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

Antibiofilm Power of Basil Essential Oil Against Fish-Originated Multidrug-Resistant Salmonella and Bacillus spp.: Targeting Biofilms on Food Contact Surfaces

The antimicrobial and antibiofilm efficacy of two Ocimum basilicum L., essential oils sourced from Colombia (BEOC) and Italy (BEOI), was evaluated against multidrug-resistant fish isolates of Salmonella enterica subsp. salamae, Bacillus thuringiensis, and Bacillus oceanisediminis-species for which such activity has not been previously reported. Using a fish-based model system (FBMS), we found that BEOI, rich in linalool (69.86%), exhibited stronger antimicrobial activity than camphor-dominated BEOC (24.61%). The antimicrobial effects of both EOs were strain- and concentration-dependent, with minimum bactericidal concentration (MBC) 3.75-15.0 µL/mL for BEOI and 15.0-30.0 µL/mL for BEOC. Pure linalool showed even greater potency (MBC: 0.0125 to 0.025 µL/mL). Confocal laser scanning microscopy revealed that BEOI induced severe membrane damage (27% of the cells within 1 h), ultimately leading to the death of 96% of the cells after 24 h. Biofilm formation, assessed in both FBMS and tryptone soy broth (TSB), was strain-dependent, with FBMS promoting higher biofilm production than TSB. Moreover, significant differences in biofilm morphotypes were observed, with the morphotype PDAR (pink dry and rough), characterized by only cellulose, being the most frequently exhibited by the strains (7/15), while BDAR (brown dry and rough), characterized by only curli, was the least expressed (7/15); the remaining strains presented morphotype RDAR. In addition, the strains in polystyrene surfaces accumulated more biomass than stainless steel 304. Notably, BEOI and linaool significantly reduced biofilm formation across all strains, with a reduction of 90% in S. enterica subsp. salamae strains (TJC19 and TJC21. These strains with the RDAR phenotype likely contribute to their strong biofilm-forming capacity. Our findings highlight BEOI's potential as a natural anti-biofilm agent in food processing environments, offering a promising strategy to combat multidrug-resistant bacteria biofilm-related challenges in the food industry.

Metataxonomic identification of microorganisms and sensory attributes of Coffea canephora under conventional processing and Self-Induced Anaerobiosis Fermentation

This study evaluates for the first time the modifications in the microbial communities and sensory attributes caused by Self-Induced Anaerobiosis Fermentation (SIAF) compared to the Conventional processing of Coffea canephora var. Conilon. Microorganisms were identified through high-throughput sequencing of the 16S rRNA V3/V4 region for bacteria and the ITS region for fungi. Sensory attributes of roasted coffee were evaluated by Q-Graders. The relationship between microbial population, processing methods, and sensory attributes was investigated using principal component analysis. Before fermentation, 74 bacterial and 21 fungal species were identified in the natural coffee, whereas 44 bacterial and 15 fungal species were found in the pulped coffee. Torulaspora, Wickerhamomyces, and Meyerozyma exhibited more ITS region sequences, while Acetobacter, Enterobacter, and Lysinibacillus were predominant in the 16S region. In the natural coffee, Wickerhamomyces showed the highest relative abundance (45%) at 0 h. After 72 h, Meyerozyma (45%) and Torulaspora (75%) prevailed in Conventional processing and SIAF, respectively. In the pulped coffee, Torulaspora was the most abundant in the SIAF method, before (92%) and after (81%) fermentation, while Wickerhamomyces (39%) dominated after 72 h in the Conventional method. Enterobacteriaceae levels decreased, while Lactobacillaceae levels increased in SIAF natural coffee during the fermentation process. SIAF favored the presence of yeast and LAB while inhibiting mycotoxigenic fungi and Enterobacteriaceae. Torulaspora, Lactiplantibacillus, and Lactococcus showed the highest Pearson correlation coefficient with flavor (0.92), aftertaste (0.99), and bitterness/sweetness (0.89), respectively. Changes in coffee microbiota during SIAF improved sensory attributes, resulting in better-quality beverages.

Pangenome analysis of Bacillus velezensis exploring the probiotic potential and plant growth promotion traits of strains isolated from fish intestines

New Bacillus velezensis strains with impressive antimicrobial activities are being continuously described. Here we performed genomic comparisons of five B. velezensis strains isolated from Amazonian fish intestines with other 266 genomes from the RefSeq database through a pangenome approach. We aimed to analyze the commonalities and specificities of each strain within this clade to explore their potential as probiotics and for promoting plant growth (PGP). High-quality draft genome sequences were obtained for strains P7 and P11, with genome metrics confirming their identification as B. velezensis. The evaluation of 271 B. velezensis genome sequences revealed an open pangenome composed of 14,918 homologs, while 16% of them represented the core genome. Therefore, the majority of genes belonged to the accessory variable genome, with many strains harboring numerous unique genes, including the Amazonian strain P45. This strain also stood out as carrying the potential to produce many hydrolytic enzymes and PGP traits. Genome mining of all five Amazonian strains annotated secondary metabolites with unknown identifications. The evaluated probiotic genes are mostly conserved in all B. velezensis strains. Moreover, the investigation of the mobilome, resistome, and virulence factors showed that these strains can be considered safe for probiotic and agricultural applications, corroborating our previous studies. This data will be useful to improve our understanding and biotechnological exploration of these strains and other B. velezensis as well.

Global Epidemiology and health risks of Bacillus cereus Infections: Special focus on infant foods

Bacillus cereus is a common pathogen responsible for gastrointestinal and other complicated disorders, yet epidemiological data and public health measures remain scarce. To bridge these gaps, a bilingual search spaning 50 years identified 266 relevant studies on global B. cereus infection, encompassing 6,135 cases. The global mortality rate for B. cereus infection is 0.9 %. Food poisoning cases account for 94.31 % (5786/6135) of the total infections, with a mortality rate of 0.05 %. B. cereus infections were primarily reported in East Asia, Europe, and North America, with frequent studies in eastern and southern China. Rice was recognized as the highest-risk food category for B. cereus-associated food poisoning, with 43 reported incidents. Younger populations, particularly infants and toddlers (<2 years) and school-age children (6-18 years), tend to exhibit more severe symptoms. These symptoms include fulminant liver failure, rhabdomyolysis, and metabolic acidosis. The outcomes of severe cases are associated with specific toxin types, with cereulide-producing strains linked to complicated clinical disorders and outcomes. These findings highlight the need for targeted epidemiological surveillance and public health interventions to mitigate B. cereus-associated infections.

BANNMDA: a computational model for predicting potential microbe-drug associations based on bilinear attention networks and nuclear norm minimization

Introduction

Predicting potential associations between microbes and drugs is crucial for advancing pharmaceutical research and development. In this manuscript, we introduced an innovative computational model named BANNMDA by integrating Bilinear Attention Networks(BAN) with the Nuclear Norm Minimization (NNM) to uncover hidden connections between microbes and drugs.

Methods

In BANNMDA, we initially constructed a heterogeneous microbe-drug network by combining multiple drug and microbe similarity metrics with known microbe-drug relationships. Subsequently, we applied both BAN and NNM to compute predicted scores of potential microbe-drug associations. Finally, we implemented 5-fold cross-validation frameworks to evaluate the prediction performance of BANNMDA.

Results and discussion

The experimental results indicated that BANNMDA outperformed state-of-the-art competitive methods. We conducted case studies on well-known drugs such as the Amoxicillin and Ceftazidime, as well as on pathogens such as Bacillus cereus and Influenza A virus, to further evaluate the efficacy of BANNMDA, and experimental outcomes showed that there were 9 out of the top 10 predicted drugs, along with 8 and 9 out of the top 10 predicted microbes having been corroborated by relevant literatures. These findings underscored the capability of BANNMDA to achieve commendable predictive accuracy.

Potential Virulence and Survival of Acid-Resistant Bacillus cereus KS100Bc Isolated from Foodservice Establishments in Korea

Bacillus cereus is an opportunistic pathogen causing food poisoning manifested by diarrheal or emetic syndromes. This study aimed to examine the potential virulence and survival of acid-resistant B. cereus strains isolated from foodservice establishments in schools. All isolates were positive for genes encoding nonhemolytic enterotoxin complexes, except for one strain that lacked nheC. More than 80% of the strains harbored enterotoxigenic genes. In contrast, cesB, which encodes an emetic toxin, was not detected. Among the isolates, the biofilm-forming activity of KS100Bc strain was 8.4 times higher than that of the type strain; therefore, KS100Bc was selected for further analyses. The KS100Bc survived in simulated gastric fluid (SGF) at pH 2.0 for 120 min, which is a major host barrier against exogenous microorganisms. The parameter Kmax of the log-linear + tail model for ATCC 14579 was up to1.31-fold higher than that for KS100Bc in SGF, indicating that it is difficult to inactivate KS100Bc in acidic gastric environments. Although whole-genome sequencing identified nucleotide sequences with high homology (>99%) between ATCC 14579 and KS100Bc, significant differences were observed in phenotypes such as biofilm formation and survival in SGF. The transcriptional profiles were compared to examine the differences in the response to acid shock. KS100Bc exhibited increased expression of genes associated with pH homeostasis, oxidative response, metabolic rearrangements, and general stress response with over twofold (P value < 0.05) relative gene expression compared with the type strain. These results suggest that identifying the characteristics of the acid-adapted isolate can broaden our understanding of therapeutic strategies and provide new directions for controlling and preventing the spread of an outbreak.

Spore-forming bacteria in gelatin: Characterization, identification by 16S rRNA and MALDI-TOF mass spectrometry (MS), and presence of heat resistance and virulence genes

Gelatin, a versatile protein derived from collagen, is widely used in the food, pharmaceutical and medical sectors. However, bacterial contamination by spore-forming bacteria during gelatin processing represents a significant concern for product safety and quality. In this study, an investigation was carried out to explore the heat and chemical resistance, as well as the identification and characterization of spore-forming bacteria isolated from gelatin processing. The methodologies involved chemical resistance tests with drastic pH in microplates and thermal resistance tests in capillary tubes of various isolates obtained at different processing stages. In addition, phenotypic and genotypic analyses were carried out to characterize the most resistant isolates of spore-forming bacteria. The findings of this study revealed the presence of several species, including Bacillus cereus, Bacillus licheniformis, Bacillus sonorensis, Bacillus subtilis, Geobacillus stearothermophilus, and Clostridium sporogenes, with some isolates exhibiting remarkable chemical and heat resistances. In addition, a significant proportion of the most resistant isolates showed gelatinase activity (n = 19/21; 90.5 %) and the presence of heat resistance (n = 5/21; 23.8 %), and virulence genes (n = 11/21; 52.4 %). The results of this study suggest that interventions should be done in quality control practices and that process parameter adjustments and effective contamination reduction strategies should be implemented through gelatin processing.

Potential risk of biofilm-forming Bacillus cereus group in fresh-cut lettuce production chain

Bacillus cereus and Bacillus thuringiensis, which belong to the B. cereus group, are widely distributed in nature and can cause food poisoning symptoms. In this study, we collected 131 isolates belonging to the B. cereus group, comprising 124B. cereus and seven B. thuringiensis isolates, from fresh-cut lettuce production chain and investigated their potential risk by analyzing genotypic (enterotoxin and emetic toxin gene profiles) and phenotypic (antibiotic susceptibility, sporulation, and biofilm formation) characteristics. Enterotoxin genes were present only in B. cereus, whereas the emetic toxin gene was not detected in any of the B. cereus isolates. All isolates were susceptible to vancomycin, which is a last resort for treating B. cereus group infection symptoms, but generally resistant to β-lactam antimicrobials, and had the ability to form spores (at an average sporulation rate of 24.6 %) and biofilms at 30 °C. Isolates that formed strong biofilms at 30 °C had a superior possibility of forming a dense biofilm by proliferating at 10 °C compared to other isolates. Additionally, confocal laser scanning microscopy (CLSM) images revealed a notable presence of spores within the submerged biofilm formed at 10 °C, and the strengthened attachment of biofilm inner cells to the substrate was further revealed through biofilm structure parameters analysis. Collectively, our study revealed the prevalence and contamination levels of B. cereus and B. thuringiensis at fresh-cut lettuce production chain and investigated their genotypic and phenotypic characteristics, aiming to provide valuable insights for the development of potential risk management strategies to ensure food safety, especially along the cold chain.

Extracellular matrix-degrading enzymes as a biofilm control strategy for food-related microorganisms

Biofilm is one of the major problems in food industries and is difficult to be removed or prevented by conventional sanitizers. In this review, we discussed the extracellular matrix-degrading enzymes as a strategy to control biofilms of foodborne pathogenic and food-contaminating bacteria. The biofilms can be degraded by using the enzymes targeting proteins, polysaccharides, extracellular DNA, or lipids which mainly constitute the extracellular polymeric substances of biofilms. However, the efficacy of enzymes varies by the growth medium, bacterial species, strains, or counterpart microorganisms due to a high variation in the composition of extracellular polymeric substances. Several studies demonstrated that the combined treatment using conventional sanitizers or multiple enzymes can synergistically enhance the biofilm removal efficacies. In this review, the application of the immobilized enzymes on solid substrates is also discussed as a potential strategy to prevent biofilm formation on food contact surfaces.

Effect of Sublethal Concentrations of Zinc Oxide Nanoparticles on Bacillus cereus

Zinc oxide nanoparticles (ZnONPs), which are produced on a large scale, pose a potential threat to various environments because they can interact with the microbial populations found in them. Bacteria that are widespread in soil, water, and plant material include the Bacillus cereus group, which plays an important role in biodegradation and the nutrient cycle and is a major factor determining ecological balance. This group includes, among others, the foodborne pathogen B. cereus sensu stricto (herein referred to as B. cereus). The aim of this study was a comprehensive assessment of the effects of commercially available ZnONPs on B. cereus. The MIC (minimum inhibitory concentration) for B. cereus was 1.6 mg/mL, and the MBC (minimum bactericidal concentration) was 1.8 mg/mL. Growth of B. cereus was inhibited by a concentration of ZnONPs lower than or equal to MIC50. Concentrations from 0.2 to 0.8 mg/mL inhibited the growth of these bacteria in liquid media, induced symptoms of oxidative stress, and stimulated an environmental stress response in the form of biofilm and endospore formation. In addition, ZnONPs negatively affected the ability of the bacteria to break down the azo dye Evans Blue but enhanced the antimicrobial properties of phenolic compounds. Sublethal concentrations of ZnONPs generally decreased the activity of B. cereus cells, especially in the presence of phenolics, which indicates their potential toxicological impact, but at the same time they induced universal defence responses in these cells, which in the case of potential pathogens can hinder their removal.