Anthrax—a Threat beyond Bacillus anthracis

A special issue of Pathogens (ISSN 2076-0817). This special issue belongs to the section "Bacterial Pathogens".

Deadline for manuscript submissions: closed (20 December 2023) | Viewed by 33484

Special Issue Editors


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Guest Editor
Robert Koch-Institut, Centre for Biological Threats and Special Pathogens (ZBS2, Highly Pathogenic Microorganisms), Berlin, Germany
Interests: characterization of B. cereus biovar anthracis; analysis of gene expression, genome sequencing; diagnostics of highly pathogenic bacteria; zoonotic diseases

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Guest Editor
Centers for Disease Control and Prevention, Bacterial Special Pathogens Branch, Atlanta, GA, USA
Interests: detection, diagnosis, and treatment of anthrax-like disease in addition to characterization of the etiologic agents of these illnesses and their environmental distribution

Special Issue Information

Dear Colleagues,

For decades, Bacillus anthracis was considered to be the only bacterial agent causing anthrax disease, which affects a large range of mammals, including humans. B. anthracis is a member of the Bacillus cereus group in which bacteria are related on the chromosomal level, but possess a variety of plasmids responsible for different pathogenicities. As exchange of genetic material occurs naturally in the genus Bacillus, it is not unexpected that B. anthracis virulence genes and plasmids could occur in other species. During the last 20 years, increasing numbers of anthrax-like cases have been detected that were caused by such atypical Bacilli. The cluster of B. cereus biovar anthracis (Bcbva) was detected in African rain forest areas where these bacteria mainly affect wildlife species, including great apes. Human exposure has been reported based on serological evidence, although human cases have not yet been described. B. tropicus (taxonomy change; formerly B. cereus) G9241 and other Bacillus spp. expressing anthrax toxins have caused severe and fatal infections amongst welders in the United States, a professional category that seems particularly susceptible to this type of pathogen. In addition, these Bacillus strains expressing anthrax toxins cause cutaneous infections resembling anthrax. One may assume that these atypical bacteria are responsible for many more anthrax-like cases that are not diagnosed as such because they can be missed by detection methods targeting classic B. anthracis.

In this Special Issue, we would like to cover all aspects of this emerging group of atypical Bacilli causing anthrax-like disease. This starts with the genetic background and plasmid content: Does the strain possess both the B. anthracis toxin and capsule plasmid, like in Bcbva, or only the toxin plasmid like in G9241? Are entire plasmids present or new plasmids with anthrax toxin genes? Which additional plasmids are present? Concerning pathogenesis, it would be interesting to know if toxins and/or the capsule are synthesized and if the strains are able to produce a capsule composed of hyaluronic acid like in Bcbva and G9241. What is known about the gene regulation and control by the regulators AtxA and/or PlcR? Which insights can be gained by animal experiments and how can disease be treated or prevented? What is known about the ecology and epidemiology, and are there any preferred hosts or ecological niches? How do the strains group into the phylogenetic tree of the Bacillus genus, and what can be speculated about their evolution? Briefly, we would like to gather the knowledge of all researchers in this fascinating field of emerging pathogens to present their data to a broader scientific community. For this Special Issue of Pathogens, we invite you to submit a review or research article related to anthrax-causing Bacilli. We look forward to your contribution.

Dr. Silke R. Klee
Dr. Alex R. Hoffmaster
Guest Editors

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Keywords

  • Bacillus anthracis
  • Bacillus tropicus
  • Bacillus cereus
  • Bacillus cereus biovar anthracis
  • pathogenesis
  • plasmids
  • gene regulation
  • phylogeny and taxonomy
  • therapy and prevention
  • ecology
  • epidemiology

Published Papers (8 papers)

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Research

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17 pages, 3404 KiB  
Article
Analysis of Sporulation in Bacillus cereus Biovar anthracis Which Contains an Insertion in the Gene for the Sporulation Factor σK
by Constanze Gummelt, Susann Dupke, Sabine Howaldt, Fee Zimmermann, Holger C. Scholz, Michael Laue and Silke R. Klee
Pathogens 2023, 12(12), 1442; https://doi.org/10.3390/pathogens12121442 - 13 Dec 2023
Viewed by 1184
Abstract
Bacillus cereus biovar anthracis (Bcbva) is an untypical pathogen causing a fatal anthrax-like disease in a variety of wildlife species in African rainforest areas. In contrast to Bacillus anthracis and most species of the B. cereus group, all strains of the [...] Read more.
Bacillus cereus biovar anthracis (Bcbva) is an untypical pathogen causing a fatal anthrax-like disease in a variety of wildlife species in African rainforest areas. In contrast to Bacillus anthracis and most species of the B. cereus group, all strains of the Bcbva cluster contain a 22 kb insertion in the sigK gene which encodes the essential late sporulation sigma factor σK. This insertion is excised during sporulation in a site-specific recombination process resulting in an intact sigK gene and a circular molecule. The sporulation kinetics of two strains each of Bcbva and B. anthracis were compared by the expression analysis of eight sporulation-associated genes, including sigK, using reverse transcriptase quantitative real-time PCR. In addition, morphological sporulation stages were analyzed and quantified by electron microscopy. Our results indicated that the necessary excision of the insertion in Bcbva neither delayed nor inhibited its sporulation. In two spontaneous mutants of Bcbva, the excision of the sigK insertion and sporulation were impeded due to mutations in the spo0A and spoVG regulator genes, respectively. The spo0A frameshift mutation was overcome by intragenic suppression in a revertant which was able to sporulate normally, despite an M171S amino acid exchange in the global regulator Spo0A. A screening of the NCBI database identified further strains of the B. cereus group which possess unrelated insertions in the sigK gene, and two strains containing almost identical insertions at the same gene position. Some of the sigK insertions encode putative prophages, whereas the Bcbva insertion encoded a type I restriction–modification system. The function of these insertions and if they are possibly essential for sporulation remains to be assessed. Full article
(This article belongs to the Special Issue Anthrax—a Threat beyond Bacillus anthracis)
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18 pages, 16402 KiB  
Article
Genomic and Phylogenetic Analysis of Bacillus cereus Biovar anthracis Isolated from Archival Bone Samples Reveals Earlier Natural History of the Pathogen
by Michael H. Norris, Diansy Zincke, David J. Daegling, John Krigbaum, W. Scott McGraw, Alexander Kirpich, Ted L. Hadfield and Jason K. Blackburn
Pathogens 2023, 12(8), 1065; https://doi.org/10.3390/pathogens12081065 - 20 Aug 2023
Viewed by 1346
Abstract
(1) Background: Bacillus cereus biovar anthracis (Bcbva) was the causative agent of an anthrax-like fatal disease among wild chimpanzees in 2001 in Côte d’Ivoire. Before this, there had not been any description of an anthrax-like disease caused by typically avirulent Bacillus cereus. Genetic [...] Read more.
(1) Background: Bacillus cereus biovar anthracis (Bcbva) was the causative agent of an anthrax-like fatal disease among wild chimpanzees in 2001 in Côte d’Ivoire. Before this, there had not been any description of an anthrax-like disease caused by typically avirulent Bacillus cereus. Genetic analysis found that B. cereus had acquired two anthrax-like plasmids, one a pXO1-like toxin producing plasmid and the other a pXO2-like plasmid encoding capsule. Bcbva caused animal fatalities in Cameroon, Democratic Republic of Congo, and the Central African Republic between 2004 and 2012. (2) Methods: The pathogen had acquired plasmids in the wild and that was discovered as the cause of widespread animal fatalities in the early 2000s. Primate bones had been shipped out of the endemic zone for anthropological studies prior to the realized danger of contamination with Bcbva. Spores were isolated from the bone fragments and positively identified as Bcbva. Strains were characterized by classical microbiological methods and qPCR. Four new Bcbva isolates were whole-genome sequenced. Chromosomal and plasmid phylogenomic analysis was performed to provide temporal and spatial context to these new strains and previously sequenced Bcbva. Tau and principal component analyses were utilized to identify genetic and spatial case patterns in the Taï National Park anthrax zone. (3) Results: Preliminary studies positively identified Bcbva presence in several archival bone fragments. The animals in question died between 1994 and 2010. Previously, the earliest archival strains of Bcbva were identified in 1996. Though the pathogen has a homogeneous genome, spatial analyses of a subset of mappable isolates from Taï National Park revealed strains found closer together were generally more similar, with strains from chimpanzees and duikers having the widest distribution. Ancestral strains were located mostly in the west of the park and had lower spatial clustering compared to more recent isolates, indicating a local increase in genetic diversity of Bcbva in the park over space and time. Global clustering analysis indicates patterns of genetic diversity and distance are shared between the ancestral and more recently isolated type strains. (4) Conclusions: Our strains have the potential to unveil historical genomic information not available elsewhere. This information sheds light on the evolution and emergence of a dangerous anthrax-causing pathogen. Full article
(This article belongs to the Special Issue Anthrax—a Threat beyond Bacillus anthracis)
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24 pages, 3269 KiB  
Article
Strains Associated with Two 2020 Welder Anthrax Cases in the United States Belong to Separate Lineages within Bacillus cereus sensu lato
by Laura M. Carroll, Chung K. Marston, Cari B. Kolton, Christopher A. Gulvik, Jay E. Gee, Zachary P. Weiner and Jasna Kovac
Pathogens 2022, 11(8), 856; https://doi.org/10.3390/pathogens11080856 - 29 Jul 2022
Cited by 1 | Viewed by 3900
Abstract
Anthrax-causing members of Bacillus cereus sensu lato (s.l.) pose a serious threat to public health. While most anthrax-causing strains resemble B. anthracis phenotypically, rare cases of anthrax-like illness caused by strains resembling “B. cereus” have been reported. Here, whole-genome [...] Read more.
Anthrax-causing members of Bacillus cereus sensu lato (s.l.) pose a serious threat to public health. While most anthrax-causing strains resemble B. anthracis phenotypically, rare cases of anthrax-like illness caused by strains resembling “B. cereus” have been reported. Here, whole-genome sequencing was used to characterize three B. cereus s.l. isolates associated with two 2020 welder anthrax cases in the United States, which resembled “B. cereus” phenotypically. Comparison of the three genomes sequenced here to all publicly available, high-quality B. cereus s.l. genomes (n = 2890 total genomes) demonstrated that genomes associated with each case effectively belonged to separate species at the conventional 95% average nucleotide identity prokaryotic species threshold. Two PubMLST sequence type 78 (ST78) genomes affiliated with a case in Louisiana were most closely related to B. tropicus and possessed genes encoding the Bps exopolysaccharide capsule, as well as hemolysin BL (Hbl) and cytotoxin K (CytK). Comparatively, a ST108 genome associated with a case in Texas was most closely related to B. anthracis; however, like other anthrax-causing strains most closely related to B. anthracis, this genome did not possess Bps-, Hbl-, or CytK-encoding genes. Overall, results presented here provide insights into the evolution of anthrax-causing B. cereus s.l. Full article
(This article belongs to the Special Issue Anthrax—a Threat beyond Bacillus anthracis)
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15 pages, 1075 KiB  
Article
Epidemiologic Investigation of Two Welder’s Anthrax Cases Caused by Bacillus cereus Group Bacteria: Occupational Link Established by Environmental Detection
by Patrick Dawson, Johanna S. Salzer, Caroline A. Schrodt, Karl Feldmann, Cari B. Kolton, Jay E. Gee, Chung K. Marston, Christopher A. Gulvik, Mindy G. Elrod, Aaron Villarma, Rita M. Traxler, María E. Negrón, Kate A. Hendricks, Heather Moulton-Meissner, Laura J. Rose, Paul Byers, Kathryn Taylor, Daphne Ware, Gary A. Balsamo, Theresa Sokol, Bret Barrett, Erica Payne, Saad Zaheer, Ga On Jung, Stephen Long, Ricardo Quijano, Lindsey LeBouf, Briana O’Sullivan, Erin Swaney, James M. Antonini, Marie A. de Perio, Zachary Weiner, William A. Bower and Alex R. Hoffmasteradd Show full author list remove Hide full author list
Pathogens 2022, 11(8), 825; https://doi.org/10.3390/pathogens11080825 - 23 Jul 2022
Cited by 3 | Viewed by 2798
Abstract
Bacillus cereus group bacteria containing the anthrax toxin genes can cause fatal anthrax pneumonia in welders. Two welder’s anthrax cases identified in 2020 were investigated to determine the source of each patient’s exposure. Environmental sampling was performed at locations where each patient had [...] Read more.
Bacillus cereus group bacteria containing the anthrax toxin genes can cause fatal anthrax pneumonia in welders. Two welder’s anthrax cases identified in 2020 were investigated to determine the source of each patient’s exposure. Environmental sampling was performed at locations where each patient had recent exposure to soil and dust. Samples were tested for the anthrax toxin genes by real-time PCR, and culture was performed on positive samples to identify whether any environmental isolates matched the patient’s clinical isolate. A total of 185 environmental samples were collected in investigation A for patient A and 108 samples in investigation B for patient B. All samples from investigation B were real-time PCR-negative, but 14 (8%) samples from investigation A were positive, including 10 from patient A’s worksite and 4 from his work-related clothing and gear. An isolate genetically matching the one recovered from patient A was successfully cultured from a worksite soil sample. All welder’s anthrax cases should be investigated to determine the source of exposure, which may be linked to their worksite. Welding and metalworking employers should consider conducting a workplace hazard assessment and implementing controls to reduce the risk of occupationally associated illnesses including welder’s anthrax. Full article
(This article belongs to the Special Issue Anthrax—a Threat beyond Bacillus anthracis)
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7 pages, 269 KiB  
Article
What Is Anthrax?
by William A. Bower, Katherine A. Hendricks, Antonio R. Vieira, Rita M. Traxler, Zachary Weiner, Ruth Lynfield and Alex Hoffmaster
Pathogens 2022, 11(6), 690; https://doi.org/10.3390/pathogens11060690 - 16 Jun 2022
Cited by 13 | Viewed by 6085
Abstract
Anthrax has been feared for its high mortality in animals and humans for centuries. The etiologic agent is considered a potentially devastating bioweapon, and since 1876―when Robert Koch demonstrated that Bacillus anthracis caused anthrax―it has been considered the sole cause of the disease. [...] Read more.
Anthrax has been feared for its high mortality in animals and humans for centuries. The etiologic agent is considered a potentially devastating bioweapon, and since 1876―when Robert Koch demonstrated that Bacillus anthracis caused anthrax―it has been considered the sole cause of the disease. Anthrax is, however, a toxin-mediated disease. The toxins edema toxin and lethal toxin are formed from protein components encoded for by the pXO1 virulence plasmid present in pathogenic B. anthracis strains. However, other members of the Bacillus cereus group, to which B. anthracis belongs, have recently been shown to harbor the pXO1 plasmid and produce anthrax toxins. Infection with these Bacillus cereus group organisms produces a disease clinically similar to anthrax. This suggests that anthrax should be defined by the exotoxins encoded for by the pXO1 plasmid rather than the bacterial species it has historically been associated with, and that the definition of anthrax should be expanded to include disease caused by any member of the B. cereus group containing the toxin-producing pXO1 plasmid or anthrax toxin genes specifically. Full article
(This article belongs to the Special Issue Anthrax—a Threat beyond Bacillus anthracis)
12 pages, 1531 KiB  
Article
Ecological Niche Model of Bacillus cereus Group Isolates Containing a Homologue of the pXO1 Anthrax Toxin Genes Infecting Metalworkers in the United States
by Mark A. Deka, Chung K. Marston, Julia Garcia-Diaz, Rahsaan Drumgoole and Rita M. Traxler
Pathogens 2022, 11(4), 470; https://doi.org/10.3390/pathogens11040470 - 14 Apr 2022
Cited by 1 | Viewed by 4013
Abstract
While Bacillus cereus typically causes opportunistic infections in humans, within the last three decades, severe and fatal infections caused by isolates of the B. cereus group harboring anthrax toxin genes have been reported in the United States. From 1994 to 2020, seven cases [...] Read more.
While Bacillus cereus typically causes opportunistic infections in humans, within the last three decades, severe and fatal infections caused by isolates of the B. cereus group harboring anthrax toxin genes have been reported in the United States. From 1994 to 2020, seven cases of anthrax-like illness resulting from these isolates have been identified. With one exception, the cases have occurred in the Gulf States region of the United States among metalworkers. We aimed to develop an ecological niche model (ENM) to estimate a spatial area conducive to the survival of these organisms based on the presence of known human infections and environmental variables. The estimated ecological niche for B. cereus was modeled with the maximum entropy algorithm (Maxent). Environmental variables contributing most to the model were soil characteristics (cation exchange capacity, carbon content, soil pH), temperature, enhanced vegetation index (EVI), and land surface temperature (LST). Much of the suitable environments were located throughout the Gulf Coast Plain, Texas Backland Prairies, East Central Texas Plains, Edwards Plateau, Cross Timbers, Mississippi Alluvial Plain, and Central Great Plains. These findings may provide additional guidance to narrow potential risk areas to efficiently communicate messages to metalworkers and potentially identify individuals who may benefit from the anthrax vaccine. Full article
(This article belongs to the Special Issue Anthrax—a Threat beyond Bacillus anthracis)
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Review

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8 pages, 281 KiB  
Review
Pathogenic Bacilli as an Emerging Biothreat?
by Lou Mondange, Émilie Tessier and Jean-Nicolas Tournier
Pathogens 2022, 11(10), 1186; https://doi.org/10.3390/pathogens11101186 - 14 Oct 2022
Cited by 3 | Viewed by 1733
Abstract
Bacillus anthracis, present as a very durable endospore in soil, causes zoonotic illness which is mainly associated with herbivores and domestic animals. Human cases are scarce and often involve populations close to infected livestock. If anthrax is no longer of public health [...] Read more.
Bacillus anthracis, present as a very durable endospore in soil, causes zoonotic illness which is mainly associated with herbivores and domestic animals. Human cases are scarce and often involve populations close to infected livestock. If anthrax is no longer of public health concern in developed countries, B. anthracis is one of the top-tier biological weapon agents. It is classified by the CDC as a category A agent. Since 1994, emerging strains of Bacillus cereus have been associated with anthrax-like disease in mammals. Some clinical strains of B. cereus harbor anthrax-like plasmid genes (pXO1 and pXO2) associated with non-human primate and human infections, with the same clinical presentation of inhalation anthrax and mortality rates. Although currently restricted to certain limited areas of circulation, the emergence of these new strains of B. cereus extends the list of potential agents possibly usable for bioterrorism or as a biological weapon. It is therefore important to improve our knowledge of the phylogeny within the B. cereus sensu lato group to better understand the origin of these strains. We can then more efficiently monitor the emergence of new strains to better control the risk of infection and limit potentially malicious uses. Full article
(This article belongs to the Special Issue Anthrax—a Threat beyond Bacillus anthracis)
14 pages, 550 KiB  
Review
Welder’s Anthrax: A Review of an Occupational Disease
by Marie A. de Perio, Katherine A. Hendricks, Chad H. Dowell, William A. Bower, Nancy C. Burton, Patrick Dawson, Caroline A. Schrodt, Johanna S. Salzer, Chung K. Marston, Karl Feldmann, Alex R. Hoffmaster and James M. Antonini
Pathogens 2022, 11(4), 402; https://doi.org/10.3390/pathogens11040402 - 26 Mar 2022
Cited by 8 | Viewed by 10524
Abstract
Since 1997, nine cases of severe pneumonia, caused by species within the B. cereus group and with a presentation similar to that of inhalation anthrax, were reported in seemingly immunocompetent metalworkers, with most being welders. In seven of the cases, isolates were found [...] Read more.
Since 1997, nine cases of severe pneumonia, caused by species within the B. cereus group and with a presentation similar to that of inhalation anthrax, were reported in seemingly immunocompetent metalworkers, with most being welders. In seven of the cases, isolates were found to harbor a plasmid similar to the B. anthracis pXO1 that encodes anthrax toxins. In this paper, we review the literature on the B. cereus group spp. pneumonia among welders and other metalworkers, which we term welder’s anthrax. We describe the epidemiology, including more information on two cases of welder’s anthrax in 2020. We also describe the health risks associated with welding, potential mechanisms of infection and pathological damage, prevention measures according to the hierarchy of controls, and clinical and public health considerations. Considering occupational risk factors and controlling exposure to welding fumes and gases among workers, according to the hierarchy of controls, should help prevent disease transmission in the workplace. Full article
(This article belongs to the Special Issue Anthrax—a Threat beyond Bacillus anthracis)
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