Incidence, Antibiotic Susceptibility, and Toxin Profiles of Bacillus cereus sensu lato Isolated from Korean Fermented Soybean Products

Investigation of Virulence and Antibiotic-Resistance of Bacillus cereus Isolated from Various Spices

Spices and herbs are potential vectors for virulent and pathogenic micro-organisms, which cause illness in consumers, contribute to spoilage, and reduce the durability of foodstuffs. The present study aims to provide relevant data about virulence and antibiotic resistance of Bacillus cereus isolated from various spices. A total of 200 samples of 8 types of spices (black pepper, chilli, white pepper, cumin, cinnamon, turmeric, curry powder, and sumac) were collected from various markets, retail shops, and sucuk production premises located in the Isfahan province of Iran. Presumptive B. cereus strains were obtained using Bacara Agar plates after enrichment in saline peptone water and final colonies were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Enterotoxin (HBL) and nonhaemolytic enterotoxin (NHE) production were assessed using the Duopath® Cereus Enterotoxins Test kit. The Kirby-Bauer disc diffusion method was applied as antibiotics susceptibility test. PCR was used to detect Emetic toxin gene (CES and CER) and enterotoxigenic toxin gene (cytK, nheA, hblC, and entFM). Results show a significant prevalence of B. cereus (42%) in spices. However, the spices meet food safety recommendations (<10⁴ cfu/g). Antibiotics susceptibility test show alarming rate of resistance to beta-lactam antibiotics specially ampicillin (83.33%) and penicillin (82.14%). Concerning the toxin producing capacity more than half of the isolates (51.19%) produce NHE toxin and 27.38% produce HBL toxin. The most abundant gene were nheA, nheB, and nheC and a combination of 4 genes (entFM, nheA, hblC, and cytK) was detected in many isolates. In conclusion, the presence of multidrug resistant B. cereus strains carrying diarrhoeal toxin-encoding genes in spices intended for human consumption represents a serious health hazard. These results indicate the need for regular surveillance of the occurrence of B. cereus strains in spices and food products in Iran.

Elucidating the genomic history of commercially used Bacillus thuringiensis subsp. tenebrionis strain NB176

Bacillus thuringiensis subsp. tenebrionis (Btt) produces a coleopteran-specific crystal protoxin protein (Cry3Aa δ-endotoxin). After its discovery in 1982, the strain NB125 (DSM 5526) was eventually registered in 1990 to control the Colorado potato beetle (Leptinotarsa decemlineata). Gamma-irradiation of NB125 resulted in strain NB176-1 (DSM 5480) that exhibited higher cry3Aa production and became the active ingredient of the plant protection product Novodor^® FC. Here, we report a comparative genome analysis of the parental strain NB125, its derivative NB176-1 and the current commercial production strain NB176. The entire genome sequences of the parental and derivative strains were deciphered by a hybrid de novo approach using short (Illumina) and long (Nanopore) read sequencing techniques. Genome assembly revealed a chromosome of 5.4 to 5.6 Mbp and six plasmids with a size range from 14.9 to 250.5 kbp for each strain. The major differences among the original NB125 and the derivative strains NB176-1 and NB176 were an additional copy of the cry3Aa gene, which translocated to another plasmid as well as a chromosomal deletion (~ 178 kbp) in NB176. The assembled genome sequences were further analyzed in silico for the presence of virulence and antimicrobial resistance (AMR) genes.

Molecular characterization and prevalence of Bacillus species isolated from Saudi hospitals

Objective

This study highlighted the dissemination of Bacillus species (including drug-resistant species) in public hospital environments and calls for the design of optimal strategies to curb their spread. This a critical consideration for all health care systems such as caring for the increasing number of immune-compromised patient.

Methods

A total of 528 swab samples were collected from the environments of different Saudi hospitals. Swab samples were collected by swabbing approximately 5 cm² of different surfaces at each site using pre-moisturized cotton swabs with 1 mL of neutralizing buffer. The swabs were transported in cool boxes with ice packs within 2 h of collection. Isolation and identification were performed according to conventional bacteriological, semi-automated and molecular characterization methods. Antibiogram typing was carried against different groups of antimicrobial agents.

Results

The most prevalent of the isolated Bacillus species were Bacillus cereus (46.6%) followed by Bacillus subtilis (38.1%); the least prevalent was Bacillus pumilus (1.1%). Most Bacillus isolates (25.6%) were isolated from the Department of Internal Medicine followed by the Emergency Department (18.8%), while the operating rooms had the lowest prevalence (4.5%). Antimicrobial susceptibility testing revealed high levels of resistance in Bacillus isolates to β-lactams and tetracycline. Overall, 21.6% of isolates showed multi-drug resistance to three or more antibiotics (21.6%). Antibiogram typing of the 176 isolates revealed 45 antibiotypes; the most common was antibiotype 31, which included 32 isolates (18.2%); this particular antibiotype was resistant to both penicillin and cefoxitin.

Conclusions

Analyses identified the high dissemination of Bacillus species in several hospital environments with high resistance to β-lactams and tetracycline antibiotics. Molecular analysis also revealed the existence of genetic diversity among the Bacillus isolates investigated. Thus, monitoring the hospital environment is an important tool in the prevention of hospital-associated infection by Bacillus species.

Prevalence and characterization of toxigenic Bacillus cereus group isolated from low-moisture food products

The present study was conducted to determine the occurrence of B. cereus group members in low-moisture food products by phenotypic and genetic assessment and to evaluate the toxigenic potential of B. cereus group isolates. According to the results of their morphological shape, growth temperature range, strain-specific gene distribution, 79.5% and 20.5% among 112 isolates were identified as B. cereus sensu stricto (s.s.) and B. thuringiensis, respectively and other toxigenic B. cereus group members was not found. All B. cereus group isolates possessed nheABC, hblACD, cytK, entFM genes, and the most frequent gene was nheA. Only three B. cereus s. s. isolates exhibited as emetic toxin gene-harboring B. cereus group. Several B. cereus s.s. and B. thuringiensis isolates from a low-moisture food products were moderate biofilm formers and showed resistance to rifampicin, tetracycline, or clindamycin. The existence of B. cereus s.s. and B. thuringiensis in low-moisture food products indicates the possible risk of foodborne infections due to their virulence potential.

Toxigenic Genes, Pathogenic Potential and Antimicrobial Resistance of Bacillus cereus Group Isolated from Ice Cream and Characterized by Whole Genome Sequencing

Bacillus cereus is isolated from a variety of foods where it may cause food spoilage and/or food poisoning due to its toxigenic and pathogenic nature. In this study, we identified members of B. cereus groups in 65% of the ice cream samples analyzed, which were characterized based on multi locus variable number tandem repeats analysis (MLVA) and whole genome sequencing (WGS). The MLVA revealed that 36 strains showed different allelic profiles. Analyses of WGS data enabled the identification of three members of the B. cereus group: B. cereus sensu stricto, B. mosaicus and B. thuringiensis. Based on the multi locus sequence typing (MLST) scheme, the strains were classified in 27 sequence types (STs), including ST26 that causes food poisoning. Toxin genes’ detection revealed the presence of the genes encoding nonhemolytic enterotoxin (NHE), hemolysin BL (HBL), cytotoxin K (cytK) and cereulide (ces) in 100%, 44%, 42% and 8% of the strains, respectively. The identification of eleven antimicrobial resistance (AMR) genes predicted the resistance to five different antimicrobials, and the resistance to beta-lactam antibiotics was confirmed with a phenotypic antimicrobial test. Taken together, the results showed that the B. cereus strains isolated from ice cream were a potential hazard for consumer safety.

Two Faces of Fermented Foods-The Benefits and Threats of Its Consumption

In underdeveloped and developing countries, due to poverty, fermentation is one of the most widely used preservation methods. It not only allows extending the shelf life of food, but also brings other benefits, including inhibiting the growth of pathogenic microorganisms, improving the organoleptic properties and product digestibility, and can be a valuable source of functional microorganisms. Today, there is a great interest in functional strains, which, in addition to typical probiotic strains, can participate in the treatment of numerous diseases, disorders of the digestive system, but also mental diseases, or stimulate our immune system. Hence, fermented foods and beverages are not only a part of the traditional diet, e.g., in Africa but also play a role in the nutrition of people around the world. The fermentation process for some products occurs spontaneously, without the use of well-defined starter cultures, under poorly controlled or uncontrolled conditions. Therefore, while this affordable technology has many advantages, it can also pose a potential health risk. The use of poor-quality ingredients, inadequate hygiene conditions in the manufacturing processes, the lack of standards for safety and hygiene controls lead to the failure food safety systems implementation, especially in low- and middle-income countries or for small-scale products (at household level, in villages and scale cottage industries). This can result in the presence of pathogenic microorganisms or their toxins in the food contributing to cases of illness or even outbreaks. Also, improper processing and storage, as by well as the conditions of sale affect the food safety. Foodborne diseases through the consumption of traditional fermented foods are not reported frequently, but this may be related, among other things, to a low percentage of people entering healthcare care or weaknesses in foodborne disease surveillance systems. In many parts of the world, especially in Africa and Asia, pathogens such as enterotoxigenic and enterohemorrhagic Escherichia coli, Shigella spp., Salmonella spp., enterotoxigenic Staphylococcus aureus, Listeria monocytogenes, and Bacillus cereus have been detected in fermented foods. Therefore, this review, in addition to the positive aspects, presents the potential risk associated with the consumption of this type of products.

Physicochemical, Microbial, and Volatile Compound Characteristics of Gochujang, Fermented Red Pepper Paste, Produced by Traditional Cottage Industries

Gochujang, fermented red pepper paste, is a grain-based Korean traditional food. The quality of gochujang produced by cottage industries is not well-documented. Thus, the present study aimed to analyze the quality of gochujang from 35 traditional cottage industries for physicochemical and microbial characteristics, along with volatile compound contents. In addition to microbial characteristics, salinity, pH, free amino nitrogen, and alcohol content were evaluated. Ethanol was detected as the predominant alcohol and 57% of tested gochujang products harbored >1% of total alcohol content, which was above the recommended level for halal products. Gochujang products contained hexadecanoic and linoleic acids predominantly and several volatile compounds belonging to the classes of alcohols, aldehydes, alkanes, nitrogen-containing compounds, and terpenes. A wide range of aerobic mesophilic bacteria (2.79–8.73 log CFU/g) and yeast counts (1.56–7.15 log CFU/g) was observed. Five distinct yeast species were identified, including Zygosaccharomyces rouxii. Eight gochujang products were found to be contaminated with Bacillus cereus (>4 log CFU/g). This study suggests that there is a need to limit B. cereus contamination in cottage industry products and reduce alcohol content to comply with halal food guidelines.

Occurrence, Antibiotic Resistance, Virulence Factors, and Genetic Diversity of Bacillus spp. from Public Hospital Environments in South Africa

This study aimed to assess the molecular dissemination of Bacillus species in public hospitals in South Africa. The study conducted over 3 months during 2017 involved representative samples obtained from three wards (general ward, intensive care unit, and pediatric unit) from four public hospitals denoted as A (Central), B (Tertiary), C (Regional), and D (District). Swabs collected from 11 distinct hospital surfaces were screened using selective media, biochemical testing, and molecular methods. Overall, 17% (135/777) isolates were identified with a prevalence of 24% (32/135) for central, 33% (45/135) for tertiary, 27% (36/135) for regional, and 16% (22/135) for district hospital. Bacillus species were further confirmed to belong to Bacillus cereus (129/135; 96%) and Bacillus subtilis (6/135; 4%). Prevalence was similar across the wards, averaging 33.3% (45/135). The highest prevalence of Bacillus isolates was found on the drip stands (11.8%), sink (11.8%), ward phone (11.5%), and nurses' tables (10.3%). Minimum inhibitory concentration analyses revealed high resistance to β-lactams, fluoroquinolones, and tetracyclines. The most common resistance genes detected were ermB (56%) and tetM (5%). Enterotoxin virulence genes hblA (77%) and hblD (88%) associated with the diarrheal syndrome were most detected; however, no ces genes (cereulide toxin) for emetic syndrome was found. The enterobacterial repetitive intergenic consensus PCR revealed considerable diversity at the different levels of health care, although the clonal spread of strains between the sites/wards within each specific hospital was revealed. The study highlighted the dissemination of drug-resistant Bacillus spp. in public hospital environments and calls for the design of optimal strategies to curb their spread.

Bacillus cereus food intoxication and toxicoinfection

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.

An Investigation on the Occurrence and Molecular Characterization of Bacillus cereus in Meat and Meat Products in China

Bacillus cereus is a common foodborne pathogen that can cause both gastrointestinal and nongastrointestinal diseases. In this study, we collected 603 meat and meat products from 39 major cities in China. The positive contamination rate of B. cereus in the collected samples was 26.37% (159/603), and the contamination level in 5.03% (8/159) positive samples exceeded 1100 most probable number/g. The detection rates of virulence genes were 89.7% for the nheABC gene group, 37.1% for the hblACD gene cluster, 82.3% for cytK-2, and 2.9% for cesB. Notably, all isolates presented with multiple antibiotic resistance, and 99.43% of isolates were resistant to five classes of antibiotics. In addition, the multilocus sequence typing results indicated that all isolates were rich in genetic diversity. Collectively, we conducted a systematic investigation on the prevalence and characterization of B. cereus in meat and meat products in China, providing crucial information for assessing the risk of B. cereus occurrence in meat and meat products.

The Food Poisoning Toxins of Bacillus cereus

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.

Multi-locus sequence typing and virulence profile in Bacillus cereus sensu lato strains isolated from dairy products

Members of Bacillus cereus group are important food contaminants and they are of relevant interest in food safety and public heath due to their ability to cause two distinct forms of food poisoning, emetic and diarrhoeal syndrome. In the present study, 90 strains of B. cereus isolated from dairy products, have been typed using Multilocus Sequence Typing (MLST) analysis and investigated for the occurrence of 10 enterotoxigenic genes (hblA, hblC, hblD, nheA, nheB, nheC, cytK, entFM, entS and bceT) and one emetogenic gene (ces), to determine their genetic diversity. A total of 58 sequence types were identified and among these 17 were signalled as new profiles. Among the virulence genes, the majority of our strains carried the entS (92%), entFM (86%), nhe (82%) and cytK (72%) genes. All remaining genes were identified in at least one strain with different prevalence, stressing the genetic diversity, how even the different grade of pathogenicity of B. cereus isolated from dairy products.

The Bacillus cereus Food Infection as Multifactorial Process

The ubiquitous soil bacterium Bacillus cereus presents major challenges to food safety. It is responsible for two types of food poisoning, the emetic form due to food intoxication and the diarrheal form emerging from food infections with enteropathogenic strains, also known as toxico-infections, which are the subject of this review. The diarrheal type of food poisoning emerges after production of enterotoxins by viable bacteria in the human intestine. Basically, the manifestation of the disease is, however, the result of a multifactorial process, including B. cereus prevalence and survival in different foods, survival of the stomach passage, spore germination, motility, adhesion, and finally enterotoxin production in the intestine. Moreover, all of these processes are influenced by the consumed foodstuffs as well as the intestinal microbiota which have, therefore, to be considered for a reliable prediction of the hazardous potential of contaminated foods. Current knowledge regarding these single aspects is summarized in this review aiming for risk-oriented diagnostics for enteropathogenic B. cereus.

Prevalence of ces and cytk Genes of Bacillus cereus Isolated From Raw Milk in Tabriz, Iran

Background: Bacillus cereus is a gram-positive and spore-forming bacterium which is widespread in nature. It also has been known as a major foodborne pathogen that often plays a role in the contamination of ready-to-eat and dairy products. It causes two different types of food poisoning in human: the diarrheal type and the emetic type. Objective: The current study was planned to determine the prevalence of ces and cytk genes of Bacillus cereus isolated from raw milk in Tabriz, Iran. Materials and Methods: In this study, 40 B. cereus strains isolated from cow raw milk, that had already been identified phenotypically, were assessed for molecular confirmation by polymerase chain reaction (PCR) method. Then, they were evaluated for presence of ces and cytK genes by specific primers. Results: Of 40 B. cereus strains, 39 strains were confirmed molecularly. The frequency of cytK and ces genes was reported 38 (97.43%) and 0 (0%), respectively. Conclusion: The results of present study showed that B. cereus strains isolated from raw milk had high potential in causing diarrhea poisoning. Therefore, using procedures to reduce the bacterial contamination during the processing of dairy product is essential.

Identification and Pathogenic Potential of Bacillus cereus Strains Isolated from a Dairy Processing Plant Producing PDO Taleggio Cheese

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.

Enterotoxin and Emetic Toxin Genes Profiles and Genetic Diversity of Bacillus cereus Isolated from Food, Environmental and Clinical Samples in Serbia

Bacillus cereus, usually ingested by food, can cause two types of disease due to the presence of toxins: vomiting and diarrhea syndrome. Systemic infections can also occur. The aim was to detect genes for enterotoxins (hblA, entFM) and emetic toxin (cer) and to investigate the genetic heterogeneity of B. cereus isolates from food, environment and human stool. Identification of B. cereus was performed by means of selective medium, classical biochemical test and polymerase chain reaction (PCR). Toxin genes were detected by PCR. Typing was performed by random amplified polymorphic DNA (RAPD). EntFM gene was present in all stool and food samples and in 28/30 environmental isolates. HblA gene was present in 29/30 stool, 23/30 food and 24/30 environmental isolates. Cer gene was present in 30/30 stool, 28/30 food and 25/30 environmental isolates. The RAPD results show high heterogeneity among the isolates from each group. In the cumulative dendrogram, representative isolates from all three groups formed two clusters with a difference of 53%. The detection of toxin genes in all B. cereus isolates indicated these bacteria as potentially pathogenic and a serious threat for human health. The presence of isolates from all three groups in the same cluster suggests the existence of similar strains in the environment, food and patients, which is in line with the circulation of strains in nature through the food chain.

Predominant Mycotoxins, Pathogenesis, Control Measures, and Detection Methods in Fermented Pastes

Fermented pastes are some of the most popular traditional products in China. Many studies reported a strong possibility that fermented pastes promote exposure to mycotoxins, including aflatoxins, ochratoxins, and cereulide, which were proven to be carcinogenic and neurotoxic to humans. The primary mechanism of pathogenicity is by inhibiting protein synthesis and inducing oxidative stress using cytochrome P450 (CYP) enzymes. The level of mycotoxin production is dependent on the pre-harvest or post-harvest stage. It is possible to implement methods to control mycotoxins by using appropriate antagonistic microorganisms, such as Aspergillus niger, Lactobacillus plantarum, and Saccharomyces cerevisiae isolated from ordinary foods. Also, drying products as soon as possible to avoid condensation or moisture absorption in order to reduce the water activity to lower than 0.82 during storage is also effective. Furthermore, organic acid treatment during the soaking process reduces toxins by more than 90%. Some novel detection technologies based on magnetic adsorption, aptamer probes, and molecular-based methods were applied to rapidly and accurately detect mycotoxins in fermented pastes.

Prevalence of Virulence Determinants among Bacillus cereus Isolated from Milk Products with Potential Public Health Concern

BACKGROUND AND OBJECTIVE

Bacillus cereus is described as one of the public health pathogen causing severe food poisoning outbreaks worldwide. Accurate surveillance about B. cereus in Egypt is scanty. For this reason, the current study was conducted to determine the prevalence of B. cereus and its virulence genes among milk powder and Ras-cheese products.

MATERIALS AND METHODS

Two hundred samples (130 and 70) from milk powder and Ras-cheese, respectively were aseptically collected and cultured onto specific media. The obtained isolates were subjected to mPCR for screening of virulence genes (nhe, cytK, pc-plc, hblD, hbI and ces) among of B. cereus isolates that obtained from milk powder and Ras-cheese.

RESULTS

The result revealed that B. cereus was recovered with 6.9 and 8.5% from milk powder and Ras-cheese, respectively. The nhe gene was detected and dominated in all isolates 100% from both products. In milk powder, pc-plc was the most prevalent gene (100%). However, cytK, hblD, hbl and ces genes were prevalent with 55.5, 33.3, 33.3 and 22.2%, respectively. Regarding to Ras-cheese, the prevalence of cytK was (83.33%) while each of hbI, hblD, pc-plc and ces genes were recovered in 50% of tested isolates.

CONCLUSION

This result provided an important epidemiological view about the contamination rate and the most prevalent virulence genes of B. cereus in milk products in Egypt.

Toxicity response of silkworm intestine to Bacillus cereus SW7-1 pathogen

Bacillus cereus is a foodborne pathogen that causes gastrointestinal disease in hosts. The interactions between pathogenic bacteria and silkworms (Bombyx mori L.) involve complex processes. This study aimed to investigate the potential genetic traits of B. cereus SW7-1 and profile the toxicity response of silkworm intestine upon infection by the SW7-1 pathogen. Bacterial genome sequencing and polymerase chain reaction (PCR) detection indicated that B. cereus SW7-1 possesses multiple antibiotic-resistant genes and nine virulence factor genes. Then, silkworm larvae were infected with SW7-1. Comparative transcriptomic analysis revealed that 273 differentially expressed genes (DEGs) with known functions were successfully annotated to the silkworm reference genome. Specifically, 18 DEGs were up-regulated, and 255 DEGs were down-regulated. Compared with the control group, the treated group revealed down-regulated DEGs that are related to stress reactions, immunity, autophagy and apoptosis, DNA replication, ribosomal stress, and carbohydrate metabolism. Quantitative real time PCR analysis showed that many key genes in the Toll pathway, immune deficiency pathway, Janus kinase/signal transducers and activators of transcription pathway, and melanization reaction were up-regulated. Thus, B. cereus SW7-1 pathogen could damage the silkworm intestine, as confirmed by the histological section assay. In addition, SW7-1 can affect the normal physiological functions of intestinal cells. This study contributes toward an improved understanding of the toxicity response of silkworm to the B. cereus pathogen and provides new insights into the molecular mechanisms of the complex interactions between pathogenic microbes and silkworms.

Antibiotics resistance and toxin profiles of Bacillus cereus-group isolates from fresh vegetables from German retail markets

BACKGROUND

This study aimed to evaluate the safety of raw vegetable products present on the German market regarding toxin-producing Bacillus cereus sensu lato (s.l.) group bacteria.

RESULTS

A total of 147 B. cereus s.l. group strains isolated from cucumbers, carrots, herbs, salad leaves and ready-to-eat mixed salad leaves were analyzed. Their toxinogenic potential was assessed by multiplex PCR targeting the hemolysin BL (hbl) component D (hblD), non-hemolytic enterotoxin (nhe) component A (nheA), cytotoxin K-2 (cytK-2) and the cereulide (ces) toxin genes. In addition, a serological test was used to detect Hbl and Nhe toxins. On the basis of PCR and serological results, none of the strains were positive for the cereulide protein/genes, while 91.2, 83.0 and 37.4% were positive for the Hbl, Nhe and CytK toxins or their genes, respectively. Numerous strains produced multiple toxins. Generally, strains showed resistance against the β-lactam antibiotics such as penicillin G and cefotaxim (100%), as well as amoxicillin/clavulanic acid combination and ampicillin (99.3%). Most strains were susceptible to ciprofloxacin (99.3%), chloramphenicol (98.6%), amikacin (98.0%), imipenem (93.9%), erythromycin (91.8%), gentamicin (88.4%), tetracycline (76.2%) and trimethoprim/sulfamethoxazole combination (52.4%). The genomes of eight selected strains were sequenced. The toxin gene profiles detected by PCR and serological test mostly agreed with those from whole-genome sequence data.

CONCLUSIONS

Our study showed that B. cereus s.l. strains encoding toxin genes occur in products sold on the German market and that these may pose a health risk to the consumer if present at elevated levels. Furthermore, a small percentage of these strains harbor antibiotic resistance genes. The presence of these bacteria in fresh produce should, therefore, be monitored to guarantee their safety.

Unraveling the Role of Vegetables in Spreading Antimicrobial-Resistant Bacteria: A Need for Quantitative Risk Assessment

In recent years, vegetables gain consumer attraction due to their reputation of being healthy in combination with low energy density. However, since fresh produce is often eaten raw, it may also be a source for foodborne illness. The presence of antibiotic-resistant bacteria might pose a particular risk to the consumer. Therefore, this review aims to present the current state of knowledge concerning the exposure of humans to antibiotic-resistant bacteria via food of plant origin for quantitative risk assessment purposes. The review provides a critical overview of available information on hazard identification and characterization, exposure assessment, and risk prevention with special respect to potential sources of contamination and infection chains. Several comprehensive studies are accessible regarding major antimicrobial-resistant foodborne pathogens (e.g., Salmonella spp., Listeria spp., Bacillus cereus, Campylobacter spp., Escherichia coli) and other bacteria (e.g., further Enterobacteriaceae, Pseudomonas spp., Gram-positive cocci). These studies revealed vegetables to be a potential—although rare—vector for extended-spectrum beta-lactamase-producing Enterobacteriaceae, mcr1-positive E. coli, colistin- and carbapenem-resistant Pseudomonas aeruginosa, linezolid-resistant enterococci and staphylococci, and vancomycin-resistant enterococci. Even if this provides first clues for assessing the risk related to vegetable-borne antimicrobial-resistant bacteria, the literature research reveals important knowledge gaps affecting almost every part of risk assessment and management. Especially, the need for (comparable) quantitative data as well as data on possible contamination sources other than irrigation water, organic fertilizer, and soil becomes obvious. Most crucially, dose–response studies would be needed to convert a theoretical “risk” (e.g., related to antimicrobial-resistant commensals and opportunistic pathogens) into a quantitative risk estimate.

Molecular Characterization and Toxin Profiles of Bacillus spp. Isolated from Retail Fish and Ground Beef

Bacillus species are common in the environment due to their spore-forming ability and nutritional versatility and cause food contamination. Bacilli play a significant role in foodborne illnesses and food spoilage. In this study, 52 Bacillus isolates from retail fish and ground beef were identified and differentiated based on 16S rRNA, gyrB, and rpoB gene sequencing. The presence of genes encoding emetic toxin (ces), hemolytic enterotoxin hemolysin BL (hbl), nonhemolytic enterotoxin (nhe) and cytotoxin K (cytK1) was assessed in all Bacillus isolates. The ability of the Bacillus isolates to produce several extracellular enzymes that contribute to pathogenicity and food spoilage was investigated. The 16S rRNA, rpoB, and gyrB gene sequence similarities of the Bacillus isolates tested were 96.1%, 83.2%, and 77.5%, respectively. The gyrB gene demonstrated a higher degree of sequence variation than the 16S rRNA and rpoB genes. The prevalence of Bacillus isolates producing at least two of the genes of the HBL and NHE complexes was 23.1% and 15.4%, respectively. Of the B. cereus isolates, 10 (41.7%) possessed two or more enterotoxin genes. None of the isolates carried the ces and cytK1 genes. All isolates were positive for the production of enzymes such as protease, lipase, gelatinase, and DNase. However, only 92.3% of the tested isolates were positive for amylase. In conclusion, our results revealed that the presence of genes involved in toxin production and enzyme production in meat-originated B. cereus and other Bacillus isolates may cause spoilage of food and pose a health risk for consumers. PRACTICAL APPLICATION: Bacillus species can be found in various foods due to their ubiquitous nature. Bacillus spp., especially B. cereus, are associated with food poisoning and other infections in humans. Toxins and many extracellular enzymes produced by Bacillus spp. are the causative agents of foodborne outbreaks, food spoilage, and low-quality food with significantly reduced edibility. This study highlights the characterization of Bacillus spp. and presence of potentially pathogenic Bacillus species in meats.

Toxins in Fermented Foods: Prevalence and Preventions-A Mini Review

Fermented foods (FF) are widely consumed around the world, and FF are one of the prime sources of toxins and pathogenic microbes that are associated with several foodborne outbreaks. Mycotoxins (aflatoxins, fumonisins, sterigmatocystin, nivalenol, deoxynivalenol, zearalenone, ochratoxin, and alternariol), bacterial toxins (shiga toxin and botulinum), biogenic amines, and cyanogenic glycosides are the common toxins found in FF in addition to the pathogenic microbes. Fermented milk products and meat sausages are extremely vulnerable to contamination. Cumulative updated information about a specific topic such as toxins in FF is essential for the improvement of safer preparation and consumption of fermented foods. Accordingly, the current manuscript summarizes the reported mycotoxins, bacterial toxins, and/or toxins from other sources; detection methods and prevention of toxins in FF (use of specific starter culture, optimized fermentation process, and pre- and post-processing treatments); and major clinical outbreaks. This literature survey was made in Scopus, Web of Science, NCBI-PubMed, and Google Scholar using the search terms "Toxins" and "Fermented Foods" as keywords. The appropriate scientific documents were screened for relevant information and they were selected without any chronological restrictions.

Prevalence, virulence factor genes and antibiotic resistance of Bacillus cereus sensu lato isolated from dairy farms and traditional dairy products

Background

B. cereus are of particular interest in food safety and public health because of their capacity to cause food spoilage and disease through the production of various toxins. The aim of this study was to determine the prevalence, virulence factor genes and antibiotic resistance profile of B. cereus sensu lato isolated from cattle grazing soils and dairy products in Ghana. A total of 114 samples made up of 25 soil collected from cattle grazing farm land, 30 raw milk, 28 nunu (yoghurt-like product) and 31 woagashie (West African soft cheese). Ninety-six B. cereus sensu lato isolates from 54 positive samples were screened by PCR for the presence of 8 enterotoxigenic genes (hblA, hblC, hblD, nheA, nheB, nheC, cytK and entFM), and one emetic gene (ces). Phenotypic resistance to 15 antibiotics were also determined for 96 B. cereus sensu lato isolates.

Results

About 72% (18 of 25 soil), 47% (14 of 30 raw milk), 35% (10 of 28 nunu) and 39% (12 of 31 woagashi) were positive for B. cereus sensu lato with mean counts (log₁₀ cfu/g) of 4.2 ± 1.8, 3.3 ± 2.0, 1.8 ± 1.4 and 2.6 ± 1.8 respectively. The distribution of enterotoxigenic genes revealed that 13% (12/96 isolates) harboured all three gene encoding for haemolytic enterotoxin HBL complex genes (hblA, hblC and hblD), 25% (24/96 isolates) possessed no HBL gene, whereas 63% (60/96 isolates) possessed at least one of the three HBL genes. All three genes encoding for non-haemolytic enterotoxin (nheA, nheB and nheC) were detected in 60% (57/96) isolates, 14% (13/96) harboured only one gene, 19% (18/96) whereas 8% possessed none of the NHE genes. The detection rates of cytk, entFM, and ces genes were 75, 67 and 9% respectively. Bacillus cereus s. l. isolates were generally resistant to β-lactam antibiotics such as ampicillin (98%), oxacillin (92%), penicillin (100%), amoxicillin (100%), and cefepime (100%) but susceptible to other antibiotics tested.

Conclusions

Bacillus cereus s. l. is prevalent in soil, raw milk and dairy products in Ghana. However, loads are at levels considered to be safe for consumption. Various enterotoxin genes associated with virulence of B. cereus are widespread among the isolates.

Production of hemolysin BL by Bacillus cereus group isolates of dairy origin is associated with whole-genome phylogenetic clade

BACKGROUND

Bacillus cereus group isolates that produce diarrheal or emetic toxins are frequently isolated from raw milk and, in spore form, can survive pasteurization. Several species within the B. cereus group are closely related and cannot be reliably differentiated by established taxonomical criteria. While B. cereus is traditionally recognized as the principal causative agent of foodborne disease in this group, there is a need to better understand the distribution and expression of different toxin and virulence genes among B. cereus group food isolates to facilitate reliable characterization that allows for assessment of the likelihood of a given isolate to cause a foodborne disease.

RESULTS

We performed whole genome sequencing of 22 B. cereus group dairy isolates, which represented considerable genetic diversity not covered by other isolates characterized to date. Maximum likelihood analysis of these genomes along with 47 reference genomes representing eight validly published species revealed nine phylogenetic clades. Three of these clades were represented by a single species (B. toyonensis -clade V, B. weihenstephanensis - clade VI, B. cytotoxicus - VII), one by two dairy-associated isolates (clade II; representing a putative new species), one by two species (B. mycoides, B. pseudomycoides - clade I) and four by three species (B. cereus, B. thuringiensis, B. anthracis - clades III-a, b, c and IV). Homologues of genes encoding a principal diarrheal enterotoxin (hemolysin BL) were distributed across all, except the B. cytotoxicus clade. Using a lateral flow immunoassay, hemolysin BL was detected in 13 out of 18 isolates that carried hblACD genes. Isolates from clade III-c (which included B. cereus and B. thuringiensis) consistently did not carry hblACD and did not produce hemolysin BL. Isolates from clade IV (B. cereus, B. thuringiensis) consistently carried hblACD and produced hemolysin BL. Compared to others, clade IV was significantly (p = 0.0001) more likely to produce this toxin. Isolates from clade VI (B. weihenstephanensis) carried hblACD homologues, but did not produce hemolysin BL, possibly due to amino acid substitutions in different toxin-encoding genes.

CONCLUSIONS

Our results demonstrate that production of diarrheal enterotoxin hemolysin BL is neither inclusive nor exclusive to B. cereus sensu stricto, and that phylogenetic classification of isolates may be better than taxonomic identification for assessment of B. cereus group isolates risk for causing a diarrheal foodborne disease.

Evaluation of the Toxicity and Toxicokinetics of Cereulide from an Emetic Bacillus cereus Strain of Milk Origin

Bacillus cereus is an opportunistic foodborne agent causing food poisoning and many infectious diseases. The heat-stable emetic toxin cereulide is one of the most prevalent toxins produced by pathogenic B. cereus, resulting in symptoms such as emesis and liver failure. In the present work, the toxicity and toxicokinetics of cereulide from an emetic B. cereus isolate (CAU45) of raw milk were evaluated. The production of cereulide was tested by a cytotoxicity test and enzyme immunoassay, and confirmed by the presence of the ces (cereulide synthetase) gene and the ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method. All results showed that the amount and toxicity of cereulide produced by CAU45 was 7 to 15.3 folds higher than the reference emetic B. cereus DSMZ 4312. Cereulide in plasma was collected at different time points after a single intravenous injection to evaluate its toxicokinetics in rabbits. The maximum concentration of cereulide was achieved in 2.6 ± 3.4 h after administration, with the elimination half-life of 10.8 ± 9.1 h, which expands our understanding of the toxic effects of cereulide. Together, it suggests that urgent sanitary practices are needed to eliminate emetic toxins and emetic B. cereus in raw milk.

Identification and Pathogenic Potential of Clinical Bacillus and Paenibacillus Isolates

The soil-related Bacillus and Paenibacillus species have increasingly been implicated in various human diseases. Nevertheless, their identification still poses problems in the clinical microbiology laboratory and, with the exception of Bacillus anthracis and Bacillus cereus, little is known on their pathogenicity for humans. In this study, we evaluated the use of matrix-assisted laser desorption—ionization time of flight mass spectrometry (MALDI-TOF MS) in the identification of clinical isolates of these genera and conducted genotypic and phenotypic analyses to highlight specific virulence properties. Seventy-five clinical isolates were subjected to biochemical and MALDI-TOF MS identification. 16S rDNA sequencing and supplemental tests were used to solve any discrepancies or failures in the identification results. MALDI-TOF MS significantly outperformed classical biochemical testing for correct species identification and no misidentification was obtained. One third of the collected strains belonged to the B. cereus species, but also Bacillus pumilus and Bacillus subtilis were isolated at high rate. Antimicrobial susceptibility testing showed that all the B. cereus, B. licheniformis, B. simplex, B. mycoides, Paenibacillus glucanolyticus and Paenibacillus lautus isolates are resistant to penicillin. The evaluation of toxin/enzyme secretion, toxin-encoding genes, motility, and biofilm formation revealed that B. cereus displays the highest virulence potential. However, although generally considered nonpathogenic, most of the other species were shown to swim, swarm, produce biofilms, and secrete proteases that can have a role in bacterial virulence. In conclusion, MALDI-TOF MS appears useful for fast and accurate identification of Bacillus and Paenibacillus strains whose virulence properties make them of increasing clinical relevance.

Identification and Characterization of Bacillus cereus SW7-1 in Bombyx mori (Lepidoptera: Bombycidae)

The bacterial diseases of silkworms cause significant reductions in sericulture and result in huge economic loss. This study aimed to identify and characterize a pathogen from diseased silkworm. SW7-1, a pathogenic bacterial strain, was isolated from the diseased silkworm. The strain was identified on the basis of its bacteriological properties and 16S rRNA gene sequence. The colony was round, slightly convex, opaque, dry, and milky on a nutrient agar medium, the colony also exhibited jagged edges. SW7-1 was Gram-positive, without parasporal crystal, and 0.8-1.2 by 2.6-3.4 µm in length, resembling long rods with rounded ends. The strain was positive to most of the physiological biochemical tests used in this study. The strain could utilize glucose, sucrose, and maltose. The results of its 16S rRNA gene sequence analysis revealed that SW7-1 shared the highest sequence identity (>99%) with Bacillus cereus strain 14. The bacterial strain was highly susceptible to gentamycin, streptomycin, erythromycin, norfloxacin, and ofloxacin and moderately susceptible to tetracycline and rifampicin. It exhibited resistance to other antibiotics. SW7-1 had hemolytic activity and could produce extracellular casease, lipase, and amylase. SW7-1 could reproduce septicemia-like symptoms with high mortality rate when re-fed to healthy silkworm. .The median lethal concentration (LC50) was 5.45 × 10(4) cfu/ml. Thus, SW7-1 was identified as B. cereus, which is a pathogen for silkworm and human infections are possible.