential of Alexa-FISH (fluorescence in situ hybridization with Alexa Fluor® 488 labeled oligonucleotide) method as a molecular diagnostic tool for enumeration of multiple sterilant-resistant B. pumilus SAFR-032 spores artificially encapsulated in, and released via organic solvent from, a model polymeric material: poly(methylmethacrylate) (Lucite, Plexiglas). Plexiglas is used extensively in various aerospace applications and in medical, pharmaceutical and food industries. Alexa-FISH signals were not detected from spores via standard methods for vegetative bacterial cells. Optimization of a spore permeabilization protocol capitalizing on the synergistic action of proteinase-K, lysozyme, mutanolysin and Triton X-100 facilitated efficient spore detection by Alexa-FISH microscopy. Neither of the Alexa-probes tested gave rise to considerable levels of Lucite- or solvent-associated background autofluorescence, demonstrating the immense potential of Alexa-FISH for rapid quantification of encapsulated B. pumilus SAFR-032 spores released from poly(methylmethacrylate).

Comparison of two suspension arrays for simultaneous detection of five biothreat bacterial in powder samples

We have developed novel Bio-Plex assays for simultaneous detection of Bacillus anthracis, Yersinia pestis, Brucella spp., Francisella tularensis, and Burkholderia pseudomallei. Universal primers were used to amplify highly conserved region located within the 16S rRNA amplicon, followed by hybridized to pathogen-specific probes for identification of these five organisms. The other assay is based on multiplex PCR to simultaneously amplify five species-specific pathogen identification-targeted regions unique to individual pathogen. Both of the two arrays are validated to be flexible and sensitive for simultaneous detection of bioterrorism bacteria. However, universal primer PCR-based array could not identify Bacillus anthracis, Yersinia pestis, and Brucella spp. at the species level because of the high conservation of 16S rDNA of the same genus. The two suspension arrays can be utilized to detect Bacillus anthracis sterne spore and Yersinia pestis EV76 from mimic "write powder" samples, they also proved that the suspension array system will be valuable tools for diagnosis of bacterial biothreat agents in environmental samples.

Real-time polymerase chain reaction assay for rapid and sensitive detection of anthrax spores in spiked soil and talcum powder

Real-time polymerase chain reaction (real-time PCR) is a laboratory technique based on PCR. This technique is able to detect sequence-specific PCR products as they accumulate in "real time" during the PCR amplification, and also to quantify the number of substrates present in the initial PCR mixture before amplification begins. In the present study, real-time PCR assay was employed for rapid and real-time detection of Bacillus anthracis spores spiked in 0.1 g of soil and talcum powder ranging from 5 to 10(7) spores. DNA was isolated from spiked soil and talcum powder, using PBS containing 1 % Triton-X-100, followed by heat treatment. The isolated DNA was used as template for real-time PCR and PCR. Real-time PCR amplification was obtained in 60 min under the annealing condition at 60°C by employing primers targeting the pag gene of B. anthracis. In the present study, the detection limit of real-time PCR assay in soil was 10(3) spores and 10(2) spores in talcum powder, respectively, whereas PCR could detect 10(4) spores in soil and 10(3) spores in talcum powder, respectively.

Molecular detection of vertebrates in stream water: a demonstration using Rocky Mountain tailed frogs and Idaho giant salamanders

Stream ecosystems harbor many secretive and imperiled species, and studies of vertebrates in these systems face the challenges of relatively low detection rates and high costs. Environmental DNA (eDNA) has recently been confirmed as a sensitive and efficient tool for documenting aquatic vertebrates in wetlands and in a large river and canal system. However, it was unclear whether this tool could be used to detect low-density vertebrates in fast-moving streams where shed cells may travel rapidly away from their source. To evaluate the potential utility of eDNA techniques in stream systems, we designed targeted primers to amplify a short, species-specific DNA fragment for two secretive stream amphibian species in the northwestern region of the United States (Rocky Mountain tailed frogs, Ascaphus montanus, and Idaho giant salamanders, Dicamptodon aterrimus). We tested three DNA extraction and five PCR protocols to determine whether we could detect eDNA of these species in filtered water samples from five streams with varying densities of these species in central Idaho, USA. We successfully amplified and sequenced the targeted DNA regions for both species from stream water filter samples. We detected Idaho giant salamanders in all samples and Rocky Mountain tailed frogs in four of five streams and found some indication that these species are more difficult to detect using eDNA in early spring than in early fall. While the sensitivity of this method across taxa remains to be determined, the use of eDNA could revolutionize surveys for rare and invasive stream species. With this study, the utility of eDNA techniques for detecting aquatic vertebrates has been demonstrated across the majority of freshwater systems, setting the stage for an innovative transformation in approaches for aquatic research.

Bovine Bacillus anthracis in Cameroon

Bovine Bacillus anthracis isolates from Cameroon were genetically characterized. They showed a strong homogeneity, and they belong, together with strains from Chad, to cluster Aβ, which appears to be predominant in western Africa. However, one strain that belongs to a newly defined clade (D) and cluster (D1) is penicillin resistant and shows certain phenotypes typical of Bacillus cereus.

An evaluation of commercial DNA extraction kits for the isolation of bacterial spore DNA from soil

AIMS

To evaluate six commercial DNA extraction kits for their ability to isolate PCR-quality DNA from Bacillus spores in various soil samples.

METHODS AND RESULTS

Three soils were inoculated with various amounts of Bacillus cereus spores to simulate an outbreak or intentional release of the threat agent Bacillus anthracis. DNA was isolated from soil samples using six commercial DNA extraction kits. Extraction and purification efficiencies were assessed using a duplex real-time PCR assay that included an internal positive control. The FastDNA(®) SPIN kit for Soil showed the highest DNA extraction yield, while the E.Z.N.A.(®) Soil DNA and PowerSoil(®) DNA Isolation kits showed the highest efficiencies in removing PCR inhibitors from loam soil extracts.

CONCLUSIONS

The results of this study suggest that commercially available extraction kits can be used to extract PCR-quality DNA from bacterial spores in soil. The selection of an appropriate extraction kit should depend on the characteristics of the soil sample and the intended downstream application.

SIGNIFICANCE AND IMPACT OF THE STUDY

  The results of this study aid in the selection of an appropriate DNA extraction kit for a given soil sample. Its application could expedite sample processing for real-time PCR detection of a pathogen in soil.

Application of genetic marker and real-time polymerase chain reaction for discrimination between Forsythia viridissima and Forsythia suspensa

Forsythiae Fructus has been used as a herbal medicine for a fruit of Forsythia viridissima LINDLEY or Forsythia suspensa VAHL (Oleaceae). In Korea, the fruit of Forsythia viridissima is used and in China, the fruit of Forsythia suspensa is used generally. There are differences in the amount and distribution of constituents between Forsythia viridissima (FV) and Forsythia suspensa (FS). Accordingly, a discrimination of these two herbal drugs is needed. In this study, we designed FV genetic marker based on the internal transcribed spacer (ITS) sequence of nuclear ribosomal DNA that can discriminate Forsythia viridissima and Forsythia suspensa and species-specific amplification product 252 bp was confirmed. Using the real-time polymerase chain reaction (PCR) (allelic discrimination) analysis, an accurate discrimination between Forsythia viridissima and Forsythia suspensa was accomplished. Accordingly, with the use of PCR analysis based on ITS region sequence of ribosomal DNA and the real-time PCR analysis which can efficiently discriminate between Forsythia viridissima and Forsythia suspensa was developed.

An ultra-high temperature flow-through capillary device for bacterial spore lysis

Rapid and specific characterization of bacterial endospores is dependent on the ability to rupture the cell wall to enable analysis of the intracellular components. In particular, bacterial spores from the bacillus genus are inherently robust and very difficult to lyze or solubilize. Standard protocols for spore inactivation include chemical treatment, sonication, pressure, and thermal lysis. Although these protocols are effective for the inactivation of these agents, they are less well suited for sample preparation for analysis using proteomic and genomic approaches. To overcome this difficulty, we have designed a simple capillary device to perform thermal lysis of bacterial spores. Using this device, we were able to super heat (195 degrees C) an ethylene glycol lysis buffer to perform rapid flow-through rupture and solubilization of bacterial endospores. We demonstrated that the lysates from this preparation method are compatible with CGE as well as DNA amplification analysis. We further demonstrated the flow-through lysing device could be directly coupled to a miniaturized electrophoresis instrument for integrated sample preparation and analysis. In this arrangement, we were enabled to perform sample lysis, fluorescent dye labeling, and protein electrophoresis analysis of bacterial spores in less than 10 min. The described sample preparation device is rapid, simple, inexpensive, and easily integratable with various microfluidic devices.

Real-time loop-mediated isothermal amplification assay for rapid and sensitive detection of anthrax spores in spiked soil and talcum powder

Loop-mediated isothermal amplification (LAMP) assay is a powerful and innovative gene amplification technique that specifically amplifies the target gene under isothermal conditions with a high degree of sensitivity, rapidity and specificity. The major advantage of the LAMP assay is monitoring of amplified products without the requirement of any sophisticated equipment. In the present study a real time LAMP assay was employed for rapid and real time detection of Bacillus anthracis spores spiked in 0.1 g of soil and talcum powder ranging from 2 to 10(7) spores. DNA was isolated from spiked soil and talcum powder using PBS containing 1% Triton X-100, and heat treatment. Isolated DNA was used as template for LAMP and PCR. LAMP amplification was obtained in 60 min under isothermal condition at 63°C by employing a set of six primers targeting the pag gene of B. anthracis. The detection limit of LAMP assay in soil and talcum powder was found to be as low as 5 spores, compared to 10(3) spores and 10(4) spores by PCR in talcum powder and soil, respectively. The findings suggest that LAMP is a more rapid and sensitive assay than PCR for detecting anthrax spores, additionally the methodology to prepare DNA from spiked samples is simple, rapid and cost effective.

Development and validation of a real-time quantitative PCR assay for rapid identification of Bacillus anthracis in environmental samples

A real-time polymerase chain reaction (PCR) assay was developed for rapid identification of Bacillus anthracis in environmental samples. These samples often harbor Bacillus cereus bacteria closely related to B. anthracis, which may hinder its specific identification by resulting in false positive signals. The assay consists of two duplex real-time PCR: the first PCR allows amplification of a sequence specific of the B. cereus group (B. anthracis, B. cereus, Bacillus thuringiensis, Bacillus weihenstephanensis, Bacillus pseudomycoides, and Bacillus mycoides) within the phosphoenolpyruvate/sugar phosphotransferase system I gene and a B. anthracis specific single nucleotide polymorphism within the adenylosuccinate synthetase gene. The second real-time PCR assay targets the lethal factor gene from virulence plasmid pXO1 and the capsule synthesis gene from virulence plasmid pXO2. Specificity of the assay is enhanced by the use of minor groove binding probes and/or locked nucleic acids probes. The assay was validated on 304 bacterial strains including 37 B. anthracis, 67 B. cereus group, 54 strains of non-cereus group Bacillus, and 146 Gram-positive and Gram-negative bacteria strains. The assay was performed on various environmental samples spiked with B. anthracis or B. cereus spores. The assay allowed an accurate identification of B. anthracis in environmental samples. This study provides a rapid and reliable method for improving rapid identification of B. anthracis in field operational conditions.

Effects of L-alanine and inosine germinants on the elasticity of Bacillus anthracis spores

The surface of dormant Bacillus anthracis spores consists of a multilayer of protein coats and a thick peptidoglycan layer that allow the cells to resist chemical and environmental insults. During germination, the spore coat is degraded, making the spore susceptible to chemical inactivation by antisporal agents as well as to mechanical inactivation by high-pressure or mechanical abrasion processes. While chemical changes during germination, especially the release of the germination marker, dipicolinic acid (DPA), have been extensively studied, there is as yet no investigation of the corresponding changes in the mechanical properties of the spore. In this work, we use atomic force microscopy (AFM) to characterize the mechanical properties of the surface of Bacillus anthracis spores during germination. The Hertz model of continuum mechanics of contact was used to evaluate the Young's moduli of the spores before and after germination by applying the model to load-indentation curves. The highest modulus was observed for dormant spores, with average elasticity values of 197 +/- 81 MPa. The elasticity decreased significantly after incubation of the spores with the germinants L-alanine or inosine (47.5 +/- 41.7 and 35.4 +/- 15.8 MPa, respectively). Exposure of B. anthracis spores to a mixture of both germinants resulted in a synergistic effect with even lower elasticity, with a Young's modulus of 23.5 +/- 14.8 MPa. The elasticity of the vegetative B. anthracis cells was nearly 15 times lower than that of the dormant spores (12.4 +/- 6.3 MPa vs 197.0 +/- 80.5 MPa, respectively). Indeed from a mechanical strength point of view, the germinated spores were closer to the vegetative cells than to the dormant spores. Further, the decrease in the elasticity of the cells was accompanied by increasing AFM tip indentation depths on the cell surfaces. Indentation depths of up to 246.2 nm were observed for vegetative B. anthracis compared to 20.5 nm for the dormant spores. These results provide quantitative information on how the mechanical properties of the cell wall change during germination, which may explain how spores become susceptible to inactivation processes based on mechanical forces during germination and outgrowth. The study of spore elasticity may be a valuable tool in the design of improved antisporal treatments.

[Mission oriented diagnostic real-time PCR]

In out of area military missions soldiers are potentially exposed to bacteria that are endemic in tropical areas and can be used as biological agents. It can be difficult to culture these bacteria due to sample contamination, low number of bacteria or pretreatment with antibiotics. Commercial biochemical identification systems are not optimized for these agents which can result in misidentification. Immunological assays are often not commercially available or not specific. Real-time PCR assays are very specific and sensitive and can shorten the time required to establish a diagnosis markedly. Therefore, real-time PCRs for the identification of Bacillus anthracis, Brucella spp., Burkholderia mallei und Burkholderia pseudomallei, Francisella tularensis und Yersinia pestis have been developed. PCR results can be false negative due to inadequate clinical samples, low number of bacteria in samples, DNA degradation, inhibitory substances and inappropriate DNA preparation. Hence, it is crucial to cultivate the organisms as a prerequisite for adequate antibiotic therapy and typing of the agent. In a bioterrorist scenario samples have to be treated according to rules applied in forensic medicine and documentation has to be flawless.

Simultaneous detection of five biothreat agents in powder samples by a multiplexed suspension array

A suspension array-based multiplexed immunoassay was developed for rapid, sensitive, specific, and simultaneous detection of multiple biothreat-associated agents in powder samples. The 5-plexed immunoassays using sets of 9-plexed coupled fluorescent beads were employed to simultaneously detect five representative biothreat agents, including B. anthracis spore, Y. pestis, SARS-CoV, staphylococcal enterotoxin B (SEB) and ricin from a single powder sample and the feasibility for field samples was demonstrated by both blinded and standard laboratory trials. The detection sensitivity and dynamic range for the five biothreat agents from different powders might be varied depending on the nature of the powder and the feature of the contaminating agent. The limit of detection for Y. pestis, B. anthracis spores, SEB, ricin, SARS-CoV N protein in milk powder was 20 cfu, 111 cfu, 110pg, 5.4 ng and 2 ng per test respectively. Compared to conventional ELISA method, the suspension array has a higher sensitive ability, and can detect five biothreat agents simultaneously with high reproducibility.

Implications of limits of detection of various methods for Bacillus anthracis in computing risks to human health

Used for decades for biological warfare, Bacillus anthracis (category A agent) has proven to be highly stable and lethal. Quantitative risk assessment modeling requires descriptive statistics of the limit of detection to assist in defining the exposure. Furthermore, the sensitivities of various detection methods in environmental matrices are vital information for first responders. A literature review of peer-reviewed journal articles related to methods for detection of B. anthracis was undertaken. Articles focused on the development or evaluation of various detection approaches, such as PCR, real-time PCR, immunoassay, etc. Real-time PCR and PCR were the most sensitive methods for the detection of B. anthracis, with median instrument limits of detection of 430 and 440 cells/ml, respectively. There were very few peer-reviewed articles on the detection methods for B. anthracis in the environment. The most sensitive limits of detection for the environmental samples were 0.1 CFU/g for soil using PCR-enzyme-linked immunosorbent assay (ELISA), 17 CFU/liter for air using an ELISA-biochip system, 1 CFU/liter for water using cultivation, and 1 CFU/cm(2) for stainless steel fomites using cultivation. An exponential dose-response model for the inhalation of B. anthracis estimates of risk at concentrations equal to the environmental limit of detection determined the probability of death if untreated to be as high as 0.520. Though more data on the environmental limit of detection would improve the assumptions made for the risk assessment, this study's quantification of the risk posed by current limitations in the knowledge of detection methods should be considered when employing those methods in environmental monitoring and cleanup strategies.

A simple and sensitive method for detection of Bacillus anthracis by loop-mediated isothermal amplification

AIMS

To develop a rapid and simple system for detection of Bacillus anthracis using a loop-mediated isothermal amplification (LAMP) method and determine the suitability of LAMP for rapid identification of B. anthracis infection.

METHODS AND RESULTS

A specific LAMP assay targeting unique gene sequences in the bacterial chromosome and two virulence plasmids, pXO1 and pXO2, was designed. With this assay, it was possible to detect more than 10 fg of bacterial DNA per reaction and obtain results within 30-40 min under isothermal conditions at 63 degrees C. No cross-reactivity was observed among Bacillus cereus group and other Bacillus species. Furthermore, in tests using blood specimens from mice inoculated intranasally with B. anthracis spores, the sensitivity of the LAMP assay following DNA extraction methods using a Qiagen DNeasy kit or boiling protocol was examined. Samples prepared by both methods showed almost equivalent sensitivities in LAMP assay. The detection limit was 3.6 CFU per test.

CONCLUSIONS

The LAMP assay is a simple, rapid and sensitive method for detecting B. anthracis.

SIGNIFICANCE AND IMPACT OF THE STUDY

The LAMP assay combined with boiling extraction could be used as a simple diagnostic method for identification of B. anthracis infection.

Risk factors associated with anthrax outbreak in animals in North Dakota, 2005: a retrospective case-control study

OBJECTIVE

We identified the risk factors associated with the anthrax outbreak Of 2005 in animals in North Dakota.

METHODS

Medical records of the 2005 anthrax outbreak were obtained from the Veterinary Diagnostic Laboratory at North Dakota State University. Additional data were obtained from the North Dakota state veterinarian's office, and supplemental questionnaires were administered to producers. The data obtained included ecological and environmental factors, animal health factors, and management factors.

RESULTS

Anthrax occurred from July 1 to October 12, 2005. The cases were located in eastern North Dakota around the Red River Basin. Ransom, LaMoure, and Barnes counties reported most cases (71%). Species affected included cattle, bison, horses, sheep, elk, deer, pigs, and llamas. The predominant symptom was sudden death (38%) followed by bleeding from orifices (17%). Chi-square analysis indicated significant differences between case and control premises on the following variables: death reported on neighboring pasture, vaccination period, dry conditions, wet conditions, antibiotic use, multiple vaccination, and type of predator (coyote). Factors that significantly (p<0.05) predicted anthrax occurrences on the final logistic regression model were vaccination, use of antibiotics during an outbreak, and period of vaccine administration (before or during the outbreak).

CONCLUSIONS

The characteristics of the anthrax outbreak regarding time and place of occurrence, animals affected, clinical signs reported, and mortality rate were consistent with previous reports of natural anthrax outbreaks in animals. A number of factors that significantly predicted anthrax occurrence in animals in the 2005 outbreak in North Dakota were identified. This information is important in planning appropriate control and prevention measures for anthrax, including recommending the right vaccination and treatment regimens in managing future anthrax outbreaks.