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Journal of Dairy Science Sep 2019Bacillus cereus sensu lato is one of the most harmful bacterial groups affecting the quality and safety of powdered infant formula (PIF). In this study, samples were...
Bacillus cereus sensu lato is one of the most harmful bacterial groups affecting the quality and safety of powdered infant formula (PIF). In this study, samples were collected from the raw materials and processing environments of PIF. A total of 84 isolates were identified as Bacillus cereus sensu stricto (B. cereus s. s.) by 16S rRNA analysis, molecular typing technology, and physiological and biochemical tests. The 84 B. cereus s. s. strains were assigned to panC group II, group III, and group IV. Then, the 7 housekeeping genes glpF, gmk, ilvD, pta, pur, pycA, and tpi were selected for multilocus sequence typing. Results showed that the 84 isolates were clustered into 24 sequence types (ST), and 14 novel ST were detected. Among the 24 ST, ST999 (19/84, 22.62%) and ST1343 (13/84, 15.48%) predominated. The correlation between processing areas and ST showed that the processing environments of the production and packing areas were the most susceptible to contamination by B. cereus s. s. Spores of these ST showed different heat resistance phenotypes evaluated by the analysis of D (time in minutes of spore decimal reduction at each temperature) and Z values (temperature increase required to reduce the D value to one-tenth of the original). Spores from group III according to panC gene analysis were the most heat resistant. These findings will help us to better understand B. cereus s. s. contamination and control in PIF processing environments.
Topics: Bacillus cereus; Food Microbiology; Hot Temperature; Humans; Infant; Infant Formula; Multilocus Sequence Typing; Phenotype; Phylogeny; Powders; RNA, Ribosomal, 16S
PubMed: 31255274
DOI: 10.3168/jds.2019-16392 -
Journal of Food Protection Oct 2019is a spore-forming gastrointestinal pathogen that can cause life-threatening diseases. Here, a simple and effective assay to detect was developed, using cross-priming...
is a spore-forming gastrointestinal pathogen that can cause life-threatening diseases. Here, a simple and effective assay to detect was developed, using cross-priming amplification (CPA). Amplicons were detected using disposable cartridges that contained nucleic acid detection strips. The sensitivity of CPA assay for was assessed using serial dilutions of genomic DNA, which indicated a detection limit of 3.6 × 10 CFU/mL. No cross-reactions were detected when genomic DNA extracted from 12 different strains and 20 other bacterial foodborne strains were tested, suggesting that the assay is highly specific. Finally, we evaluated the practical applications of the CPA assay for the detection of in 150 food samples and found that its sensitivity and specificity, compared with real-time PCR, were approximately 98.18 and 100%, respectively. In conclusion, CPA combined with nucleic acid detection strips is easy to perform, requires simple equipment, and offers highly specific and sensitive detection.
Topics: Bacillus cereus; DNA, Bacterial; Food Microbiology; Nucleic Acid Amplification Techniques; Real-Time Polymerase Chain Reaction; Sensitivity and Specificity
PubMed: 31536421
DOI: 10.4315/0362-028X.JFP-19-156 -
Journal of Food Protection Feb 2016The emetic toxin cereulide, which can be produced by Bacillus cereus, can be the cause of food poisoning upon ingestion by the consumer. The toxin causes vomiting and is...
The emetic toxin cereulide, which can be produced by Bacillus cereus, can be the cause of food poisoning upon ingestion by the consumer. The toxin causes vomiting and is mainly produced in farinaceous food products. This article includes the prevalence of B. cereus and of cereulide in food products in The Netherlands, a characterization of B. cereus isolates obtained, cereulide production conditions, and a comparison of consumer exposure estimates with those of a previous exposure assessment. Food samples (n = 1,489) were tested for the presence of B. cereus; 5.4% of the samples contained detectable levels (>10(2) CFU/g), and 0.7% contained levels above 10(5) CFU/g. Samples (n = 3,008) also were tested for the presence of cereulide. Two samples (0.067%) contained detectable levels of cereulide at 3.2 and 5.4 μg/kg of food product. Of the 481 tested isolates, 81 produced cereulide and/or contained the ces gene. None of the starch-positive and hbl-containing isolates possessed the ces gene, whereas all strains contained the nhe genes. Culture of emetic B. cereus under nonoptimal conditions revealed a delay in onset of cereulide production compared with culture under optimal conditions, and cereulide was produced in all cases when B. cereus cells had been in the stationary phase for some time. The prevalence of cereulide-contaminated food approached the prevalence of contaminated products estimated in an exposure assessment. The main food safety focus associated with this pathogen should be to prevent germination and growth of any B. cereus present in food products and thus prevent cereulide production in foods.
Topics: Bacillus cereus; Depsipeptides; Emetics; Food Contamination; Food Handling; Food Microbiology; Netherlands
PubMed: 26818983
DOI: 10.4315/0362-028X.JFP-15-217 -
The Veterinary Quarterly Dec 2023An outbreak of a disease with a high mortality rate occurred in a Chinese Softshell Turtle () farm in Hubei Province. This study isolated a highly pathogenic strain...
An outbreak of a disease with a high mortality rate occurred in a Chinese Softshell Turtle () farm in Hubei Province. This study isolated a highly pathogenic strain (Y271) from diseased . Y271 has hemolysis, containing both Hemolysin BL (, and ), Non-hemolytic enterotoxin, NHE (, and ), and Enterotoxin FM () genes. Y271 is highly pathogenic against with an LD = 6.80 × 10 CFU/g weight. was detected in multiple tissues of the infected . Among them, spleen tissue showed the highest copy number density (1.54 ± 0.12 × 10 copies/mg). Multiple tissues and organs of diseased exhibited significant pathological damage, especially the spleen, liver, kidney, and intestine. It showed obvious tissue structure destruction, lesions, necrosis, red blood cells, and inflammatory cell infiltration. proliferating in the spleen, liver, and other tissues was observed. The intestinal microbiota of the diseased was altered, with a greater abundance of Firmicutes, Fusobacterium, and Actinomyces than in the healthy group. , , and abundance were higher in the diseased group than in the healthy group. The number of unique microbial taxa (472) in the disease group was lower than that of the healthy group (705). Y271 was sensitive to multiple drugs, including florfenicol, enrofloxacin, neomycin, and doxycycline. is the etiological agent responsible for the massive death of and reveals its potential risks during cultivation.
Topics: Animals; Bacillus cereus; Food Microbiology; Enterotoxins
PubMed: 38010068
DOI: 10.1080/01652176.2023.2287191 -
Microbiology Spectrum Feb 2016The three main species of the Bacillus cereus sensu lato, B. cereus, B. thuringiensis, and B. anthracis, were recognized and established by the early 1900 s because they...
The three main species of the Bacillus cereus sensu lato, B. cereus, B. thuringiensis, and B. anthracis, were recognized and established by the early 1900 s because they each exhibited distinct phenotypic traits. B. thuringiensis isolates and their parasporal crystal proteins have long been established as a natural pesticide and insect pathogen. B. anthracis, the etiological agent for anthrax, was used by Robert Koch in the 19th century as a model to develop the germ theory of disease, and B. cereus, a common soil organism, is also an occasional opportunistic pathogen of humans. In addition to these three historical species designations, are three less-recognized and -understood species: B. mycoides, B. weihenstephanensis, and B. pseudomycoides. All of these "species" combined comprise the Bacillus cereus sensu lato group. Despite these apparently clear phenotypic definitions, early molecular approaches to separate the first three by various DNA hybridization and 16S/23S ribosomal sequence analyses led to some "confusion" because there were limited differences to differentiate between these species. These and other results have led to frequent suggestions that a taxonomic change was warranted to reclassify this group to a single species. But the pathogenic properties of B. anthracis and the biopesticide applications of B. thuringiensis appear to "have outweighed pure taxonomic considerations" and the separate species categories are still being maintained. B. cereus sensu lato represents a classic example of a now common bacterial species taxonomic quandary.
Topics: Bacillus anthracis; Bacillus cereus; Bacillus thuringiensis; Humans; Phylogeny
PubMed: 26999390
DOI: 10.1128/microbiolspec.TBS-0012-2012 -
BMC Microbiology Jun 2021Bacillus cereus 0-9, a Gram-positive, endospore-forming bacterium isolated from healthy wheat roots in our previous research, is considered to be an effective biocontrol...
BACKGROUND
Bacillus cereus 0-9, a Gram-positive, endospore-forming bacterium isolated from healthy wheat roots in our previous research, is considered to be an effective biocontrol strain against several soil-borne plant diseases. SpoVG, a regulator that is broadly conserved among many Gram-positive bacteria, may help this organism coordinate environmental growth and virulence to survive. This study aimed to explore the multiple functions of SpoVG in B. cereus 0-9.
METHODS
The gene knockout strains were constructed by homologous recombination, and the sporulation process of B. cereus 0-9 and its mutants were observed by fluorescence staining method. We further determined the spore yields and biofilm formation abilities of test strains. Transcriptional fusion strains were constructed by overlapping PCR technique, and the promoter activity of the target gene was detected by measuring its fluorescence intensity. The biofilm production and colonial morphology of B. cereus 0-9 and its mutants were determined to study the functions of the target genes, and the transcription level of the target gene was determined by qRT-PCR.
RESULTS
According to observation of the sporulation process of B. cereus 0-9 in germination medium, SpoVG is crucial for regulating sporulation stage V of B. cereus 0-9, which is identical to that of Bacillus subtilis but differs from that of Bacillus anthracis. In addition, SpoVG could influence biofilm formation of B. cereus 0-9. The transcription levels of two genes closely related to biofilm-formation, sipW and calY, were downregulated in a ΔspoVG mutant. The role of SpoVG in regulating biofilm formation was further explored by deleting the genes abrB and sinR in the ΔspoVG mutant, respectively, generating the double mutant strains ΔspoVGΔabrB and ΔspoVGΔsinR. The phenotypes of these double mutants were congruent with those of the single abrB and sinR deletion strains, respectively, which showed increased biofilm formation. This indicated that spoVG was located upstream of abrB and sinR in the regulatory pathway of B. cereus biofilm formation. Further, the results of qRT-PCR and the luminescence intensity of transcriptional fusion strains indicated that spoVG gene deletion could inhibit the transcription of Spo0A.
CONCLUSIONS
SpoVG, an important regulator in the sporulation of B. cereus, is located upstream of Spo0A and participates in regulation of biofilm formation of B. cereus 0-9 through regulating the transcription level of spo0A. Sporulation and biofilm formation are crucial mechanisms by which bacteria respond to adverse conditions. SpoVG is therefore an important regulator of Spo0A and is crucial for both sporulation and biofilm formation of B. cereus 0-9. This study provides a new insight into the regulatory mechanism of environmental adaptation in bacteria and a foundation for future studies on biofilm formation of B. cereus.
Topics: Bacillus cereus; Bacterial Proteins; Gene Expression Regulation, Bacterial; Promoter Regions, Genetic; Spores, Bacterial; Transcription Factors; Transcription, Genetic
PubMed: 34102998
DOI: 10.1186/s12866-021-02239-6 -
Microbial Cell Factories Aug 2011The ability of microorganisms to adapt to changing environments and gain cell robustness, challenges the prediction of their history-dependent behaviour. Using our model... (Review)
Review
The ability of microorganisms to adapt to changing environments and gain cell robustness, challenges the prediction of their history-dependent behaviour. Using our model organism Bacillus cereus, a notorious Gram-positive food spoilage and pathogenic spore-forming bacterium, a strategy will be described that allows for identification of biomarkers for robustness. First an overview will be presented of its two-component systems that generally include a transmembrane sensor histidine kinase and its cognate response regulator, allowing rapid and robust responses to fluctuations in the environment. The role of the multisensor hybrid kinase RsbK and the PP2C-type phosphatase RsbY system in activation of the general stress sigma factor σB is highlighted. An extensive comparative analysis of transcriptional landscapes derived from B. cereus exposed to mild stress conditions such as heat, acid, salt and oxidative stress, revealed that, amongst others σB regulated genes were induced in most conditions tested. The information derived from the transcriptome data was subsequently implemented in a framework for identifying and selecting cellular biomarkers at their mRNA, protein and/or activity level, for mild stressinduced microbial robustness towards lethal stresses. Exposure of unstressed and mild stress-adapted cells to subsequent lethal stress conditions (heat, acid and oxidative stress) allowed for quantification of the robustness advantage provided by mild stress pretreatment using the plate-count method. The induction levels of the selected candidate-biomarkers, σB protein, catalase activity and transcripts of certain proteases upon mild stress treatment, were significantly correlated to mild stress-induced enhanced robustness towards lethal thermal, oxidative and acid stresses, and were therefore suitable to predict these adaptive traits. Cellular biomarkers that are quantitatively correlated to adaptive behavior will facilitate our ability to predict the impact of adaptive behavior on cell robustness and will allow to control and/or exploit these adaptive traits. Extrapolation to other species and genera is discussed such as avenues towards mechanism-based design of microbial fitness and robustness.
Topics: Bacillus cereus; Biomarkers; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Genes, Bacterial; Humans; Oxidative Stress; Signal Transduction; Transcription, Genetic
PubMed: 21995521
DOI: 10.1186/1475-2859-10-S1-S9 -
Applied and Environmental Microbiology Mar 2018While some species in the group are well-characterized human pathogens (e.g., and ), the pathogenicity of other species (e.g., ) either has not been characterized or...
While some species in the group are well-characterized human pathogens (e.g., and ), the pathogenicity of other species (e.g., ) either has not been characterized or is presently not well understood. To provide an updated characterization of the pathogenic potential of species in the group, we classified a set of 52 isolates, including 8 type strains and 44 isolates from dairy-associated sources, into 7 phylogenetic clades and characterized them for (i) the presence of toxin genes, (ii) phenotypic characteristics used for identification, and (iii) cytotoxicity to human epithelial cells. Overall, we found that toxin genes are broadly distributed but are not consistently present within individual species and/or clades. After growth at 37°C, isolates within a clade did not typically show a consistent cytotoxicity phenotype, except for isolates in clade VI (/), where none of the isolates were cytotoxic, and isolates in clade I (), which consistently displayed cytotoxic activity. Importantly, our study highlights that is cytotoxic toward human cells. Our results indicate that the detection of toxin genes does not provide a reliable approach to predict the pathogenic potential of group isolates, as the presence of toxin genes is not always consistent with cytotoxicity phenotype. Overall, our results suggest that isolates from multiple group clades have the potential to cause foodborne illness, although cytotoxicity is not always consistently found among isolates within each clade. Despite the importance of the group as a foodborne pathogen, characterizations of the pathogenic potential of all group species were lacking. We show here that (clade I), which has been considered a harmless environmental microorganism, produces toxins and exhibits a phenotype consistent with the production of pore-forming toxins. Furthermore, isolates (clade VI) did not show cytotoxicity when grown at 37°C, despite carrying multiple toxin genes. Overall, we show that the current standard methods to characterize group isolates and to detect the presence of toxin genes are not reliable indicators of species, phylogenetic clades, or an isolate's cytotoxic capacity, suggesting that novel methods are still needed for differentiating pathogenic from nonpathogenic species within the group. Our results also contribute data that are necessary to facilitate risk assessments and a better understanding as to which group species are likely to cause foodborne illness.
Topics: Bacillus; Bacillus cereus; Bacterial Toxins; Genome, Bacterial; Phylogeny
PubMed: 29330180
DOI: 10.1128/AEM.02479-17 -
Journal of Proteomics Oct 2023Bacillus cereus is a food-borne Gram-positive pathogen. The emetic reference strain B. cereus AH187 is surrounded by a proteinaceous surface layer (S-layer) that...
Bacillus cereus is a food-borne Gram-positive pathogen. The emetic reference strain B. cereus AH187 is surrounded by a proteinaceous surface layer (S-layer) that contributes to its physico-chemical surface properties, and promotes its adhesion in response to starvation conditions. The S-layer produced by B. cereus AH187 is composed of two proteins, SL2 and EA1, which are incorporated at different growth stages. Here, we showed that deletion of the genes encoding SL2 and EA1 produced viable cells, but decreased the glucose uptake rate at the start of growth, and induced extensive reorganization of the cellular and exoproteomes upon entry into the stationary phase. As a consequence, stationary cells were less resistant to abiotic stress. Taken together, our data indicate that the S-layer is crucial but comes at a metabolic cost that modulates the stationary phase response. SIGNIFICANCE: The emetic strains of Bacillus cereus are known to cause severe food poisoning, making it crucial to understand the factors contributing to their selective enrichment in foods. Most emetic strains are surrounded by a crystalline S-layer, which is a costly protein structure to produce. In this study, we used high-throughput proteomics to investigate how S-layer synthesis affects the allocation of cellular resources in the emetic B. cereus strain AH187. Our results demonstrate that the synthesis of the S-layer plays a crucial role in the pathogen's ability to thrive under stationary growth phase conditions by modulating the stress response, thereby promoting its lifestyle as an emetic pathogen. We conclude that the synthesis of the S-layer is a critical adaptation for emetic B. cereus to successfully colonize specific niches.
Topics: Humans; Bacillus cereus; Food Microbiology; Emetics; Food Contamination; Foodborne Diseases
PubMed: 37730087
DOI: 10.1016/j.jprot.2023.105007 -
Characterization and genomic analysis of chromate resistant and reducing Bacillus cereus strain SJ1.BMC Microbiology Aug 2010Chromium is a toxic heavy metal, which primarily exists in two inorganic forms, Cr(VI) and Cr(III). Chromate [Cr(VI)] is carcinogenic, mutational, and teratogenic due to...
BACKGROUND
Chromium is a toxic heavy metal, which primarily exists in two inorganic forms, Cr(VI) and Cr(III). Chromate [Cr(VI)] is carcinogenic, mutational, and teratogenic due to its strong oxidizing nature. Biotransformation of Cr(VI) to less-toxic Cr(III) by chromate-resistant and reducing bacteria has offered an ecological and economical option for chromate detoxification and bioremediation. However, knowledge of the genetic determinants for chromate resistance and reduction has been limited so far. Our main aim was to investigate chromate resistance and reduction by Bacillus cereus SJ1, and to further study the underlying mechanisms at the molecular level using the obtained genome sequence.
RESULTS
Bacillus cereus SJ1 isolated from chromium-contaminated wastewater of a metal electroplating factory displayed high Cr(VI) resistance with a minimal inhibitory concentration (MIC) of 30 mM when induced with Cr(VI). A complete bacterial reduction of 1 mM Cr(VI) was achieved within 57 h. By genome sequence analysis, a putative chromate transport operon, chrIA1, and two additional chrA genes encoding putative chromate transporters that likely confer chromate resistance were identified. Furthermore, we also found an azoreductase gene azoR and four nitroreductase genes nitR possibly involved in chromate reduction. Using reverse transcription PCR (RT-PCR) technology, it was shown that expression of adjacent genes chrA1 and chrI was induced in response to Cr(VI) but expression of the other two chromate transporter genes chrA2 and chrA3 was constitutive. In contrast, chromate reduction was constitutive in both phenotypic and gene expression analyses. The presence of a resolvase gene upstream of chrIA1, an arsenic resistance operon and a gene encoding Tn7-like transposition proteins ABBCCCD downstream of chrIA1 in B. cereus SJ1 implied the possibility of recent horizontal gene transfer.
CONCLUSION
Our results indicate that expression of the chromate transporter gene chrA1 was inducible by Cr(VI) and most likely regulated by the putative transcriptional regulator ChrI. The bacterial Cr(VI)-resistant level was also inducible. The presence of an adjacent arsenic resistance gene cluster nearby the chrIA1 suggested that strong selective pressure by chromium and arsenic could cause bacterial horizontal gene transfer. Such events may favor the survival and increase the resistance level of B. cereus SJ1.
Topics: Bacillus cereus; Bacterial Proteins; Biotransformation; Chromates; Drug Resistance, Bacterial; Gene Expression Regulation, Bacterial; Genomics; Molecular Sequence Data; Oxidation-Reduction; Sewage
PubMed: 20723231
DOI: 10.1186/1471-2180-10-221