Toxins

Editorial

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3 pages, 226 KiB

Open AccessEditorial

Bacillus cereus Toxins

by Erwin Märtlbauer and Per Einar Granum

Toxins 2021, 13(5), 295; https://doi.org/10.3390/toxins13050295 - 21 Apr 2021

Cited by 9 | Viewed by 2812

Abstract

Bacillus cereus sensu stricto is an important pathogen causing food poisoning, as well as extraintestinal diseases [...] Full article

(This article belongs to the Special Issue Bacillus cereus Toxins)

Research

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13 pages, 30772 KiB

Open AccessArticle

The Crystal Structure of Bacillus cereus HblL₁

by Harley L. Worthy, Lainey J. Williamson, Husam Sabah Auhim, Stephen H. Leppla, Inka Sastalla, D. Dafydd Jones, Pierre J. Rizkallah and Colin Berry

Toxins 2021, 13(4), 253; https://doi.org/10.3390/toxins13040253 - 31 Mar 2021

Cited by 7 | Viewed by 3969

Abstract

The Hbl toxin is a three-component haemolytic complex produced by Bacillus cereus sensu lato strains and implicated as a cause of diarrhoea in B. cereus food poisoning. While the structure of the HblB component of this toxin is known, the structures of the [...] Read more.

The Hbl toxin is a three-component haemolytic complex produced by Bacillus cereus sensu lato strains and implicated as a cause of diarrhoea in B. cereus food poisoning. While the structure of the HblB component of this toxin is known, the structures of the other components are unresolved. Here, we describe the expression of the recombinant HblL₁ component and the elucidation of its structure to 1.36 Å. Like HblB, it is a member of the alpha-helical pore-forming toxin family. In comparison to other members of this group, it has an extended hydrophobic beta tongue region that may be involved in pore formation. Molecular docking was used to predict possible interactions between HblL₁ and HblB, and suggests a head to tail dimer might form, burying the HblL₁ beta tongue region. Full article

(This article belongs to the Special Issue Bacillus cereus Toxins)

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10 pages, 1710 KiB

Open AccessArticle

Enterotoxin Gene Distribution and Genotypes of Bacillus cereus sensu lato Isolated from Cassava Starch

by Jennifer Sánchez-Chica, Margarita M. Correa, Angel E. Aceves-Diez and Laura M. Castañeda-Sandoval

Toxins 2021, 13(2), 131; https://doi.org/10.3390/toxins13020131 - 10 Feb 2021

Cited by 6 | Viewed by 2612

Abstract

Bacillus cereus is a human pathogenic bacterium found in foods with the potential to cause emesis and diarrhea. This study estimated the presence, toxigenic and genomic diversity of B. cereus s.l. obtained from cassava starch samples collected in bakeries and powdered food companies [...] Read more.

Bacillus cereus is a human pathogenic bacterium found in foods with the potential to cause emesis and diarrhea. This study estimated the presence, toxigenic and genomic diversity of B. cereus s.l. obtained from cassava starch samples collected in bakeries and powdered food companies in Medellín (Colombia). Bacillus cereuss.l. was found in 43 of 75 (57%) cassava starch samples and 98 isolates were obtained. The nheABC, hblCDAB, cytK2, entFM and cesB toxin genes were detected by multiplex PCR and the most frequent operon was nheABC, whereas cesB gene was not found. Twelve toxigenic profiles were determined by the detection of toxin genes, and the most frequent profiles harbored all enterotoxin genes. A broad genomic diversity was detected according to GTG₅-PCR fingerprinting results with 76 B. cereus s.l. grouped in sixteen clusters and the 22 isolates clustering separately. No relationship was observed between genomic background and toxigenic profiles. In general, the results showed a high genomic and enterotoxigenic diversity in B. cereus s.l. found in cassava starch. These results should incentive future studies to understand the distribution of B. cereus s.l. isolated on raw materials in comparison with finished products. Full article

(This article belongs to the Special Issue Bacillus cereus Toxins)

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14 pages, 2507 KiB

Open AccessCommunication

Detection and Isolation of Emetic Bacillus cereus Toxin Cereulide by Reversed Phase Chromatography

by Eva Maria Kalbhenn, Tobias Bauer, Timo D. Stark, Mandy Knüpfer, Gregor Grass and Monika Ehling-Schulz

Toxins 2021, 13(2), 115; https://doi.org/10.3390/toxins13020115 - 4 Feb 2021

Cited by 4 | Viewed by 4003

Abstract

The emetic toxin cereulide is a 1.2 kDa dodecadepsipeptide produced by the food pathogen Bacillus cereus. As cereulide poses a serious health risk to humans, sensitive and specific detection, as well as toxin purification and quantification, methods are of utmost importance. Recently, [...] Read more.

The emetic toxin cereulide is a 1.2 kDa dodecadepsipeptide produced by the food pathogen Bacillus cereus. As cereulide poses a serious health risk to humans, sensitive and specific detection, as well as toxin purification and quantification, methods are of utmost importance. Recently, a stable isotope dilution assay tandem mass spectrometry (SIDA–MS/MS)-based method has been described, and an method for the quantitation of cereulide in foods was established by the International Organization for Standardization (ISO). However, although this SIDA–MS/MS method is highly accurate, the sophisticated high-end MS equipment required for such measurements limits the method’s suitability for microbiological and molecular research. Thus, we aimed to develop a method for cereulide toxin detection and isolation using equipment commonly available in microbiological and biochemical research laboratories. Reproducible detection and relative quantification of cereulide was achieved, employing reversed phase chromatography (RPC). Chromatographic signals were cross validated by ultraperformance liquid chromatography–mass spectrometry (UPLC–MS/MS). The specificity of the RPC method was tested using a test panel of strains that included non-emetic representatives of the B. cereus group, emetic B. cereus strains, and cereulide-deficient isogenic mutants. In summary, the new method represents a robust, economical, and easily accessible research tool that complements existing diagnostics for the detection and quantification of cereulide. Full article

(This article belongs to the Special Issue Bacillus cereus Toxins)

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21 pages, 2773 KiB

Open AccessArticle

Characteristics of the Protein Complexes and Pores Formed by Bacillus cereus Hemolysin BL

by Nadja Jessberger, Richard Dietrich, Kristina Schauer, Stefanie Schwemmer, Erwin Märtlbauer and Roland Benz

Toxins 2020, 12(11), 672; https://doi.org/10.3390/toxins12110672 - 24 Oct 2020

Cited by 10 | Viewed by 2888

Abstract

Bacillus cereus Hemolysin BL is a tripartite toxin responsible for a diarrheal type of food poisoning. Open questions remain regarding its mode of action, including the extent to which complex formation prior to cell binding contributes to pore-forming activity, how these complexes are [...] Read more.

Bacillus cereus Hemolysin BL is a tripartite toxin responsible for a diarrheal type of food poisoning. Open questions remain regarding its mode of action, including the extent to which complex formation prior to cell binding contributes to pore-forming activity, how these complexes are composed, and the properties of the pores formed in the target cell membrane. Distinct complexes of up to 600 kDa were found on native gels, whose structure and size were primarily defined by Hbl B. Hbl L1 and L2 were also identified in these complexes using Western blotting and an LC-MS approach. LC-MS also revealed that many other proteins secreted by B. cereus exist in complexes. Further, a decrease of toxic activity at temperatures ≥60 °C was shown, which was unexpectedly restored at higher temperatures. This could be attributed to a release of Hbl B monomers from tight complexation, resulting in enhanced cell binding. In contrast, Hbl L1 was rather susceptible to heat, while heat treatment of Hbl L2 seemed not to be crucial. Furthermore, Hbl-induced pores had a rather small single-channel conductance of around 200 pS and a probable channel diameter of at least 1 nm on planar lipid bilayers. These were highly instable and had a limited lifetime, and were also slightly cation-selective. Altogether, this study provides astonishing new insights into the complex mechanism of Hbl pore formation, as well as the properties of the pores. Full article

(This article belongs to the Special Issue Bacillus cereus Toxins)

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28 pages, 8708 KiB

Open AccessArticle

Structural Modeling of Cell Wall Peptidase CwpFM (EntFM) Reveals Distinct Intrinsically Disordered Extensions Specific to Pathogenic Bacillus cereus Strains

by Seav-Ly Tran, Delphine Cormontagne, Jasmina Vidic, Gwenaëlle André-Leroux and Nalini Ramarao

Toxins 2020, 12(9), 593; https://doi.org/10.3390/toxins12090593 - 14 Sep 2020

Cited by 10 | Viewed by 3345

Abstract

The emergence of B. cereus as an opportunistic food-borne pathogen has intensified the need to distinguish strains of public health concern. The heterogeneity of the diseases associated with B. cereus infections emphasizes the versatility of these bacteria strains to colonize their host. Nevertheless, [...] Read more.

The emergence of B. cereus as an opportunistic food-borne pathogen has intensified the need to distinguish strains of public health concern. The heterogeneity of the diseases associated with B. cereus infections emphasizes the versatility of these bacteria strains to colonize their host. Nevertheless, the molecular basis of these differences remains unclear. Several toxins are involved in virulence, particularly in gastrointestinal disorders, but there are currently no biological markers able to differentiate pathogenic from harmless strains. We have previously shown that CwpFM is a cell wall peptidase involved in B. cereus virulence. Here, we report a sequence/structure/function characterization of 39 CwpFM sequences, chosen from a collection of B. cereus with diverse virulence phenotypes, from harmless to highly pathogenic strains. CwpFM is homology-modeled in silico as an exported papain-like endopeptidase, with an N-terminal end composed of three successive bacterial Src Homology 3 domains (SH3b_1–3) likely to control protein–protein interactions in signaling pathways, and a C-terminal end that contains a catalytic NLPC_P60 domain primed to form a competent active site. We confirmed in vitro that CwpFM is an endopeptidase with a moderate peptidoglycan hydrolase activity. Remarkably, CwpFMs from pathogenic strains harbor a specific stretch of twenty residues intrinsically disordered, inserted between the SH3b₃ and the catalytic NLPC_P60 domain. This strongly suggests this linker as a marker of differentiation between B. cereus strains. We believe that our findings improve our understanding of the pathogenicity of B. cereus while advancing both clinical diagnosis and food safety. Full article

(This article belongs to the Special Issue Bacillus cereus Toxins)

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Review

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26 pages, 2248 KiB

Open AccessReview

Bacillus cereus Induces Severe Infections in Preterm Neonates: Implication at the Hospital and Human Milk Bank Level

by Delphine Cormontagne, Virginie Rigourd, Jasmina Vidic, Francesco Rizzotto, Emmanuelle Bille and Nalini Ramarao

Toxins 2021, 13(2), 123; https://doi.org/10.3390/toxins13020123 - 7 Feb 2021

Cited by 34 | Viewed by 4862

Abstract

Human breast milk (HBM) is a source of essential nutrients for infants and is particularly recommended for preterm neonates when their own mother’s milk is not available. It provides protection against infections and decreases necrotizing enterocolitis and cardiovascular diseases. Nevertheless, HBM spoilage can [...] Read more.

Human breast milk (HBM) is a source of essential nutrients for infants and is particularly recommended for preterm neonates when their own mother’s milk is not available. It provides protection against infections and decreases necrotizing enterocolitis and cardiovascular diseases. Nevertheless, HBM spoilage can occur due to contamination by pathogens, and the risk of a shortage of HBM is very often present. B. cereus is the most frequent ubiquitous bacteria responsible for HBM being discarded. It can contaminate HBM at all stages, from its collect point to the storage and delivery. B. cereus can induce severe infection in newborns with very low birth weight, with sometimes fatal outcomes. Although the source of contamination is rarely identified, in some cases, HBM was suspected as a potential source. Even if the risk is low, as infection due to B. cereus in preterm infants should not be overlooked, human milk banks follow strict procedures to avoid contamination, to accurately identify remaining bacteria following pasteurization and to discard non-compliant milk samples. In this review, we present a literature overview of B. cereus infections reported in neonates and the suspected sources of contamination. We highlight the procedures followed by the human milk banks from the collection of the milk to its microbiological characterization in Europe. We also present improved detection and decontamination methods that might help to decrease the risk and to preserve the public’s confidence in this vital biological product for infants whose mothers cannot breastfeed. Full article

(This article belongs to the Special Issue Bacillus cereus Toxins)

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48 pages, 3370 KiB

Open AccessEditor’s ChoiceReview

The Food Poisoning Toxins of Bacillus cereus

by Richard Dietrich, Nadja Jessberger, Monika Ehling-Schulz, Erwin Märtlbauer and Per Einar Granum

Toxins 2021, 13(2), 98; https://doi.org/10.3390/toxins13020098 - 28 Jan 2021

Cited by 158 | Viewed by 22779

Abstract

Bacillus cereus is a ubiquitous soil bacterium responsible for two types of food-associated gastrointestinal diseases. While the emetic type, a food intoxication, manifests in nausea and vomiting, food infections with enteropathogenic strains cause diarrhea and abdominal pain. Causative toxins are the cyclic dodecadepsipeptide [...] Read more.

Bacillus cereus is a ubiquitous soil bacterium responsible for two types of food-associated gastrointestinal diseases. While the emetic type, a food intoxication, manifests in nausea and vomiting, food infections with enteropathogenic strains cause diarrhea and abdominal pain. Causative toxins are the cyclic dodecadepsipeptide cereulide, and the proteinaceous enterotoxins hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe) and cytotoxin K (CytK), respectively. This review covers the current knowledge on distribution and genetic organization of the toxin genes, as well as mechanisms of enterotoxin gene regulation and toxin secretion. In this context, the exceptionally high variability of toxin production between single strains is highlighted. In addition, the mode of action of the pore-forming enterotoxins and their effect on target cells is described in detail. The main focus of this review are the two tripartite enterotoxin complexes Hbl and Nhe, but the latest findings on cereulide and CytK are also presented, as well as methods for toxin detection, and the contribution of further putative virulence factors to the diarrheal disease. Full article

(This article belongs to the Special Issue Bacillus cereus Toxins)

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37 pages, 652 KiB

Open AccessEditor’s ChoiceReview

The Bacillus cereus Food Infection as Multifactorial Process

by Nadja Jessberger, Richard Dietrich, Per Einar Granum and Erwin Märtlbauer

Toxins 2020, 12(11), 701; https://doi.org/10.3390/toxins12110701 - 5 Nov 2020

Cited by 108 | Viewed by 18856

Abstract

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, [...] Read more.

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. Full article

(This article belongs to the Special Issue Bacillus cereus Toxins)

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18 pages, 2102 KiB

Open AccessEditor’s ChoiceReview

Characterization of Bacillus cereus in Dairy Products in China

by Xiao-Ye Liu, Qiao Hu, Fei Xu, Shuang-Yang Ding and Kui Zhu

Toxins 2020, 12(7), 454; https://doi.org/10.3390/toxins12070454 - 14 Jul 2020

Cited by 53 | Viewed by 11167

Abstract

Bacillus cereus is a common and ubiquitous foodborne pathogen with an increasing prevalence rate in dairy products in China. High and unmet demands for such products, particularly milk, raise the risk of B. cereus associated contamination. The presence of B. cereus and its [...] Read more.

Bacillus cereus is a common and ubiquitous foodborne pathogen with an increasing prevalence rate in dairy products in China. High and unmet demands for such products, particularly milk, raise the risk of B. cereus associated contamination. The presence of B. cereus and its virulence factors in dairy products may cause food poisoning and other illnesses. Thus, this review first summarizes the epidemiological characteristics and analytical assays of B. cereus from dairy products in China, providing insights into the implementation of intervention strategies. In addition, the recent achievements on the cytotoxicity and mechanisms of B. cereus are also presented to shed light on the therapeutic options for B. cereus associated infections. Full article

(This article belongs to the Special Issue Bacillus cereus Toxins)

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