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Tamura H. Bacterial Pesticides: Mechanism of Action, Possibility of Food Contamination, and Residue Analysis Using MS. JOURNAL OF PESTICIDE SCIENCE 2024; 49:135-147. [PMID: 39398503 PMCID: PMC11464265 DOI: 10.1584/jpestics.d24-006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 06/02/2024] [Indexed: 10/15/2024]
Abstract
As Sustainable Development Goals (SDGs) and the realities of climate change become widely accepted around the world, the next-generation of integrated pest management will become even more important for establishing a sustainable food production system. To meet the current challenge of food security and climate change, biological control has been developed as one sustainable crop protection technology. However, most registered bacteria are ubiquitous soil-borne bacteria that are closely related to food poisoning and spoilage bacteria. Therefore, this review outlined (1) the mechanism of action of bacterial pesticides, (2) potential concerns about secondary contamination sources associated with past food contamination, and, as a prospective solution, focused on (3) principles and methods of bacterial identification, and (4) the possibility of identifying residual bacteria based on mass spectrometry.
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Koike H, Kanda M, Monma C, Yoshikawa S, Hayashi H, Matsushima Y, Ohba Y, Hayashi M, Furuta N, Okada W, Nagano C, Yokoyama K, Yokoyama T, Sasamoto T. Development of a simple screening method for analyzing cereulide toxin in fried rice using liquid chromatography-tandem mass spectrometry. Forensic Toxicol 2024; 42:163-171. [PMID: 38519777 PMCID: PMC11269499 DOI: 10.1007/s11419-024-00683-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 02/08/2024] [Indexed: 03/25/2024]
Abstract
PURPOSE The presence of cereulide, an emetic toxin produced by Bacillus cereus, in fried rice samples is critical evidence of food poisoning even in situations where B. cereus could not be detected. This study aims to develop a screening method for analyzing cereulide in fried rice using the QuEChERS procedure and liquid chromatography-tandem mass spectrometry (LC-MS/MS). METHODS Cereulide was identified and quantified in fried rice samples using the QuEChERS extraction method and LC-MS/MS. The accuracies of the methods were determined by analyzing fortified blank samples at two concentrations (10 and 50 µg/kg) conducted on three samples daily for five days. RESULTS The QuEChERS procedure removed matrix compounds from fried rice. Characteristic MS/MS spectra enabled the identification of cereulide. As the matrix effects in seven fried rice samples were within ± 6%, an external solvent calibration curve could be used for quantification. This method exhibited good accuracy ranging from 88 to 89%. The relative standard deviations for both repeatability and intra-laboratory reproducibility were < 4%. These standard deviations satisfied the criteria of the Japanese validation guidelines for residues (MHLW 2010, Director Notice, Syoku-An No. 1224-1). The limit of quantification was 2 μg/kg. The applicability of this method was confirmed using the analysis of cereulide in fried rice samples incubated with emetic Bacillus cereus. CONCLUSIONS The QuEChERS extraction procedure described herein showed substantial promise as a reliable screening tool for cereulide in fried rice sample.
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Affiliation(s)
- Hiroshi Koike
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health, Tokyo, Japan.
| | - Maki Kanda
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health, Tokyo, Japan
| | - Chie Monma
- Department of Microbiology, Tokyo Metropolitan Institute of Public Health, 3-24-1, Hyakunin-Cho, Shinjuku-Ku, Tokyo, 169-0073, Japan
| | - Souichi Yoshikawa
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health, Tokyo, Japan
| | - Hiroshi Hayashi
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health, Tokyo, Japan
| | - Yoko Matsushima
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health, Tokyo, Japan
| | - Yumi Ohba
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health, Tokyo, Japan
| | - Momoka Hayashi
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health, Tokyo, Japan
| | - Natsumi Furuta
- Department of Microbiology, Tokyo Metropolitan Institute of Public Health, 3-24-1, Hyakunin-Cho, Shinjuku-Ku, Tokyo, 169-0073, Japan
| | - Wakaba Okada
- Department of Microbiology, Tokyo Metropolitan Institute of Public Health, 3-24-1, Hyakunin-Cho, Shinjuku-Ku, Tokyo, 169-0073, Japan
| | - Chieko Nagano
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health, Tokyo, Japan
| | - Keiko Yokoyama
- Department of Microbiology, Tokyo Metropolitan Institute of Public Health, 3-24-1, Hyakunin-Cho, Shinjuku-Ku, Tokyo, 169-0073, Japan
| | - Tomoko Yokoyama
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health, Tokyo, Japan
| | - Takeo Sasamoto
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health, Tokyo, Japan
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Masquelier J, Segers C, Jacobs B, Van Nieuwenhuysen T, Delbrassinne L, Van Hoeck E. Validation of a Targeted LC-MS/MS Method for Cereulide and Application in Food and Faeces. Toxins (Basel) 2023; 16:13. [PMID: 38251230 PMCID: PMC10819378 DOI: 10.3390/toxins16010013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 12/11/2023] [Accepted: 12/21/2023] [Indexed: 01/23/2024] Open
Abstract
Cereulide is an emetic toxin produced by some strains of Bacillus cereus. This bacterial toxin, a cyclic 1.2 kDa dodecadepsipeptide, is stable to heat and acids and causes nausea and vomiting when ingested via contaminated food. This work aimed to develop and validate a targeted analytical method applying liquid chromatography-tandem mass spectrometry (LC-MS/MS) to quantify this toxin in food and human faeces. Samples were extracted with acetonitrile in the presence of 13C6-cereulide, a labelled internal standard, and purified by centrifugation and filtration. The limits of quantification were 0.5 and 0.3 µg kg-1 for food and faeces, respectively. The linearity of the method was very good, with calculated R2 values above 0.995. The mean recovery of the method was within the acceptable range of 70.0%-120.0%, the repeatability was not higher than 7.3%, and the highest intra-laboratory reproducibility was 8.9%. The estimated range for the expanded measurement uncertainty was between 5.1% and 18.0%. The LC-MS/MS method was used to analyse one food sample (rice) from a Belgian foodborne outbreak and five faecal samples from patients with clinical symptoms after consumption of the contaminated rice. The levels of cereulide were 12.22 µg g-1 for food and between 6.32 and 773.37 ng g-1 for faecal samples.
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Affiliation(s)
- Julien Masquelier
- Organic Contaminants and Additives, Sciensano, Scientific Institute of Public Health, 1050 Brussels, Belgium
| | - Céline Segers
- Organic Contaminants and Additives, Sciensano, Scientific Institute of Public Health, 1050 Brussels, Belgium
| | - Bram Jacobs
- Food Pathogens, Sciensano, Scientific Institute of Public Health, 1050 Brussels, Belgium
| | - Tom Van Nieuwenhuysen
- Food Pathogens, Sciensano, Scientific Institute of Public Health, 1050 Brussels, Belgium
| | - Laurence Delbrassinne
- Food Pathogens, Sciensano, Scientific Institute of Public Health, 1050 Brussels, Belgium
| | - Els Van Hoeck
- Organic Contaminants and Additives, Sciensano, Scientific Institute of Public Health, 1050 Brussels, Belgium
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Abdelli M, Falaise C, Morineaux-Hilaire V, Cumont A, Taysse L, Raynaud F, Ramisse V. Get to Know Your Neighbors: Characterization of Close Bacillus anthracis Isolates and Toxin Profile Diversity in the Bacillus cereus Group. Microorganisms 2023; 11:2721. [PMID: 38004733 PMCID: PMC10673079 DOI: 10.3390/microorganisms11112721] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Revised: 10/27/2023] [Accepted: 11/06/2023] [Indexed: 11/26/2023] Open
Abstract
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.
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Affiliation(s)
- Mehdi Abdelli
- DGA CBRN Defence Center, Biology Division, French Ministry of the Armed Forces, 91710 Vert-le-Petit, France; (M.A.); (V.M.-H.); (A.C.); (L.T.); (F.R.)
- Institute for Integrative Biology of the Cell (I2BC), CNRS, Université Paris-Saclay, 91190 Gif-sur-Yvette, France
| | - Charlotte Falaise
- DGA CBRN Defence Center, Biology Division, French Ministry of the Armed Forces, 91710 Vert-le-Petit, France; (M.A.); (V.M.-H.); (A.C.); (L.T.); (F.R.)
| | - Valérie Morineaux-Hilaire
- DGA CBRN Defence Center, Biology Division, French Ministry of the Armed Forces, 91710 Vert-le-Petit, France; (M.A.); (V.M.-H.); (A.C.); (L.T.); (F.R.)
| | - Amélie Cumont
- DGA CBRN Defence Center, Biology Division, French Ministry of the Armed Forces, 91710 Vert-le-Petit, France; (M.A.); (V.M.-H.); (A.C.); (L.T.); (F.R.)
| | - Laurent Taysse
- DGA CBRN Defence Center, Biology Division, French Ministry of the Armed Forces, 91710 Vert-le-Petit, France; (M.A.); (V.M.-H.); (A.C.); (L.T.); (F.R.)
| | - Françoise Raynaud
- DGA CBRN Defence Center, Biology Division, French Ministry of the Armed Forces, 91710 Vert-le-Petit, France; (M.A.); (V.M.-H.); (A.C.); (L.T.); (F.R.)
| | - Vincent Ramisse
- DGA CBRN Defence Center, Biology Division, French Ministry of the Armed Forces, 91710 Vert-le-Petit, France; (M.A.); (V.M.-H.); (A.C.); (L.T.); (F.R.)
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Takahashi N, Nagai S, Tomimatsu Y, Saito A, Kaneta N, Tsujimoto Y, Tamura H. Simultaneous Discrimination of Cereulide-Producing Bacillus cereus and Psychrotolerant B. cereus Group by Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry. J Food Prot 2022; 85:1192-1202. [PMID: 35687734 DOI: 10.4315/jfp-21-450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 06/01/2022] [Indexed: 11/11/2022]
Abstract
ABSTRACT Cereulide-producing Bacillus cereus, which causes foodborne illnesses with vomiting, and psychrotolerant B. cereus group strains such as Bacillus mycoides, which can grow at ≥7°C and cause spoilage of refrigerated foods, are significant concerns for the food industry. Rapid and simple methods to discriminate the cereulide-producing B. cereus and psychrotolerant B. cereus group strains from other B. cereus group strains are needed. We developed a novel, rapid, and simple method with matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) analysis for simultaneous discrimination of these two groups from other B. cereus group strains. A potassium adduct of cereulide was used to detect cereulide-producing B. cereus, and three ribosomal subunit proteins (L30, S16, and S20) were used to detect psychrotolerant B. cereus group. A total of 51 B. cereus group strains were analyzed by MALDI-TOF MS. The biomarkers allowed successful discrimination of 16 cereulide-producing B. cereus and 15 psychrotolerant B. cereus group strains from other B. cereus group strains. The results showed that this MALDI-TOF MS analysis allows simultaneous discrimination of cereulide-producing B. cereus and psychrotolerant B. cereus group strains from other B. cereus group strains. This efficient method has the potential to be a valuable tool for ensuring food safety. HIGHLIGHTS
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Affiliation(s)
- Naomi Takahashi
- Food Quality and Safety Research Laboratories, Meiji Co., Ltd., 1-29-1 Nanakuni, Hachioji, Tokyo, 192-0919, Japan
| | - Satomi Nagai
- Faculty of Agriculture, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya, Aichi 468-8502, Japan
| | - Yumiko Tomimatsu
- Food Quality and Safety Research Laboratories, Meiji Co., Ltd., 1-29-1 Nanakuni, Hachioji, Tokyo, 192-0919, Japan
| | - Ayumi Saito
- Food Quality and Safety Research Laboratories, Meiji Co., Ltd., 1-29-1 Nanakuni, Hachioji, Tokyo, 192-0919, Japan
| | - Naoko Kaneta
- Food Quality and Safety Research Laboratories, Meiji Co., Ltd., 1-29-1 Nanakuni, Hachioji, Tokyo, 192-0919, Japan
| | - Yoshinori Tsujimoto
- Food Quality and Safety Research Laboratories, Meiji Co., Ltd., 1-29-1 Nanakuni, Hachioji, Tokyo, 192-0919, Japan
| | - Hiroto Tamura
- Faculty of Agriculture, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya, Aichi 468-8502, Japan
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Detection of emetic Bacillus cereus and the emetic toxin cereulide in food matrices: Progress and perspectives. Trends Food Sci Technol 2022. [DOI: 10.1016/j.tifs.2022.03.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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7
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Wang L, Yang H, Wang K, Yang H, Zhao M, Shang Y, Wang F, Dong J, Zhao W, Li L, Liang W, Wang Y. A Visualized Isothermal Amplification Method for Rapid and Specific Detection of Emetic and Non-emetic Bacillus cereus in Dairy Products. Front Microbiol 2022; 13:802656. [PMID: 35418965 PMCID: PMC8996228 DOI: 10.3389/fmicb.2022.802656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 02/03/2022] [Indexed: 11/13/2022] Open
Abstract
Bacillus cereus is widely distributed in foods, especially dairy products, and can lead to diarrhea (non-emetic B. cereus) and emesis (emetic B. cereus). Although diarrhea due to B. cereus is usually mild, emesis can lead to acute encephalopathy and even death. To develop rapid and sensitive detection methods for B. cereus in foods, specific primers targeting the gyrase B (gyrB) and cereulide synthetase (ces) genes were designed and screened using recombinase polymerase amplification (RPA). Probes and base substitutions were introduced to improve specificity and eliminate primer-dependent artifacts. The 5' ends of the reverse primers and probes were modified with biotin and fluorescein isothiocyanate for detection of RPA products on a lateral flow strip (LFS). The developed RPA-LFS assay allows detection within 20 min at 37°C with no cross-reactivity with other foodborne pathogens. The limit of detection was 104 copies/ml and 102 CFU/ml in pure cultures and milk, respectively. Comparisons with established methods using cream obtained similar results. A specific, rapid, and sensitive RPA-LFS assay was successfully developed for on-site detection of B. cereus in dairy products to distinguish emetic from non-emetic strains.
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Affiliation(s)
- Lei Wang
- Department of Central Laboratory, Lianyungang Hospital Affiliated to Jiangsu University, Lianyungang, China.,School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, China
| | - Huansen Yang
- Lianyungang Center for Disease Control and Prevention, Lianyungang, China
| | - Kun Wang
- Department of Central Laboratory, Lianyungang Hospital Affiliated to Jiangsu University, Lianyungang, China
| | - Haitao Yang
- Jiangsu Key Laboratory of Marine Biological Resources and Environment, Jiangsu Key Laboratory of Marine Pharmaceutical Compound Screening, Co-Innovation Center of Jiangsu Marine Bio-industry Technology, Jiangsu Ocean University, Lianyungang, China
| | - Mengdi Zhao
- Department of Materials Science and Engineering, Suzhou University of Science and Technology, Suzhou, China
| | - Yuping Shang
- Department of Central Laboratory, Lianyungang Hospital Affiliated to Jiangsu University, Lianyungang, China
| | - Fang Wang
- Department of Central Laboratory, Lianyungang Hospital Affiliated to Jiangsu University, Lianyungang, China
| | - Jingquan Dong
- Jiangsu Key Laboratory of Marine Biological Resources and Environment, Jiangsu Key Laboratory of Marine Pharmaceutical Compound Screening, Co-Innovation Center of Jiangsu Marine Bio-industry Technology, Jiangsu Ocean University, Lianyungang, China
| | - Weiguo Zhao
- School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, China
| | - Li Li
- Lianyungang Center for Disease Control and Prevention, Lianyungang, China
| | - Wei Liang
- Laboratory Department of Ningbo First Hospital, Ningbo Hospital of Zhejiang University, Ningbo, China
| | - Yan Wang
- Department of Central Laboratory, Lianyungang Hospital Affiliated to Jiangsu University, Lianyungang, China
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Dorotíková K, Kameník J, Bogdanovičová K, Křepelová S, Strejček J, Haruštiaková D. Microbial contamination and occurrence of Bacillus cereus sensu lato, Staphylococcus aureus, and Escherichia coli on food handlers’ hands in mass catering: Comparison of the glove juice and swab methods. Food Control 2022. [DOI: 10.1016/j.foodcont.2021.108567] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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9
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Emetic toxin production of Bacillus cereus in a biofilm. Lebensm Wiss Technol 2022. [DOI: 10.1016/j.lwt.2021.112840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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10
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Aus der § 64 LFGB-Arbeitsgruppe MALDI-TOF: Leitlinien für die Validierung von Spezies-Identifizierungen mittels MALDI-TOF-MS. J Verbrauch Lebensm 2021. [DOI: 10.1007/s00003-021-01353-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
AbstractMatrix-assisted laser-desorption/ionization-time-of-flight-mass-spectrometry (MALDI-TOF-MS) is widely used to identify microorganisms. Recently, new applications such as identification of the animal species from meat, milk or fish are emerging. Standards for the validation of species identifications are still missing. Now, the § 64-LFGB working-group “MALDI-TOF”, established at the Federal Office of Consumer Protection and Food Safety, has compiled a guideline for the validation of species identifications. This guideline is intended for single laboratories as well as for lab networks and shows practical ways for validation of qualitative MALDI-TOF-MS methods. The special opportunities of the technology, in particular the use of extended reference databases and of collections of well-documented individual spectra for validation, have been taken into account in the guideline presented.
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Uehara S, Kobayashi M, Kimura K, Suzuki J, Sadamasu K. Rapid identification of histamine-producing bacteria isolated from fish using MALDI-TOF MS. JOURNAL OF FOOD SCIENCE AND TECHNOLOGY 2021; 58:4055-4061. [PMID: 34471328 PMCID: PMC8357883 DOI: 10.1007/s13197-021-05092-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Revised: 02/24/2021] [Accepted: 04/04/2021] [Indexed: 06/13/2023]
Abstract
Histamine-producing bacteria (HPB) produce histamine from histidine contained in food through the action of histidine decarboxylase. To identify HPB isolated from food, it is necessary to detect histamine produced by the bacteria. In this study, we concurrently identified HPB and detected histamine by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. After 24 h of incubation, 30 of 34 bacterial strains were correctly identified. Histamine was detected in all HPB cultured on Niven's medium, and 94% of HPB cultured in histidine broth, except for two strains with low histamine production. This method may greatly simplify the procedure and reduce the time required to identify HPB.
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Affiliation(s)
- Satomi Uehara
- Department of Microbiology, Tokyo Metropolitan Institute of Public Health, 3-24-1, Hyakunin-cho, Shinjuku-ku, Tokyo, 169-0073 Japan
| | - Makiko Kobayashi
- Department of Microbiology, Tokyo Metropolitan Institute of Public Health, 3-24-1, Hyakunin-cho, Shinjuku-ku, Tokyo, 169-0073 Japan
| | - Keisuke Kimura
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health, 3-24-1, Hyakunin-cho, Shinjuku-ku, Tokyo, 169-0073 Japan
| | - Jun Suzuki
- Department of Microbiology, Tokyo Metropolitan Institute of Public Health, 3-24-1, Hyakunin-cho, Shinjuku-ku, Tokyo, 169-0073 Japan
| | - Kenji Sadamasu
- Department of Microbiology, Tokyo Metropolitan Institute of Public Health, 3-24-1, Hyakunin-cho, Shinjuku-ku, Tokyo, 169-0073 Japan
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Jovanovic J, Ornelis VFM, Madder A, Rajkovic A. Bacillus cereus food intoxication and toxicoinfection. Compr Rev Food Sci Food Saf 2021; 20:3719-3761. [PMID: 34160120 DOI: 10.1111/1541-4337.12785] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 05/13/2021] [Accepted: 05/15/2021] [Indexed: 12/12/2022]
Abstract
Bacillus cereus is one of the leading etiological agents of toxin-induced foodborne diseases. Its omnipresence in different environments, spore formation, and its ability to adapt to varying conditions and produce harmful toxins make this pathogen a health hazard that should not be underestimated. Food poisoning by B. cereus can manifest itself as an emetic or diarrheal syndrome. The former is caused by the release of the potent peptide toxin cereulide, whereas the latter is the result of proteinaceous enterotoxins (e.g., hemolysin BL, nonhemolytic enterotoxin, and cytotoxin K). The final harmful effect is not only toxin and strain dependent, but is also affected by the stress responses, accessory virulence factors, and phenotypic properties under extrinsic, intrinsic, and explicit food conditions and host-related environment. Infamous portrait of B. cereus as a foodborne pathogen, as well as a causative agent of nongastrointestinal infections and even nosocomial complications, has inspired vast volumes of multidisciplinary research in food and clinical domains. As a result, extensive original data became available asking for a new, both broad and deep, multifaceted look into the current state-of-the art regarding the role of B. cereus in food safety. In this review, we first provide an overview of the latest knowledge on B. cereus toxins and accessory virulence factors. Second, we describe the novel taxonomy and some of the most pertinent phenotypic characteristics of B. cereus related to food safety. We link these aspects to toxin production, overall pathogenesis, and interactions with its human host. Then we reflect on the prevalence of different toxinotypes in foods opening the scene for epidemiological aspects of B. cereus foodborne diseases and methods available to prevent food poisoning including overview of the different available methods to detect B. cereus and its toxins.
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Affiliation(s)
- Jelena Jovanovic
- Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Vincent F M Ornelis
- Department of Organic and Macromolecular Chemistry, Faculty of Sciences, Ghent University, Ghent, Belgium
| | - Annemieke Madder
- Department of Organic and Macromolecular Chemistry, Faculty of Sciences, Ghent University, Ghent, Belgium
| | - Andreja Rajkovic
- Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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13
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Kalbhenn EM, Bauer T, Stark TD, Knüpfer M, Grass G, Ehling-Schulz M. Detection and Isolation of Emetic Bacillus cereus Toxin Cereulide by Reversed Phase Chromatography. Toxins (Basel) 2021; 13:toxins13020115. [PMID: 33557428 PMCID: PMC7915282 DOI: 10.3390/toxins13020115] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/30/2021] [Accepted: 02/01/2021] [Indexed: 12/17/2022] Open
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, 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.
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Affiliation(s)
- Eva Maria Kalbhenn
- Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, 1210 Vienna, Austria; (E.M.K.); (T.B.)
| | - Tobias Bauer
- Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, 1210 Vienna, Austria; (E.M.K.); (T.B.)
| | - Timo D. Stark
- Chair of Food Chemistry and Molecular Sensory Science, Technical University of Munich, Lise-Meitner-Straße 34, 85354 Freising, Germany;
| | - Mandy Knüpfer
- Bundeswehr Institute of Microbiology, Neuherbergstraße 11, 80937 Munich, Germany; (M.K.); (G.G.)
| | - Gregor Grass
- Bundeswehr Institute of Microbiology, Neuherbergstraße 11, 80937 Munich, Germany; (M.K.); (G.G.)
| | - Monika Ehling-Schulz
- Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, 1210 Vienna, Austria; (E.M.K.); (T.B.)
- Correspondence:
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The Food Poisoning Toxins of Bacillus cereus. Toxins (Basel) 2021; 13:toxins13020098. [PMID: 33525722 PMCID: PMC7911051 DOI: 10.3390/toxins13020098] [Citation(s) in RCA: 113] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/14/2021] [Accepted: 01/25/2021] [Indexed: 12/13/2022] Open
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 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.
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15
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Review on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for the rapid screening of microbial species: A promising bioanalytical tool. Microchem J 2020. [DOI: 10.1016/j.microc.2020.105387] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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16
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Doellinger J, Schneider A, Stark TD, Ehling-Schulz M, Lasch P. Evaluation of MALDI-ToF Mass Spectrometry for Rapid Detection of Cereulide From Bacillus cereus Cultures. Front Microbiol 2020; 11:511674. [PMID: 33329410 PMCID: PMC7709880 DOI: 10.3389/fmicb.2020.511674] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 09/16/2020] [Indexed: 12/20/2022] Open
Abstract
Bacillus cereus plays an often unrecognized role in food borne diseases. Food poisoning caused by this pathogen is manifested by either diarrhea or emesis. Due to the relatively high prevalence of emetic toxin cereulide associated food poisoning, methods for simple and reliable detection of cereulide producing strains are of utmost importance. Recently, two different studies reported on the application of MALDI-ToF MS for either the differentiation of emetic and non-emetic strains of B. cereus or for direct detection of cereulide from bacterial colony smears. However, for implementation of cereulide detection using MALDI-ToF MS in routine microbiological diagnostics additional investigations on the sensitivity and specificity as well as on the fitting into common workflows for bacterial identification are needed. These aspects prompted us to investigate open issues and to test sample preparation methods, commonly used for microbial identification for their suitability to detect the emetic toxin from bacteria. Based on our experimental findings we propose a workflow that allows identification of B. cereus and sensitive detection of cereulide in parallel, using linear-mode MALDI-ToF MS equipment. The protocol was validated in a blinded study and is based on the well-established ethanol/formic acid extraction method. Cereulide is detected in the ethanol wash solution of samples identified as B. cereus as peaks at m/z 1175 and 1191. Peak position difference of 16 Th (Thomson) indicates detection of the sodium and potassium adducts of cereulide. This sample treatment offers possibilities for further characterization by more sophisticated LC-MS-based methods. In summary, the ease of use and the achieved level of analytical sensitivity as well as the wide-spread availability of MALDI-ToF MS equipment in clinical microbiological laboratories provides a promising tool to improve and to facilitate routine diagnostics of B. cereus associated food intoxications.
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Affiliation(s)
- Joerg Doellinger
- Proteomics and Spectroscopy Unit (ZBS 6), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Andy Schneider
- Proteomics and Spectroscopy Unit (ZBS 6), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
| | - Timo D Stark
- Food Chemistry and Molecular Sensory Science, Technical University of Munich, Munich, Germany
| | - Monika Ehling-Schulz
- Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Peter Lasch
- Proteomics and Spectroscopy Unit (ZBS 6), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, Berlin, Germany
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Carroll LM, Cheng RA, Kovac J. No Assembly Required: Using BTyper3 to Assess the Congruency of a Proposed Taxonomic Framework for the Bacillus cereus Group With Historical Typing Methods. Front Microbiol 2020; 11:580691. [PMID: 33072050 PMCID: PMC7536271 DOI: 10.3389/fmicb.2020.580691] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 08/25/2020] [Indexed: 12/19/2022] Open
Abstract
The Bacillus cereus group, also known as B. cereus sensu lato (s.l.), is a species complex comprising numerous closely related lineages, which vary in their ability to cause illness in humans and animals. The classification of B. cereus s.l. isolates into species-level taxonomic units is essential for facilitating communication between and among microbiologists, clinicians, public health officials, and industry professionals, but is not always straightforward. A recently proposed genomospecies-subspecies-biovar taxonomic framework aims to provide a standardized nomenclature for this species complex but relies heavily on whole-genome sequencing (WGS). It thus is unclear whether popular, low-cost typing methods (e.g., single- and multi-locus sequence typing) remain congruent with the proposed taxonomy. Here, we characterize 2,231 B. cereus s.l. genomes using a combination of in silico (i) average-nucleotide identity (ANI)-based genomospecies assignment, (ii) ANI-based subspecies assignment, (iii) seven-gene multi-locus sequence typing (MLST), (iv) single-locus panC group assignment, (v) rpoB allelic typing, and (vi) virulence factor detection. We show that sequence types (STs) assigned using MLST can be used for genomospecies assignment, and we provide a comprehensive list of ST/genomospecies associations. For panC group assignment, we show that an adjusted, eight-group framework is largely, albeit not perfectly, congruent with the proposed eight-genomospecies taxonomy, as panC alone may not distinguish (i) B. luti from Group II B. mosaicus and (ii) B. paramycoides from Group VI B. mycoides. We additionally provide a list of loci that capture the topology of the whole-genome B. cereus s.l. phylogeny that may be used in future sequence typing efforts. For researchers with access to WGS, MLST, and/or panC data, we showcase how our recently released software, BTyper3 (https://github.com/lmc297/BTyper3), can be used to assign B. cereus s.l. isolates to taxonomic units within this proposed framework with little-to-no user intervention or domain-specific knowledge of B. cereus s.l. taxonomy. We additionally outline a novel method for assigning B. cereus s.l. genomes to pseudo-gene flow units within proposed genomospecies. The results presented here highlight the backward-compatibility and accessibility of the recently proposed genomospecies-subspecies-biovar taxonomic framework and illustrate that WGS is not a necessity for microbiologists who want to use the proposed nomenclature effectively.
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Affiliation(s)
- Laura M. Carroll
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Rachel A. Cheng
- Department of Food Science, College of Agriculture and Life Sciences, Cornell University, Ithaca, NY, United States
| | - Jasna Kovac
- Department of Food Science, College of Agricultural Sciences, The Pennsylvania State University, University Park, PA, United States
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18
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Identification and Pathogenic Potential of Bacillus cereus Strains Isolated from a Dairy Processing Plant Producing PDO Taleggio Cheese. Microorganisms 2020; 8:microorganisms8060949. [PMID: 32599708 PMCID: PMC7356821 DOI: 10.3390/microorganisms8060949] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 06/09/2020] [Accepted: 06/22/2020] [Indexed: 12/11/2022] Open
Abstract
Low levels of contamination by Bacillus cereus at the cheese farm is essential for reducing any opportunity for growth prior consumption. In this study, B. cereus distribution in a plant producing Protected Designation of Origin Taleggio cheese was investigated and the virulence potential of the isolates was evaluated. Seventy-four samples were collected from Food and Non Food Contact Surfaces (FCS, NFCS), saline curd, and Taleggio. The eleven isolates were identified, typified, and clustered. Strains were tested for the production of hemolysins, hemolysin BL (HBL), phosphatidylcholine-specific phospholipase C (PC-PLC), proteases, and biofilm, and for the presence of chromosomal toxin-encoding genes (sph, plcA, cytK, entFM, bcet, entS, nheA, nheB, nheC). B. cereus was detected on NFCS, FCS, and curd, but not in Taleggio. The isolates were grouped into six clusters, and all produced PC-PLC, hemolysins, and proteases, and most of them HBL (66.7%). All the clusters harbored the nheA, sph, plcA, entFM, and cytK genes, and some also nheB (83.3%), nheC (66.7%), bcet (50.0%), and entS (66.7%). All strains showed biofilm-forming ability. Our data reveal possible contamination of production plants and cheese curd by potentially virulent B. cereus, but bacterial absence in Taleggio highlights the efficacy of a proper management of the production phases in assuring consumer's protection.
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Takahashi N, Nagai S, Fujita A, Ido Y, Kato K, Saito A, Moriya Y, Tomimatsu Y, Kaneta N, Tsujimoto Y, Tamura H. Discrimination of psychrotolerant Bacillus cereus group based on MALDI-TOF MS analysis of ribosomal subunit proteins. Food Microbiol 2020; 91:103542. [PMID: 32539947 DOI: 10.1016/j.fm.2020.103542] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/28/2020] [Accepted: 05/03/2020] [Indexed: 02/06/2023]
Abstract
Psychrotolerant species of the Bacillus cereus group, Bacillus mycoides and Bacillus weihenstephanensis, can grow at ≥ 7 °C and are significant concerns for the food industry due to their ability to cause spoilage of refrigerated food. In addition to that, some strains of B. weihenstephanensis can produce emetic toxin, namely cereulide, which is known to cause vomiting. Therefore, rapid and simple methods to discriminate psychrotolerant B. cereus group species are crucial. Here, matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) and the S10-spc-alpha operon gene encoded ribosomal protein mass spectrum (S10-GERMS) method were used to discriminate psychrotolerant species of the B. cereus group based on a set of four ribosomal subunit proteins (S10, S16, S20 and L30). A total of 36 strains of B. cereus group were cultured on LB agar, and analyzed by MALDI-TOF MS. The four biomarkers successfully discriminated 12 strains of psychrotolerant species from mesophilic species of the B. cereus group. Furthermore, the four biomarkers also classified some Bacillus thuringiensis strains. MALDI-TOF MS analysis using the S10-GERMS method allowed simple and rapid discrimination of psychrotolerant species of the B. cereus group from other mesophilic species. This method has a possibility to enable manufacturers and distributors of refrigerated foods to control psychrotolerant species of the B. cereus group effectively.
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Affiliation(s)
- Naomi Takahashi
- Food Quality and Safety Research Laboratories, Meiji Co., Ltd., 1-29-1, Nanakuni, Hachiouji, Tokyo, 192-0919, Japan.
| | - Satomi Nagai
- Faculty of Agriculture, Meijo University, 1-501, Shiogamaguchi, Tempaku-ku, Nagoya, Aichi, 468-8502, Japan
| | - Akane Fujita
- Faculty of Agriculture, Meijo University, 1-501, Shiogamaguchi, Tempaku-ku, Nagoya, Aichi, 468-8502, Japan
| | - Yousuke Ido
- Faculty of Agriculture, Meijo University, 1-501, Shiogamaguchi, Tempaku-ku, Nagoya, Aichi, 468-8502, Japan
| | - Kenji Kato
- Faculty of Agriculture, Meijo University, 1-501, Shiogamaguchi, Tempaku-ku, Nagoya, Aichi, 468-8502, Japan
| | - Ayumi Saito
- Food Quality and Safety Research Laboratories, Meiji Co., Ltd., 1-29-1, Nanakuni, Hachiouji, Tokyo, 192-0919, Japan
| | - Yuka Moriya
- Food Quality and Safety Research Laboratories, Meiji Co., Ltd., 1-29-1, Nanakuni, Hachiouji, Tokyo, 192-0919, Japan
| | - Yumiko Tomimatsu
- Food Quality and Safety Research Laboratories, Meiji Co., Ltd., 1-29-1, Nanakuni, Hachiouji, Tokyo, 192-0919, Japan
| | - Naoko Kaneta
- Food Quality and Safety Research Laboratories, Meiji Co., Ltd., 1-29-1, Nanakuni, Hachiouji, Tokyo, 192-0919, Japan
| | - Yoshinori Tsujimoto
- Food Quality and Safety Research Laboratories, Meiji Co., Ltd., 1-29-1, Nanakuni, Hachiouji, Tokyo, 192-0919, Japan
| | - Hiroto Tamura
- Faculty of Agriculture, Meijo University, 1-501, Shiogamaguchi, Tempaku-ku, Nagoya, Aichi, 468-8502, Japan.
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20
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Ramarao N, Tran SL, Marin M, Vidic J. Advanced Methods for Detection of Bacillus cereus and Its Pathogenic Factors. SENSORS (BASEL, SWITZERLAND) 2020; 20:E2667. [PMID: 32392794 PMCID: PMC7273213 DOI: 10.3390/s20092667] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 05/02/2020] [Accepted: 05/05/2020] [Indexed: 12/21/2022]
Abstract
Bacillus cereus is an opportunistic foodborne pathogen causing food intoxication and infectious diseases. Different toxins and pathogenic factors are responsible for diarrheal syndrome, like nonhemolytic enterotoxin Nhe, hemolytic enterotoxin Hbl, enterotoxin FM and cytotoxin K, while emetic syndrome is caused by the depsipeptide cereulide toxin. The traditional method of B. cereus detection is based on the bacterial culturing onto selective agars and cells enumeration. In addition, molecular and chemical methods are proposed for toxin gene profiling, toxin quantification and strain screening for defined virulence factors. Finally, some advanced biosensors such as phage-based, cell-based, immunosensors and DNA biosensors have been elaborated to enable affordable, sensitive, user-friendly and rapid detection of specific B. cereus strains. This review intends to both illustrate the state of the B. cereus diagnostic field and to highlight additional research that is still at the development level.
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Affiliation(s)
- Nalini Ramarao
- INRAE, AgroParisTech, Micalis Institute, Université Paris-Saclay, 78350 Jouy-en-Josas, France; (S.-L.T.); (M.M.)
| | | | | | - Jasmina Vidic
- INRAE, AgroParisTech, Micalis Institute, Université Paris-Saclay, 78350 Jouy-en-Josas, France; (S.-L.T.); (M.M.)
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21
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Jessberger N, Kranzler M, Da Riol C, Schwenk V, Buchacher T, Dietrich R, Ehling-Schulz M, Märtlbauer E. Assessing the toxic potential of enteropathogenic Bacillus cereus. Food Microbiol 2019; 84:103276. [PMID: 31421762 DOI: 10.1016/j.fm.2019.103276] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 07/18/2019] [Accepted: 07/20/2019] [Indexed: 12/17/2022]
Abstract
The diarrheal type of food poisoning caused by enteropathogenic Bacillus cereus has been linked to various exotoxins. Best described are the non-hemolytic enterotoxin (Nhe), hemolysin BL (Hbl), and cytotoxin K (CytK). Due to the ubiquitous prevalence of B. cereus in soil and crops and its ability to form highly resistant endospores, contaminations during food production and processing cannot be completely avoided. Although phylogenetically closely related, enteropathogenic B. cereus strains show a high versatility of their toxic potential. Thus, functional tools for evaluating the pathogenic potential are urgently needed in order to predict hazardous food contaminations. As the diarrheal syndrome is the result of a toxico-infection with enterotoxin production in the intestine, the entire passage of the bacteria within the host, from spore survival in the stomach, spore germination, host cell adherence, and motility, to enterotoxin production under simulated intestinal conditions was compared in a panel of 20 strains, including high pathogenic as well as apathogenic ones. This approach resulted in an overarching virulence analysis scheme. In parallel, we searched for potential toxico-specific secreted markers to discriminate low and high pathogenic strains. To this end, we targeted known exotoxins using an easy to implement immunoblotting approach as well as a caseinolytic exoprotease activity assay. Overall, Nhe component B, sphingomyelinase, and exoproteases showed good correlation with the complex virulence analysis scheme and can serve as a template for future fast and easy risk assessment tools to be implemented in routine diagnostic procedures and HACCP studies.
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Affiliation(s)
- Nadja Jessberger
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764, Oberschleißheim, Germany.
| | - Markus Kranzler
- Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, 1210, Vienna, Austria
| | - Claudia Da Riol
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764, Oberschleißheim, Germany
| | - Valerie Schwenk
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764, Oberschleißheim, Germany
| | - Tanja Buchacher
- Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, 1210, Vienna, Austria
| | - Richard Dietrich
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764, Oberschleißheim, Germany
| | - Monika Ehling-Schulz
- Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, 1210, Vienna, Austria
| | - Erwin Märtlbauer
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität München, Schönleutnerstr. 8, 85764, Oberschleißheim, Germany
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