Extended multiple-locus variable-number tandem-repeat analysis of Bacillus anthracis strains isolated in Poland

Twenty-one variable-number tandem-repeat (VNTR) marker loci were used for extended multiple locus VNTR analysis (MLVA) of 14 laboratory strains of Bacillus anthracis isolated in Poland and vaccine strain Sterne 34F2A. The extended MLVA (MLVA-21) distinguished six genotypes clustered in three main branches. Monomorphic branch 1 consisted of the vaccine strain and six isolates from distinct samples of a cow died from anthrax. This group also encompassed three haemolytic isolates of B. anthracis. Branches 2 and 3 were heterogeneous and consisted of five and three isolates of the phylogenetic lineages B2 and A1, respectively. MLVA-21 supported thesis on the anthrax agent heterogeneity in Poland. This study brought an additional evidence that haemolytic B. anthracis strains isolated in Poland are closely related to the vaccine strain Stere 34F2 and may together constitute the same sensu stricto strain. No epidemiological link could be however traced between both the vaccine and the haemolytic strains.

Bacillus anthracis: balancing innocent research with dual-use potential

Anthrax Euronet, a Coordination Action of the EU 6th Framework Programme, was designed to strengthen networking activities between anthrax research groups in Europe and to harmonise protocols for testing anthrax vaccines and therapeutics. Inevitably, the project also addressed aspects of the current political issues of biosecurity and dual-use research, i.e. research into agents of important diseases of man, livestock or agriculture that could be used as agents of bioterrorism. This review provides a comprehensive overview of the biology of Bacillus anthracis, of the pathogenesis, epidemiology and diagnosis of anthrax, as well as vaccine and therapeutic intervention strategies. The proposed requirement for a code of conduct for working with dual-use agents such as the anthrax bacillus is also discussed.

Inhalation anthrax: dose response and risk analysis

The notion that inhalation of a single Bacillus anthracis spore is fatal has become entrenched nearly to the point of urban legend, in part because of incomplete articulation of the scientific basis for microbial risk assessment, particularly dose-response assessment. Risk analysis (ie, risk assessment, risk communication, risk management) necessitates transparency: distinguishing scientific facts, hypotheses, judgments, biases in interpretations, and potential misinformation. The difficulty in achieving transparency for biothreat risk is magnified by misinformation and poor characterization of both dose-response relationships and the driving mechanisms that cause susceptibility or resistance to disease progression. Regrettably, this entrenchment unnecessarily restricts preparedness planning to a single response scenario: decontaminate until no spores are detectable in air, water, or on surfaces-essentially forcing a zero-tolerance policy inconsistent with the biology of anthrax. We present evidence about inhalation anthrax dose-response relationships, including reports from multiple studies documenting exposures insufficient to cause inhalation anthrax in laboratory animals and humans. The emphasis of the article is clarification about what is known from objective scientific evidence for doses of anthrax spores associated with survival and mortality. From this knowledge base, we discuss the need for future applications of more formal risk analysis processes to guide development of alternative non-zero criteria or standards based on science to inform preparedness planning and other risk management activities.

Experimental respiratory anthrax infection in the common marmoset (Callithrix jacchus)

Inhalational anthrax is a rare but potentially fatal infection in man. The common marmoset (Callithrix jacchus) was evaluated as a small non-human primate (NHP) model of inhalational anthrax infection, as an alternative to larger NHP species. The marmoset was found to be susceptible to inhalational exposure to Bacillus anthracis Ames strain. The pathophysiology of infection following inhalational exposure was similar to that previously reported in the rhesus and cynomolgus macaque and humans. The calculated LD(50) for B. anthracis Ames strain in the marmoset was 1.47 x 10(3) colony-forming units, compared with a published LD(50) of 5.5 x 10(4) spores in the rhesus macaque and 4.13 x 10(3) spores in the cynomolgus macaque. This suggests that the common marmoset is an appropriate alternative NHP and will be used for the evaluation of medical countermeasures against respiratory anthrax infection.

Bacillus anthracis spores influence ATP synthase activity in murine macrophages

Anthrax is an infectious disease caused by toxigenic strains of the Gram-positive bacterium Bacillus anthracis. To identify the mitochondrial proteins that are expressed differently in murine macrophages infected with spores of B. anthracis Sterne, proteomic and MALDI-TOF/MS analyses of uninfected and infected macrophages were conducted. As a result, 13 mitochondrial proteins with different expression patterns were discovered in the infected murine macrophages, and some were identified as ATP5b, NIAP-5, ras-related GTP binding protein B isoform CRAa, along with several unnamed proteins. Among these proteins, ATP5b is related to energy production and cytoskeletal rearrangement, whereas NIAP-5 causes apoptosis of host cells due to binding with caspase-9. Therefore, this paper focused on ATP5b, which was found to be downregulated following infection. The downregulated ATP5b also reduced ATP production in the murine macrophages infected with B. anthracis spores. Consequently, this study represents the first mitochondrial proteome analysis of infected macrophages.

Differential analysis of Bacillus anthracis after pX01 plasmid curing and comprehensive data on Bacillus anthracis infection in macrophages and glial cells

Bacillus anthracis is a gram-positive bacterial organism responsible for anthrax. This organism has two pathogenic plasmids: pX01 and pX02. The genetic function of pX01, which comprises about 198 kb, is not known, except for a region called the pathogenic island, which contains three genes-pag, lef, and cya-that code for three toxic proteins. A 2-D difference gel electrophoresis (2-D DIGE) system was used to verify the existence of proteins controlled by the pX01 plasmid, and protein regulation data were obtained using DeCyder software. A total of 1728 proteins were identified in the wild-type strain of this organism and 1684 in the pX01 plasmid. Twenty-seven of these proteins disappeared and eight appeared when the pX01 plasmid was removed. An additional 52 proteins were downregulated and 15 were upregulated when this plasmid was removed. A total of 102 proteins have been identified using the MALDI-TOF method of analysis, including 49 whose functions are unknown. Among these, 31 participate in metabolic processes, two in cellular processes, 15 in the processing of genetic information, and five in the processing of extracellular information. Another seven proteins participate in bacterial virulence and pathogenesis. We investigated the functions of these proteins in other bacteria, particularly the B. anthracis derivative H9041. Bacterial growth differed between pX01+/pX02+ B. anthracis and its pX01-/pX02+ derivative as did the cytotoxicity of macrophages infected by pX01+/pX02+ B. anthracis and the pX01-pX02+ derivative. We also found that S100B protein levels increased in the host infected with pX01+/pX02+ B. anthracis or its pX01-/pX02+ derivative. These data suggest that the pX01 plasmid plays a key role in the regulation of protein functions in B. anthracis.

Bacillus anthracis: interactions with the host and establishment of inhalational anthrax

Due to its potential as a bioweapon, Bacillus anthracis has received a great deal of attention in recent years, and a significant effort has been devoted to understanding how this organism causes anthrax. There has been a particular focus on the inhalational form of the disease, and studies over the past several years have painted an increasingly complex picture of how B. anthracis enters the mammalian host, survives the host's defense mechanisms, disseminates throughout the body and causes death. This article reviews recent advances in these areas, with a focus on how the bacterium interacts with its host in establishing infection and causing anthrax.

Primary involvement of pharynx and peyer's patch in inhalational and intestinal anthrax

Bacillus anthracis causes three forms of anthrax: inhalational, gastrointestinal, and cutaneous. Anthrax is characterized by both toxemia, which is caused by secretion of immunomodulating toxins (lethal toxin and edema toxin), and septicemia, which is associated with bacterial encapsulation. Here we report that, contrary to the current view of B. anthracis pathogenesis, B. anthracis spores germinate and establish infections at the initial site of inoculation in both inhalational and cutaneous infections without needing to be transported to draining lymph nodes, and that inhaled spores establish initial infection in nasal-associated lymphoid tissues. Furthermore, we found that Peyer's patches in the mouse intestine are the primary site of bacterial growth after intragastric inoculation, thus establishing an animal model of gastrointestinal anthrax. All routes of infection progressed to the draining lymph nodes, spleen, lungs, and ultimately the blood. These discoveries were made possible through the development of a novel dynamic mouse model of B. anthracis infection using bioluminescent non-toxinogenic capsulated bacteria that can be visualized within the mouse in real-time, and demonstrate the value of in vivo imaging in the analysis of B. anthracis infection. Our data imply that previously unrecognized portals of bacterial entry demand more intensive investigation, and will significantly transform the current perception of inhalational, gastrointestinal, and cutaneous B. anthracis pathogenesis.

Anthrax is caused by Bacillus anthracis, a bacterial pathogen that forms spores, dormant bacteria that are highly resistant to destruction. Infections initiate from the introduction of spores into airways or damaged skin, or from the consumption of contaminated food. Within the host, spores germinate, then bacteria secrete toxins that cripple the immune response and sheath themselves in a capsule that prevents them from being phagocytosed. We strove to determine in real space and time where and when spores introduced by these three routes of infection germinate and how bacteria subsequently disseminate in a mouse model. This was achieved through the development of light-emitting B. anthracis that could be tracked inside a living mouse. Contrary to current models, our studies indicated that spores germinated in situ in the skin, the intestines, and the nasal passages without needing to be transported to lymph nodes. Furthermore, bacteria disseminate from initial sites of infection in a similar fashion, first to the draining lymph nodes, then the spleen, and finally the lungs and blood. These findings imply that spore interactions with local sites of entry are critical in the development of systemic disease and that disruption of these interactions may offer new methods of anthrax prevention.

Pharmacokinetics-pharmacodynamics of gatifloxacin in a lethal murine Bacillus anthracis inhalation infection model

We determined the pharmacokinetic-pharmacodynamic (PK-PD) measure most predictive of gatifloxacin efficacy and the magnitude of this measure necessary for survival in a murine Bacillus anthracis inhalation infection model. We then used population pharmacokinetic models for gatifloxacin and simulation to identify dosing regimens with high probabilities of attaining exposures likely to be efficacious in adults and children. In this work, 6- to 8-week-old nonneutropenic female BALB/c mice received aerosol challenges of 50 to 75 50% lethal doses of B. anthracis (Ames strain, for which the gatifloxacin MIC is 0.125 mg/liter). Gatifloxacin was administered at 6- or 8-h intervals beginning 24 h postchallenge for 21 days, and dosing was designed to produce profiles mimicking fractionated concentration-time profiles for humans. Mice were evaluated daily for survival. Hill-type models were fitted to survival data. To identify potentially effective dosing regimens, adult and pediatric population pharmacokinetic models for gatifloxacin and Monte Carlo simulation were used to generate 5,000 individual patient exposure estimates. The ratio of the area under the concentration-time curve from 0 to 24 h (AUC(0-24)) to the MIC of the drug for the organism (AUC(0-24)/MIC ratio) was the PK-PD measure most predictive of survival (R(2) = 0.96). The 50% effective dose (ED(50)) and the ED(90) and ED(99) corresponded to AUC(0-24)/MIC ratios of 11.5, 15.8, and 30, respectively, where the maximum effect was 97% survival. Simulation results indicate that a daily gatifloxacin dose of 400 mg for adults and 10 mg/kg of body weight for children gives a 100% probability of attaining the PK-PD target (ED(99)). Sensitivity analyses suggest that the probability of PK-PD target attainment in adults and children is not affected by increases in MICs for strains of B. anthracis to levels as high as 0.5 mg/liter.

Comparison of real-time polymerase chain reaction and conventional polymerase chain reaction methods for the rapid identification of Bacillus anthracis

Bacillus anthracis spores have been shown to be one of the most effective biological weapons. For the rapid detection of B. anthracis spores, several genetic markers, including chromosomal and plasmid-based sequences, were studied with polymerase chain reaction (PCR) methods. In the present study, a method using a primer/probe set based on the pXO1-encoded pag gene for the detection of B. anthracis was tested in addition to culture. Eight pathological samples (four blood-immersed cotton specimens, two spleen tissue specimens, and two blood smears) with confirmed positive results for anthrax were used. All samples were suspended in saline solution and fixed with Gram and Giemsa stains for examination of colony and capsule formation. Amplicons were analyzed on 2% agarose gels with the classic PCR method. For real-time PCR, a fluorescently labeled TaqMan probe was used with a Smartcycler. Positive smear and cotton samples were confirmed with the standard culture and real-time PCR methods, but the same samples were found to be negative with the classic PCR method. A spleen sample known to be positive for B. anthracis was found to be negative with the culture method because of possible contamination with Proteus-type bacteria.

Simultaneous real-time PCR detection of Bacillus anthracis, Francisella tularensis and Yersinia pestis

This report describes the development of in-house real-time PCR assays using minor groove binding probes for simultaneous detection of the Bacillus anthracis pag and cap genes, the Francisella tularensis 23 KDa gene, as well as the Yersinia pestis pla gene. The sensitivities of these assays were at least 1 fg, except for the assay targeting the Bacillus anthracis cap gene, which showed a sensitivity of 10 fg when total DNA was used as a template in a serial dilution. The clinical value of the Bacillus anthracis- and Francisella tularensis-specific assays was demonstrated by successful amplification of DNA from cases of cow anthrax and hare tularemia, respectively. No cross-reactivity between these species-specific assays or with 39 other bacterial species was noted. These assays may provide a rapid tool for the simultaneous detection and identification of the three category A bacterial species listed as biological threats by the Centers for Disease Control and Prevention.

In vitro screen of bioinformatically selected Bacillus anthracis vaccine candidates by coupled transcription, translation, and immunoprecipitation analysis

The availability of the Bacillus anthracis genome sequence allowed for in silico selection of a few hundred open reading frames (ORFs) as putative vaccine candidates. To screen such a vast number of candidate ORFs, without resorting to laborious cloning and protein purification procedures, methods were developed for generation of PCR elements, compatible with in vitro transcription-translation and immunoprecipitation, as well as with their evaluation as DNA vaccines. Protocols will be provided for application of these methods to analyze the anti-B. anthracis antibody repertoire of hyperimmune sera or sera from convalescent and from DNA-vaccinated animals.

Lung dendritic cells rapidly mediate anthrax spore entry through the pulmonary route

Inhalational anthrax is a life-threatening infectious disease of considerable concern, especially because anthrax is an emerging bioterrorism agent. The exact mechanisms leading to a severe clinical form through the inhalational route are still unclear, particularly how immobile spores are captured in the alveoli and transported to the lymph nodes in the early steps of infection. We investigated the roles of alveolar macrophages and lung dendritic cells (LDC) in spore migration. We demonstrate that alveolar macrophages are the first cells to phagocytose alveolar spores, and do so within 10 min. However, interstitial LDCs capture spores present in the alveoli within 30 min without crossing the epithelial barrier suggesting a specific mechanism for rapid alveolus sampling by transepithelial extension. We show that interstitial LDCs constitute the cell population that transports spores into the thoracic lymph nodes from within 30 min to 72 h after intranasal infection. Our results demonstrate that LDCs are central to spore transport immediately after infection. The rapid kinetics of pathogen transport may contribute to the clinical features of inhalational anthrax.

Facilitation of risk communication during the anthrax attacks of 2001: the organizational backstory

The anthrax attacks of 2001 created risk communication problems that cannot be fully understood without appreciating the dynamics among organizations. Case studies of communication in New Jersey, consisting of interviews with a range of participants, found that existing organizational and professional networks facilitated trust among decisionmakers. This interpersonal trust improved communication among agencies and thereby risk communication with the public. For example, "white powder scares" were a problem even in places without contamination. Professionals' trust in each other was vital for responding productively. Conversely, organizational challenges, including conflict among agencies, hindered communication with key audiences. Although centralization and increased control are often seen as the remedy for communicative confusion, they also can quash the improvisational responses needed during crises.

Noncapsulated toxinogenic Bacillus anthracis presents a specific growth and dissemination pattern in naive and protective antigen-immune mice

Bacillus anthracis is a spore-forming bacterium that causes anthrax. B. anthracis has three major virulence factors, namely, lethal toxin, edema toxin, and a poly-gamma-D-glutamic acid capsule. The toxins modulate host immune responses, and the capsule inhibits phagocytosis. With the goal of increasing safety, decreasing security concerns, and taking advantage of mammalian genetic tools and reagents, mouse models of B. anthracis infection have been developed using attenuated bacteria that produce toxins but no capsule. While these models have been useful in studying both toxinogenic infections and antitoxin vaccine efficacy, we questioned whether eliminating the capsule changed bacterial growth and dissemination characteristics. Thus, the progression of infection by toxinogenic noncapsulated B. anthracis was analyzed and compared to that by previously reported nontoxinogenic capsulated bacteria, using in vivo bioluminescence imaging. The influence of immunization with the toxin component protective antigen (PA) on the development of infection was also examined. The toxinogenic noncapsulated bacteria were initially confined to the cutaneous site of infection. Bacteria then progressed to the draining lymph nodes and, finally, late in the infection, to the lungs, kidneys, and frequently the gastrointestinal tract. There was minimal colonization of the spleen. PA immunization reduced bacterial growth from the outset and limited infection to the site of inoculation. These in vivo observations show that dissemination by toxinogenic noncapsulated strains differs markedly from that by nontoxinogenic capsulated strains. Additionally, PA immunization counters bacterial growth and dissemination in vivo from the onset of infection.

Transcriptional profiling of Bacillus anthracis during infection of host macrophages

The interaction between Bacillus anthracis and the mammalian phagocyte is one of the central stages in the progression of inhalational anthrax, and it is commonly believed that the host cell plays a key role in facilitating germination and dissemination of inhaled B. anthracis spores. Given this, a detailed definition of the survival strategies used by B. anthracis within the phagocyte is critical for our understanding of anthrax. In this study, we report the first genome-wide analysis of B. anthracis gene expression during infection of host phagocytes. We developed a technique for specific isolation of bacterial RNA from within infected murine macrophages, and we used custom B. anthracis microarrays to characterize the expression patterns occurring within intracellular bacteria throughout infection of the host phagocyte. We found that B. anthracis adapts very quickly to the intracellular environment, and our analyses identified metabolic pathways that appear to be important to the bacterium during intracellular growth, as well as individual genes that show significant induction in vivo. We used quantitative reverse transcription-PCR to verify that the expression trends that we observed by microarray analysis were valid, and we chose one gene (GBAA1941, encoding a putative transcriptional regulator) for further characterization. A deletion strain missing this gene showed no phenotype in vitro but was significantly attenuated in a mouse model of inhalational anthrax, suggesting that the microarray data described here provide not only the first comprehensive view of how B. anthracis survives within the host cell but also a number of promising leads for further research in anthrax.

Bacillus anthracis anthrolysin O and three phospholipases C are functionally redundant in a murine model of inhalation anthrax

Although traditionally considered to be an extracellular pathogen, Bacillus anthracis has a brief intracellular step to initiate anthrax. At the onset of infection, B. anthracis must withstand the bactericidal activities of the macrophage. Recently, three phospholipases C (PLCs) were shown to contribute to macrophage-associated growth of B. anthracis by presumably aiding in the escape of the bacterium from phagocytic vacuoles following phagocytosis. However, in the absence of all three PLCs, vegetative bacilli were still observed growing in association with the macrophage, albeit to a lesser extent, implicating that additional factors are involved in this process. In this study, the contributions of the previously identified cholesterol-dependent cytolysin anthrolysin O (ALO) to B. anthracis pathogenesis were investigated following challenges of bone marrow-derived macrophages and intratracheal inoculations of mice. Disruption of ALO alone yielded no differences in virulence in mice. However, combinatorial deletions of ALO with the three PLCs resulted in attenuation in both tissue culture and murine challenges, suggesting that these toxins may have overlapping roles in anthrax pathogenesis.

Factors involved in the germination and inactivation of Bacillus anthracis spores in murine primary macrophages

Since macrophages have been implicated in inhalation anthrax either for defense and/or as enablers for spore trafficking, their function has been further defined. Spores were efficiently taken up by primary mouse bone marrow-derived macrophages even in the absence of serum but a minimal amount was required for spore germination and subsequent inactivation. With 10% fetal bovine serum (FBS) virtually all of the spores germinated but when the concentration of FBS was lowered to 1.0% or less, or when 10% horse serum replaced FBS, only 50% of the spores were inactivated within 1 h with no subsequent loss. Chloramphenicol, which blocks spore outgrowth but not germination, did not inhibit spore killing in macrophages. Based on complete inhibition of germination by d-alanine plus d-histidine, it is likely that only two of the several Bacillus anthracis germination systems are involved within macrophages. d-Histidine inhibits the gerH system previously implicated in germination within macrophages. d-Alanine is likely to block the gerX system since disruption of the gerXA gene resulted in little germination within 4 h in macrophages. Macrophages provide a major line of defense against infection by efficiently sequestering spores and in the presence of minimal nutrients effectively killing those that germinate before outgrowth.

Density-equalizing Euclidean minimum spanning trees for the detection of all disease cluster shapes

Existing disease cluster detection methods cannot detect clusters of all shapes and sizes or identify highly irregular sets that overestimate the true extent of the cluster. We introduce a graph-theoretical method for detecting arbitrarily shaped clusters based on the Euclidean minimum spanning tree of cartogram-transformed case locations, which overcomes these shortcomings. The method is illustrated by using several clusters, including historical data sets from West Nile virus and inhalational anthrax outbreaks. Sensitivity and accuracy comparisons with the prevailing cluster detection method show that the method performs similarly on approximately circular historical clusters and greatly improves detection for noncircular clusters.

Evaluating detection of an inhalational anthrax outbreak

Timely detection of an inhalational anthrax outbreak is critical for clinical and public health management. Syndromic surveillance has received considerable investment, but little is known about how it will perform relative to routine clinical case finding for detection of an inhalational anthrax outbreak. We conducted a simulation study to compare clinical case finding with syndromic surveillance for detection of an outbreak of inhalational anthrax. After simulated release of 1 kg of anthrax spores, the proportion of outbreaks detected first by syndromic surveillance was 0.59 at a specificity of 0.9 and 0.28 at a specificity of 0.975. The mean detection benefit of syndromic surveillance was 1.0 day at a specificity of 0.9 and 0.32 days at a specificity of 0.975. When syndromic surveillance was sufficiently sensitive to detect a substantial proportion of outbreaks before clinical case finding, it generated frequent false alarms.

Human monoclonal antibody AVP-21D9 to protective antigen reduces dissemination of the Bacillus anthracis Ames strain from the lungs in a rabbit model

Dutch-belted and New Zealand White rabbits were passively immunized with AVP-21D9, a human monoclonal antibody to protective antigen (PA), at the time of Bacillus anthracis spore challenge using either nasal instillation or aerosol challenge techniques. AVP-21D9 (10 mg/kg) completely protected both rabbit strains against lethal infection with Bacillus anthracis Ames spores, regardless of the inoculation method. Further, all but one of the passively immunized animals (23/24) were completely resistant to rechallenge with spores by either respiratory challenge method at 5 weeks after primary challenge. Analysis of the sera at 5 weeks after primary challenge showed that residual human anti-PA levels decreased by 85 to 95%, but low titers of rabbit-specific anti-PA titers were also measured. Both sources of anti-PA could have contributed to protection from rechallenge. In a subsequent study, bacteriological and histopathology analyses revealed that B. anthracis disseminated to the bloodstream in some naïve animals as early as 24 h postchallenge and increased in frequency with time. AVP-21D9 significantly reduced the dissemination of the bacteria to the bloodstream and to various organs following infection. Examination of tissue sections from infected control animals, stained with hematoxylin-eosin and the Gram stain, showed edema and/or hemorrhage in the lungs and the presence of bacteria in mediastinal lymph nodes, with necrosis and inflammation. Tissue sections from infected rabbits dosed with AVP-21D9 appeared comparable to corresponding tissues from uninfected animals despite lethal challenge with B. anthracis Ames spores. Concomitant treatment with AVP-21D9 at the time of challenge conferred complete protection in the rabbit inhalation anthrax model. Early treatment increased the efficacy progressively and in a dose-dependent manner. Thus, AVP-21D9 could offer an adjunct or alternative clinical treatment regimen against inhalation anthrax.

[Molecular study of Argentine strains of Bacillus anthracis]

Bacillus anthracis is one of the most monomorphic bacteria known and epidemiological studies of this microorganism have been hampered by the lack of molecular markers. For the genotyping of fourteen Argentine field strains and the vaccine strain Steme 34F2 the presence or absence of the virulence plasmids as well as vrrA locus containing a variable-number tandem repeat (VNTR) and presenting a polymorphism involving five variants, were analyzed. Strains were isolated from cows, sheep and pigs during outbreaks occurred in Buenos Aires, Entre Ríos, Santa Fe and La Pampa in the past fifty years. All of the field strains presented plasmids pXO1 and pXO2, except for a strain isolated from pig that only presented plasmid pXO2. All the strains and the vaccine strain belonged to the same VNTR variant that was defined by sequencing the vrrA locus from three of the isolates and the strain 34F2. These sequences were completely identical and corresponded to the variant VNTR4. Thus, the fourteen Argentine B. anthracis strains studied showed great uniformity at molecular level even though they had been isolated from different mammal species within a wide time period and covering an extensive geographical area.

Genetic diversity in a Bacillus anthracis historical collection (1954 to 1988)

Bacillus anthracis, the etiologic agent of anthrax, has been widely described as a genetically monomorphic species. We used both multiple-locus variable-number tandem-repeat analysis (MLVA) and pagA gene sequencing to determine the genetic diversity of a historical collection of B. anthracis isolates collected from the 1950s to the 1980s from various geographic locations and sources. We sequenced the pagA gene of 124 diverse B. anthracis isolates and found all previously identified B. anthracis pagA types except type 4. Sixty-three of the 124 B. anthracis strains were identified as pagA type 6, while 44 were pagA type 5, 12 were pagA type 1, and individual isolates were identified for types 2 and 3, respectively. Two new pagA genotypes were discovered in three environmental isolates within the historical collection. Two isolates had the same new genotype, and an additional isolate produced a second new genotype. MLVA detected 22 previously described genotypes in the historical collection. In addition, 33 new MLVA genotypes were found. For 11 isolates, an MLVA genotype could not be assigned because one or more alleles did not amplify. While only two additional B. anthracis pagA types were identified, in two instances, the use of pagA sequencing discriminated isolates with the same MLVA genotype. MLVA revealed that 39 of the 124 isolates were previously undocumented genotypes and that 1 isolate was found to be in the C cluster when it was subtyped by MLVA.

Manipulation of host signalling pathways by anthrax toxins

Infectious microbes face an unwelcoming environment in their mammalian hosts, which have evolved elaborate multicelluar systems for recognition and elimination of invading pathogens. A common strategy used by pathogenic bacteria to establish infection is to secrete protein factors that block intracellular signalling pathways essential for host defence. Some of these proteins also act as toxins, directly causing pathology associated with disease. Bacillus anthracis, the bacterium that causes anthrax, secretes two plasmid-encoded enzymes, LF (lethal factor) and EF (oedema factor), that are delivered into host cells by a third bacterial protein, PA (protective antigen). The two toxins act on a variety of cell types, disabling the immune system and inevitably killing the host. LF is an extraordinarily selective metalloproteinase that site-specifically cleaves MKKs (mitogen-activated protein kinase kinases). Cleavage of MKKs by LF prevents them from activating their downstream MAPK (mitogen-activated protein kinase) substrates by disrupting a critical docking interaction. Blockade of MAPK signalling functionally impairs cells of both the innate and adaptive immune systems and induces cell death in macrophages. EF is an adenylate cyclase that is activated by calmodulin through a non-canonical mechanism. EF causes sustained and potent activation of host cAMP-dependent signalling pathways, which disables phagocytes. Here I review recent progress in elucidating the mechanisms by which LF and EF influence host signalling and thereby contribute to disease.

Transcriptional stimulation of anthrax toxin receptors by anthrax edema toxin and Bacillus anthracis Sterne spore

We used quantitative real-time RT-PCR to not only investigate the mRNA levels of anthrax toxin receptor 1 (ANTXR1) and 2 (ANTXR2) in the murine J774A.1 macrophage cells and different tissues of mice, but also evaluate the effect of anthrax edema toxin and Bacillus anthracis Sterne spores on the expression of mRNA of these receptors. The mRNA transcripts of both receptors were detected in J774A.1 cells and mouse tissues such as the lung, heart, kidney, spleen, stomach, jejunum, brain, skeleton muscle, and skin. The ANTXR2 mRNA level was significantly higher than that of ANTXR1 in J774A.1 cells and all tissues examined. The mRNA expression of both receptors in the lung was the highest among the tissues evaluated. Interestingly, the mRNA expression of both receptors in J774A.1 cells was upregulated by edema toxin. In addition, ANTXR mRNA expression in the lung was downregulated after subcutaneous inoculation of B. anthracis Sterne spores as well as after intranasal administration of anthrax toxin-based vaccine BioThrax. These results suggest that anthrax edema toxin and B. anthracis Sterne spore are involved in the ANTXR mRNA regulation in host cells.

Pathobiology and management of laboratory rodents administered CDC category A agents

The Centers for Disease Control and Prevention Category A infectious agents include Bacillus anthracis (anthrax), Clostridium botulinum toxin (botulism), Yersinia pestis (plague), variola major virus (smallpox), Francisella tularensis (tularemia), and the filoviruses and arenaviruses that induce viral hemorrhagic fevers. These agents are regarded as having the greatest potential for adverse impact on public health and therefore are a focus of renewed attention in infectious disease research. Frequently rodent models are used to study the pathobiology of these agents. Although much is known regarding naturally occurring infections in humans, less is documented on the sources of exposures and potential risks of infection to researchers and animal care personnel after the administration of these hazardous substances to laboratory animals. Failure to appropriately manage the animals can result both in the creation of workplace hazards if human exposures occur and in disruption of the research if unintended animal exposures occur. Here we review representative Category A agents, with a focus on comparing the biologic effects in naturally infected humans and rodent models and on considerations specific to the management of infected rodent subjects. The information reviewed for each agent has been curated manually and stored in a unique Internet-based database system called HazARD (Hazards in Animal Research Database, http://helab.bioinformatics.med.umich.edu/hazard/) that is designed to assist researchers, administrators, safety officials, Institutional Biosafety Committees, and veterinary personnel seeking information on the management of risks associated with animal studies involving hazardous substances.

Protection against anthrax by needle-free mucosal immunization with human anthrax vaccine

Human vaccination with BioThrax requires six injections followed by annual boosters. This makes it difficult for the compliance of the immunization program and underscores the need for development of a new and optimized vaccination protocol. Current research aims to demonstrate the proof of concept to develop a needle-free mucosal immunization protocol using a murine anthrax model. A/J mice were immunized with BioThrax via an intranasal route. Sera, saliva, vaginal, and nasal washes were evaluated for protective antigen (PA) specific antibody responses by ELISA. Antigen-specific, antibody-secreting lymphocytes were measured by ELISPOT. Sera neutralization antibody titers were determined by in vitro anthrax lethal toxin (Letx) neutralization assay. Immunized animals were challenged by a lethal dose of Bacillus anthracis Sterne spores to determine the efficacy of the vaccination. Nasal mucosal immunization with BioThrax elicited robust serum and mucosal antibody responses against PA. The antigen specific antibodies neutralized anthrax Letx, as demonstrated by in vitro neutralization assays. Two doses of intranasal BioThrax were sufficient to completely protect A/J mice against challenge with 100xLD50B. anthracis Sterne spores. The data suggests that intranasal administration may be an effective immunization modality for an improved immunization program against anthrax.

Murine innate immune response to virulent toxigenic and nontoxigenic Bacillus anthracis strains

Effective treatment of anthrax is hampered by our limited understanding of the pathophysiology of Bacillus anthracis infection. We used a genetically complete (pXO1(+) pXO2(+)) virulent B. anthracis strain and four isogenic toxin-null mutants to determine the effects of the anthrax edema toxin (ET; edema factor [EF] plus protective antigen [PA]) and lethal toxin (LT; lethal factor [LF] plus PA) on the host innate response during systemic infection. Using the spleen as an indicator for host response, we found that intravenous inoculation of LT-deficient mutants into C57BL/6 mice significantly increased production of several cytokines over that observed after infection with the parent strain or an EF-deficient mutant. Bacteria producing one or both of the toxins were capable of inducing significant apoptosis of cells present in spleens, whereas apoptosis was greatly reduced in mice infected with nontoxigenic mutants. Mice infected with toxin-producing strains also showed increased splenic neutrophil recruitment compared to mice infected with nontoxigenic strains and neutrophil depletion prior to infection with toxin-producing strains, leading to decreased levels of apoptosis. Together, these studies indicate that anthrax LT suppresses cytokine secretion during infection, but both EF and LF play roles in inducing neutrophil recruitment and enhancing apoptosis. Interestingly, in the absence of LF the effect of EF-induced cell recruitment is further enhanced, perhaps because LF so effectively suppresses the secretion of chemokines.

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.

Technological advancements for the detection of and protection against biological and chemical warfare agents

There is a growing need for technological advancements to combat agents of chemical and biological warfare, particularly in the context of the deliberate use of a chemical and/or biological warfare agent by a terrorist organization. In this tutorial review, we describe methods that have been developed both for the specific detection of biological and chemical warfare agents in a field setting, as well as potential therapeutic approaches for treating exposure to these toxic species. In particular, nerve agents are described as a typical chemical warfare agent, and the two potent biothreat agents, anthrax and botulinum neurotoxin, are used as illustrative examples of potent weapons for which countermeasures are urgently needed.

Bacillus anthracis edema and lethal toxin have different hemodynamic effects but function together to worsen shock and outcome in a rat model

INTRODUCTION

To better define the contribution of edema toxins (ETx) and lethal toxins (LeTx) to shock with Bacillus anthracis, recombinant preparations of each were investigated alone or together in rats.

METHODS AND RESULTS

Lethal dose ranges (0%-100% lethality) of ETx (200-800 microg/kg as a 24-h infusion) were higher than those of LeTx (12.5-200 microg/kg) (P<.0001). However, compared with LeTx, similarly lethal ETx doses produced earlier and greater reductions in mean blood pressure (MBP) and increased, rather than decreased, heart rate (HR) (P<.05 for all). Combining either similar weight or lethal doses of ETx and LeTx increased the hazard ratio for death (log +/- standard error) similar to the sum calculated with the toxin's effects alone (2.6+/-1.1 observed vs. 2.9+/-1.0 calculated for similar weight and 3.1+/-1.0 vs. 3.9+/-1.5 for similar lethal doses; P=.5 for both). Early (< or =10 h) and late during infusion, ETx and LeTx together also altered MBP and HR in patterns consistent with the sum of their individual effects.

CONCLUSIONS

ETx was approximately 10 times less lethal than LeTx but produced greater hypotension and added to the latter's harmful effects. These findings suggest that it may be appropriate for antitoxin therapies for B. anthracis to target both ETx and LeTx.

[The relationship between the conditions of cultivation and sporification of various Bacillus strains and the results of the evaluation of the sporocidal activity of chemical desinfectants]

The researchers compared the main microbiological characteristics of some Bacillus antracoides strains after their cultivation in different nutrient media. The study found that the growth and sporification rate, R-S dissociation ability, and sensitivity to disinfectants are strain properties and significantly depend on the composition of the nutrient medium.

[Indication of extremely dangerous infectious pathogens using immunochromatography and digital video analysis]

The use of immunochromatographic indicatory elements based on antibody conjugates and colloidal gold was suggested to detect cells and the antigens of extremely dangerous infectious pathogens. The specificity and specific activity (sensitivity) of the mentioned elements were studied on vaccinal strains of plague, anthrax, and tularemia pathogens. The researchers studied a possibility to increase the sensitivity of immunochromatographic analysis using computed scanning and Reflecom, a specialized digital video recorder of immunochromatogramms. The study demonstrated that the use of electronic devices to record immunochromatogramms increased the sensitivity to microbial cells and antigens 1.5 to 2 times vs. visual registration and simplified documentation of the results.

[A research into the possibility of the application of new peroxosolvate-based compounds as chemical disinfectants]

A newly synthesized peroxosolvate, ammonium sulphate peroxosolvate, can be used in disinfectology and other areas along with other hard forms of hydrogen. Optimal conditions for ammonium sulphate peroxosolvate synthesis were determined by this study. It was established that (NH4)2SO4 . H2O2 stabilized with carboxylic acids did not lose active oxygen when stored in dry atmosphere. The sporocidal activity of the compound against the suspension of B. cereus var. anthracoides 250 was studied. The results demonstrate that thanks to the high decontaminating activity of the solvate its solutions can be used to produce disinfecting preparations.

[Fluoroquinolones: antimicrobial activity and chemotherapeutic efficacy with respect to various pathogens in highly dangerous diseases]

Comparative in vitro and in vivo efficacy of new fluoroquinolones with respect to pathogens of tularemia, glanders, melioidosis and anthrax was estimated. It was shown that the strains of the tularemia, glanders, melioidosis and anthrax pathogens were in vitro highly susceptible to the new agents. The experiments on laboratory animals demonstrated that pefloxacin and sparfloxacin had extremely broad spectra and were of special value in emergency prophylaxis of tularemia, glanders, melioidosis and anthrax.

Anthrax toxin receptor 2-dependent lethal toxin killing in vivo

Anthrax toxin receptors 1 and 2 (ANTXR1 and ANTXR2) have a related integrin-like inserted (I) domain which interacts with a metal cation that is coordinated by residue D683 of the protective antigen (PA) subunit of anthrax toxin. The receptor-bound metal ion and PA residue D683 are critical for ANTXR1-PA binding. Since PA can bind to ANTXR2 with reduced affinity in the absence of metal ions, we reasoned that D683 mutant forms of PA might specifically interact with ANTXR2. We show here that this is the case. The differential ability of ANTXR1 and ANTXR2 to bind D683 mutant PA proteins was mapped to nonconserved receptor residues at the binding interface with PA domain 2. Moreover, a D683K mutant form of PA that bound specifically to human and rat ANTXR2 mediated killing of rats by anthrax lethal toxin, providing strong evidence for the physiological importance of ANTXR2 in anthrax disease pathogenesis.

The bacterium that causes anthrax produces a toxin which is largely responsible for the symptoms and death associated with this disease. The toxin acts by first docking onto specific proteins, called receptors, located on the host cell surface, and it is then taken up into cells where it can act on its cellular substrates. There are two known receptors for the toxin, anthrax toxin receptors 1 and 2 (ANTXR1 and ANTXR2). However, the physiological importance of each receptor in host organisms is not yet understood. To address this issue directly, the authors designed a form of the toxin which binds specifically to ANTXR2 but not to ANTXR1. They show that this ANTXR2-specific form of the toxin is capable of killing rats following intravenous injection. These studies provide direct evidence for the physiological importance of ANTXR2 in anthrax toxin action in a model host organism.

Inactivation of Bacillus anthracis spores in murine primary macrophages

The current model for pathogenesis of inhalation anthrax indicates that the uptake and fate of Bacillus anthracis spores in alveolar macrophages are critical to the infection process. We have employed primary macrophages, which are more efficient for spore uptake than the macrophage-like cell line RAW264.7, to investigate spore uptake and survival. We found that at a multiplicity of infection (moi) of 5, greater than 80% of the spores of the Sterne strain containing only the pXO1 plasmid were internalized within 1 h. Within 4 h post infection, viability of internalized Sterne spores decreased to approximately 40%. Intracellular vegetative bacteria represented less than 1% of the total spore inoculum throughout the course of infection suggesting effective killing of germinated spores and/or vegetative bacteria. The Sterne spores trafficked quickly to phagolysosomes as indicated by colocalization with lysosome-associated membrane protein 1 (LAMP1). Expression of a dominant-negative Rab7 that blocked lysosome fusion enhanced Sterne spore survival. Addition of d-alanine to the infection resulted in 75% inhibition of spore germination and increased survival of internalized spores of the Sterne strain and a pathogenic strain containing both the pXO1 and pXO2 plasmids. Inhibition was reversed by the addition of l-alanine, which resumed spore germination and subsequent spore killing. Our data indicate that B. anthracis spores germinate in and are subsequently killed by primary macrophages.

Anthrax vaccines: Pasteur to the present

Anthrax has been a major cause of death in grazing animals and an occasional cause of death in humans for thousands of years. Since the late 1800s there has been an exceptional international history of anthrax vaccine development. Due to animal vaccinations, the rate of infection has dropped dramatically. Anthrax vaccines have progressed from uncharacterized whole-cell vaccines in 1881, to pXO2-negative spores in the 1930s, to culture filtrates absorbed to aluminum hydroxide in 1970, and likely to recombinant protective antigen in the near future. Each of these refinements has increased safety without significant loss of efficacy. The threat of genetically engineered, antibiotic and vaccine resistant strains of Bacillus anthracis is fueling hypothesis-driven research and global techniques--including genomics, proteomics and transposon site hybridization--to facilitate the discovery of novel vaccine targets. This review highlights historical achievements and new developments in anthrax vaccine research.

Anthrax pathogen evades the mammalian immune system through stealth siderophore production

Systemic anthrax, caused by inhalation or ingestion of Bacillus anthracis spores, is characterized by rapid microbial growth stages that require iron. Tightly bound and highly regulated in a mammalian host, iron is scarce during an infection. To scavenge iron from its environment, B. anthracis synthesizes by independent pathways two small molecules, the siderophores bacillibactin (BB) and petrobactin (PB). Despite the great efficiency of BB at chelating iron, PB may be the only siderophore necessary to ensure full virulence of the pathogen. In the present work, we show that BB is specifically bound by siderocalin, a recently discovered innate immune protein that is part of an antibacterial iron-depletion defense. In contrast, neither PB nor its ferric complex is bound by siderocalin. Although BB incorporates the common 2,3-dihydroxybenzoyl iron-chelating subunit, PB is novel in that it incorporates the very unusual 3,4-dihydroxybenzoyl chelating subunit. This structural variation results in a large change in the shape of both the iron complex and the free siderophore that precludes siderocalin binding, a stealthy evasion of the immune system. Our results indicate that the blockade of bacterial siderophore-mediated iron acquisition by siderocalin is not restricted to enteric pathogenic organisms and may be a general defense mechanism against several different bacterial species. Significantly, to evade this innate immune response, B. anthracis produces PB, which plays a key role in virulence of the organism. This analysis argues for antianthrax strategies targeting siderophore synthesis and uptake.

Strain-specific single-nucleotide polymorphism assays for the Bacillus anthracis Ames strain

Highly precise diagnostics and forensic assays can be developed through a combination of evolutionary analysis and the exhaustive examination of genomic sequences. In Bacillus anthracis, whole-genome sequencing efforts revealed ca. 3,500 single-nucleotide polymorphisms (SNPs) among eight different strains and evolutionary analysis provides the identification of canonical SNPs. We have previously shown that SNPs are highly evolutionarily stable, and the clonal nature of B. anthracis makes them ideal signatures for subtyping this pathogen. Here we identified SNPs that define the lineage of B. anthracis that contains the Ames strain, the strain used in the 2001 bioterrorist attacks in the United States. Sequencing and real-time PCR were used to validate these SNPs across B. anthracis strains, including (i) 88 globally and genetically diverse isolates; (ii) isolates that were shown to be genetic relatives of the Ames strain by multiple-locus variable number tandem repeat analysis (MLVA); and (iii) several different lab stocks of the Ames strain, including a clinical isolate from the 2001 letter attack. Six SNPs were found to be highly specific for the Ames strain; four on the chromosome, one on the pX01 plasmid, and one on the pX02 plasmid. All six SNPs differentiated the B. anthracis Ames strain from the 88 unique B. anthracis strains, while five of the six separated Ames from its close genetic relatives. The use of these SNPs coupled with real-time PCR allows specific and sensitive (<100 fg of template DNA) identification of the Ames strain. This evolutionary and genomics-based approach provides an effective means for the discovery of strain-specific SNPs in B. anthracis.

Rapid discrimination of Bacillus anthracis from other members of the B. cereus group by mass and sequence of “intact” small acid soluble proteins (SASPs) using mass spectrometry

The intentional contamination of buildings, e.g. anthrax in the bioterrorism attacks of 2001, demonstrated that the population can be affected rapidly and lethally if the appropriate treatment is not provided at the right time. Molecular approaches, primarily involving PCR, have proved useful in characterizing "white powders" used in these attacks as well as isolated organisms. However there is a need for a simpler approach, which does not involve temperamental reagents (e.g. enzymes and primers) which could potentially be used by first responders. It is demonstrated here that small acid-soluble proteins (SASPs), located in the core region of Bacillus spores, are reliable biomarkers for identification. The general strategy used in this study was to measure the molecular weight (MW) of an intact SASP by electrospray ionization mass spectrometry (ESI MS) followed by generation of sequence-specific information by ESI MS/MS (tandem mass spectrometry). A prominent SASP of mass 6679 was present in all B. anthracis strains. For B. cereus and B. thuringiensis strains the SASP had a mass of 6712. This represents a two amino acid substitution (serine to alanine; phenylalanine to tyrosine). The only SASP present in the B. anthracis genome consistent with this sequence is encoded by the gene ssB. This protein has a predicted mass of 6810, presumably post-translational processing leads to loss of methionine (mass 131) generating a SASP of mass 6679. This study showed that intact SASPs can be used as a biomarker for identification of B. anthracis; the protocol is simple and rapid. Extrapolation of this approach might prove important for real-time biodetection.

Antibiotic susceptibility and molecular diversity of Bacillus anthracis strains in Chad: detection of a new phylogenetic subgroup

We genotyped 15 Bacillus anthracis isolates from Chad, Africa, using multiple-locus variable-number tandem repeat analysis and three additional direct-repeat markers. We identified two unique genotypes that represent a novel genetic lineage in the A cluster. Chadian isolates were susceptible to 11 antibiotics and free of 94 antibiotic resistance genes.

Anthrax lethal toxin impairs innate immune functions of alveolar macrophages and facilitates Bacillus anthracis survival

Alveolar macrophages (AM) are very important for pulmonary innate immune responses against invading inhaled pathogens because they directly kill the organisms and initiate a cascade of innate and adaptive immune responses. Although several factors contribute to inhalational anthrax, we hypothesized that unimpeded infection of Bacillus anthracis is directly linked to disabling the innate immune functions contributed by AM. Here, we investigated the effects of lethal toxin (LT), one of the binary complex virulence factors produced by B. anthracis, on freshly isolated nonhuman primate AM. Exposure of AM to doses of LT that killed susceptible macrophages had no effect on the viability of AM, despite complete MEK1 cleavage. Intoxicated AM remained fully capable of B. anthracis spore phagocytosis. However, pretreatment of AM with LT resulted in a significant decrease in the clearance of both the Sterne strain and the fully virulent Ames strain of B. anthracis, which may have been a result of impaired AM secretion of proinflammatory cytokines. Our data imply that cytolysis does not correlate with MEK1 cleavage, and this is the first report of LT-mediated impairment of nonhuman primate AM bactericidal activity against B. anthracis.

Heat activation/shock temperatures for Bacillus anthracis spores and the issue of spore plate counts versus true numbers of spores

Assessing true numbers of viable anthrax spores is complex. Optimal heat activation conditions vary with species, media and germinants. Published time/temperature combinations for Bacillus anthracis spores range from 60 degrees C for <or=90 min to boiling for 1 min. Results presented here indicate that temperatures are best kept to <or=70 degrees C and holding times need not exceed 15-30 min. Under conditions of 60 degrees C for 90 min, 62-23 degrees C for 15 min and 70 degrees C for 15 or 30 min, although the ratio of heated:unheated counts ranged from <1 to >1, post-heating counts were less than their pre-heating counterparts on between 71% and 88% of occasions. A high probability was found of viable spore counts differing significantly from counts determined microscopically, with differences of almost 1 log possible. Viable counts were lower than microscopic counts in 15 of 18 tests.

Diversity of Bacillus anthracis strains in Georgia and of vaccine strains from the former Soviet Union

Despite the increased number of anthrax outbreaks in Georgia and the other Caucasian republics of the former Soviet Union, no data are available on the diversity of the Bacillus anthracis strains involved. There is also little data available on strains from the former Soviet Union, including the strains previously used for vaccine preparation. In this study we used eight-locus variable-number tandem repeat analyses to genotype 18 strains isolated from infected animals and humans at different sites across Georgia, where anthrax outbreaks have occurred in the last 10 years, and 5 strains widely used for preparation of human and veterinary vaccines in the former Soviet Union. Three different genotypes affiliated with the A3.a cluster were detected for the Georgian isolates. Two genotypes were previously shown to include Turkish isolates, indicating that there is a regional strain pattern in the South Caucasian-Turkish region. Four of the vaccine strains were polymorphic, exhibiting three different patterns of the cluster A1.a genotype and the cluster A3.b genotype. The genotype of vaccine strain 71/12, which is considered an attenuated strain in spite of the presence of both of the virulence pXO plasmids, appeared to be a novel genotype in the A1.a cluster.

Molecular study of genes involved in virulence regulatory pathways in Bacillus anthracis vaccine strain "Carbosap"

This study investigated the genetic bases of attenuation in the Bacillus anthracis vaccine strain "Carbosap" used in Italy against anthrax in cattle and sheep. Twelve genes involved in virulence regulatory pathways underwent sequence analysis in comparison with a B. anthracis virulent strain.