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Fichant A, Lanceleur R, Hachfi S, Brun-Barale A, Blier AL, Firmesse O, Gallet A, Fessard V, Bonis M. New Approach Methods to Assess the Enteropathogenic Potential of Strains of the Bacillus cereus Group, including Bacillus thuringiensis. Foods 2024; 13:1140. [PMID: 38672813 PMCID: PMC11048917 DOI: 10.3390/foods13081140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 04/03/2024] [Accepted: 04/04/2024] [Indexed: 04/28/2024] Open
Abstract
Bacillus cereus (Bc) is a wide group of Gram-positive and spore-forming bacteria, known to be the etiological agents of various human infections, primarily food poisoning. The Bc group includes enteropathogenic strains able to germinate in the digestive tract and to produce enterotoxins such as Nhe, Hbl, and CytK. One species of the group, Bacillus thuringiensis (Bt), has the unique feature of producing insecticidal crystals during sporulation, making it an important alternative to chemical pesticides to protect crops from insect pest larvae. Nevertheless, several studies have suggested a link between the ingestion of pesticide strains and human cases of food poisoning, calling their safety into question. Consequently, reliable tools for virulence assessment are worth developing to aid decision making in pesticide regulation. Here, we propose complementary approaches based on two biological models, the human intestinal Caco-2 cell line and the insect Drosophila melanogaster, to assess and rank the enteric virulence potency of Bt strains in comparison with other Bc group members. Using a dataset of 48 Bacillus spp. strains, we showed that some Bc group strains, including Bt, were able to induce cytotoxicity in Caco-2 cells with concomitant release of IL-8 cytokine, a landmark of pro-inflammatory response. In the D. melanogaster model, we were able to sort a panel of 39 strains into four different classes of virulence, ranging from no virulence to strong virulence. Importantly, for the most virulent strains, mortality was associated with a loss of intestinal barrier integrity. Interestingly, although strains can share a common toxinotype, they display different degrees of virulence, suggesting the existence of specific mechanisms of virulence expression in vivo in the intestine.
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Affiliation(s)
- Arnaud Fichant
- Laboratory for Food Safety, University Paris-Est, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), 94700 Maisons-Alfort, France; (A.F.); (O.F.)
- Université Côte d’Azur, CNRS, INRAE, ISA, 06903 Sophia-Antipolis, France; (S.H.); (A.B.-B.); (A.G.)
| | - Rachelle Lanceleur
- Fougères Laboratory, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), 35306 Fougères, France; (R.L.); (A.-L.B.); (V.F.)
| | - Salma Hachfi
- Université Côte d’Azur, CNRS, INRAE, ISA, 06903 Sophia-Antipolis, France; (S.H.); (A.B.-B.); (A.G.)
| | - Alexandra Brun-Barale
- Université Côte d’Azur, CNRS, INRAE, ISA, 06903 Sophia-Antipolis, France; (S.H.); (A.B.-B.); (A.G.)
| | - Anne-Louise Blier
- Fougères Laboratory, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), 35306 Fougères, France; (R.L.); (A.-L.B.); (V.F.)
| | - Olivier Firmesse
- Laboratory for Food Safety, University Paris-Est, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), 94700 Maisons-Alfort, France; (A.F.); (O.F.)
| | - Armel Gallet
- Université Côte d’Azur, CNRS, INRAE, ISA, 06903 Sophia-Antipolis, France; (S.H.); (A.B.-B.); (A.G.)
| | - Valérie Fessard
- Fougères Laboratory, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), 35306 Fougères, France; (R.L.); (A.-L.B.); (V.F.)
| | - Mathilde Bonis
- Laboratory for Food Safety, University Paris-Est, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), 94700 Maisons-Alfort, France; (A.F.); (O.F.)
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Liao Y, Wu S, Zhou G, Mei S, Yang Z, Li S, Jin Z, Deng Y, Wen M, Yang Y. Cellulolytic Bacillus cereus produces a variety of short-chain fatty acids and has potential as a probiotic. Microbiol Spectr 2024; 12:e0326723. [PMID: 38441475 PMCID: PMC10986558 DOI: 10.1128/spectrum.03267-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 01/24/2024] [Indexed: 04/06/2024] Open
Abstract
Cellulolytic bacteria ferment dietary fiber into short-chain fatty acids, which play an important role in improving fiber utilization and maintaining intestinal health. Safe and effective cellulolytic bacteria are highly promising probiotic candidates. In this study, we isolated three strains of Bacillus cereus, which exhibited cellulolytic properties, from Kele pig feces. To assess the genetic basis of cellulose degradation by the isolates, whole-genome sequencing was used to detect functional genes associated with cellulose metabolism. Subsequently, we identified that the B. cereus CL2 strain was safe in mice by monitoring body weight changes, performing histopathologic evaluations, and determining routine blood indices. We next evaluated the biological characteristics of the CL2 strain in terms of its growth, tolerance, and antibiotic susceptibility, with a focus on its ability to produce short-chain fatty acids. Finally, the intestinal flora structure of the experimental animals was analyzed to assess the intestinal environment compatibility of the CL2 strain. In this study, we isolated a cellulolytic B. cereus CL2, which has multiple cellulolytic functional genes and favorable biological characteristics, from the feces of Kele pigs. Moreover, CL2 could produce a variety of short-chain fatty acids and does not significantly affect the diversity of the intestinal flora. In summary, the cellulolytic bacterium B. cereus CL2 is a promising strain for use as a commercial probiotic or in feed supplement. IMPORTANCE Short-chain fatty acids are crucial constituents of the intestinal tract, playing an important and beneficial role in preserving the functional integrity of the intestinal barrier and modulating both immune responses and the structure of the intestinal flora. In the intestine, short-chain fatty acids are mainly produced by bacterial fermentation of cellulose. Therefore, we believe that safe and efficient cellulolytic bacteria have the potential to be novel probiotics. In this study, we systematically evaluated the safety and biological characteristics of the cellulolytic bacterium B. cereus CL2 and provide evidence for its use as a probiotic.
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Affiliation(s)
- Yixiao Liao
- College of Animal Science, Guizhou University, Guiyang, China
- Institute of Animal Diseases, Guizhou University, Guiyang, China
| | - Shihui Wu
- College of Animal Science, Guizhou University, Guiyang, China
- Institute of Animal Diseases, Guizhou University, Guiyang, China
| | - Guixian Zhou
- College of Animal Science, Guizhou University, Guiyang, China
- Institute of Animal Diseases, Guizhou University, Guiyang, China
| | - Shihui Mei
- College of Animal Science, Guizhou University, Guiyang, China
- Institute of Animal Diseases, Guizhou University, Guiyang, China
| | - Zemin Yang
- College of Animal Science, Guizhou University, Guiyang, China
- Institute of Animal Diseases, Guizhou University, Guiyang, China
| | - Shuang Li
- College of Animal Science, Guizhou University, Guiyang, China
- Institute of Animal Diseases, Guizhou University, Guiyang, China
| | - Zhengyu Jin
- College of Animal Science, Guizhou University, Guiyang, China
- Institute of Animal Diseases, Guizhou University, Guiyang, China
| | - Yongjun Deng
- College of Animal Science, Guizhou University, Guiyang, China
- Institute of Animal Diseases, Guizhou University, Guiyang, China
| | - Ming Wen
- College of Animal Science, Guizhou University, Guiyang, China
- Institute of Animal Diseases, Guizhou University, Guiyang, China
- Engineering Research Center of Animal Biological Products, Guiyang, China
| | - Ying Yang
- College of Animal Science, Guizhou University, Guiyang, China
- Institute of Animal Diseases, Guizhou University, Guiyang, China
- Engineering Research Center of Animal Biological Products, Guiyang, China
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Etter D, Biggel M, Greutmann M, Cernela N, Johler S. New insights into Bacillus cytotoxicus sources, screening, toxicity, and persistence in food production facilities. Food Microbiol 2024; 117:104399. [PMID: 37919007 DOI: 10.1016/j.fm.2023.104399] [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: 05/26/2023] [Revised: 10/03/2023] [Accepted: 10/06/2023] [Indexed: 11/04/2023]
Abstract
Bacillus cytotoxicus is a thermotolerant member of the Bacillus cereus group. It has been linked to rare, but at times fatal cases of diarrheal disease and might be missed at routine diagnostic screening temperatures commonly used for the B. cereus group. The pathogen is mostly found on dehydrated foods containing potato starch or insects. How it enters the food chain or whether it persists in food producing environments is largely unknown. Increased consumption of insects and convenience foods in Europe and the lack of information on the persistence of B. cytotoxicus in food environments and its virulence demand for further characterization. In this study, we aimed to obtain a better understanding of i) the food sources of B. cytotoxicus, ii) screening temperatures needed for its isolation from food matrices, iii) cytotoxicity of the organism, and iv) its ecological niche and potential epidemiological links. To this end, 112 food samples were collected, with a focus on foods exhibiting low water activity. The samples were screened for B. cytotoxicus at 42 °C and at 50 °C. Presumptive isolates were characterized by cytK-1 toxin gene PCR for differentiation of B. cytotoxicus from other B. cereus group members. Vero cell cytotoxicity assays were performed, and selected isolates were sequenced. Our results show that screening at 42 °C might be insufficient for detecting B. cytotoxicus in foods that harbor other less thermophilic Bacillus species. When screening at 50 °C, B. cytotoxicus was detected in 23% of the food samples (n = 26 isolates). The highest prevalence was detected in mashed potato products (82%) and potato flakes (67%). In contrast, a wide range of products not containing any potato ingredients did not yield B. cytotoxicus isolates. All B. cytotoxicus isolates exhibited either low or no detectable cytotoxicity. WGS analysis revealed that a highly toxic isolate is closely related to the French outbreak strain NVH 391-98. In addition, we could show that two isolates sampled 5 years apart from the same production facility only differed by seven SNPs, making it likely that B. cytotoxicus is able to persist in production facilities over a long time. Interestingly, the reoccurring strain possessed an additional plasmid and did not show cytotoxic potential when re-isolated after 5 years.
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Affiliation(s)
- Danai Etter
- Institute for Food Safety and Hygiene, University of Zurich, Zurich, Switzerland
| | - Michael Biggel
- Institute for Food Safety and Hygiene, University of Zurich, Zurich, Switzerland
| | - Mariella Greutmann
- Institute for Food Safety and Hygiene, University of Zurich, Zurich, Switzerland
| | - Nicole Cernela
- Institute for Food Safety and Hygiene, University of Zurich, Zurich, Switzerland
| | - Sophia Johler
- Institute for Food Safety and Hygiene, University of Zurich, Zurich, Switzerland.
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Sokolov S, Brovko F, Solonin A, Nikanova D, Fursova K, Artyemieva O, Kolodina E, Sorokin A, Shchannikova M, Dzhelyadin T, Ermakov A, Boziev K, Zinovieva N. Genomic analysis and assessment of pathogenic (toxicogenic) potential of Staphylococcus haemolyticus and Bacillus paranthracis consortia isolated from bovine mastitis in Russia. Sci Rep 2023; 13:18646. [PMID: 37903798 PMCID: PMC10616132 DOI: 10.1038/s41598-023-45643-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 10/22/2023] [Indexed: 11/01/2023] Open
Abstract
Three stable microbial consortia, each composed of Bacillus paranthracis and Staphylococcus haemolyticus strains, were isolated from milk of cows diagnosed with mastitis in three geographically remote regions of Russia. The composition of these consortia remained stable following multiple passages on culture media. Apparently, this stability is due to the structure of the microbial biofilms formed by the communities. The virulence of the consortia depended on the B. paranthracis strains. It seems plausible that the ability of the consortia to cause mastitis in cattle was affected by mutations of the cytK gene of B. paranthracis.
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Affiliation(s)
- Sergei Sokolov
- Laboratory of Microbiology, L.K. Ernst Federal Science Center for Animal Husbandry, Dubrovitsy, 142132, Russia.
- Laboratory of Plasmid Biology, Federal Research Center "Pushchino Scientific Center for Biological Researches", G.K. Skryabin Institute of Biochemistry & Physiology of Microorganisms of the Russian Academy of Sciences, Pushchino, 142290, Russia.
| | - Fedor Brovko
- Laboratory of Microbiology, L.K. Ernst Federal Science Center for Animal Husbandry, Dubrovitsy, 142132, Russia
- Laboratory of Immunochemistry, Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Pushchino, 142290, Russia
| | - Alexander Solonin
- Laboratory of Plasmid Biology, Federal Research Center "Pushchino Scientific Center for Biological Researches", G.K. Skryabin Institute of Biochemistry & Physiology of Microorganisms of the Russian Academy of Sciences, Pushchino, 142290, Russia
| | - Daria Nikanova
- Laboratory of Microbiology, L.K. Ernst Federal Science Center for Animal Husbandry, Dubrovitsy, 142132, Russia
| | - Ksenia Fursova
- Laboratory of Immunochemistry, Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Pushchino, 142290, Russia
| | - Olga Artyemieva
- Laboratory of Microbiology, L.K. Ernst Federal Science Center for Animal Husbandry, Dubrovitsy, 142132, Russia
| | - Evgenia Kolodina
- Laboratory of Microbiology, L.K. Ernst Federal Science Center for Animal Husbandry, Dubrovitsy, 142132, Russia
| | - Anatoly Sorokin
- Laboratory of Cell Genome Functioning Mechanisms, Federal Research Center "Pushchino Scientific Center for Biological Researches", Institute of Cell Biophysics of the Russian Academy of Sciences, Pushchino, 142290, Russia
| | - Margarita Shchannikova
- Laboratory of Immunochemistry, Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Pushchino, 142290, Russia
| | - Timur Dzhelyadin
- Laboratory of Cell Genome Functioning Mechanisms, Federal Research Center "Pushchino Scientific Center for Biological Researches", Institute of Cell Biophysics of the Russian Academy of Sciences, Pushchino, 142290, Russia
| | - Artem Ermakov
- Laboratory of Cell Genome Functioning Mechanisms, Federal Research Center "Pushchino Scientific Center for Biological Researches", Institute of Cell Biophysics of the Russian Academy of Sciences, Pushchino, 142290, Russia
| | - Khanafy Boziev
- Laboratory of Immunochemistry, Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Pushchino, 142290, Russia
| | - Natalia Zinovieva
- Laboratory of Microbiology, L.K. Ernst Federal Science Center for Animal Husbandry, Dubrovitsy, 142132, Russia
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Hinnekens P, Fayad N, Gillis A, Mahillon J. Conjugation across Bacillus cereus and kin: A review. Front Microbiol 2022; 13:1034440. [PMID: 36406448 PMCID: PMC9673590 DOI: 10.3389/fmicb.2022.1034440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 10/11/2022] [Indexed: 11/06/2022] Open
Abstract
Horizontal gene transfer (HGT) is a major driving force in shaping bacterial communities. Key elements responsible for HGT are conjugation-like events and transmissible plasmids. Conjugative plasmids can promote their own transfer as well as that of co-resident plasmids. Bacillus cereus and relatives harbor a plethora of plasmids, including conjugative plasmids, which are at the heart of the group species differentiation and specification. Since the first report of a conjugation-like event between strains of B. cereus sensu lato (s.l.) 40 years ago, many have studied the potential of plasmid transfer across the group, especially for plasmids encoding major toxins. Over the years, more than 20 plasmids from B. cereus isolates have been reported as conjugative. However, with the increasing number of genomic data available, in silico analyses indicate that more plasmids from B. cereus s.l. genomes present self-transfer potential. B. cereus s.l. bacteria occupy diverse environmental niches, which were mimicked in laboratory conditions to study conjugation-related mechanisms. Laboratory mating conditions remain nonetheless simplistic compared to the complex interactions occurring in natural environments. Given the health, economic and ecological importance of strains of B. cereus s.l., it is of prime importance to consider the impact of conjugation within this bacterial group.
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Affiliation(s)
- Pauline Hinnekens
- Laboratory of Food and Environmental Microbiology, Earth and Life Institute, Louvain-la-Neuve, Belgium
| | - Nancy Fayad
- Multi-Omics Laboratory, School of Pharmacy, Lebanese American University, Byblos, Lebanon
| | - Annika Gillis
- Laboratory of Food and Environmental Microbiology, Earth and Life Institute, Louvain-la-Neuve, Belgium
| | - Jacques Mahillon
- Laboratory of Food and Environmental Microbiology, Earth and Life Institute, Louvain-la-Neuve, Belgium
- *Correspondence: Jacques Mahillon,
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Hinnekens P, Mahillon J. Conjugation-mediated transfer of pXO16, a large plasmid from Bacillus thuringiensis sv. israelensis, across the Bacillus cereus group and its impact on host phenotype. Plasmid 2022; 122:102639. [PMID: 35842001 DOI: 10.1016/j.plasmid.2022.102639] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 06/27/2022] [Accepted: 07/10/2022] [Indexed: 11/17/2022]
Abstract
pXO16, the 350 kb-conjugative plasmid from Bacillus thuringiensis sv. israelensis promotes its own transfer at high efficiency, triggers the transfer of mobilizable and non-mobilizable plasmids, as well as the transfer of host chromosomal loci. Naturally found in B. thuringiensis sv. israelensis, pXO16 transfers to various strains of Bacillus cereus sensu lato (s.l.) at a wide range of frequencies. Despite this host diversity, a paradox remains between the relatively large host spectrum and the natural occurrence of pXO16, so far restricted to B. thuringiensis sv. israelensis. Proposing first insights exploring this paradox, we investigated the behaviour of pXO16 amongst different members of the B. cereus group. We first looked at the transfer of pXO16 to two new host clusters of B. cereus s.l., Bacillus mycoides and Bacillus anthracis clusters. This examination brought to light the impairment of the characteristic rhizoidal phenotype of B. mycoides in presence of pXO16. We also explored the stability of pXO16 at different temperatures as some B. cereus group members are well-known for their psychro- or thermo-tolerance. This shed light on the thermo-sensitivity of the plasmid. The influence of pXO16 on its host cell growth and on swimming capacity also revealed no or limited impact on its natural host B. thuringiensis sv. israelensis. On the contrary, pXO16 affected more strongly both the growth and swimming capacity of other B. cereus s.l. hosts. This reinforced the running hypothesis of a co-evolution between pXO16 and B. thuringiensis sv. israelensis, enabling the plasmid maintenance without impairing the host strain development.
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Affiliation(s)
- Pauline Hinnekens
- Laboratory of Food and Environmental Microbiology, Earth and Life Institute, Université Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
| | - Jacques Mahillon
- Laboratory of Food and Environmental Microbiology, Earth and Life Institute, Université Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium.
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