Cereulide and Emetic Bacillus cereus: Characterizations, Impacts and Public Precautions

Unraveling the ecological interactions between dairy strains Bacillus licheniformis and Bacillus cereus during the dual-species biofilm formation

Bacillus cereus and Bacillus licheniformis are widely presented in dairy products. They can form thick biofilms on surfaces of dairy processing equipment, which may pose serious safety issues and spoilage of final dairy products. However, how ecological interactions between B. cereus and B. licheniformis affect the functions and stability of mixed-species biofilm remains uncovered. In this work, the altered profiles of a dual-species biofilm by dairy-derived B. cereus 121 and B. licheniformis 919 were investigated by RNA-sequencing analysis in combined with phenotype validation (bacterial growth, biofilm-forming capacity, biofilm EPS production, and biofilm structures). The results confirmed that the presence of B. cereus 121 reduced the growth of B. licheniformis 919 planktonic cells, and decreased the biofilm cell numbers of B. licheniformis 919 in the dual-species biofilm when compared to that in its single-species biofilm. The bacterial interaction also reduced the amount of proteins and carbohydrates in the biofilm matrix, and decreased the coverage, average thickness, and total biomass of biofilms. In addition, results from RNA-sequencing analysis showed that the bacterial interaction caused a total of 128 (B. licheniformis 919) and 216 (B. cereus 121) differentially expressed genes (DEGs) during the co-culture of planktonic cells. Functional annotation revealed that the DEGs of B. licheniformis 919 were mainly involved in 10 downregulated pathways including citrate cycle, pyruvate metabolism, nonribosomal peptide structures, glycolysis/gluconeogenesis, quorum sensing, alanine, aspartate and glutamate metabolism, oxidative phosphorylation, beta-Lactam resistance, arginine and proline metabolism, and beta-Alanine metabolism when co-cultured with B. cereus 121. On the other hand, the DEGs from B. cereus 121 were significantly enriched for two downregulated pathways (cysteine and methionine metabolism, and inositol phosphate metabolism) and four upregulated pathways (nitrogen metabolism, glyoxylate and dicarboxylate metabolism, glycine, serine and threonine metabolism, and propanoate metabolism). Results of this study facilitate updated knowledge of how bacterial interaction during the biofilm formation shapes the features of the mixed-species biofilm.

Comprehensive Phenotypic Characterization and Genomic Analysis Unveil the Probiotic Potential of Bacillus velezensis K12

Bacillus spp. have emerged as pivotal sources of probiotic preparations, garnering considerable attention in recent years owing to their vigorous bacteriostatic activity and antimicrobial resistance. This study aimed to investigate these probiotic characteristics in depth and verify the safety of Bacillus velezensis K12, a strain isolated from broiler intestine. The K12 strain was identified as Bacillus velezensis based on its morphology and 16S rDNA sequence homology analysis. Subsequently, B. velezensis K12 was evaluated for acid resistance, bile salt resistance, gastrointestinal tolerance, drug sensitivity, and antimicrobial activity. Additionally, whole-genome sequencing technology was employed to dissect its genomic components further, aiming to explore its potential applications as a probiotic strain. B. velezensis K12 was sensitive to six antibiotics and had acid tolerance. Furthermore, it showed potent antimicrobial activity against a wide range of pathogenic bacteria, including Escherichia coli (E. coli), Staphylococcus aureus, Salmonella, Clostridium perfringens, Bacillus cereus, and Vibrio parahaemolyticus. The complete genome sequencing of B. velezensis K12 revealed a genomic length of 3,973,105 base pairs containing 4123 coding genes, among which 3973 genes were functionally annotated. The genomic analysis identified genes associated with acid and bile tolerance, adhesion, antioxidants, and secondary metabolite production, whereas no functional genes related to enterotoxins or transferable antibiotic resistance were detected, thereby confirming the probiotic properties of B. velezensis K12. B. velezensis K12 exhibits broad-spectrum bacteriostatic activity and in vitro safety, positioning it as a potential candidate strain for developing probiotic Bacillus preparations.

A novel method of species-specific molecular target mining and accurate discrimination of Bacillus cereus sensu lato

Bacillus cereus, a member of the Bacillus cereus sensu lato (B. cereus s.l.), is widely distributed in nature and can contaminate a variety of foods, leading to foodborne illnesses and substantial losses in the food industry. Although culture-based methods remain the gold standard for identifying B. cereus due to their high sensitivity under specific conditions, they are often complex and labor-intensive to implement. Furthermore, the high genetic similarity among certain members of the B. cereus s.l. makes it challenging to identify species-specific molecular targets, hindering the rapid and accurate differentiation of these bacteria. In this study, we introduce a novel method, comparative analysis based on whole genome slices (CAWGS), combined with the Basic Local Alignment Search Tool (BLAST) for efficient molecular target mining. Using CAWGS-BLAST and pan-genome analysis, we successfully identified new molecular targets for B. cereus, Bacillus thuringiensis, emetic B. cereus, Bacillus anthracis, Bacillus mycoides, Bacillus weihenstephanensis, and Bacillus megaterium. Based on these newly discovered targets, we developed a PCR-CRISPR/Cas12a method for detecting B. cereus s.l. and related species. Our research not only provides a rapid and accurate approach for discriminating B. cereus s.l. and related species, but also offers a universal and valuable reference for detecting foodborne pathogens, especially those with highly similar phenotypic and genetic characteristics.

Emerging threat to antibiotic resistance: Impact of mycotoxin deoxynivalenol on gut microbiota and clonal expansion of extensively drug-resistant enterococci

Mycotoxins, antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARGs) are significant environmental pollutants that pose considerable threats to environmental health and human safety through the food chain. This study is the first to investigate the impact of deoxynivalenol (DON), the most common mycotoxin, on antibiotic resistance dynamics in gut microbiota, demonstrating that DON exposure significantly selects for ARB and ARGs. Results indicated that 80.69 % of the ARGs with the highest increase in the DON group were exclusive to gram-positive bacteria, particularly those related to daptomycin. DON exposure enhanced the expression of virulence factors in gram-positive bacteria and increased reactive oxygen species (ROS) production and membrane permeability, compromising bacterial integrity and amplifying resistance mechanisms. DON also boosted the diversity and co-occurrence of ARGs and mobile genetic elements (MGEs), potentially facilitating the horizontal transfer of resistance traits. Notably, the dominant bacterial species isolated from broiler gut microbiota was identified as Enterococcus faecalis, which exhibited clonal expansion of sequence type ST123. This ST123 clone accounted for 86 % of the DON group and was associated with an extensively drug-resistant (XDR) phenotype, showing resistance levels exceeding 128 μg/mL to last-resort antibiotics such as daptomycin, vancomycin, and linezolid. Additionally, DON upregulated the expression of critical daptomycin resistance genes (liaR, walK, liaS, mprF, and cls) in vancomycin-resistant enterococci (VRE) isolates. This study highlights the microbiological and environmental hazards that mycotoxins pose to the antibiotic resistance crisis.

Antiviral defence arsenal across members of the Bacillus cereus group

Bacteria co-evolve with bacteriophages to overcome each other's defence arsenal. Bacillus cereus group gathers bacteria of medical and agricultural importance, including foodborne pathogens. So far, few studies have portrayed a complete defence arsenal of microorganisms, and the role of antiviral systems in the Bacillus cereus group has been overlooked. Here, we investigate the repertoire of defence systems in 6354 B. cereus group's genomic assemblies, using bioinformatics tools DefenseFinder and PADLOC. Our analyses provide an overview of the diversity and abundance of defence systems in this group, with 83,738 systems distributed by 2 to 33 within each assembly. Comparing PADLOC and DefenseFinder predictions showed that the most prevalent strategy is Restriction-Modification, but many abortive infection systems also intervene in the group's defence, such as Septu, Gabija and Lamassu. Most defences were encoded on both plasmids and the chromosome, though some tend to have a preferential genomic location. We also studied the defence systems associations within the genomic assemblies. Overall, our results establish a baseline picturing the rich and complex antiviral arsenal encoded by B. cereus group's species and provide clues for studying co-existing strategies displayed by these bacteria to subvert phages and other MGEs invasions.

Cytotoxicity and Genome Characteristics of an Emetic Toxin-Producing Bacillus cereus Group sp. Isolated from Raw Milk

The Bacillus cereus group frequently contaminates milk and dairy products. Some members of this group can produce the heat-stable pre-formed toxin cereulide, which causes emetic foodborne intoxication. This study characterised emetic B. cereus group isolates from raw cow's milk in the biochemical, genetic, and toxigenic aspects. Of the 158 B. cereus group isolates derived from 99 raw milk samples, 7 (4.43%) harboured cereulide synthetase A (cesA), which encodes a cereulide synthetase associated with the emetic phenotype. Heat-treated culture filtrates from the cesA-positive isolates demonstrated cytotoxicity to HepG2 and Caco-2 cells, resulting in cell viabilities of 32.22-36.57% and 44.41-47.08%, respectively. The cytotoxicity levels were comparable to those of the reference emetic strain, F4810/72 (alternately termed AH187). Genome analysis of a representative isolate, CSB98, revealed the complete ces gene cluster with additional virulence factors such as non-haemolytic enterotoxin, haemolysins and phospholipases, suggesting that the isolate could be both emetic and diarrhoeagenic. CSB98 exhibited a closer relationship to the type strain of B. paranthracis than to that of B. cereus sensu stricto (ATCC 14579). The genomes of CSB98 and AH187 were indistinguishable through OrthoANI analysis, but 13 variants were identified via SNP calling. These results affirm genetic conservation among the emetic traits.

Characterization of the Bacillus cereus Group Isolated from Ready-to-Eat Foods in Poland by Whole-Genome Sequencing

Bacillus cereus sensu lato can contaminate food and cause food poisoning by producing toxins such as cereulide, toxin BL, and cytotoxin K. In this study, we retrospectively analyzed B. cereus sensu lato from retail food products and food poisoning cases using PCR methods to determine their virulence profiles. A new toxin profile, encoding all four toxins (hbl, nhe, cytK, ces), was found in 0.4% of isolates. The toxin profiles, classified into A-J, revealed that 91.8% harbored nhe genes, while hbl, cytK, and ces were detected in 43.8%, 46.9%, and 4.2% of isolates, respectively. Whole-genome sequencing (WGS) identified four distinct species within the B. cereus group, with 21 isolates closely related to B. cereus sensu stricte, 25 to B. mosaicus, 2 to B. toyonensis, and 1 to B. mycoides. Three novel sequence types (STs 3297, 3298, 3299) were discovered. Antibiotic resistance genes were common, with 100% of isolates carrying beta-lactam resistance genes. Fosfomycin (80%), vancomycin (8%), streptothricin (6%), tetracycline (4%), and macrolide resistance (2%) genes were also detected. These results highlight the genetic diversity and antibiotic resistance potential of B. cereus sensu lato strains in Polish food products.

Characterization of the novel bequatrovirus vB-BcgM and its antibacterial effects in a food matrix

Bacteria belonging to the Bacillus cereus group are ubiquitous in nature, causing food spoilage and food poisoning cases. A bequatrovirus, vB-BcgM, belonging to the C3 cluster infecting B. cereus group members, was isolated and characterized. Its 160-kb linear dsDNA genome contains a number of replication-related coding sequences (CDSs) and displays a collinear relationship with that of the virulent phage B4, with variations in its structural and replication regions. vB-BcgM has a relatively broad host range, with the ability to infect 33.3% of the B. cereus group isolates tested, including B. cereus, B. thuringiensis, B. anthracis, B. paranthracis, B. mycoides, and B. cytotoxicus. Moreover, vB-BcgM displays efficient infection and high replication capacity. It was found that 96.5% of the virions complete the adsorption process within 5 min. The optimal multiplicity of infection (MOI) is 10-7, and the burst size is 63 plaque-forming units (PFU)/cell. This phage showed stability over a broad pH range (4-12) and at temperatures up to 70 °C. Furthermore, vB-BcgM displays significant antibacterial effects in processed food matrices (ultra-high temperature [UHT] sterilized milk [GB 25190], UHT refrigerated milk [GB 25190], pasteurized milk [GB 19645], mashed meat, and cereals) and fresh foods (lettuce, apple, and potato). The antibacterial effects were found to be dependent on the dose of viral inoculum, incubation conditions (food matrix and temperature), and time. The data indicate that vB-BcgM has good potential as an antibacterial agent.

Bacillus cereus containing nheA, hblC and cytk enterotoxin genes is associated with acute childhood gastroenteritis in Nigeria

Bacillus cereus is rarely implicated when diarrheal cases in children are diagnosed in developing countries due to the lack of molecular methods to identify its enterotoxigenic genes. We report that out of 62 enterobacteria isolated from 70 stool samples collected from children hospitalized at the Mile 4 Hospital, Ebonyi State, Nigeria, 24 isolates were identified as B. cereus based on 16SrRNA gene sequence. The enterotoxins genes nheA and cytK2 were detected in 23 out of the 24 isolates, while hblC was detected in 19 isolates. B. cereus may be responsible for greater number of yearly incidences of acute childhood gastroenteritis in Nigeria.

Origin and characterization of cyclodepsipeptides: Comprehensive structural approaches with focus on mass spectrometry analysis of alkali-cationized molecular species

Cyclodepsipeptides (CDPs) represent a huge family of chemically and structurally diverse molecules with a wide ability for molecular interactions. CDPs are cyclic peptide-related natural products made up of both proteinogenic and nonproteinogenic amino acids linked by amide and ester bonds. The combined use of different analytical methods is required to accurately determine their integral structures including stereochemistry, thus allowing deeper insights into their often-intriguing bioactivities and their possible usefulness. Our goal is to present the various methods developed to accurately characterize CDPs. Presently, Marfey's method and NMR (nuclear magnetic resonance) are still considered the best for characterizing CDP configuration. Nevertheless, electrospray-high resolution tandem mass spectrometry (ESI-HRMS/MS) is of great value for efficiently resolving CDP's composition and sequences. For instance, recent data shows that the fragmentation of cationized CDPs (e.g., [M + Li]+ and [M + Na]+) leads to selective cleavage of ester bonds and specific cationized product ions (b series) useful to get unprecedented sequence information. Thus, after a brief presentation of their structure, biological functions, and biosynthesis, we also provide a historic overview of these various analytical approaches as well as their advantages and limitations with a special emphasis on the emergence of methods based on HRMS/MS through recent fundamental works and applications.

Late-onset sepsis in newborns caused by Bacillus Cereus: a case report and literature review

Bacillus cereus is a bacterium capable of causing late-onset neonatal sepsis. By analyzing 11 cases, this study investigates the diagnosis, treatment, and prognosis of Bacillus cereus infections, aiming to provide insights into clinical diagnosis and therapy. The study scrutinized 11 instances of late-onset neonatal sepsis, including two fatalities attributable to Bacillus cereus, one accompanied by cerebral hemorrhage. An examination and analysis of these cases' symptoms, signs, laboratory tests, and treatment processes, along with a review of related literature from 2010 to 2020, revealed a high mortality rate of 41.38% in non-gastrointestinal infections caused by Bacillus cereus. Our findings underscore the critical importance of rapid diagnosis and effective antimicrobial therapy in reducing mortality rates. Once the source of infection is identified, implementing effective infection control measures is essential.

Evaluating the Safety of Bacillus cereus GW-01 Obtained from Sheep Rumen Chyme

Bacillus cereus is responsible for 1.4-12% food poisoning outbreaks worldwide. The safety concerns associated with the applications of B. cereus in health and medicine have been controversial due to its dual role as a pathogen for foodborne diseases and a probiotic in humans and animals. In this study, the pathogenicity of B. cereus GW-01 was assessed by comparative genomic, and transcriptome analysis. Phylogenetic analysis based on a single-copy gene showed clustering of the strain GW-01, and 54 B. cereus strains from the NCBI were classified into six major groups (I-VI), which were then associated with the source region and sequence types (STs). Transcriptome results indicated that the expression of most genes related with toxins secretion in GW-01 was downregulated compared to that in the lag phase. Overall, these findings suggest that GW-01 is not directly associated with pathogenic Bacillus cereus and highlight an insightful strategy for assessing the safety of novel B. cereus strains.

Microbiological hazards in infant and toddler food in China: A comprehensive study between 2004 and 2022

Infant and toddler food (ITF), including powdered infant and follow-up formula (PIFF) and complementary food (CF), provides the majority of early-life nutrients for young children. As infants and toddlers are more vulnerable to foodborne diseases, the safety concern of ITF is the ultimate priority. However, nationwide surveillance for the presence of hazards, specifically microbiological hazards, in the Chinese ITF is partially known, posing a significant knowledge gap for risk ranking. Most importantly, the related regional surveys were largely published in Chinese, making the data unavailable for global sharing. To bridge these gaps, we screened 5,306 publications and conducted a comprehensive meta-analysis for microbiological hazards using 129 qualified studies. The four most reported microbiological hazards in ITF were Bacillus cereus (13.4 %), Cronobacter (4.8 %), Staphylococcus aureus (1.3 %), and Salmonella (1.1 %). B. cereus is a risk factor in ITF, specifically in PIFF, cereals, and ready-to-eat food. The prevalence of B. cereus was high in Northern and Southern China, while the prevalence of Cronobacter was high in Central China. Cronobacter is a microbiological hazard, specifically in PIFF, with a prevalence of 3.0 %. Interestingly, the prevalence dynamics of Cronobacter and B. cereus in ITF were rising and stable, respectively, whereas the prevalence of S. aureus and Salmonella decreased over time. Together, our analysis will promote the global sharing of these critical findings and may guide future policy making.

A web-based microbiological hazard identification tool for infant foods

An integrated approach to identify and assess Microbiological Hazards (MHs) and mitigate risks in infant food chains is crucial to ensure safe foods for infants and young children. A systematic procedure was developed to identify MHs in specific infant foods. This includes five major steps: 1) relevant hazard-food pairing, 2) process inactivation efficiency, 3) recontamination possibility after processing, 4) MHs growth opportunity, and 5) MHs-food association level. These steps were integrated into an online tool called the Microbiological Hazards IDentification (MiID) decision support system (DSS), targeting food companies, governmental agencies and academia users, and is accessible at https://foodmicrobiologywur.shinyapps.io/Microbial_hazards_ID/. The MiID DSS was validated in four case studies, focussing on infant formula, fruit puree, cereal-based meals, and fresh fruits, each representing distinct products and processing characteristics. The results obtained through the application of the MiID DSS, compared with identification by food safety experts, consistently identified the top MHs in these food products. This process affirms its effectiveness in systematic hazard identification. The introduction of the MiID DSS helps to structure the first steps in HACCP (hazard analysis) and in risk assessment (hazard identification) to follow a structured and well-documented procedure, balancing the risk of overlooking relevant MHs or including too many irrelevant MHs. It is a valuable addition to risk analysis/assessment in infant food chains and has the potential for future extension. This includes the incorporation of newly acquired data related to infant foods via a semi-publicly hosted platform, or it can be adapted for hazard identification in general food products using a similar framework.

Enhancing food safety in soybean fermentation through strategic implementation of starter cultures

Fermented soybean products have played a significant role in Asian diets for a long time. Due to their diverse flavours, nutritional benefits, and potential health-promoting properties, they have gained a huge popularity globally in recent years. Traditionally, soybean fermentation is conducted spontaneously, using microorganisms naturally present in the environment, or inoculating with traditional starter cultures. However, many potential health risks are associated with consumption of these traditionally fermented soybean products due to the presence of food pathogens, high levels of biogenic amines and mycotoxins. The use of starter culture technology in fermentation has been well-studied in recent years and confers significant advantages over traditional fermentation methods due to strict control of the microorganisms inoculated. This review provides a comprehensive review of microbial safety and health risks associated with consumption of traditional fermented soybean products, and how adopting starter culture technology can help mitigate these risks to ensure the safety of these products.

Antibacterial Effect and Possible Mechanism of Sesamol against Foodborne Pathogens

Food safety problems caused by foodborne pathogens have become a major public issue, and the search for efficient and safe bacteriostatic agents has gained attention. Sesamol (SE), a phenolic compound abundant in sesame oil, offers numerous health benefits and exhibits certain antibacterial properties. The purpose of this study was to evaluate the antibacterial effect and potential mechanisms of SE against representative foodborne pathogens, including Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Salmonella serovar Enteritidis. The results showed that SE significantly inhibited the growth of the five pathogenic bacteria in sterile saline and pasteurized milk by 2.16-4.16 log10 CFU/g within 48 h. The results of the minimum bactericidal concentration and time-kill assay showed that SE had a greater inhibitory effect on L. monocytogenes compared with other bacteria. Additionally, SE was found to alter the cell membranes' permeability in these bacteria, resulting in the release of intercellular proteins and DNA. A scanning electron microscopy analysis showed that exposure to SE resulted in significant changes in bacterial morphology, producing cell shrinkage and deformation. These findings suggest that SE could inhibit both Gram-negative and Gram-positive bacteria by interfering with the function and morphology of bacterial cells.

Validation of a Targeted LC-MS/MS Method for Cereulide and Application in Food and Faeces

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.

Recent Advances in the Detection of Food Toxins Using Mass Spectrometry

Edibles are the only source of nutrients and energy for humans. However, ingredients of edibles have undergone many physicochemical changes during preparation and storage. Aging, hydrolysis, oxidation, and rancidity are some of the major changes that not only change the native flavor, texture, and taste of food but also destroy the nutritive value and jeopardize public health. The major reasons for the production of harmful metabolites, chemicals, and toxins are poor processing, inappropriate storage, and microbial spoilage, which are lethal to consumers. In addition, the emergence of new pollutants has intensified the need for advanced and rapid food analysis techniques to detect such toxins. The issue with the detection of toxins in food samples is the nonvolatile nature and absence of detectable chromophores; hence, normal conventional techniques need additional derivatization. Mass spectrometry (MS) offers high sensitivity, selectivity, and capability to handle complex mixtures, making it an ideal analytical technique for the identification and quantification of food toxins. Recent technological advancements, such as high-resolution MS and tandem mass spectrometry (MS/MS), have significantly improved sensitivity, enabling the detection of food toxins at ultralow levels. Moreover, the emergence of ambient ionization techniques has facilitated rapid in situ analysis of samples with lower time and resources. Despite numerous advantages, the widespread adoption of MS in routine food safety monitoring faces certain challenges such as instrument cost, complexity, data analysis, and standardization of methods. Nevertheless, the continuous advancements in MS-technology and its integration with complementary techniques hold promising prospects for revolutionizing food safety monitoring. This review discusses the application of MS in detecting various food toxins including mycotoxins, marine biotoxins, and plant-derived toxins. It also explores the implementation of untargeted approaches, such as metabolomics and proteomics, for the discovery of novel and emerging food toxins, enhancing our understanding of potential hazards in the food supply chain.

Characterization of the Toxigenic Potential of Bacillus cereus sensu lato Isolated from Raw Berries and Their Products

Bacillus cereus is estimated to be responsible for 1.4-12% of all food poisoning outbreaks worldwide. The objective of this study was to investigate the toxigenic potential of 181 isolates of B. cereus previously recovered from different types of berries and berry products (strawberries, raspberries, blackberries, and blueberries) by assessing the presence of enterotoxin genes (hblA, hblC, hblD, nheA, nheB, nheC, and cytK) and an emetic toxin cereulide synthetase gene (ces). The cytotoxic activity on Caco-2 cells was also evaluated for the two isolates containing the gene cytK. Twenty-three toxigenic profiles were found. The nheABC (91.7%) and hblACD (89.0%) complexes were the most prevalent among the isolates, while the cytK and ces genes were detected in low percentages, 1.1% and 3.3%, respectively. In addition, the nheABC/hblACD complex and ces genes were detected in isolates recovered throughout the production process of blackberries and strawberries. The cytotoxic activity on Caco-2 cells was also observed to be greater than 60% for isolates containing the cytK gene.

Bactericidal efficacy difference between air and nitrogen cold atmospheric plasma on Bacillus cereus: Inactivation mechanism of Gram-positive bacteria at the cellular and molecular level

As an emerging food processing technology, cold atmospheric plasma (CAP) has attracted great attention in the field of microbial inactivation. Although CAP has been proven to effectively inactivate a variety of foodborne pathogens, there is less research on the inactivation of Bacillus cereus, and the exact inactivation mechanism is still unclear. Elucidating the inactivation mechanism will help to develop and optimize this sterilization method, with the prospective application in industrialized food production. This study aims to explore the bactericidal efficacy difference between air and nitrogen CAP on B. cereus, a typical Gram-positive bacterium, and reveals the inactivation mechanism of CAP at the cellular and molecular level, by observing the change of the cell membrane, cell morphological damage, intracellular antioxidant enzyme activity and cellular biomacromolecules changes. The results showed that both air CAP and nitrogen CAP could effectively inactivate B. cereus, which was due to the reactive oxygen and nitrogen species (RONS) generated by the plasma causing bacterial death. The damage pathways of CAP on Gram-positive bacteria could be explained by disrupting the bacterial cell membrane and cell morphology, disturbing the intracellular redox homeostasis, and destroying biomacromolecules in the cells. The differences in active species generated by the plasma were the main reason for the different bactericidal efficiencies of air CAP and nitrogen CAP, where air CAP producing RONS with stronger oxidative capacity in a shorter time. This study indicates that air CAP is an effective, inexpensive and green technology for B. cereus inactivation, providing a basis for industrial application in food processing.

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.

A foodborne outbreak linked to Bacillus cereus at two middle schools in a rural area of Chongqing, China, 2021

Bacillus cereus (B. cereus) is a common cause of foodborne illness. An outbreak of acute gastrointestinal illness occurred at two middle schools in a rural region of Chongqing, China, in 2021. This study aimed to elucidate the outbreak's characteristics, identify risk factors, and determine the source of contamination. A retrospective cohort study and an environmental investigation were conducted. Vomit samples, anal swabs, and food samples were collected and tested by RT-PCR for 18 species of bacteria and viruses, including B. cereus. Positive samples of B. cereus underwent biochemical experiments and bacterial quantification. A total of 198 cases were reported in this outbreak, with an attack rate of 24.63%. The main symptoms were vomiting (100%), bellyache (83.33%), and dizziness (62.63%). The retrospective cohort study showed a significant association between the outbreak and rice noodles provided by a nearby food manufacturer (RR = 39.63, p < 0.001). B. cereus was detected in 20 vomit samples, three anal swabs, and seven rice noodles samples, with a count exceeding 103 CFU/g. These findings strongly suggested that the outbreak was linked to B. cereus-contaminated rice noodles. Enhancing food safety surveillance and promoting health measures among schools and food manufacturers in rural areas is crucial to prevent similar incidents in the future in Chongqing, China.

Epidemiological Evaluation of Bacillus cereus-Induced Foodborne Outbreaks - China, 2010-2020

INTRODUCTION

Bacillus cereus (B. cereus) is a common gram-positive bacterium that contaminates starch-rich food and can cause outbreaks of foodborne diseases. This study describes the characteristics of outbreaks caused by B. cereus in China during 2010-2020 and explore the possible reasons for changes in the number of outbreaks over time. Results of this analysis can efficiently help guide and allocate public resources to prevent B. cereus-caused foodborne diseases.

METHODS

Descriptive statistical methods were used to analyze the data on B. cereus outbreaks in China during this period. The data were identified and reported at all levels in China through National Foodborne Disease Outbreak Surveillance System.

RESULTS

From 2010 to 2020, a total of 419 foodborne outbreaks prompted by B. cereus were reported in China, leading to 7,892 cases, 2,786 hospital admissions, and 5 fatalities. The bulk of the outbreaks were recorded in the summer, primarily between May and September. The most recurrent food vehicle was linked with rice or flour-based products, notably those made with rice or fried rice. School canteens bore the brunt of the B. cereus outbreaks. In multifactor outbreaks, food contamination was identified as the most common culprit; while in instances where only one factor contributed, improper storage was most frequently implicated.

CONCLUSION

The prevalence of B. cereus outbreaks remained relatively consistent throughout the studied period. Understanding the types of foods, causative factors, and contributing elements leading to B. cereus outbreaks can help inform prevention strategies for foodborne illnesses. The majority of outbreaks were associated with rice- or flour-based foods in school canteens, suggesting contamination and improper storage during food preparation. Consequently, it is essential to prioritize continuous education for canteen staff on food safety, efficacious management, and proper practices. The implementation of comprehensive guidelines, encompassing multiple critical aspects, can potentially reduce the occurrence of B. cereus outbreaks.

Construction and optimization of a multiplex PMAxx-qPCR assay for viable Bacillus cereus and development of a detection kit

In this study, a PMAxx-qPCR method for the detection and quantification of viable Bacillus cereus (B. cereus) was established based on the cesA gene that is involved in cereulide synthesis, enterotoxin gene bceT and hemolytic enterotoxin gene hblD combined with modified propidium monoazide (PMAxx). The sensitivity detection limit of the method was as follows: the DNA extracted by the kit reached 140 fg/μL, and the bacterial suspension without enrichment reached 2.24 × 10¹ CFU/mL; 14 nonB. cereus strains of the 17 tested strains all tested as negative, whereas the 2 strains of B. cereus carrying the target virulence gene(s) could be accurately detected. In terms of application, we assembled the constructed PMAxx-qPCR reaction into a detection kit and evaluated its application performance. The results showed that the detection kit has high sensitivity, strong anti-interference capability, and has good application potential. The purpose of this study is to provide a reliable detection method for the prevention and traceability of B. cereus infections.