Microbial toxins and low level of foodborne exposure

Recent Advances in Aptamer-Based Biosensors for Bacterial Detection

The rapid and sensitive detection of pathogenic bacteria is becoming increasingly important for the timely prevention of contamination and the treatment of infections. Biosensors based on nucleic acid aptamers, integrated with optical, electrochemical, and mass-sensitive analytical techniques, have garnered intense interest because of their versatility, cost-efficiency, and ability to exhibit high affinity and specificity in binding bacterial biomarkers, toxins, and whole cells. This review highlights the development of aptamers, their structural characterization, and the chemical modifications enabling optimized recognition properties and enhanced stability in complex biological matrices. Furthermore, recent examples of aptasensors for the detection of bacterial cells, biomarkers, and toxins are discussed. Finally, we explore the barriers to and discuss perspectives on the application of aptamer-based bacterial detection.

Functionalized nanoencapsulated Curcuma longa essential oil in chitosan nanopolymer and their application for antioxidant and antimicrobial efficacy

The present study reports on the encapsulation of Curcuma longa (L.) essential oil (CLEO) in chitosan nanopolymer as a novel nanotechnology preservative for enhancing its antibacterial, antifungal, and mycotoxin inhibitory efficacy. GC-MS analysis of CLEO showed the presence of α-turmerone (42.6 %) and β- turmerone (14.0 %) as the major components. CLEO-CSNPs were prepared through the ionic-gelation technique and confirmed by TEM micrograph, DLS, XRD, and FTIR. In vitro, bactericidal activity of CLEO-CSNPs at a concentration of 100 μg/mL showed significant antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa, which mostly rely on ROS production and depend on its penetration and interaction with bacterial cells. Furthermore, the CLEO-CSNPs during in vitro investigation against F. graminearum completely inhibited the growth and zearalenone and deoxynivalenol production at 0.75 μL/mL, respectively. Further, CLEO-CSNPs enhanced antioxidant activity against DPPH• and ABTS•+ with IC50 values 0.95 and 0.66 μL/mL, respectively, and without any negative impacts on germinating seeds were observed during the phytotoxicity investigation. Overall, experiments concluded that encapsulated CLEO enhances antimicrobial inhibitory efficiency against stored foodborne pathogens.

Foodborne Toxigenic Agents Investigated in Central Italy: An Overview of a Three-Year Experience (2018-2020)

Foodborne diseases (FBDs) represent a worldwide public health issue, given their spreadability and the difficulty of tracing the sources of contamination. This report summarises the incidence of foodborne pathogens and toxins found in food, environmental and clinical samples collected in relation to diagnosed or suspected FBD cases and submitted between 2018 and 2020 to the Food Microbiology Unit of the Istituto Zooprofilattico Sperimentale del Lazio e della Toscana (IZSLT). Data collected from 70 FBD investigations were analysed: 24.3% of them started with an FBD diagnosis, whereas a further 41.4% involved clinical diagnoses based on general symptomatology. In total, 5.6% of the 340 food samples analysed were positive for the presence of a bacterial pathogen, its toxins or both. Among the positive samples, more than half involved meat-derived products. Our data reveal the probable impact of the COVID-19 pandemic on the number of FBD investigations conducted. In spite of the serious impact of FBDs on human health and the economy, the investigation of many foodborne outbreaks fails to identify the source of infection. This indicates a need for the competent authorities to continue to develop and implement a more fully integrated health network.

Toxigenic Potential of Bacillus cereus Strains Isolated from Retail Dairy Products in Egypt

Little is known about the virulence in Bacillus cereus strains isolated from retail dairy products in the Middle East and particularly from Egypt. In this study, the occurrence of B. cereus in 290 samples of dairy products (raw milk, Ras cheese, pasteurized extended shelf life [ESL] milk) collected from retail shops was investigated. The potential of 126 selected isolates of B. cereus to possess genes encoding nonhemolytic enterotoxin, hemolysin BL, and cytotoxin K (cytK), and to grow at 7°C was verified. The highest occurrence of B. cereus was found in raw milk (85%, 85/100) followed by Ras cheese (10%, 10/100) and ESL milk samples (8.8%, 8/90). A large proportion of the B. cereus isolates from raw milk (48.9%, 48/99) and Ras cheese (71.4%, 10/14) had at least one complete set of toxin genes (nhe or hbl). Enterotoxin genes, nheA, nheB, nheC, hblA, hblD, and hblC, were detected in 38.4% (5/13), 53.8% (7/13), 61.5% (8/13), 46.1% (6/13), 46.1% (6/13), and 23.1% (3/13) of ESL milk isolates, respectively. cytK was identified in 42.4% (42/99), 50% (7/14), and 46.2% (6/13) of raw milk, Ras cheese, and ESL milk isolates, respectively. The psychrotrophic ability was observed in 22.2% and 15.3% of isolates recovered from raw milk and ESL milk, respectively. The toxigenic potential of B. cereus strains described in this study may pose a health risk to the consumer and, therefore, the presence of these bacteria in retail dairy products should be monitored to ensure consumers' safety.

Essential Oils and Their Application in Food Safety

Food industries are facing a great challenge due to contamination of food products with different microbes such as bacteria, fungi, viruses, parasites, etc. These microbes deteriorate food items by producing different toxins during pre- and postharvest processing. Mycotoxins are one of the most potent and well-studied toxic food contaminants of fungal origin, causing a severe health hazard to humans. The application of synthetic chemicals as food preservatives poses a real scourge in the present scenario due to their bio-incompatibility, non-biodegradability, and environmental non-sustainability. Therefore, plant-based antimicrobials, including essential oils, have developed cumulative interest as a potential alternative to synthetic preservatives because of their ecofriendly nature and generally recognized as safe status. However, the practical utilization of essential oils as an efficient antimicrobial in the food industry is challenging due to their volatile nature, less solubility, and high instability. The recent application of different delivery strategies viz. nanoencapsulation, active packaging, and polymer-based coating effectively addressed these challenges and improved the bioefficacy and controlled release of essential oils. This article provides an overview of essential oils for the preservation of stored foods against bacteria, fungi, and mycotoxins, along with the specialized mechanism of action and technological advancement by using different delivery systems for their effective application in food and agricultural industries smart green preservative.

Bacillus cereus: public health burden associated with ready-to-eat foods in Himachal Pradesh, India

The study determined incidence, enterotoxigenecity and antimicrobial susceptibility profiles of Bacillus cereus isolated from ready-to-eat (RTE) milk products (n = 80), RTE meat products (n = 40), beverages (n = 40) and water samples (n = 60, from food preparing and serving outlets/restaurants) collected from eight different tourist places of Himachal Pradesh. 11.4% (25/220) samples were contaminated with Bacillus and isolates were identified as B. cereus (76.0%, n = 19), B. alvei (12.0%, n = 3), B. polymyxa (8.0%, n = 2) and B. firmus (4.0%, n = 1) by conventional and molecular methods. B. cereus incidence was highest in cheese based foods (25.0%) followed by vegetable soups (16.7%), khoa based foods (14.0%), milk based beverages (10.5%), paneer based foods (8.6%), cream based foods (8.3%) and water (8.3%) samples. Multiplex polymerase chain reaction detected enterotoxigenic genes only in B. cereus isolates. nhe complex (encoding non-haemolytic enterotoxins, ABC) genes were detected only in B. cereus isolates. 57.6% (11/19), 36.8% (7/19) and 5.3% (1/19) harboured all three (nheA, nheB, nheC), two (nheB, nheC) and one (nheC) nhe gene, respectively. Among hbl complex genes (encoding haemolytic enterotoxins CAD), only hblC (36.8%, 7/19) was detected. Incidence B. cereus cytK (encoding cytotoxin enterotoxin) was 52.6% (10/19). Each B. cereus isolate harboured two or more enterotoxigenic genes. Seven isolates had at least one gene from haemolytic and non-haemolytic complexes along with cytK. High levels (> 50%) of antimicrobial resistance were recorded for penicillin, amoxicillin, ampicillin cefixime and ceftazidine in tested B. cereus isolates. Two isolates were identified as multidrug resistant isolates with resistance to ≥ 3 antibiotic classes.

Oxygen Consumption Rate Analysis of Mitochondrial Dysfunction Caused by Bacillus cereus Cereulide in Caco-2 and HepG2 Cells

The emetic syndrome of Bacillus cereus is a food intoxication caused by cereulide (CER) and manifested by emesis, nausea and in most severe cases with liver failure. While acute effects have been studied in the aftermath of food intoxication, an exposure to low doses of cereulide might cause unnoticed damages to the intestines and liver. The toxicity which relies on the mitochondrial dysfunction was assessed on Caco-2 and HepG2 cells after exposure of one, three and ten days to a range of low doses of cereulide. Oxygen consumption rate analyses were used to study the impact of low doses of CER on the bioenergetics functions of undifferentiated Caco-2 and HepG2 cells using Seahorse XF extracellular flux analyzer. Both Caco-2 and HepG2 cells experienced measurable mitochondrial impairment after prolonged exposure of 10 days to 0.25 nM of cereulide. Observed mitochondrial dysfunction was greatly reflected in reduction of maximal cell respiration. At 0.50 nM CER, mitochondrial respiration was almost completely shut down, especially in HepG2 cells. These results corresponded with a severe reduction in the amount of cells and an altered morphology, observed by microscopic examination of the cells. Accurate and robust quantification of basal respiration, ATP production, proton leak, maximal respiration, spare respiratory capacity, and non-mitochondrial respiration allowed better understanding of the effects of cereulide in underlying respiratory malfunctions in low-dose exposure.

Food-Borne Outbreak Investigation and Molecular Typing: High Diversity of Staphylococcus aureus Strains and Importance of Toxin Detection

Staphylococcus aureus is an important aetiological agent of food intoxications in the European Union as it can cause gastro-enteritis through the production of various staphylococcal enterotoxins (SEs) in foods. Reported enterotoxin dose levels causing food-borne illness are scarce and varying. Three food poisoning outbreaks due to enterotoxin-producing S. aureus strains which occurred in 2013 in Belgium are described. The outbreaks occurred in an elderly home, at a barbecue event and in a kindergarten and involved 28, 18, and six cases, respectively. Various food leftovers contained coagulase positive staphylococci (CPS). Low levels of staphylococcal enterotoxins ranging between 0.015 ng/g and 0.019 ng/g for enterotoxin A (SEA), and corresponding to 0.132 ng/g for SEC were quantified in the food leftovers for two of the reported outbreaks. Molecular typing of human and food isolates using pulsed-field gel electrophoresis (PFGE) and enterotoxin gene typing, confirmed the link between patients and the suspected foodstuffs. This also demonstrated the high diversity of CPS isolates both in the cases and in healthy persons carrying enterotoxin genes encoding emetic SEs for which no detection methods currently exist. For one outbreak, the investigation pointed out to the food handler who transmitted the outbreak strain to the food. Tools to improve staphylococcal food poisoning (SFP) investigations are presented.

Development and validation of ultra-high-performance liquid chromatography-tandem mass spectrometry methods for the simultaneous determination of beauvericin, enniatins (A, A1, B, B1) and cereulide in maize, wheat, pasta and rice

Rapid and accurate UPLC-MS/MS methods for the simultaneous determination of beauvericin and the related enniatins (A, A1, B, B1), together with cereulide were successfully developed and validated in cereal and cereal-based food matrices such as wheat, maize, rice and pasta. Although these emerging foodborne toxins are of different microbial origin, the similar structural, toxicological and food safety features provided rationale for their concurrent detection in relevant food matrices. A Waters Acquity UPLC system coupled to a Waters Quattro Premier XE™ Mass Spectrometer operating in ESI+ mode was employed. Sample pretreatment involved a fast and simple liquid extraction of the target toxins without any further clean-up step. For all toxins the sample preparation resulted in acceptable extraction recoveries with values of 85-105% for wheat, 87-106% for maize, 84-106% for rice and 85-105% for pasta. The efficient extraction protocol, together with a fast chromatographic separation of 7min allowed substantial saving costs and time showing its robustness and performance. The validation of the developed method was performed based on Commission Decision 2002/657/EC. The obtained limits of detection ranged from 0.1 to 1.0μgkg^-1 and the limits of quantification from 0.3 to 2.9μgkg^-1 for the targeted toxins in the selected matrices. The obtained sensitivities allow detection of relevant toxicological concentrations. All relative standard deviations for repeatability (intra-day) and intermediate precision (inter-day) were lower than 20%. Trueness, expressed as the apparent recovery varied from 80 to 107%. The highly sensitive and repeatable validated method was applied to 57 naturally contaminated samples allowing detection of sub-clinical doses of the toxins.

Foodborne pathogens and their toxins

Foodborne pathogens, mostly bacteria and fungi, but also some viruses, prions and protozoa, contaminate food during production and processing, but also during storage and transport before consuming. During their growth these microorganisms can secrete different components, including toxins, into the extracellular environment. Other harmful substances can be also liberated and can contaminate food after disintegration of food pathogens. Some bacterial and fungal toxins can be resistant to inactivation, and can survive harsh treatment during food processing. Many of these molecules are involved in cellular processes and can indicate different mechanisms of pathogenesis of foodborne organisms. More knowledge about food contaminants can also help understand their inactivation. In the present review the use of proteomics, peptidomics and metabolomics, in addition to other foodomic methods for the detection of foodborne pathogenic fungi and bacteria, is overviewed. Furthermore, it is discussed how these techniques can be used for discovering biomarkers for pathogenicity of foodborne pathogens, determining the mechanisms by which they act, and studying their resistance upon inactivation in food of animal and plant origin.

BIOLOGICAL SIGNIFICANCE

Comprehensive and comparative view into the genome and proteome of foodborne pathogens of bacterial or fungal origin and foodomic, mostly proteomic, peptidomic and metabolomic investigation of their toxin production and their mechanism of action is necessary in order to get further information about their virulence, pathogenicity and survival under stress conditions. Furthermore, these data pave the way for identification of biomarkers to trace sources of contamination with food-borne microorganisms and their endo- and exotoxins in order to ensure food safety and prevent the outbreak of food-borne diseases. Therefore, detection of pathogens and their toxins during production, transport and before consume of food produce, as well as protection against food spoilage is a task of great social, economic and public health importance.

The importance of multiparasitism: examining the consequences of co-infections for human and animal health

Most parasites co-occur with other parasites, although the importance of such multiparasitism has only recently been recognised. Co-infections may result when hosts are independently infected by different parasites at the same time or when interactions among parasite species facilitate co-occurrence. Such interactions can have important repercussions on human or animal health because they can alter host susceptibility, infection duration, transmission risks, and clinical symptoms. These interactions may be synergistic or antagonistic and thus produce diverse effects in infected humans and animals. Interactions among parasites strongly influence parasite dynamics and therefore play a major role in structuring parasite populations (both within and among hosts) as well as host populations. However, several methodological challenges remain when it comes to detecting parasite interactions. The goal of this review is to summarise current knowledge on the causes and consequences of multiparasitism and to discuss the different methods and tools that researchers have developed to study the factors that lead to multiparasitism. It also identifies new research directions to pursue.

Emerging applications of low temperature gas plasmas in the food industry

The global burden of foodborne disease due to the presence of contaminating micro-organisms remains high, despite some notable examples of their successful reduction in some instances. Globally, the number of species of micro-organisms responsible for foodborne diseases has increased over the past decades and as a result of the continued centralization of the food processing industry, outbreaks now have far reaching consequences. Gas plasmas offer a broad range of microbicidal capabilities that could be exploited in the food industry and against which microbial resistance would be unlikely to occur. In addition to reducing the incidence of disease by acting on the micro-organisms responsible for food spoilage, gas plasmas could also play a role in increasing the shelf-life of perishable foods and thereby reduce food wastage with positive financial and environmental implications. Treatment need not be confined to the food itself but could include food processing equipment and also the environment in which commercial food processing occurs. Moreover, gas plasmas could also be used to bring about the degradation of undesirable chemical compounds, such as allergens, toxins, and pesticide residues, often encountered on foods and food-processing equipment. The literature on the application of gas plasmas to food treatment is beginning to reveal an appreciation that attention needs also to be paid to ensuring that the key quality attributes of foods are not significantly impaired as a result of treatment. A greater understanding of both the mechanisms by which micro-organisms and chemical compounds are inactivated, and of the plasma species responsible for this is forming. This is significant, as this knowledge can then be used to design plasma systems with tailored compositions that will achieve maximum efficacy. Better understanding of the underlying interactions will also enable the design and implementation of control strategies capable of minimizing variations in plasma treatment efficacy despite perturbations in environmental and operational conditions.

Quantitative analysis of cereulide toxin from Bacillus cereus in rice and pasta using synthetic cereulide standard and 13C6-cereulide standard - a short validation study

A single laboratory validation study of a rapid and sensitive quantitative method for the analysis of cereulide toxin produced by Bacillus cereus using ultra high performance liquid chromatography-electrospray-tandem mass spectrometry is presented. The analysis of this cyclic peptide toxin was validated for pasta and rice samples using a newly presented synthetic cereulide peptide standard, together with ¹³C₆-cereulide that previously have not been commercially available. The use of cereulide standard was also compared to the most frequently used surrogate standard, the antibiotic valinomycin. The performance of the method was evaluated by analyzing spiked sample pools from different types of rice and pasta, as well as 21 individual rice and pasta samples from differently prepared meals. Inoculation of samples with three cereulide toxin-producing strains of Bacillus cereus was finally used to mimic naturally contaminated foods. The quantification range of the method was 1–500 ng/g (R² = 0.999) and the limits of detection and quantification were 0.1 and 1 ng/g, respectively. The precision varied from 3% to 7% relative standard deviation and the trueness from −2% to +6% relative bias at different concentration levels in cooked rice and pasta.

Sub-emetic toxicity of Bacillus cereus toxin cereulide on cultured human enterocyte-like Caco-2 cells

Cereulide (CER) intoxication occurs at relatively high doses of 8 µg/kg body weight. Recent research demonstrated a wide prevalence of low concentrations of CER in rice and pasta dishes. However, the impact of exposure to low doses of CER has not been studied before. In this research, we investigated the effect of low concentrations of CER on the behavior of intestinal cells using the Caco-2 cell line. The MTT (mitochondrial 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and the SRB (sulforhodamine B) reactions were used to measure the mitochondrial activity and cellular protein content, respectively. Both assays showed that differentiated Caco-2 cells were sensitive to low concentrations of CER (in a MTT reaction of 1 ng/mL after three days of treatment; in an SRB reaction of 0.125 ng/mL after three days of treatment). Cell counts revealed that cells were released from the differentiated monolayer at 0.5 ng/mL of CER. Additionally, 0.5 and 2 ng/mL of CER increased the lactate presence in the cell culture medium. Proteomic data showed that CER at a concentration of 1 ng/mL led to a significant decrease in energy managing and H2O2 detoxification proteins and to an increase in cell death markers. This is amongst the first reports to describe the influence of sub-emetic concentrations of CER on a differentiated intestinal monolayer model showing that low doses may induce an altered enterocyte metabolism and membrane integrity.