High prevalence of Clostridium botulinum in vegetarian sausages

The microbial contaminants of plant-based meat analogues from the retail market

The aim of the study was to analyse the key microbial contaminants of plant-based meat analogues (PBMA) from retail. A total of 43 samples of PBMAs (12 frozen/31 chilled) in the "ready-to-cook" category, such as hamburgers, meatballs or breaded imitation steaks were purchased in retail stores in the Czech Republic in summer (n = 21) and autumn 2022 (n = 22). The detected indicator bacteria (total viable count, lactic acid bacteria, Enterobacteriaceae, yeasts, moulds) had relatively low values in the analysed PBMA samples and only rarely reached levels of 7 log CFU/g. E. coli, STEC and coagulase-positive staphylococci were not detected by isolation from plates in any of analysed samples. Mannitol positive Bacillus spp. were isolated from almost half of the analysed samples of the PBMA. B. cereus sensu lato was isolated from 3 samples by isolation from plates, and after enrichment in 35 samples (81 %). Clostridium perfringens could not be detected by isolation from plates, nevertheless after multiplication, it was detected in 21 % of samples. Analyses of PBMA samples revealed considerable variability in microbial quality. The presence of spore-forming bacteria with the potential to cause foodborne diseases is alarming. However, to evaluate the risks, further research focused on the possibilities of growth under different conditions of culinary treatment and preservation is needed.

Infant Botulism: In Search of Clostridium botulinum Spores

Infant botulism is now the most common form of human botulism in Canada and the United States. Infant botulism is a severe neuroparalytic disease caused by ingestion of the spore-forming neurotoxic clostridia, including Clostridium botulinum that colonize the large intestine and subsequently produce botulinum neurotoxin in situ. It has been over a century since the first surveys documenting the ubiquitous prevalence of C. botulinum in soils around the world. Since then, honey has been identified as the only well-known risk factor for infant botulism despite a multitude of international environmental surveys isolating C. botulinum spores from ground soil, aquatic sediments, and commonly available infant foods. Associations of infant botulism cases with confirmed sources of C. botulinum exposure have primarily implicated outdoor soil and indoor dust, as well as commonly ingested foods including honey, dry cereals, and even powdered infant formula. Yet the origin of infection remains unknown for most infant botulism cases. This review summarizes the various surveys from around the world for C. botulinum in environmental soils and sediments, honey, and other infant foods, as well as laboratory-confirmed associations with documented infant botulism cases. Additional factors are also discussed, including the composition of infant gut microbiota and the practice of breastfeeding. We make several recommendations to better identify sources of exposure to C. botulinum spores that could lead to effective preventive measures and help reduce the incidence of this rare but life-threatening disease.

Comprehensive identification of pathogenic microbes and antimicrobial resistance genes in food products using nanopore sequencing-based metagenomics

Foodborne pathogens, particularly antimicrobial-resistant (AMR) bacteria, remain a significant threat to global health. Given the limitations of conventional culture-based approaches, which are limited in scope and time-consuming, metagenomic sequencing of food products emerges as a promising solution. This method provides a fast and comprehensive way to detect the presence of pathogenic microbes and antimicrobial resistance genes (ARGs). Notably, nanopore long-read sequencing provides more accurate bacterial taxonomic classification in comparison to short-read sequencing. Here, we revealed the impact of food types and attributes (origin, retail place, and food processing methods) on microbial communities and the AMR profile using nanopore metagenomic sequencing. We analyzed a total of 260 food products, including raw meat, sashimi, and ready-to-eat (RTE) vegetables. Clostridium botulinum, Acinetobacter baumannii, and Vibrio parahaemolyticus were identified as the top three foodborne pathogens in raw meat and sashimi. Importantly, even with low pathogen abundance, higher percentages of samples containing carbapenem and cephalosporin resistance genes were identified in chicken and RTE vegetables, respectively. In parallel, our results demonstrated that fresh, peeled, and minced foods exhibited higher levels of pathogenic bacteria. In conclusion, this comprehensive study offers invaluable data that can contribute to food safety assessments and serve as a basis for quality indicators.

Levels and types of microbial contaminants in different plant-based ingredients used in dairy alternatives

In this study levels and types of microbial contaminants were investigated in 88 different plant-based ingredients including many that are used to manufacture dairy alternatives. Studied ingredients encompassed samples of pulses (pea, faba bean, chickpea, and mung bean), cereals/pseudocereals (oat, rice, amaranth and quinoa) and drupes (coconut, almond and cashew). The microbial analysis included: i) total viable count (TVC), ii) total aerobic mesophilic spore count (TMS), iii) heat resistant aerobic thermophilic spore count (HRTS), iv) anaerobic sulfite reducing Clostridium spore count (SRCS), and v) Bacillus cereus spore count (BCES). Microorganisms isolated from the counting plates with the highest sample dilutions were identified using 16S rRNA and MALDI-TOF MS analyses. Many of the investigated ingredients showed a high proportion of spores as part of their total aerobic mesophilic counts. In 63 % of the samples, the difference between TVC and TMS counts was 1 Log10 unit or less. This was particularly the case for the majority of pea isolates and concentrates, faba bean isolates, oat kernels and flakes, and for single samples of chickpea isolate, almond, amaranth, rice, quinoa, and coconut flours. Concentrations of TVC ranged between <1.0 and 5.3 Log10 CFU/g in different samples, and TMS varied between <1.0 and 4.1 Log10 CFU/g. Levels of HTRS, BCES and SRCS were generally low, typically around or below the LOD of 1.0 Log10 CFU/g. In total, 845 individual bacterial colonies were isolated belonging to 33 different genera. Bacillus licheniformis and B. cereus group strains were most frequently detected among Bacillus isolates, and these species originated primarily from pea and oat samples. Geobacillus stearothermophilus was the main species encountered as part of the HRTS. Among the Clostridium isolates, Clostridum sporogenes/tepidum were predominant species, which were mostly found in pea and almond samples. Strains with potential to cause foodborne infection or intoxication were typed using the PCR-based method for toxin genes detection. In the B. cereus group, 9 % of isolates contained the ces gene, 28 % contained hbl, 42 % cytK, and 69 % were positive for the nhe gene. Absence of the boNT-A and -B genes was confirmed for all isolated C. sporogenes/tepidum strains. Nearly all (98 %) B. licheniformis isolates were positive for the lchAA gene. Insight into the occurrence of microbial contaminants in plant-based ingredients, combined with knowledge of their key inactivation and growth characteristics, can be used for the microbial risk assessment and effective design of plant-based food processing conditions and formulations to ensure food safety and prevent spoilage.

Facile detection of botulinum neurotoxin using LSPR nanosensor based on Langmuir-Blodgett films of gold nanoparticles

In this exploratory study, Langmuir-Blodgett (LB) films of gold nanoparticles (Au NPs) were utilized for the first time to detect botulinum neurotoxin (BoNT) based on localized surface plasmon resonance (LSPR), acting as biosensors. Monolayers of Au NPs were initially transferred onto a transparent polymer substrate using the LB technique. This substrate was then used as the base material for subsequent depositions of capping ligands, and eventually, the BoNT at different concentrations. Upon each deposition, LSPR signals were recorded employing UV-Vis spectroscopy. As a result, it was demonstrated that the LB films transferred at a surface pressure of 35 mN m-1 were the optimal choice, capable of detecting BoNT at a concentration as low as 1 pg ml-1. Furthermore, it was discovered that the formation of Au NP clusters reduced the sensing capacity of the LB films. This sensor offers advantages such as easy fabrication and a quick detection process that utilizes visible light.

Microbiology of street food: understanding risks to improve safety

Street foods play important socioeconomic and cultural roles and are popular worldwide. In addition to providing convenient and low-cost meals for urban populations, street food offers an essential source of income for vendors, especially women, and it can reflect traditional local culture, which is an important attraction for tourists. Despite these benefits, the microbiological safety of street food has become a worldwide concern because it is often prepared and sold under inadequate safety conditions, without legal control and sanitary surveillance. Consequently, high counts of fecal indicator bacteria and several foodborne pathogens have been detected in street foods. This review provides insight into the microbiology of street food, focus on the associated microbiological safety aspects and main pathogens, and the global status of this important economic activity. Furthermore, the need to apply molecular detection rather than traditional culture-based methods is discussed to better understand the actual risks of microbial infection associated with street foods. Recognition is always the first step toward addressing a problem.

Microbial Risks Caused by Livestock Excrement: Current Research Status and Prospects

Livestock excrement is a major pollutant yielded from husbandry and it has been constantly imported into various related environments. Livestock excrement comprises a variety of microorganisms including certain units with health risks and these microorganisms are transferred synchronically during the management and utilization processes of livestock excrement. The livestock excrement microbiome is extensively affecting the microbiome of humans and the relevant environments and it could be altered by related environmental factors as well. The zoonotic microorganisms, extremely zoonotic pathogens, and antibiotic-resistant microorganisms are posing threats to human health and environmental safety. In this review, we highlight the main feature of the microbiome of livestock excrement and elucidate the composition and structure of the repertoire of microbes, how these microbes transfer from different spots, and they then affect the microbiomes of related habitants as a whole. Overall, the environmental problems caused by the microbiome of livestock excrement and the potential risks it may cause are summarized from the microbial perspective and the strategies for prediction, prevention, and management are discussed so as to provide a reference for further studies regarding potential microbial risks of livestock excrement microbes.

Physical Treatments to Control Clostridium botulinum Hazards in Food

Clostridium botulinum produces Botulinum neurotoxins (BoNTs), causing a rare but potentially deadly type of food poisoning called foodborne botulism. This review aims to provide information on the bacterium, spores, toxins, and botulisms, and describe the use of physical treatments (e.g., heating, pressure, irradiation, and other emerging technologies) to control this biological hazard in food. As the spores of this bacterium can resist various harsh environmental conditions, such as high temperatures, the thermal inactivation of 12-log of C. botulinum type A spores remains the standard for the commercial sterilization of food products. However, recent advancements in non-thermal physical treatments present an alternative to thermal sterilization with some limitations. Low- (<2 kGy) and medium (3-5 kGy)-dose ionizing irradiations are effective for a log reduction of vegetative cells and spores, respectively; however, very high doses (>10 kGy) are required to inactivate BoNTs. High-pressure processing (HPP), even at 1.5 GPa, does not inactivate the spores and requires heat combination to achieve its goal. Other emerging technologies have also shown some promise against vegetative cells and spores; however, their application to C. botulinum is very limited. Various factors related to bacteria (e.g., vegetative stage, growth conditions, injury status, type of bacteria, etc.) food matrix (e.g., compositions, state, pH, temperature, aw, etc.), and the method (e.g., power, energy, frequency, distance from the source to target, etc.) influence the efficacy of these treatments against C. botulinum. Moreover, the mode of action of different physical technologies is different, which provides an opportunity to combine different physical treatment methods in order to achieve additive and/or synergistic effects. This review is intended to guide the decision-makers, researchers, and educators in using physical treatments to control C. botulinum hazards.

Attribution Analysis of Foodborne Disease Outbreaks Related to Meat and Meat Products in China, 2002-2017

This study aimed to understand the epidemiological characteristics of foodborne disease outbreaks related to meat and meat products in China from 2002 to 2017. Data collected from the National Foodborne Diseases Surveillance System and searched databases were analyzed. From 2002 to 2017, China reported 2815 outbreaks caused by foodborne diseases related to meat and meat products, resulting in 52,122 illnesses and 25,361 hospitalizations, and 96 deaths. Outbreaks were markedly seasonal and concentrated from May to September, accounting for 66.93%. Outbreaks were concentrated mainly in China's eastern coastal and southern regions. Unidimensional attribution analysis revealed that livestock meat was the most commonly implicated food category causing the outbreaks, accounting for 28.67%. Bacteria were the most common pathogenic cause of outbreaks, accounting for 51.94%. Clostridium botulinum was the most common pathogenic cause of death, accounting for 34.38%. Improper processing was the most common contributing factor, accounting for 27.89%. Households were the most common food preparation location causing the outbreak, accounting for 34.39%. Two-dimensional and multidimensional attribution analysis found that Salmonella contamination occurred in different locations and regions, mainly caused by various contributing factors and improper processing. Nitrite poisoning is caused by improper processing in households in East China. Bacterial causes were the commonest agents associated with foodborne diseases related to meat and meat products, and improving the safety and quality of meat and meat product should be a priority.

Regional pattern and signatures of gut microbiota in rural residents with coronary heart disease: A metagenomic analysis

Coronary heart disease (CHD) is tightly associated with gut microbiota, but microbiota heterogeneity limits the application of microbial biomarkers and personalized interventions demand regional-specific features. The purpose of this study was to comprehensively characterize the regional pattern of gut microbiota in rural residents with CHD and assess the predictive value and clinical correlations of local microbial signatures. We profiled the gut microbiota by shotgun metagenomic sequencing from 19 CHD and 19 healthy residents in rural Xinxiang, China, and tested the physiological parameters. The results indicated that microbial diversity, as well as KEGG orthology (KO) and carbohydrate-active enzymes (CAZymes) functions, deserved no significant disparities between CHD and healthy residents. The relative abundance of Bacteroidetes phylum was significantly lower and unclassified Lachnospiraceae genus, and Eubacterium rectale species were markedly higher in CHD residents compared with the healthy control. Co-occurrence network revealed a more diverse and scattered ecology in CHD residents. LEfSe identified 39 potential biomarkers and butanoate metabolism and glycosyltransferases families were the enhanced KO and CAZymes in CHD residents, respectively. Twenty key signatures were determined by the random forest algorithm and most of them belonged to the Clostridium cluster. These key signatures harbored a superior accuracy of 83.9% to distinguish CHD and healthy residents and, fasting serum insulin, diastolic blood pressure, and body mass index were the top three clinical parameters influencing the gut bacterial community. Furthermore, we also found that low-density lipoprotein and waist circumference had significantly positive correlations with the members of the Clostridium cluster. These findings expand our knowledge in the regional-specific pattern of gut microbiota for rural CHD residents and highlight the non-invasive diagnostic value and clinical correlations of microbial signatures.

The antibacterial mechanism of perilla rosmarinic acid

Rosmarinic acid (RosA) is a phenolic acid compound extracted from perilla. In this experiment, the Oxford cup method was used to verify the antibacterial activity of PerillaRosA against Escherichia coli, Staphylococcus aureus, Salmonella, and Bacillus subtilis. By polyacrylamide gel electrophoresis, the effect of RosA on bacterial nucleic acid and bacterial Na+ /K+ -ATP-ase activity, and scanning electron microscope to exploration of its antibacterial mechanism preliminarily. The results showed that RosA had antibacterial properties against all four bacteria. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of E. coli were 0.8 and 0.9 mg/ml, respectively. The MIC and MBC of Salmonella were 0.9 and 1.0 mg/ml, respectively. The MIC and MBC of S. aureus and B. subtilis were both 1.0 and 1.1 mg/ml. RosA has the bacteriostasis function, which can destroy bacterial cells and cell proteins and inhibit the activity of Na+ /K+ -ATP-ase in cells.

Extensive growth and growth boundary model for non-proteolytic Clostridium botulinum - Evaluation and validation with MAP and smoked foods

The growth inhibiting effect of lactic acid bacteria (LAB) on non-proteolytic Clostridium botulinum was studied. LAB had no significant effect on growth of C. botulinum and their effect was not included in the model to be evaluated. An available cardinal parameter growth and growth boundary model for non-proteolytic C. botulinum (Koukou et al., 2021; https://doi.org/10.1016/j.ijfoodmicro.2021.109162) was evaluated using a total of 822 time-to-toxin (TTT) formation data extracted from the scientific literature for seafood, poultry, vegetables and meat products. These data included smoked products and food stored in air, vacuum or modified atmosphere packaging (MAP) with added CO₂. The available extensive model predicted TTT formation without bias (B_f-TTT value = 0.99) and with a reasonable accuracy (A_f-TTT value = 1.76). The model was successfully validated for seafood and poultry products. This study substantially increased the range of applicability of the available growth and growth boundary model for non-proteolytic C. botulinum. The performed evaluation showed this model can be used to predict environmental conditions to prevent growth in seafood and poultry products including smoked fish and MAP foods. It is expected that this validated model will contribute to product development and innovation including new sodium reduced foods.

Cardinal parameter growth and growth boundary model for non-proteolytic Clostridium botulinum - Effect of eight environmental factors

A new cardinal parameter growth and growth boundary model for non-proteolytic C. botulinum was developed and validated for fresh and lightly preserved seafood and poultry products. 523 growth rates in broth were used to determine cardinal parameter values and terms for temperature, pH, NaCl/water activity, acetic, benzoic, citric, lactic and sorbic acids. The new growth and growth boundary model included the inhibiting interactive effect between these factors and it was calibrated using growth curves from 10 challenge tests with unprocessed seafood. For model evaluation, 40 challenge tests with well characterized fresh and lightly preserved seafood were performed. Comparison of these observed growth curves and growth rates (μ_max-values) predicted by the new model resulted in a bias factor (B_f) of 1.12 and an accuracy factor (A_f) of 1.40. Furthermore, the new model was evaluated with 94 growth rates and 432 time to toxin formation data extracted from the scientific literature for seafood, poultry, meat, pasta and prepared meals. These data included responses for 36 different toxigenic strains of non-proteolytic C. botulinum. The obtained B_f-/A_f-values were 0.97/2.04 for μ_max-values and 0.96/1.80 for time to toxin formation. The model correctly predicted 93.8% of the growth responses with 5.6% being fail-safe and <1% fail-dangerous. A cocktail of four non-toxin producing Clostridium spp. isolates was used to develop the new model and these isolates had more than 99.8% 16S rRNA gene similarity to non-proteolytic C. botulinum (Group II). The high number of environmental factors included in the new model makes it a flexible tool to facilitate development or reformulation of seafood and poultry products that do not support the growth of non-proteolytic C. botulinum. Further, evaluation of the new model with well characterized products is desirable particularly for meat, vegetables, pasta and prepared meals as well as for dairy products that was not included in the present study.

Potentially probiotic or postbiotic pre-converted nitrite from celery produced by an axenic culture system with probiotic lacticaseibacilli strain

The present study evaluated the use of the probiotic Lacticaseibacillus paracasei DTA-83 as a nitrite-reducing agent to produce potentially probiotic or postbiotic pre-converted nitrite from celery. The results obtained were compared to those achieved by direct addition of sodium nitrite for the typical reddish color formation in cooked pork sausages and the inhibitory potential against the growth of target microorganisms, including the clostridia group. Regarding the sausages color, similar findings were observed when comparing the use of pre-converted nitrite from celery produced by L. paracasei DTA-83 and the direct addition of sodium nitrite. Additionally, it presented an inhibitory effect against Salmonella spp., which was not observed with the direct addition of nitrite, revealing a potential strategy to control salmonellosis in the matrix. However, a non-equivalent preservative effect against Clostridium perfringens (INCQS 215) was determined. The results highlight a promising alternative to produce probiotic or postbiotic meat ingredients; however, further studies should be conducted to investigate doses that achieve microbial control.

Phage lysin that specifically eliminates Clostridium botulinum Group I cells

Clostridium botulinum poses a serious threat to food safety and public health by producing potent neurotoxin during its vegetative growth and causing life-threatening neuroparalysis, botulism. While high temperature can be utilized to eliminate C. botulinum spores and the neurotoxin, non-thermal elimination of newly germinated C. botulinum cells before onset of toxin production could provide an alternative or additional factor controlling the risk of botulism in some applications. Here we introduce a putative phage lysin that specifically lyses vegetative C. botulinum Group I cells. This lysin, called CBO1751, efficiently kills cells of C. botulinum Group I strains at the concentration of 5 µM, but shows little or no lytic activity against C. botulinum Group II or III or other Firmicutes strains. CBO1751 is active at pH from 6.5 to 10.5. The lytic activity of CBO1751 is tolerant to NaCl (200 mM), but highly susceptible to divalent cations Ca2+ and Mg2+ (50 mM). CBO1751 readily and effectively eliminates C. botulinum during spore germination, an early stage preceding vegetative growth and neurotoxin production. This is the first report of an antimicrobial lysin against C. botulinum, presenting high potential for developing a novel antibotulinal agent for non-thermal applications in food and agricultural industries.