Category Archives: Research

Research – A Quantitative Risk Assessment Model for Listeria monocytogenes in Ready-to-Eat Smoked and Gravad Fish

Posted on December 8, 2024 by | Leave a comment

MDPI

Abstract

This study introduces a quantitative risk assessment (QRA) model aimed at evaluating the risk of invasive listeriosis linked to the consumption of ready-to-eat (RTE) smoked and gravad fish. The QRA model, based on published data, simulates the production process from fish harvest through to consumer intake, specifically focusing on smoked brine-injected, smoked dry-salted, and gravad fish. In a reference scenario, model predictions reveal substantial probabilities of lot and pack contamination at the end of processing (38.7% and 8.14% for smoked brined fish, 34.4% and 6.49% for smoked dry-salted fish, and 52.2% and 11.1% for gravad fish), although the concentrations of L. monocytogenes are very low, with virtually no packs exceeding 10 CFU/g at the point of sale. The risk of listeriosis for an elderly consumer per serving is also quantified. The lot-level mean risk of listeriosis per serving in the elderly population was 9.751 × 10−8 for smoked brined fish, 9.634 × 10−8 for smoked dry-salted fish, and 2.086 × 10−7 for gravad fish. Risk reduction strategies were then analyzed, indicating that the application of protective cultures and maintaining lower cold storage temperatures significantly mitigate listeriosis risk compared to reducing incoming fish lot contamination. The model also addresses the effectiveness of control measures during processing, such as minimizing cross-contamination. The comprehensive QRA model has been made available as a fully documented qraLm R package. This facilitates its adaptation for risk assessment of other RTE seafood, making it a valuable tool for public health officials to evaluate and manage food safety risks more effectively.

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Posted in Food Microbiology Research, Listeria, Listeria monocytogenes, Listeria Smoked Fish, Research, Technology

Research – From Germination to Stagnation: Sodium Diacetate’s Impact on Clostridium perfringens Spores

Posted on December 7, 2024 by | Leave a comment

Wiley Online

ABSTRACT

Sodium diacetate is recognized for its high efficiency as a preservative, demonstrating strong antibacterial properties that help extend the shelf life of food products. However, it is still unclear how it influences spores. This research investigated the influence of sodium diacetate on the germination and outgrowth stage in the revival process of Clostridium perfringens (C. perfringens) spores. The germination and outgrowth rate of spores after sodium diacetate treatment were measured. The changes of spore inner membrane were monitored by laser confocal microscope, electron scanning microscope and macromolecular leakage. The interaction between sodium diacetate and DNA was investigated by EB fluorescence probe, and the finding was verified by the outgrowth of spores in ham sausage. An investigation into the effects of sodium diacetate treatment on the biological activity, inner membrane permeability, morphology, and DNA integrity of spores devoid of both the coat and cortex revealed that sodium diacetate significantly hindered the transition of germinated spores into vegetative cells. In the presence of sodium diacetate, C. perfringens spores underwent germination, characterized by the hydrolysis of the spore cortex and the disassembly of the spore coat. As the spores advanced into the outgrowth phase, sodium diacetate penetrated their structure, causing damage to the inner membrane and compromising DNA integrity. Moreover, sodium diacetate was demonstrated to effectively inhibit spore outgrowth in ham sausage. This study provided theoretical guidance and references for the application of sodium diacetate in food to control the germination and outgrowth of spore-forming bacteria.

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Posted in Bacterial Spores, Clostridium, Clostridium perfringens, Food Microbiology Research, Food Technology, Research, Spores, Technology

Research – Occurrence, Antibiotic Resistance and Biofilm-Forming Ability of Listeria monocytogenes in Chicken Carcasses and Cuts

Posted on December 6, 2024 by | Leave a comment

MDPI

A total of 104 samples of chicken meat acquired on the day of slaughter from two slaughterhouses in northwestern Spain were analyzed. These comprised 26 carcasses and 26 cuts from each of the two establishments. An average load of 5.39 ± 0.61 log10 cfu/g (total aerobic counts) and 4.90 ± 0.40 log10 cfu/g (psychrotrophic microorganisms) were obtained, with differences (p < 0.05) between types of samples and between slaughterhouses. Culturing methods involving isolation based on the UNE-EN-ISO 11290-1:2018 norm and identification of isolates by polymerase chain reaction (PCR) to detect the lmo1030 gene allowed the detection of Listeria monocytogenes in 75 samples (72.1% of the total; 50.0% of the carcasses and 94.2% of the cuts). The 75 isolates, one for each positive sample, were tested for resistance against a panel of 15 antibiotics of clinical interest by the disc diffusion method. All isolates belonged to the serogroup IIa (multiplex PCR assay) and showed resistance to between four and ten antibiotics, with an average value of 5.7 ± 2.0 resistances per isolate, this rising to 7.0 ± 2.1 when strains with resistance and reduced susceptibility were taken together. A high prevalence of resistance was observed for antibiotics belonging to the cephalosporin and quinolone families. However, the level of resistance was low for antibiotics commonly used to treat listeriosis (e.g., ampicillin or gentamicin). Nine different resistance patterns were noted. One isolate with each resistance pattern was tested for its ability to form biofilms on polystyrene during 72 h at 12 °C. The total biovolume of the biofilms registered through confocal laser scanning microscopy (CLSM) in the observation field of 16,078.24 μm2 ranged between 13,967.7 ± 9065.0 μm3 and 33,478.0 ± 23,874.1 μm3, and the biovolume of inactivated bacteria between 0.5 ± 0.4 μm3 and 179.1 ± 327.6 μm3. A direct relationship between the level of resistance to antibiotics and the ability of L. monocytogenes strains to form biofilms is suggested.

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Posted in Antibiotic Resistance, antimicrobial resistance, Biofilm, Food Microbiology Research, Listeria, Listeria monocytogenes, PCR, Research

Research – Surveillance of Vibrio cholerae serogroups (O1 and O139) from surface and ground water sources in the Vhembe district, Limpopo Province, South Africa

Posted on December 5, 2024 by | Leave a comment

Frontiers In.org

Vibrio cholera is increasingly emerging as a significant public health concern in developing countries. Choleragenic V. cholerae O1 and O139 has reported to cause devastating disease and economic burdens in developing countries. In rural areas of the Vhembe district, most rivers and several communal boreholes are polluted as a result of sanitation issues around these water sources. The aim of this study was to determine the presence of choleragenic V. cholerae O1 and O139 in rivers and communal boreholes. The analysis of physicochemical parameters and molecular techniques was used to establish the adaptation and detect the serogroups of V. cholerae in the water samples. The results reported that electrical conductivities (EC) ranged between 18.78 and 154 μS/cm, with rivers such as Madandze and Mvudi recording >80 μS/cm, and those of the communal boreholes were ranged between 23.4 and 295 μS/cm, which were above the acceptable South African water quality guidelines of 0-70 μS/cm for rivers and communal boreholes. The results further revealed that most of the rivers detected positive for Vibrio cholerae, except for the Mukhase river; the downstream points of Livuvhu and Nwedi rivers and the upstream point of the Nzhelele river; and several of the communal boreholes (Mak B1, B2, Kwe B3, 4, and 6) also tested positive for the presence of Vibrio cholerae. The toxigenic Vibrios was also reported in Mutshundudi, Tshinane rivers, the upstream of Dzindi, Madanzhe, Nwedi, and the downstream of Sambandou rivers, as well as Mak B1, B2, and Kwe3 of communal boreholes. The serogroup O1 was detected on the Mutshundudi and Tshinane rivers, while serogroup O139 was detected upstream of the Dzindi, Madanzhe, Mutshundudi, and Tshinane rivers. There was also detection of the O1 serogroup in the communal boreholes (Mak B1 and Kwe B3), while O139 was only detected in one communal borehole (Mak B2). The development of robust policies, including an integrated water and sanitation safety surveillance web tool for monitoring water resources and public health protection, is required to make sure that drinking water in rural communities is safe for consumption.

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Posted in Food Microbiology Research, Research, Vibrio, Vibrio cholera

Research – How safe is the US food supply?

Posted on December 3, 2024 by | Leave a comment

New Scientist

Food in the US has a bad rap thanks to outbreaks caused by bacteria, plus processing, additives and food dyes, but the food supply is actually much less risky than people think.

Apple sauce containing lead. Onions carrying E. coli. Deli meat spreading listeria. The past year has seen alert after alert from US public health officials warning of contamination in the food supply, both in packaged and prepared foods. Going to the grocery store – or even out to eat – has seemingly become a real gamble.

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Posted in E.coli, food bourne outbreak, Food Microbiology Research, foodborne outbreak, foodbourne outbreak, Listeria, Listeria monocytogenes, outbreak, Research

Research – Simple lab-free test to detect bacteria in fluids from water to urine

Posted on December 2, 2024 by | Leave a comment

Science Daily

A novel new test for bacteria in fluids makes it as easy as observing a colour change to confirm the presence of disease-causing pathogens, promising much easier diagnostic tests and greater food safety.

Engineers and biochemists at McMaster university have brought their skills together to make it possible for untrained users to confirm contamination in fluids using a biogel test that changes colour in the presence of such bacteria as E. coli, listeria and other frequent testing targets.

The test uses harmless bacteriophages embedded in the gel to locate target bacteria in a sample of fluid such as lake water, urine or a container of milk, even in low concentrations.

Bacteriophages are the most common form of life on Earth. Each form of bacteriophage is specialized to destroy one form of bacteria.

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Posted in Bacteriophage, Bio-Preservative, E.coli, Food Technology, Research, Technology

Research – Isolation and Detection of the Emerging Pathogen Escherichia albertii in Clinical Stool Samples and the Potential Transmission by Meat Samples in Retail

Posted on November 30, 2024 by | Leave a comment

MDPI

Abstract

The significance of Escherichia albertii as a foodborne pathogen is increasingly acknowledged, but the assessment of its occurrence and transmission remains challenging due to the lack of validation of selective isolation, detection, and identification methods. The aim of the present study was to examine its presence on various meat samples at the retail level in order to assess a potential foodborne transmission and its occurrence in clinical stool samples. First, the evaluation and selection of a selective enrichment broth and isolation medium, combined with an optimized identification by MALDI-TOF MS, as well as a suitable DNA extraction method and a PCR-based detection strategy were developed. After the evaluation of existing isolation strategies and the formulation of an adapted enrichment and isolation medium, 100% isolation specificity was not achieved. An identity confirmation of suspected colonies remains necessary. A total of 292 samples, including 45 beef fillet, 51 minced beef, 50 pork fillet, 30 minced pork, 30 chicken carcass, 51 chicken fillet, and 35 minced chicken samples were examined. Samples were all collected at the retail level, including supermarkets and local butcheries. Escherichia albertii was isolated from two chicken fillets (3.9%) and additionally detected in one minced chicken (4.5%) and two other chicken fillet (4.5%) samples by a PCR assay. All beef and pork samples tested negative for its presence, but transmission through these meat types cannot be excluded, as it potentially correlates with the level of fecal contamination that was significantly higher on poultry products. With other hygienic conditions and processing steps applied, the presence of E. albertii on food can therefore differ in other parts of the world. Escherichia albertii was present in 0.4% of the 2419 clinical stool samples examined. The future development of a chromogenic isolation medium, as well as further extensive epidemiologic approaches and a genomic comparison of human, food, and animal isolates, could enhance the assessment of the emerging pathogen status and its potential as a foodborne hazard.

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Posted in E.albertii, Escherichia albertii, Food Microbiology Research, Food Technology, Research, Technology

EU – Outbreak results reported at ECDC conference

Posted on November 29, 2024 by | Leave a comment

Food Safety News

Experts have shared findings from Cryptosporidium, Listeria, Trichinella, and Salmonella outbreaks at an event in Europe.

Among presentations at the European Scientific Conference on Applied Infectious Disease Epidemiology (ESCAIDE) was one about the Danish perspective on two multi-country outbreaks. These included a Salmonella outbreak linked to chicken meat from Poland and Listeria in fish from a Danish producer.

The meeting organized by the European Centre for Disease Prevention and Control (ECDC) also discussed a July 2023 botulism outbreak linked to potato omelets (tortilla de patata) eaten in Spain. Italy and Norway had two cases of people who had been to Spain. Potential contamination pathways remain unknown.

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Posted in Cryptosporidiosis, Cryptosporidium, ECDC, food bourne outbreak, Food Illness, Food Microbiology Research, Foodborne Illness, foodborne outbreak, foodbourne outbreak, Illness, Listeria, Listeria monocytogenes, outbreak, Research, Salmonella

Research – Microbiological quality of plant-based meat alternatives in Switzerland

Posted on November 25, 2024 by | Leave a comment

ACSA

The aim of this study was to assess the microbiological quality and occurrence of foodborne pathogens in plant-based meat alternative (PBMA) products collected at retail level in Switzerland. A total of 100 PBMA (84 vegan and 16 vegetarian products) were qualitatively analysed for the presence of Salmonella , Listeria monocytogenes and quantitatively for Staphylococcus aureus , members of the Bacillus cereus group , Enterobacteriaceae and total viable count. In addition, pH measurements were performed and the AW value was determined.
This study provides data that are relevant to the Hazard Analysis and Critical Control Point (HACCP) concepts of companies producing plant-based meat alternatives and helps define the microbiological parameters to be included when testing these products.
Isolates were analysed by whole genome sequencing. Total viable counts before the expiration date ranged from <2 log to 7 log CFU/g (mean: 5.97 log CFU/g). Enterobacteriaceae with 2 log to 3 log CFU/g were detected in six (6%) samples. Salmonella and Listeria monocytogenes were not detected . However, seven products (7%) were contaminated with other Listeria spp. (six L. inocua and one L. seeligeri ). Other findings included two (2%) Staphylococcus aureus ST8 with presence of selx and tsst-1 genes, and five (5%) members of the Bacillus cereus group (three B. paranthracis , one B. cereus sensu stricto and one B. cytotoxicus ) which were strains associated with diarrhoea.
Characteristics of plant-based meat alternative products, such as high water activity, high nutrient content, and high pH, ​​make them susceptible to microbial spoilage. Therefore, these products must be kept refrigerated. Since the products in this study were purchased at the retail level, there was no control over their storage conditions prior to testing. This lack of control may have contributed to the variability of the microbial load, as inconsistent storage practices can affect microbial findings. The predominance of members of the lactic acid bacteria group in PBMA may be relevant to product stability.
PBMA products are usually subjected to a heating stage that would control contamination. However, unlike raw meat, heating does not result in a colour change of PBMA, which makes it sometimes difficult for the consumer to determine whether it has been sufficiently heated. In addition, consumers should be aware that compliance with basic hygiene measures to avoid cross-contamination is especially important when handling foods that are not ready to eat immediately. Increasing consumer awareness regarding food handling and storage is recommended.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, microbial contamination, Microbial growth, Microbial Spoilage, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, Research

Research – Effects of Sodium Chloride, Sodium Lactate, and Sodium Diacetate on the Growth Probabilities of Salmonella Spp. and Staphylococcus Aureus

Posted on November 25, 2024 by | Leave a comment

Wiley Online

ABSTRACT

Salmonella spp. and Staphylococcus aureus have been linked to foodborne illnesses caused by the consumption of processed meat products. This study examined the growth probabilities of these two pathogens as affected by sodium chloride (salt), sodium lactate, and sodium diacetate in a solid medium for using these three additives to improve the microbial safety of processed meat. Sterilized tryptic soy agar (TSA, 200 μL) formulated with a combination of salt (3%–8%, aw 0.98–0.93), lactate (0%–2.4%), and diacetate (0%–0.25%) and inoculated with Salmonella spp. or S. aureus was dispersed into 96-well microplates and incubated at 37°C for 7 days. After incubation, a well showing any Salmonella spp. or S. aureus colonies was denoted as a growth event, otherwise a no-growth event. The number of growth events for each formulation was recorded. The effects of the additives on the growth event were analyzed by logistic regression to identify the growth and no-growth boundaries and the formulations that may prevent the growth of Salmonella spp. or S. aureus. For Salmonella spp., the observed minimum no-growth concentrations in TSA were 3% salt with 0.8% lactate+0.2% diacetate or 1.6% lactate+0.1% diacetate, 4% salt with 2.4% lactate, 5% salt with 0.25% diacetate, 6% salt with 0.8% lactate+0.15% diacetate, 7% salt with 0.8% lactate or 0.15% diacetate, and 8% salt alone. For S. aureus, the concentrations were 3% salt with 2.4% lactate+0.2 diacetate, 5% salt with 1.6% lactate+0.2% diacetate, 7% salt with 0.8% lactate+0.25% diacetate, and 8% salt with 0.8% lactate+0.20% diacetate or 1.6% lactate+0.15% diacetate. These no-growth formulations also inhibited the growth of both pathogens in cooked meat samples. Mathematical models were developed to describe the effects of the additives on the growth probabilities of Salmonella spp. and S. aureus. Findings from this study may be used for formulating refrigerated and shelf-stable meat products to reduce Salmonella spp. and S. aureus risk.

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Posted in Antibacterial, Bio-Preservative, Food Microbiology Research, Research, Salmonella, Staphylococcal Toxin, Staphylococcus aureus