Characterization of Bacillus anthracis-like bacteria isolated from wild great apes from Cote d'Ivoire and Cameroon

Mapping high probability area for the Bacillus anthracis occurrence in wildlife protected area, South Omo, Ethiopia

Anthrax is a zoonotic disease caused by a spore-forming gram-positive bacterium, Bacillus anthracis. Increased anthropogenic factors inside wildlife-protected areas may worsen the spillover of the disease at the interface. Consequently, environmental suitability prediction for B. anthracis spore survival to locate a high-risk area is urgent. Here, we identified a potentially suitable habitat and a high-risk area for appropriate control measures. Our result revealed that a relatively largest segment of Omo National Park, about 23.7% (1,218 square kilometers) of the total area; 36.6% (711 square kilometers) of Mago National Park, and 29.4% (489 square kilometers) of Tama wildlife Reserve predicted as a high-risk area for the anthrax occurrence in the current situation. Therefore, the findings of this study provide the priority area to focus on and allocate resources for effective surveillance, prevention, and control of anthrax before it causes devastating effects on wildlife.

Early Circulating Edema Factor in Inhalational Anthrax Infection: Does It Matter?

Anthrax toxins are critical virulence factors of Bacillus anthracis and Bacillus cereus strains that cause anthrax-like disease, composed of a common binding factor, the protective antigen (PA), and two enzymatic proteins, lethal factor (LF) and edema factor (EF). While PA is required for endocytosis and activity of EF and LF, several studies showed that these enzymatic factors disseminate within the body in the absence of PA after intranasal infection. In an effort to understand the impact of EF in the absence of PA, we used a fluorescent EF chimera to facilitate the study of endocytosis in different cell lines. Unexpectedly, EF was found inside cells in the absence of PA and showed a pole-dependent endocytosis. However, looking at enzymatic activity, PA was still required for EF to induce an increase in intracellular cAMP levels. Interestingly, the sequential delivery of EF and then PA rescued the rise in cAMP levels, indicating that PA and EF may functionally associate during intracellular trafficking, as well as it did at the cell surface. Our data shed new light on EF trafficking and the potential location of PA and EF association for optimal cytosolic delivery.

Bacillus anthracis, "la maladie du charbon", Toxins, and Institut Pasteur

Institut Pasteur and Bacillus anthracis have enjoyed a relationship lasting almost 120 years, starting from its foundation and the pioneering work of Louis Pasteur in the nascent fields of microbiology and vaccination, and blooming after 1986 following the molecular biology/genetic revolution. This contribution will give a historical overview of these two research eras, taking advantage of the archives conserved at Institut Pasteur. The first era mainly focused on the production, characterisation, surveillance and improvement of veterinary anthrax vaccines; the concepts and technologies with which to reach a deep understanding of this research field were not yet available. The second period saw a new era of B. anthracis research at Institut Pasteur, with the anthrax laboratory developing a multi-disciplinary approach, ranging from structural analysis, biochemistry, genetic expression, and regulation to bacterial-host cell interactions, in vivo pathogenicity, and therapy development; this led to the comprehensive unravelling of many facets of this toxi-infection. B. anthracis may exemplify some general points on how science is performed in a given society at a given time and how a scientific research domain evolves. A striking illustration can be seen in the additive layers of regulations that were implemented from the beginning of the 21st century and their impact on B. anthracis research. B. anthracis and anthrax are complex systems that raise many valuable questions regarding basic research. One may hope that B. anthracis research will be re-initiated under favourable circumstances later at Institut Pasteur.

Molecular characterization of an outbreak-involved Bacillus anthracis strain confirms the spillover of anthrax from West Africa

BACKGROUND

Anthrax, a zoonotic disease caused by the spore-forming bacterium Bacillus anthracis, remains a major global public health concern, especially in countries with limited resources. Sierra Leone, a West African country historically plagued by anthrax, has almost been out of report on this disease in recent decades. In this study, we described a large-scale anthrax outbreak affecting both animals and humans and attempted to characterize the pathogen using molecular techniques.

METHODS

The causative agent of the animal outbreak in Port Loko District, Sierra Leone, between March and May 2022 was identified using the nanopore sequencing technique. A nationwide active surveillance was implemented from May 2022 to June 2023 to monitor the occurrence of anthrax-specific symptoms in humans. Suspected cases were subsequently verified using quantitative polymerase chain reaction. Full-genome sequencing was accomplished by combining long-read and short-read sequencing methods. Subsequent phylogenetic analysis was performed based on the full-chromosome single nucleotide polymorphisms.

RESULTS

The outbreak in Port Loko District, Sierra Leone, led to the death of 233 animals between March 26th and May 16th, 2022. We ruled out the initial suspicion of Anaplasma species and successfully identified B. anthracis as the causative agent of the outbreak. As a result of the government's prompt response, out of the 49 suspected human cases identified during the one-year active surveillance, only 6 human cases tested positive, all within the first month after the official declaration of the outbreak. The phylogenetic analysis indicated that the BaSL2022 isolate responsible for the outbreak was positioned in the A.Br.153 clade within the TransEuroAsian group of B. anthracis.

CONCLUSIONS

We successfully identified a large-scale anthrax outbreak in Sierra Leone. The causative isolate of B. anthracis, BaSL2022, phylogenetically bridged other lineages in A.Br.153 clade and neighboring genetic groups, A.Br.144 and A.Br.148, eventually confirming the spillover of anthrax from West Africa. Given the wide dissemination of B. anthracis spores, it is highly advisable to effectively monitor the potential reoccurrence of anthrax outbreaks and to launch campaigns to improve public awareness regarding anthrax in Sierra Leone.

Analysis of Sporulation in Bacillus cereus Biovar anthracis Which Contains an Insertion in the Gene for the Sporulation Factor σK

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.

Get to Know Your Neighbors: Characterization of Close Bacillus anthracis Isolates and Toxin Profile Diversity in the Bacillus cereus Group

Unexpected atypical isolates of Bacillus cereus s.l. occasionally challenge conventional microbiology and even the most advanced techniques for anthrax detection. For anticipating and gaining trust, 65 isolates of Bacillus cereus s.l. of diverse origin were sequenced and characterized. The BTyper3 tool was used for assignation to genomospecies B. mosaicus (34), B. cereus s.s (29) and B. toyonensis (2), as well as virulence factors and toxin profiling. None of them carried any capsule or anthrax-toxin genes. All harbored the non-hemolytic toxin nheABC and sphygomyelinase spH genes, whereas 41 (63%), 30 (46%), 11 (17%) and 6 (9%) isolates harbored cytK-2, hblABCD, cesABCD and at least one insecticidal toxin gene, respectively. Matrix-assisted laser desorption ionization-time of flight mass spectrometry confirmed the production of cereulide (ces genes). Phylogeny inferred from single-nucleotide polymorphisms positioned isolates relative to the B. anthracis lineage. One isolate (BC38B) was of particular interest as it appeared to be the closest B. anthracis neighbor described so far. It harbored a large plasmid similar to other previously described B. cereus s.l. megaplasmids and at a lower extent to pXO1. Whereas bacterial collection is enriched, these high-quality public genetic data offer additional knowledge for better risk assessment using future NGS-based technologies of detection.

Plant-Associated Representatives of the Bacillus cereus Group Are a Rich Source of Antimicrobial Compounds

Seventeen bacterial strains able to suppress plant pathogens have been isolated from healthy Vietnamese crop plants and taxonomically assigned as members of the Bacillus cereus group. In order to prove their potential as biocontrol agents, we perform a comprehensive analysis that included the whole-genome sequencing of selected strains and the mining for genes and gene clusters involved in the synthesis of endo- and exotoxins and secondary metabolites, such as antimicrobial peptides (AMPs). Kurstakin, thumolycin, and other AMPs were detected and characterized by different mass spectrometric methods, such as MALDI-TOF-MS and LIFT-MALDI-TOF/TOF fragment analysis. Based on their whole-genome sequences, the plant-associated isolates were assigned to the following species and subspecies: B. cereus subsp. cereus (6), B. cereus subsp. bombysepticus (5), Bacillus tropicus (2), and Bacillus pacificus. These three isolates represent novel genomospecies. Genes encoding entomopathogenic crystal and vegetative proteins were detected in B. cereus subsp. bombysepticus TK1. The in vitro assays revealed that many plant-associated isolates enhanced plant growth and suppressed plant pathogens. Our findings indicate that the plant-associated representatives of the B. cereus group are a rich source of putative antimicrobial compounds with potential in sustainable agriculture. However, the presence of virulence genes might restrict their application as biologicals in agriculture.

Genomic and Phylogenetic Analysis of Bacillus cereus Biovar anthracis Isolated from Archival Bone Samples Reveals Earlier Natural History of the Pathogen

(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.

Retrospective Screening of Anthrax-like Disease Induced by Bacillus tropicus str. JMT from Chinese Soft-Shell Turtles in Taiwan

Bacillus cereus is ubiquitous in the environment and a well-known causative agent of foodborne disease. Surprisingly, more and more emerging strains of atypical B. cereus have been identified and related to severe disease in humans and mammals such as chimpanzees, apes, and bovine. Recently, the atypical B. cereus isolates, which mainly derive from North America and Africa, have drawn great attention due to the potential risk of zoonosis. The cluster of B. cereus carries several anthrax-like virulent genes that are implicated in lethal disease. However, in non-mammals, the distribution of atypical B. cereus is still unknown. In this study, we conducted a retrospective screening of the 32 isolates of Bacillus spp. from diseased Chinese soft-shelled turtles from 2016 to 2020. To recognize the causative agent, we used various methods, such as sequencing analysis using PCR-amplification of the 16S rRNA gene, multiplex PCR for discriminating, and colony morphology by following previous studies. Furthermore, the digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values were calculated, respectively, below the 70 and 96% cutoff to define species boundaries. According to the summarized results, the pathogen is taxonomically classified as Bacillus tropicus str. JMT (previous atypical Bacillus cereus). Subsequently, analyses such as targeting the unique genes using PCR and visual observation of the bacteria under various staining techniques were implemented in our study. Our findings show that all (32/32, 100%) isolates in this retrospective screening share similar phenotypical properties and carry the protective antigen (PA), edema factor (EF), hyaluronic acid (HA), and exopolysaccharide (Bps) genes on their plasmids. In this study, the results indicate that the geographic distribution and host range of B. tropicus were previously underestimated.

Pathogenic Bacilli as an Emerging Biothreat?

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.

Identification of Universally Applicable and Species-Specific Marker Peptides for Bacillus anthracis

Anthrax is a zoonotic infection caused by the bacterium Bacillus anthracis (BA). Specific identification of this pathogen often relies on targeting genes located on two extrachromosomal plasmids, which represent the major pathogenicity factors of BA. However, more recent findings show that these plasmids have also been found in other closely related Bacillus species. In this study, we investigated the possibility of identifying species-specific and universally applicable marker peptides for BA. For this purpose, we applied a high-resolution mass spectrometry-based approach for 42 BA isolates. Along with the genomic sequencing data and by developing a bioinformatics data evaluation pipeline, which uses a database containing most of the publicly available protein sequences worldwide (UniParc), we were able to identify eleven universal marker peptides unique to BA. These markers are located on the chromosome and therefore, might overcome known problems, such as observable loss of plasmids in environmental species, plasmid loss during cultivation in the lab, and the fact that the virulence plasmids are not necessarily a unique feature of BA. The identified chromosomally encoded markers in this study could extend the small panel of already existing chromosomal targets and along with targets for the virulence plasmids, may pave the way to an even more reliable identification of BA using genomics- as well as proteomics-based techniques.

Allelic Polymorphism of Anthrax Pathogenicity Factor Genes as a Means of Estimating Microbiological Risks Associated with Climate Change

Abstract

Climate change brings new risks of emergence of especially dangerous diseases. The paper reports the possibility of assessing the pathogenic potential of bacteria as demonstrated by studying the allelic polymorphism of anthrax bacterium pathogenicity factor genes, which is a prerequisite for assessing the associated microbiological risks. The allelic polymorphism of the capBCADE operon (capB, capC, capA, capD, and capE genes) encoding the capsule biosynthesis proteins of Bacillus anthracis, and the acpA and acpB genes encoding the expression regulators of this operon have been studied for the first time. A number of single nucleotide polymorphisms (SNPs) were described in the strains of the studied sample, including 5 SNPs in the capB gene, 3 in capC, 4 in capA, 14 in capD, 2 in capE, and 15 in acpB, as well as 7 SNPs and one insertion in the acpA gene. As a result, the sample has been divided into sequence types for each gene and 17 genotypes, which are combinations of the identified sequence types. In silico translation of the detected alleles of the studied genes revealed three isoforms of the CapB and CapA proteins, two isoforms of the CapC and CapE proteins, six isoforms of the CapD protein, five isoforms of the AcpA protein, and four isoforms in the AcpB protein. It has been demonstrated that the SNP in the 351A → G position of capC is a marker of A.Br.Aust94 group strains. Based on the results, A.Br.Vollum group strains were divided into two subgroups. The strains in the evolutionary lines B and C differed from the line A strains by the presence of an 853G → A SNP in the acpA gene. In addition, a previously unknown variable number tandem repeat (VNTR), has been found in the acpA gene and the possibility of using it for differentiating and genotyping of B. anthracis strains has been demonstrated.

Strains Associated with Two 2020 Welder Anthrax Cases in the United States Belong to Separate Lineages within Bacillus cereus sensu lato

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.

Bacillus anthracis Phylogeography: New Clues From Kazakhstan, Central Asia

This article describes Bacillus anthracis strains isolated in Kazakhstan since the 1950s until year 2016 from sixty-one independent events associated with anthrax in humans and animals. One hundred and fifty-four strains were first genotyped by Multiple Locus VNTR (variable number of tandem repeats) Analysis (MLVA) using 31 VNTR loci. Thirty-five MLVA31 genotypes were resolved, 28 belong to the A1/TEA group, five to A3/Sterne-Ames group, one to A4/Vollum and one to the B clade. This is the first report of the presence of the B-clade in Kazakhstan. The MLVA31 results and epidemiological data were combined to select a subset of seventy-nine representative strains for draft whole genome sequencing (WGS). Strains from Kazakhstan significantly enrich the known phylogeny of the Ames group polytomy, including the description of a new branch closest to the Texas, United States A.Br.Ames sublineage stricto sensu. Three among the seven currently defined branches in the TEA polytomy are present in Kazakhstan, “Tsiankovskii”, “Heroin”, and “Sanitary Technical Institute (STI)”. In particular, strains from the STI lineage are largely predominant in Kazakhstan and introduce numerous deep branching STI sublineages, demonstrating a high geographic correspondence between “STI” and Kazakhstan, Central Asia. This observation is a strong indication that the TEA polytomy emerged after the last political unification of Asian steppes in the fourteenth century of the Common Era. The phylogenetic analysis of the Kazakhstan data and of currently available WGS data of worldwide origin strengthens our understanding of B. anthracis geographic expansions in the past seven centuries.

Phenotypic Variants of Bacterial Colonies in Microbiological Diagnostics: How Often Are They Indicative of Differing Antimicrobial Susceptibility Patterns?

Phenotypic variants (PV) are colonies of the same species in the same specimen with different morphological features. It is controversial whether antimicrobial susceptibility testing (AST) should be done for all PV. The objectives of this study were to quantify the proportion of differing antimicrobial susceptibility patterns (dASP) among PV and to identify species and antimicrobial compounds that are mostly affected. All PV from routine diagnostics (University Hospital Münster, Germany; 1 September 2019 to 31 August 2020) were subjected to species identification (matrix-assisted laser desorption ionization-time of flight mass spectrometry [MALDI-TOF MS]) and AST (Vitek 2). To assess the dASP, only antimicrobial agents were considered for which Vitek-derived MIC were available (interpreted according to the EUCAST clinical breakpoints). The categorical agreement (CA; agreement with the AST categories S [susceptible, standard dosing regimen], I [susceptible, increased exposure], R [resistant]) of the PV was calculated. The PV of Escherichia coli (n = 260), Pseudomonas aeruginosa (n = 86), Klebsiella pneumoniae (n = 47), Enterobacter cloacae complex (n = 45), and Staphylococcus aureus (n = 38) were included. The median CA was 95% (range, 80 to 100%, depending on the species). The colony characteristics (e.g., form/size, color, margin, hemolysis) were not indicative for dASP. PV showed a high categorical agreement in the AST categories. This observation supports a test strategy to perform AST for only one colony of PV. IMPORTANCE Phenotypic variants of bacteria are frequent in routine diagnostics and can display differing antimicrobial susceptibility patterns. We found that the likelihood of different antimicrobial susceptibility is low among PV. To save laboratory resources, only one isolate per PV could be tested to guide the antimicrobial treatment of patients.

Isolation and identification of avirulent strains of Bacillus anthracis from environmental samples in Central Java, Indonesia

Background and Aim: Anthrax is a non-contagious infectious disease caused by Bacillus anthracis. The bacteria form spores that are resistant to extreme conditions and can contaminate the environment for decades. This study aimed to detect and characterize B. anthracis found in endemic areas of anthrax in Yogyakarta and Central Java province, Indonesia. Materials and Methods: Soil samples were collected from Gunungkidul regency, Yogyakarta province (n=315) and Boyolali regency, Central Java province (n=100). Additional soil samples (n=10) and straw samples (n=5) were obtained from Pati regency, Central Java province. The isolation and identification of B. anthracis were performed using conventional methods: Morphology of bacteria colony in solid media, Gram staining, capsule staining, spores staining, and motility test. Isolates were further identified using polymerase chain reaction (PCR) against Ba813, lef (pXO1), and capC (pXO2) gene. An avirulent vaccine strain of B. anthracis (strain 34F2) was used as a control. Results: Only four samples grew on blood agar with a ground-glass appearance, white-gray colony (Gunungkidul and avirulent strain) or yellowish (Boyolali and Pati). All were Gram-positive, presented chains, square-ended rods, spores, and were then identified as B. anthracis. Boyolali, Pati, and avirulent strain isolates had slightly different characteristics, including the growth of non-mucoid in the bicarbonate agar medium, and their uncapsulated form. The PCR showed two Gunungkidul isolates which amplified three genes, including Ba813, lef, and capC. Contrarily, the other isolates did not amplify the capC gene. Conclusion: Gunungkidul isolates were identified as virulent strains of B. anthracis while Boyolali and Pati isolates were proposed as avirulent strains. This is the first report of isolation and identification of avirulent strains of B. anthracis in Central Java, Indonesia.

Complement C5 inhibition protects against hemolytic anemia and acute kidney injury in anthrax peptidoglycan-induced sepsis in baboons

Late-stage anthrax infections are characterized by dysregulated immune responses and hematogenous spread of Bacillus anthracis, leading to extreme bacteremia, sepsis, multiple organ failure, and, ultimately, death. Despite the bacterium being nonhemolytic, some fulminant anthrax patients develop a secondary atypical hemolytic uremic syndrome (aHUS) through unknown mechanisms. We recapitulated the pathology in baboons challenged with cell wall peptidoglycan (PGN), a polymeric, pathogen-associated molecular pattern responsible for the hemostatic dysregulation in anthrax sepsis. Similar to aHUS anthrax patients, PGN induces an initial hematocrit elevation followed by progressive hemolytic anemia and associated renal failure. Etiologically, PGN induces erythrolysis through direct excessive activation of all three complement pathways. Blunting terminal complement activation with a C5 neutralizing peptide prevented the progressive deposition of membrane attack complexes on red blood cells (RBC) and subsequent intravascular hemolysis, heme cytotoxicity, and acute kidney injury. Importantly, C5 neutralization did not prevent immune recognition of PGN and shifted the systemic inflammatory responses, consistent with improved survival in sepsis. Whereas PGN-induced hemostatic dysregulation was unchanged, C5 inhibition augmented fibrinolysis and improved the thromboischemic resolution. Overall, our study identifies PGN-driven complement activation as the pathologic mechanism underlying hemolytic anemia in anthrax and likely other gram-positive infections in which PGN is abundantly represented. Neutralization of terminal complement reactions reduces the hemolytic uremic pathology induced by PGN and could alleviate heme cytotoxicity and its associated kidney failure in gram-positive infections.

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.

TaqMan Assays for Simultaneous Detection of Bacillus anthracis and Bacillus cereus biovar anthracis

Anthrax is a worldwide zoonotic disease caused by the spore-forming bacterium Bacillus anthracis. Primarily a disease of herbivores, human infections often result from direct contact with contaminated animal products (cutaneous and inhalational anthrax) or through consumption of infected meat (gastrointestinal anthrax). The genetic near neighbor, Bacillus cereus biovar anthracis (Bcbva), causes an anthrax-like illness in the wildlife and livestock of west and central Africa due to the presence and expression of B. anthracis-specific virulence factors in this background. While Bcbva infections have not been reported in humans, a recent seroprevalence study detected Bcbva antibodies in the rural population around Taï National Park. This work describes the development of new TaqMan multiplex PCRs for the simultaneous detection of B. anthracis and Bcbva. The assays are designed to amplify Ba-1, capB, and lef markers in B. anthracis and genomic island IV (GI4), capB, and lef in Bcbva. Our assays allow for the rapid discrimination of B. anthracis and Bcbva and will provide insights into the molecular epidemiology of these two important pathogens that share an overlapping geographical range in west and central Africa.

Novel Strategy for Rapidly and Safely Distinguishing Bacillus anthracis and Bacillus cereus by Use of Peptide Mass Fingerprints Based on Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

The objective of this study was to construct a rapid, high-throughput, and biosafety-compatible screening method for Bacillus anthracis and Bacillus cereus based on matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). MALDI-TOF MS coupled to ClinProTools was used to discover MALDI-TOF MS biomarker peaks and generate a classification model based on a genetic algorithm (GA) to differentiate between different Bacillus anthracis and Bacillus cereus isolates. Thirty Bacillus anthracis and 19 Bacillus cereus strains were used to construct and analyze the model, and 40 Bacillus strains were used for validation. For the GA screening model, the cross-validation values, which reflect the ability of the model to handle variability among the test spectra, and the recognition capability values, which reflect the model's ability to correctly identify its component spectra, were all 100%. This model contained 10 biomarker peaks (m/z 3,339.9, 3,396.3, 3,682.4, 5,476.7, 6,610.6, 6,680.1, 7,365.3, 7,792.4, 9,475.8, and 10,934.1) used to correctly identify 28 Bacillus anthracis and 12 Bacillus cereus isolates from 40 Bacillus isolates, with a sensitivity and specificity of 100%. With the obvious advantages of being rapid, highly accurate, and highly sensitive and having a low cost and high throughput, MALDI-TOF MS ClinProTools is a powerful and reliable tool for screening Bacillus anthracis and Bacillus cereus strains.

The Bacillus cereus Food Infection as Multifactorial Process

The ubiquitous soil bacterium Bacillus cereus presents major challenges to food safety. It is responsible for two types of food poisoning, the emetic form due to food intoxication and the diarrheal form emerging from food infections with enteropathogenic strains, also known as toxico-infections, which are the subject of this review. The diarrheal type of food poisoning emerges after production of enterotoxins by viable bacteria in the human intestine. Basically, the manifestation of the disease is, however, the result of a multifactorial process, including B. cereus prevalence and survival in different foods, survival of the stomach passage, spore germination, motility, adhesion, and finally enterotoxin production in the intestine. Moreover, all of these processes are influenced by the consumed foodstuffs as well as the intestinal microbiota which have, therefore, to be considered for a reliable prediction of the hazardous potential of contaminated foods. Current knowledge regarding these single aspects is summarized in this review aiming for risk-oriented diagnostics for enteropathogenic B. cereus.

Novel Effective Bacillus cereus Group Species "Bacillus clarus" Is Represented by Antibiotic-Producing Strain ATCC 21929 Isolated from Soil

The B. cereus group comprises numerous closely related lineages with various degrees of pathogenic potential and industrial relevance. Species-level taxonomic classification of B. cereus group strains is important for risk evaluation and communication but remains challenging. Biochemical and phenotypic assays are often used to assign B. cereus group strains to species but are insufficient for accurate taxonomic classification on a genomic scale. Here, we show that antibiotic-producing ATCC 21929 represents a novel lineage within the B. cereus group that, by all metrics used to delineate prokaryotic species, exemplifies a novel effective species. Furthermore, we show that ATCC 21929 is incapable of producing enterotoxins Hbl and Nhe or exhibiting cytotoxic effects on HeLa cells at human body temperature in vitro. These results provide greater insight into the genomic and phenotypic diversity of the B. cereus group and may be leveraged to inform future public health and food safety efforts.

Gram-positive, spore-forming members of the Bacillus cereus group species complex are widespread in natural environments and display various degrees of pathogenicity. Recently, B. cereus group strain Bacillus mycoides Flugge ATCC 21929 was found to represent a novel lineage within the species complex, sharing a relatively low degree of genomic similarity with all B. cereus group genomes (average nucleotide identity [ANI] < 88). ATCC 21929 has been previously associated with the production of a patented antibiotic, antibiotic 60-6 (i.e., cerexin A); however, the virulence potential and growth characteristics of this lineage have never been assessed. Here, we provide an extensive genomic and phenotypic characterization of ATCC 21929, and we assess its pathogenic potential in vitro. ATCC 21929 most closely resembles Bacillus paramycoides NH24A2^T (ANI and in silico DNA-DNA hybridization values of 86.70 and 34.10%, respectively). Phenotypically, ATCC 21929 does not possess cytochrome c oxidase activity and is able to grow at a range of temperatures between 15 and 43°C and a range of pH between 6 and 9. At 32°C, ATCC 21929 shows weak production of diarrheal enterotoxin hemolysin BL (Hbl) but no production of nonhemolytic enterotoxin (Nhe); at 37°C, neither Hbl nor Nhe is produced. Additionally, at 37°C, ATCC 21929 does not exhibit cytotoxic effects toward HeLa cells. With regard to fatty acid composition, ATCC 21929 has iso-C17:0 present in highest abundance. Based on the characterization provided here, ATCC 21929^T (= PS00077A^T = PS00077B^T = PSU-0922^T = BHP^T) represents a novel effective B. cereus group species, which we propose as effective species “Bacillus clarus.”

IMPORTANCE The B. cereus group comprises numerous closely related lineages with various degrees of pathogenic potential and industrial relevance. Species-level taxonomic classification of B. cereus group strains is important for risk evaluation and communication but remains challenging. Biochemical and phenotypic assays are often used to assign B. cereus group strains to species but are insufficient for accurate taxonomic classification on a genomic scale. Here, we show that antibiotic-producing ATCC 21929 represents a novel lineage within the B. cereus group that, by all metrics used to delineate prokaryotic species, exemplifies a novel effective species. Furthermore, we show that ATCC 21929 is incapable of producing enterotoxins Hbl and Nhe or exhibiting cytotoxic effects on HeLa cells at human body temperature in vitro. These results provide greater insight into the genomic and phenotypic diversity of the B. cereus group and may be leveraged to inform future public health and food safety efforts.

You Can't B. cereus - A Review of Bacillus cereus Strains That Cause Anthrax-Like Disease

Emerging strains of Bacillus cereus, traditionally considered a self-limiting foodborne pathogen, have been associated with anthrax-like disease in mammals, including humans. The strains have emerged by divergent evolution and, as exchange of genetic material in the Bacillus genus occurs naturally, it is possible that further isolates will be identified in the future. The strains vary in their genotypes and phenotypes, combining traits of both B. cereus and B. anthracis species. Cases of anthrax-like disease associated with these strains result in similar symptoms and mortality rates as those caused by B. anthracis. The strains are susceptible to frontline antibiotics used in the treatment of anthrax and existing vaccines provide protection in animal models. The emergence of these strains has reignited the debate surrounding classification of the B. cereus sensu lato group and serves as a reminder that the field of medical microbiology is constantly changing and remains an important and ongoing area of research.

Bacillus paranthracis Isolate from Blood of Fatal Ebola Virus Disease Case

A Bacillus paranthracis isolate was cultured from the blood of a fatal Ebola virus disease (EVD) case in Liberia and was identified by whole genome sequencing. Although B. paranthracis has only recently been described and is poorly characterized, this case may represent the bacterial co-infection of an EVD patient.

Rapid Presumptive Identification of Bacillus anthracis Isolates Using the Tetracore RedLine Alert™ Test

A comprehensive laboratory evaluation of the Tetracore RedLine Alert test, a lateral flow immunoassay (LFA) for the rapid presumptive identification of Bacillus anthracis, was conducted at 2 different test sites. The study evaluated the sensitivity of this assay using 16 diverse strains of B. anthracis grown on sheep blood agar (SBA) plates. In addition, 83 clinically relevant microorganisms were tested to assess the specificity of the RedLine Alert test. The results indicated that the RedLine Alert test for the presumptive identification of B. anthracis is highly robust, specific, and sensitive. RedLine Alert is a rapid test that has applicability for use in a clinical setting for ruling-in or ruling-out nonhemolytic colonies of Bacillus spp. grown on SBA medium as presumptive isolates of B. anthracis.

Serological evidence for human exposure to Bacillus cereus biovar anthracis in the villages around Taï National Park, Côte d'Ivoire

Bacillus cereus biovar anthracis (Bcbva) is an untypical anthrax-causing pathogen responsible for high wildlife mortality in Taï National Park (TNP), Côte d’Ivoire. However, nothing is known about its effect on the rural population living in the region bordering TNP. Contact to bushmeat is a known risk factor for exposure to a variety of zoonotic pathogens, but no human infections with Bcbva were noted so far. Therefore, we performed a retrospective seroprevalence analysis with sera from 1,386 study volunteers. We used assays which detect antibodies against the protective antigen PA, which is synthesized by both Bcbva and classic B. anthracis, and against the recently described antigen pXO2-60, a 35-kDa protein only produced by Bcbva. We found a high seroprevalence (22.37%) of antibodies against PA, and approximately half of those sera (10.46%) were also positive for the Bcbva-specific antigen pXO2-60. All sera negative for PA were also negative for antibodies against pXO2-60, confirming specificity and suitability of the PA/pXO2-60 combined serological assay. The fact that a large fraction of sera was positive for PA but negative for pXO2-60 can most likely be explained by lower immunogenicity of pXO2-60, but exposure to classic B. anthracis cannot be excluded. As only Bcbva has been detected in the TNP area so far, exposure to Bcbva can be suspected from the presence of antibodies against PA alone. In a questionnaire, most study participants reported contact to bushmeat and livestock carcasses. Unfortunately, risk factor analysis indicated that neither animal contacts, sex, age, nor country of origin were significant predictors of Bcbva seroprevalence. Nevertheless, our study added to an assessment of the distribution of Bcbva and its impact on the human population, and our data can serve to raise awareness of anthrax in the affected regions.

Anthrax is a zoonotic disease transmitted from animals to humans and normally caused by B. anthracis mainly in savanna regions. However, untypical bacteria named Bacillus cereus biovar anthracis (Bcbva) were detected in a variety of wild animals in the rain forest region of the Taï National Park (TNP) in Côte d’Ivoire. No anthrax infections in humans living in the region around TNP were reported until now. Therefore, we assessed exposure to the pathogen by analysis of sera from human volunteers for the presence of antibodies against the protective antigen (PA), which is produced by B. anthracis and Bcbva, and against the Bcbva-specific protein pXO2-60. We found antibodies against PA in more than 20% of sera from humans living in the TNP region, and around 10% possessed also antibodies against pXO2-60, confirming exposure to Bcbva. As only Bcbva, but not classic B. anthracis was found in TNP, we assume that the majority of humans had contact with Bcbva and that pXO2-60 is less immunogenic than PA. Although most people reported animal contacts, there was no statistically significant correlation with the presence of antibodies against Bcbva. Nevertheless, our study confirmed that Bcbva represents a danger for humans living in the affected area.

Potential distributions of Bacillus anthracis and Bacillus cereus biovar anthracis causing anthrax in Africa

BACKGROUND

Bacillus cereus biovar anthracis (Bcbva) is an emergent bacterium closely related to Bacillus anthracis, the etiological agent of anthrax. The latter has a worldwide distribution and usually causes infectious disease in mammals associated with savanna ecosystems. Bcbva was identified in humid tropical forests of Côte d'Ivoire in 2001. Here, we characterize the potential geographic distributions of Bcbva in West Africa and B. anthracis in sub-Saharan Africa using an ecological niche modeling approach.

METHODOLOGY/PRINCIPAL FINDINGS

Georeferenced occurrence data for B. anthracis and Bcbva were obtained from public data repositories and the scientific literature. Combinations of temperature, humidity, vegetation greenness, and soils values served as environmental variables in model calibrations. To predict the potential distribution of suitable environments for each pathogen across the study region, parameter values derived from the median of 10 replicates of the best-performing model for each pathogen were used. We found suitable environments predicted for B. anthracis across areas of confirmed and suspected anthrax activity in sub-Saharan Africa, including an east-west corridor from Ethiopia to Sierra Leone in the Sahel region and multiple areas in eastern, central, and southern Africa. The study area for Bcbva was restricted to West and Central Africa to reflect areas that have likely been accessible to Bcbva by dispersal. Model predicted values indicated potential suitable environments within humid forested environments. Background similarity tests in geographic space indicated statistical support to reject the null hypothesis of similarity when comparing environments associated with B. anthracis to those of Bcbva and when comparing humidity values and soils values individually. We failed to reject the null hypothesis of similarity when comparing environments associated with Bcbva to those of B. anthracis, suggesting that additional investigation is needed to provide a more robust characterization of the Bcbva niche.

CONCLUSIONS/SIGNIFICANCE

This study represents the first time that the environmental and geographic distribution of Bcbva has been mapped. We document likely differences in ecological niche-and consequently in geographic distribution-between Bcbva and typical B. anthracis, and areas of possible co-occurrence between the two. We provide information crucial to guiding and improving monitoring efforts focused on these pathogens.

The Bacillus cereus Group: Bacillus Species with Pathogenic Potential

The Bacillus cereus group includes several Bacillus species with closely related phylogeny. The most well-studied members of the group, B. anthracis, B. cereus, and B. thuringiensis, are known for their pathogenic potential. Here, we present the historical rationale for speciation and discuss shared and unique features of these bacteria. Aspects of cell morphology and physiology, and genome sequence similarity and gene synteny support close evolutionary relationships for these three species. For many strains, distinct differences in virulence factor synthesis provide facile means for species assignment. B. anthracis is the causative agent of anthrax. Some B. cereus strains are commonly recognized as food poisoning agents, but strains can also cause localized wound and eye infections as well as systemic disease. Certain B. thuringiensis strains are entomopathogens and have been commercialized for use as biopesticides, while some strains have been reported to cause infection in immunocompromised individuals. In this article we compare and contrast B. anthracis, B. cereus, and B. thuringiensis, including ecology, cell structure and development, virulence attributes, gene regulation and genetic exchange systems, and experimental models of disease.

Nucleotide polymorphism assay for the identification of west African group Bacillus anthracis: a lineage lacking anthrose

Background

The exosporium of the anthrax-causing Bacillus anthracis endospores display a tetrasaccharide composed of three rhamnose residues and an unusual sugar termed anthrose. Anthrose is a proposed potential target for immunotherapy and for specific detection of B. anthracis. Although originally thought to be ubiquitous in B. anthracis, previous work identified an anthrose negative strain from a West African lineage isolated from cattle that could represent a vaccine escape mutant. These strains carry genes required for expression of the anthrose operon but premature stop codons resulting from an 8-bp insertion in BAS3320 (an amino-transferase) and a C/T substitution at position 892 of the BAS3321 (a glycosyltransferase) gene prevent anthrose expression. Various other single nucleotide polymorphisms (SNPs) have been identified throughout the operon and could be the basis for detection of anthrose-deficient strains.

Results

In this study, we evaluated rhAmp genotypic assays based on SNPs at positions 892 and 1352 of BAS3321 for detection and differentiation of anthrose negative (Ant⁻) West African strains. Discrimination of anthrose negative West African isolates was achieved with as low as 100 fg of DNA, whereas consistent genotyping of Sterne necessitated at least 1 pg of DNA.

Conclusions

Screening of a global panel of B. anthracis isolates showed anthrose-expressing alleles are prevalent worldwide whereas the anthrose-deficient phenotype is to date limited to West Africa. Our work also revealed a third, previously unreported anthrose genotype in which the operon is altogether missing from a Polish B. anthracis isolate.

Tropical rainforest flies carrying pathogens form stable associations with social nonhuman primates

Living in groups provides benefits but also incurs costs such as attracting disease vectors. For example, synanthropic flies associate with human settlements, and higher fly densities increase pathogen transmission. We investigated whether such associations also exist in highly mobile nonhuman primate (NHP) Groups. We studied flies in a group of wild sooty mangabeys (Cercocebus atys atys) and three communities of wild chimpanzees (Pan troglodytes verus) in Taï National Park, Côte d'Ivoire. We observed markedly higher fly densities within both mangabey and chimpanzee groups. Using a mark-recapture experiment, we showed that flies stayed with the sooty mangabey group for up to 12 days and for up to 1.3 km. We also tested mangabey-associated flies for pathogens infecting mangabeys in this ecosystem, Bacillus cereus biovar anthracis (Bcbva), causing sylvatic anthrax, and Treponema pallidum pertenue, causing yaws. Flies contained treponemal (6/103) and Bcbva (7/103) DNA. We cultured Bcbva from all PCR-positive flies, confirming bacterial viability and suggesting that this bacterium might be transmitted and disseminated by flies. Whole genome sequences of Bcbva isolates revealed a diversity of Bcbva, probably derived from several sources. We conclude that flies actively track mangabeys and carry infectious bacterial pathogens; these associations represent an understudied cost of sociality and potentially expose many social animals to a diversity of pathogens.

Elucidating the Hot Spot Residues of Quorum Sensing Peptidic Autoinducer PapR by Multiple Amino Acid Replacements

The quorum sensing (QS) system of Bacillus cereus, an opportunistic human pathogen, utilizes the autoinducing PapR peptide signal that mediates the activation of the pleiotropic virulence regulator PlcR. A set of synthetic 7-mer PapR-derived peptides (PapR₇; ADLPFEF) have been shown to inhibit efficiently the PlcR regulon activity and the production of virulence factors, reflected by a loss in hemolytic activity without affecting bacterial growth. Interestingly, these first potent synthetic inhibitors involved D-amino acid or alanine replacements of three amino acids; proline, glutamic acid, and phenylalanine of the heptapeptide PapR. To better understand the role of these three positions in PlcR activity, we report herein the second generation design, synthesis, and characterization of PapR₇-derived combinations, alternate double and triple alanine and D-amino acids replacement at these positions. Our findings generate a new set of non-native PapR₇-derived peptides that inhibit the PlcR regulon activity and the production of virulence factors. Using the amino acids substitution strategy, we revealed the role of proline and glutamic acid on PlcR regulon activation. Moreover, we demonstrated that the D-Glutamic acid substitution was crucial for the design of stronger PlcR antagonists. These peptides represent potent synthetic inhibitors of B. cereus QS and constitute new and readily accessible chemical tools for the study of the PlcR system. Our method might be applied to other quorum sensing systems to design new anti-virulence agents.

Decontamination of Personal Protective Equipment

Exploratory field analyses of the inactivation capacity of disinfectants on contaminated personal protective equipment (PPE) are required to select a suitable surrogate for biohazardous agents like spores of Bacillus anthracis. The objectives of our study were (1) the determination of an appropriate surrogate for the inactivation of spores of B. anthracis with peracetic acid (PAA), and (2) application of optimized inactivation conditions for an effective decontamination of PPE with PAA under field conditions. For inactivation studies, B. anthracis spores from different strains and B. thuringiensis spores were fixed by air drying on carriers prepared from PPE fabric. Time and concentration studies with PAA-based disinfectants revealed that the spores of the B. thuringiensis strain DSM 350 showed an inactivation profile comparable to that of the spores of the B. anthracis strain with the highest stability, implying that B. thuringiensis can serve as an appropriate surrogate. Rapid (3 to 5 minutes) and effective surface decontamination was achieved with 2% PAA/0.2% surfactant. In field studies, PPE contaminated with spores of B. thuringiensis was treated with the disinfectant. Optimizing the decontamination technique revealed that spraying in combination with brushing was effective within 5 minutes of exposure.

Detection of Bacillus anthracis in animal tissues using InBios active anthrax detect rapid test lateral flow immunoassay

The Active Anthrax Detect (AAD) Rapid Test lateral flow immunoassay is a point-of-care assay that was under investigational use for detecting Bacillus anthracis capsular polypeptide (polyglutamic acid) in human blood, serum and plasma. Small sample volumes, rapid results and no refrigeration required allow for easy use in either the field or laboratory. Although the test was developed for use in suspect cases of human inhalation anthrax, its features also make it a potentially powerful tool for testing suspect animal cases. We tested animal tissue samples that were confirmed or ruled out for B. anthracis. The AAD Rapid Tests were also deployed in the field, testing animal carcasses during an anthrax outbreak in hippopotami (Hippopotamus amphibius) and Cape buffalo (Syncerus caffer) in Namibia. Evaluation of all samples showed a specificity of 82% and sensitivity of 98%. However, when the assay was used on specimens from only fresh carcasses (dead for <24 h), the specificity increased to 96%. The AAD Rapid Test is a rapid and simple screening assay, but confirmatory testing needs to be done, especially when the age of the sample (days animal has been deceased) is unknown. SIGNIFICANCE AND IMPACT OF THE STUDY: In countries where anthrax is endemic, many human outbreaks are often caused by epizootics. Earlier detection of infected animals may allow for identification of exposed people, early implementation of prevention and control methods, and ultimately lessen the number of people and animals affected. Detection of Bacillus anthracis in animal tissues using a simple, rapid and field-deployable method would allow for faster outbreak response. We evaluated a simple sample collection and processing method for use with the Active Anthrax Detect Rapid Test lateral flow immunoassay to screen dead animals for anthrax.

Analysis of a newly discovered antigen of Bacillus cereus biovar anthracis for its suitability in specific serological antibody testing

AIMS

The aim of this work was to identify a protein which can be used for specific detection of antibodies against Bacillus cereus biovar anthracis (Bcbva), an anthrax-causing pathogen that so far has been described in African rainforest areas.

METHODS AND RESULTS

Culture supernatants of Bcbva and classic Bacillus anthracis (Ba) were analysed by gel electrophoresis, and a 35-kDa protein secreted only by Bcbva and not Ba was detected. The protein was identified as pXO2-60 by mass spectrometry. Sequence analysis showed that Ba is unable to secrete this protein due to a premature stop codon in the sequence for the signal peptide. Immunization of five outbred mice with sterile bacterial culture supernatants of Bcbva revealed an immune response in ELISA against pXO2-60 (three mice positive, one borderline) and the protective antigen (PA; four mice). When supernatants of classic Ba were injected into mice or human sera from anthrax patients were analysed, only antibodies against PA were detected.

CONCLUSIONS

In combination with PA, the pXO2-60 protein can be used for the detection of antibodies specific against Bcbva and discriminating from Ba.

SIGNIFICANCE AND IMPACT OF THE STUDY

After further validation, serological assays based on pXO2-60 can be used to perform seroprevalence studies to determine the epidemiology of B. cereus bv anthracis in affected countries and assess its impact on the human population.

Expression and contribution to virulence of each polysaccharide capsule of Bacillus cereus strain G9241

Bacillus cereus strain G9241 was isolated from a patient with pneumonia who had an anthrax-like illness. Like Bacillus anthracis, the virulence of G9241 is dependent on two large plasmids. In G9241 those plasmids are pBCXO1 and pBC210. There is a multi-gene capsule locus on each of these virulence plasmids, and both capsules are produced by G9241 in vitro and in mice. The hasACB operon on pBCXO1 is responsible for production of a hyaluronic acid (HA) capsule. The locus on pBC210 encodes a putative tetrasaccharide (TS) capsule that assembles in a Wzy-dependent manner. We found that the pBC210 capsule locus is transcribed as two operons and identified the promoter regions responsible for transcription. We constructed isogenic mutants to assess the role of genes in the two TS capsule operons in production of the capsule. Spores of strains deficient in production of either the HA or TS capsule were inoculated subcutaneously or intranasally into A/J and C57BL/6 mice to determine the lethal dose 50% of each bacterial mutant by each route of infection. The loss of the HA capsule attenuated G9241 more than the loss of the TS capsule for both infection routes in both mouse strains. Overall, our data further characterize the unique TS capsule on pBC210 and demonstrate that the two capsules do not have the same impact on virulence of G9241.

Genomic Characterization and Copy Number Variation of Bacillus anthracis Plasmids pXO1 and pXO2 in a Historical Collection of 412 Strains

Bacillus anthracis microorganisms are of historical and epidemiological importance and are among the most homogenous bacterial groups known, even though the B. anthracis genome is rich in mobile elements. Mobile elements can trigger the diversification of lineages; therefore, characterizing the extent of genomic variation in a large collection of strains is critical for a complete understanding of the diversity and evolution of the species. Here, we sequenced a large collection of B. anthracis strains (>400) that were recovered from human, animal, and environmental sources around the world. Our results confirmed the remarkable stability of gene content and synteny of the anthrax plasmids and revealed no signal of plasmid exchange between B. anthracis and pathogenic B. cereus isolates but rather predominantly vertical descent. These findings advance our understanding of the biology and pathogenomic evolution of B. anthracis and its plasmids.

Bacillus anthracis plasmids pXO1 and pXO2 carry the main virulence factors responsible for anthrax. However, the extent of copy number variation within the species and how the plasmids are related to pXO1/pXO2-like plasmids in other species of the Bacillus cereussensu lato group remain unclear. To gain new insights into these issues, we sequenced 412 B. anthracis strains representing the total phylogenetic and ecological diversity of the species. Our results revealed that B. anthracis genomes carried, on average, 3.86 and 2.29 copies of pXO1 and pXO2, respectively, and also revealed a positive linear correlation between the copy numbers of pXO1 and pXO2. No correlation between the plasmid copy number and the phylogenetic relatedness of the strains was observed. However, genomes of strains isolated from animal tissues generally maintained a higher plasmid copy number than genomes of strains from environmental sources (P < 0.05 [Welch two-sample t test]). Comparisons against B. cereus genomes carrying complete or partial pXO1-like and pXO2-like plasmids showed that the plasmid-based phylogeny recapitulated that of the main chromosome, indicating limited plasmid horizontal transfer between or within these species. Comparisons of gene content revealed a closed pXO1 and pXO2 pangenome; e.g., plasmids encode <8 unique genes, on average, and a single large fragment deletion of pXO1 in one B. anthracis strain (2000031682) was detected. Collectively, our results provide a more complete view of the genomic diversity of B. anthracis plasmids, their copy number variation, and the virulence potential of other Bacillus species carrying pXO1/pXO2-like plasmids.

IMPORTANCEBacillus anthracis microorganisms are of historical and epidemiological importance and are among the most homogenous bacterial groups known, even though the B. anthracis genome is rich in mobile elements. Mobile elements can trigger the diversification of lineages; therefore, characterizing the extent of genomic variation in a large collection of strains is critical for a complete understanding of the diversity and evolution of the species. Here, we sequenced a large collection of B. anthracis strains (>400) that were recovered from human, animal, and environmental sources around the world. Our results confirmed the remarkable stability of gene content and synteny of the anthrax plasmids and revealed no signal of plasmid exchange between B. anthracis and pathogenic B. cereus isolates but rather predominantly vertical descent. These findings advance our understanding of the biology and pathogenomic evolution of B. anthracis and its plasmids.

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.

Certhrax Is an Antivirulence Factor for the Anthrax-Like Organism Bacillus cereus Strain G9241

Bacillus cereus G9241 caused a life-threatening anthrax-like lung infection in a previously healthy human. This strain harbors two large virulence plasmids, pBCXO1 and pBC210, that are absent from typical B. cereus isolates. The pBCXO1 plasmid is nearly identical to pXO1 from Bacillus anthracis and carries genes (pagA1, lef, and cya) for anthrax toxin components (protective antigen [called PA1 in G9241], lethal factor [LF], and edema factor [EF], respectively). The plasmid also has an intact hyaluronic acid capsule locus. The pBC210 plasmid has a tetrasaccharide capsule locus, a gene for a PA1 homolog called PA2 (pagA2), and a gene (cer) for Certhrax, an ADP-ribosyltransferase toxin that inactivates vinculin. LF, EF, and Certhrax require PA for entry into cells. In this study, we asked what role PA1, PA2, LF, and Certhrax play in the pathogenicity of G9241. To answer this, we generated isogenic deletion mutations in the targeted toxin gene components and then assessed the strains for virulence in highly G9241-susceptible (A/J) and moderately G9241-sensitive (C57BL/6) mice. We found that full virulence of G9241 required PA1 and LF, while PA2 contributed minimally to pathogenesis of G9241 but could not functionally replace PA1 as a toxin-binding subunit in vivo Surprisingly, we discovered that Certhrax attenuated the virulence of G9241; i.e., a Δcer Δlef mutant strain was more virulent than a Δlef mutant strain following subcutaneous inoculation of A/J mice. Moreover, the enzymatic activity of Certhrax contributed to this phenotype. We concluded that Certhrax acts as an antivirulence factor in the anthrax-like organism B. cereus G9241.

Assembly and Function of the Bacillus anthracis S-Layer

Bacillus anthracis, the anthrax agent, is a member of the Bacillus cereus sensu lato group, which includes invasive pathogens of mammals or insects as well as nonpathogenic environmental strains. The genes for anthrax pathogenesis are located on two large virulence plasmids. Similar virulence plasmids have been acquired by other B. cereus strains and enable the pathogenesis of anthrax-like diseases. Among the virulence factors of B. anthracis is the S-layer-associated protein BslA, which endows bacilli with invasive attributes for mammalian hosts. BslA surface display and function are dependent on the bacterial S-layer, whose constituents assemble by binding to the secondary cell wall polysaccharide (SCWP) via S-layer homology (SLH) domains. B. anthracis and other pathogenic B. cereus isolates harbor genes for the secretion of S-layer proteins, for S-layer assembly, and for synthesis of the SCWP. We review here recent insights into the assembly and function of the S-layer and the SCWP.

Spores and soil from six sides: interdisciplinarity and the environmental biology of anthrax (Bacillus anthracis)

Environmentally transmitted diseases are comparatively poorly understood and managed, and their ecology is particularly understudied. Here we identify challenges of studying environmental transmission and persistence with a six-sided interdisciplinary review of the biology of anthrax (Bacillus anthracis). Anthrax is a zoonotic disease capable of maintaining infectious spore banks in soil for decades (or even potentially centuries), and the mechanisms of its environmental persistence have been the topic of significant research and controversy. Where anthrax is endemic, it plays an important ecological role, shaping the dynamics of entire herbivore communities. The complex eco-epidemiology of anthrax, and the mysterious biology of Bacillus anthracis during its environmental stage, have necessitated an interdisciplinary approach to pathogen research. Here, we illustrate different disciplinary perspectives through key advances made by researchers working in Etosha National Park, a long-term ecological research site in Namibia that has exemplified the complexities of the enzootic process of anthrax over decades of surveillance. In Etosha, the role of scavengers and alternative routes (waterborne transmission and flies) has proved unimportant relative to the long-term persistence of anthrax spores in soil and their infection of herbivore hosts. Carcass deposition facilitates green-ups of vegetation to attract herbivores, potentially facilitated by the role of anthrax spores in the rhizosphere. The underlying seasonal pattern of vegetation, and herbivores' immune and behavioural responses to anthrax risk, interact to produce regular 'anthrax seasons' that appear to be a stable feature of the Etosha ecosystem. Through the lens of microbiologists, geneticists, immunologists, ecologists, epidemiologists, and clinicians, we discuss how anthrax dynamics are shaped at the smallest scale by population genetics and interactions within the bacterial communities up to the broadest scales of ecosystem structure. We illustrate the benefits and challenges of this interdisciplinary approach to disease ecology, and suggest ways anthrax might offer insights into the biology of other important pathogens. Bacillus anthracis, and the more recently emerged Bacillus cereus biovar anthracis, share key features with other environmentally transmitted pathogens, including several zoonoses and panzootics of special interest for global health and conservation efforts. Understanding the dynamics of anthrax, and developing interdisciplinary research programs that explore environmental persistence, is a critical step forward for understanding these emerging threats.

Persistent anthrax as a major driver of wildlife mortality in a tropical rainforest

Anthrax is a globally important animal disease and zoonosis. Despite this, our current knowledge of anthrax ecology is largely limited to arid ecosystems, where outbreaks are most commonly reported. Here we show that the dynamics of an anthrax-causing agent, Bacillus cereus biovar anthracis, in a tropical rainforest have severe consequences for local wildlife communities. Using data and samples collected over three decades, we show that rainforest anthrax is a persistent and widespread cause of death for a broad range of mammalian hosts. We predict that this pathogen will accelerate the decline and possibly result in the extirpation of local chimpanzee (Pan troglodytes verus) populations. We present the epidemiology of a cryptic pathogen and show that its presence has important implications for conservation.

Bacillus anthracis gamma phage lysis among soil bacteria: an update on test specificity

BACKGROUND

Bacillus anthracis, which causes anthrax in humans and animals, is enzootic in parts of the U.S. state of Texas where cases are typically reported in animals annually. The gamma phage lysis assay is a common diagnostic method for identification of B. anthracis and is based on the bacterium's susceptibility to lysis. This test has been shown to be 97% specific for B. anthracis, as a small number of strains of other Bacillus spp. are known to be susceptible. In this study, we evaluated the performance of a combination of B. anthracis diagnostic assays on 700 aerobic, spore-forming isolates recovered from soil collected in Texas. These assays include phenotypic descriptions, gamma phage susceptibility, and real-time polymerase chain reaction specific for B. anthracis. Gamma phage-susceptible isolates were also tested using cell wall and capsule direct fluorescent-antibody assays specific for B. anthracis. Gamma phage-susceptible isolates that were ruled out as B. anthracis were identified by 16S rRNA gene sequencing.

FINDINGS

We identified 29 gamma phage-susceptible isolates. One was confirmed as B. anthracis, while the other 28 isolates were ruled out for B. anthracis by the other diagnostic tests. Using 16S rRNA gene sequencing results, we identified these isolates as members of the B. cereus group, Bacillus sp. (not within B. cereus group), Lysinibacillus spp., and Solibacillus silvestris. Based on these results, we report a specificity of 96% for gamma phage lysis as a diagnostic test for B. anthracis, and identified susceptible isolates outside the Bacillus genus.

CONCLUSIONS

In this study we found gamma phage susceptibility to be consistent with previously reported results. However, we identified non-B. anthracis environmental isolates (including isolates from genera other than Bacillus) that are susceptible to gamma phage lysis. To date, susceptibility to gamma phage lysis has not been reported in genera other than Bacillus. Though these isolates are not of clinical origin, description of unexpected positives is important, especially as new diagnostic assays for B. anthracis are being developed based on gamma phage lysis or gamma phage proteins.

Low antibody prevalence against Bacillus cereus biovar anthracis in Taï National Park, Côte d'Ivoire, indicates high rate of lethal infections in wildlife

Bacillus cereus biovar anthracis (Bcbva) is a member of the B. cereus group which carries both B. anthracis virulence plasmids, causes anthrax-like disease in various wildlife species and was described in several sub-Saharan African rainforests. Long-term monitoring of carcasses in Taï National Park, Côte d'Ivoire, revealed continuous wildlife mortality due to Bcbva in a broad range of mammalian species. While non-lethal anthrax infections in wildlife have been described for B. anthracis, nothing is known about the odds of survival following an anthrax infection caused by Bcbva. To address this gap, we present the results of a serological study of anthrax in five wildlife species known to succumb to Bcbva in this ecosystem. Specific antibodies were only detected in two out of 15 wild red colobus monkeys (Procolobus badius) and one out of 10 black-and-white colobus monkeys (Colobus polykomos), but in none of 16 sooty mangabeys (Cercocebus atys), 9 chimpanzees (Pan troglodytes verus) and 9 Maxwell's duikers (Cephalophus maxwellii). The combination of high mortality and low antibody detection rates indicates high virulence of this disease across these different mammalian species.

Structural and immunochemical relatedness suggests a conserved pathogenicity motif for secondary cell wall polysaccharides in Bacillus anthracis and infection-associated Bacillus cereus

Bacillus anthracis (Ba) and human infection-associated Bacillus cereus (Bc) strains Bc G9241 and Bc 03BB87 have secondary cell wall polysaccharides (SCWPs) comprising an aminoglycosyl trisaccharide repeat: →4)-β-d-ManpNAc-(1→4)-β-d-GlcpNAc-(1→6)-α-d-GlcpNAc-(1→, substituted at GlcNAc residues with both α- and β-Galp. In Bc G9241 and Bc 03BB87, an additional α-Galp is attached to O-3 of ManNAc. Using NMR spectroscopy, mass spectrometry and immunochemical methods, we compared these structures to SCWPs from Bc biovar anthracis strains isolated from great apes displaying “anthrax-like” symptoms in Cameroon (Bc CA) and Côte d’Ivoire (Bc CI). The SCWPs of Bc CA/CI contained the identical HexNAc trisaccharide backbone and Gal modifications found in Ba, together with the α-Gal-(1→3) substitution observed previously at ManNAc residues only in Bc G9241/03BB87. Interestingly, the great ape derived strains displayed a unique α-Gal-(1→3)-α-Gal-(1→3) disaccharide substitution at some ManNAc residues, a modification not found in any previously examined Ba or Bc strain. Immuno-analysis with specific polyclonal anti-Ba SCWP antiserum demonstrated a reactivity hierarchy: high reactivity with SCWPs from Ba 7702 and Ba Sterne 34F2, and Bc G9241 and Bc 03BB87; intermediate reactivity with SCWPs from Bc CI/CA; and low reactivity with the SCWPs from structurally distinct Ba CDC684 (a unique strain producing an SCWP lacking all Gal substitutions) and non-infection-associated Bc ATCC10987 and Bc 14579 SCWPs. Ba-specific monoclonal antibody EAII-6G6-2-3 demonstrated a 10–20 fold reduced reactivity to Bc G9241 and Bc 03BB87 SCWPs compared to Ba 7702/34F2, and low/undetectable reactivity to SCWPs from Bc CI, Bc CA, Ba CDC684, and non-infection-associated Bc strains. Our data indicate that the HexNAc motif is conserved among infection-associated Ba and Bc isolates (regardless of human or great ape origin), and that the number, positions and structures of Gal substitutions confer unique antigenic properties. The conservation of this structural motif could open a new diagnostic route in detection of pathogenic Bc strains.

Draft Genome Sequence of Bacillus cereus LA2007, a Human-Pathogenic Isolate Harboring Anthrax-Like Plasmids

We present the genome sequence of Bacillus cereus LA2007, a strain isolated in 2007 from a fatal pneumonia case in Louisiana. Sequence-based genome analysis revealed that LA2007 carries a plasmid highly similar to Bacillus anthracis pXO1, including the genes responsible for the production and regulation of anthrax toxin.

Bacillus cereus Biovar Anthracis Causing Anthrax in Sub-Saharan Africa-Chromosomal Monophyly and Broad Geographic Distribution

Through full genome analyses of four atypical Bacillus cereus isolates, designated B. cereus biovar anthracis, we describe a distinct clade within the B. cereus group that presents with anthrax-like disease, carrying virulence plasmids similar to those of classic Bacillus anthracis. We have isolated members of this clade from different mammals (wild chimpanzees, gorillas, an elephant and goats) in West and Central Africa (Côte d'Ivoire, Cameroon, Central African Republic and Democratic Republic of Congo). The isolates shared several phenotypic features of both B. anthracis and B. cereus, but differed amongst each other in motility and their resistance or sensitivity to penicillin. They all possessed the same mutation in the regulator gene plcR, different from the one found in B. anthracis, and in addition, carry genes which enable them to produce a second capsule composed of hyaluronic acid. Our findings show the existence of a discrete clade of the B. cereus group capable of causing anthrax-like disease, found in areas of high biodiversity, which are possibly also the origin of the worldwide distributed B. anthracis. Establishing the impact of these pathogenic bacteria on threatened wildlife species will require systematic investigation. Furthermore, the consumption of wildlife found dead by the local population and presence in a domestic animal reveal potential sources of exposure to humans.

The roles of AtxA orthologs in virulence of anthrax-like Bacillus cereus G9241

AtxA is a critical transcriptional regulator of plasmid-encoded virulence genes in Bacillus anthracis. Bacillus cereus G9241, which caused an anthrax-like infection, has two virulence plasmids, pBCXO1 and pBC210, that each harbor toxin genes and a capsule locus. G9241 also produces two orthologs of AtxA: AtxA1, encoded on pBCXO1, and AtxA2, encoded on pBC210. The amino acid sequence of AtxA1 is identical to that of AtxA from B. anthracis, while the sequences of AtxA1 and AtxA2 are 79% identical and 91% similar to one another. We found by qRT-PCR that AtxA1 and AtxA2 function as positive regulators of toxin (AtxA1) and capsule operon (both) transcription in G9241 and that a ΔatxA1 mutant produced lower levels of the anthrax toxins and no hyaluronic acid capsule. Deletion of atxA1 or atxA2 decreased the virulence of spores administered intranasally or subcutaneously to C57BL/6 mice but not to A/J mice, and deletion of both genes rendered spores avirulent in A/J mice. In addition, unlike AtxA1, AtxA2 did not form stable homomultimers in vitro, although AtxA1 and AtxA2 formed heterodimers. Our data show that AtxA1 is the primary regulator of G9241 virulence factor expression and that AtxA1 and AtxA2 are both required for full virulence.

Discovery of a Unique Extracellular Polysaccharide in Members of the Pathogenic Bacillus That Can Co-form with Spores

An exopolysaccharide, produced during the late stage of stationary growth phase, was discovered and purified from the culture medium of Bacillus cereus, Bacillus anthracis, and Bacillus thuringiensis when strains were grown in a defined nutrient medium that induces biofilm. Two-dimensional NMR structural characterization of the polysaccharide, named pzX, revealed that it is composed of an unusual three amino-sugar sequence repeat of [-3)XylNAc4OAc(α1-3)GlcNAcA4OAc(α1-3)XylNAc(α1-]n The sugar residue XylNAc had never been described previously in any glycan structure. The XNAC operon that contains the genes for the assembly of pzX is also unique and so far has been identified only in members of the Bacillus cereus sensu lato group. Microscopic and biochemical analyses indicate that pzX co-forms during sporulation, so that upon the release of the spore to the extracellular milieu it becomes surrounded by pzX. The relative amounts of pzX produced can be manipulated by specific nutrients in the medium, but rich medium appears to suppress pzX formation. pzX has the following unique characteristics: a surfactant property that lowers surface tension, a cell/spore antiaggregant, and an adherence property that increases spores binding to surfaces. pzX in Bacillus could represent a trait shared by many spore-producing microorganisms. It suggests pzX is an active player in spore physiology and may provide new insights to the successful survival of the B. cereus species in natural environments or in the hosts.