Category Archives: Research

Research – Rapid detection of the source of a Listeria monocytogenes outbreak in Switzerland through routine interviewing of patients and whole-genome sequencing

Posted on May 19, 2024 | Leave a comment

SMW

In summer 2022, 20 patient-derived L. monocytogenes serotype 4b sequence type 388 strains were found to belong to an outbreak cluster (≤10 different alleles between neighbouring isolates) based on core genome multilocus sequence typing analysis. Geographically, 18 of 20 outbreak cases occurred in northeastern Switzerland. The median age of patients was 77.4 years (range: 58.1–89.7), with both sexes equally affected. Rolling analysis of the interview data revealed smoked trout from a local producer as a suspected infection source, triggering an on-site investigation of the production facility and sampling of the suspected products by the responsible cantonal food inspection team on 15 July 2022. Seven of ten samples tested positive for L. monocytogenes and the respective cantonal authority ordered a ban on production and distribution as well as a product recall. The Federal Food Safety and Veterinary Office released a nationwide public alert covering the smoked fish products concerned. Whole-genome sequencing analysis confirmed the interrelatedness of the L. monocytogenes smoked trout product isolates and the patient-derived isolates. Following the ban on production and distribution and the product recall, reporting of new outbreak-related cases rapidly dropped to zero.

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Posted in food bourne outbreak, Food Illness, Food Microbiology Research, Foodborne Illness, foodborne outbreak, foodbourne outbreak, Illness, Listeria, Listeria monocytogenes, Listeria Smoked Fish, outbreak, Research

Research – Inactivation mechanism of phenyllactic acid against Bacillus cereus spores and its application in milk beverage

Posted on May 19, 2024 | Leave a comment

Science Direct

Phenyllactic acid (PLA) as a natural phenolic acid exhibits antibacterial activity against non-spore-forming bacteria, while the inhibitory effect against bacterial spore remained unknown. Herein, this study investigated the inactivation effect of PLA against Bacillus cereus spores. The results revealed that the minimum inhibitory concentration of PLA was 1.25 mg/mL. PLA inhibited the outgrowth of germinated spores into vegetative cells rather than germination of spores. PLA disrupted the spore coat, and damaged the permeability and integrity of inner membrane. Moreover, PLA disturbed the establishment of membrane potential due to the inhibition of oxidative metabolism. SEM observations further visualized the morphological changes and structural disruption caused by PLA. Besides, PLA caused the degradation of DNA of germinated spores. Finally, PLA was applied in milk beverage, and showed promising inhibitory effect against B. cereus spores. This finding could provide scientific basis for the application of PLA against spore-forming bacteria in food industry.

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Posted in Bacillus, Bacillus cereus, Bacterial Spores, Food Microbiology Research, Food Technology, Phenyllactic Acid, Research, Technology

Research -Shiga Toxin–Producing Escherichia coli O157:H7 Illness Outbreak Associated with Untreated, Pressurized, Municipal Irrigation Water — Utah, 2023

Posted on May 18, 2024 | Leave a comment

CDC

During July–September 2023, an outbreak of Shiga toxin–producing Escherichia coli O157:H7 illness among children in city A, Utah, caused 13 confirmed illnesses; seven patients were hospitalized, including two with hemolytic uremic syndrome. Local, state, and federal public health partners investigating the outbreak linked the illnesses to untreated, pressurized, municipal irrigation water (UPMIW) exposure in city A; 12 of 13 ill children reported playing in or drinking UPMIW. Clinical isolates were genetically highly related to one another and to environmental isolates from multiple locations within city A’s UPMIW system. Microbial source tracking, a method to indicate possible contamination sources, identified birds and ruminants as potential sources of fecal contamination of UPMIW. Public health and city A officials issued multiple press releases regarding the outbreak reminding residents that UPMIW is not intended for drinking or recreation. Public education and UPMIW management and operations interventions, including assessing and mitigating potential contamination sources, covering UPMIW sources and reservoirs, indicating UPMIW lines and spigots with a designated color, and providing conspicuous signage to communicate risk and intended use might help prevent future UPMIW-associated illnesses.

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Posted in Boil Water Notice, Contaminated water, E.coli O157, E.coli O157:H7, food bourne outbreak, Food Illness, Food Microbiology Research, Foodborne Illness, foodborne outbreak, foodbourne outbreak, Illness, outbreak, Research, Water, water microbiology, Water Safety

Research – Differential mechanism between Listeria monocytogenes strains with different virulence contaminating ready-to-eat sausages during the simulated gastrointestinal tract

Posted on May 18, 2024 | Leave a comment

Science Direct

Listeria monocytogenes exhibits varying levels of pathogenicity when entering the host through contaminated food. However, little is known regarding the stress response and environmental tolerance mechanism of different virulence strains to host gastrointestinal (GI) stimuli. This study analyzed the differences in the survival and genes of stress responses among two strains of L. monocytogenes 10403S (serotype 1/2a, highly virulent strain) and M7 (serotype 4a, low-virulence strain) during simulated gastrointestinal digestion. The results indicated that L. monocytogenes 10403S showed greater acid and bile salt tolerance than L. monocytogenes M7, with higher survival rates and less cell deformation and cell membrane permeability during the in vitro digestion. KEGG analysis of the transcriptomes indicated that L. monocytogenes 10403S displayed significant activity in amino acid metabolism, such as glutamate and arginine, associated with acid tolerance. Additionally, L. monocytogenes 10403S demonstrated a higher efficacy in promoting activities that preserve bacterial cell membrane integrity and facilitate flagellar protein synthesis. These findings will contribute valuable practical insights into the tolerance distinctions among different virulence strains of L. monocytogenes in the GI environment.

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Posted in Food Microbiology Research, Listeria, Listeria monocytogenes, Research

Research – Inactivation of Salmonella Typhimurium, Escherichia coli, and Staphylococcus aureus in Tilapia Fillets (Oreochromis niloticus) with Lactic and Peracetic Acid through Fogging and Immersion

Posted on May 18, 2024 | Leave a comment

MDPI

Abstract

This study investigated the antimicrobial effects of lactic acid (LA) (3%) and peracetic acid (PA) (300 ppm) on tilapia fillets (Oreochromis niloticus) by fogging (15 min) or by immersion (2 s) in a pool of Escherichia coli (NEWP 0022, ATCC 25922, and a field-isolated strain), Staphylococcus aureus (ATCC 25923 and a field-isolated strain), and Salmonella Typhimurium (ATCC 13311 and ATCC 14028), as well as the effects on the physicochemical characteristics of the fillets. Fogging was effective and the best application method to control S. Typhimurium regardless of the acid used, promoting reductions of 1.66 and 1.23 log CFU/g with PA and LA, respectively. Regarding E. coli, there were significant reductions higher than 1 log CFU/g, regardless of the treatment or acid used. For S. aureus, only immersion in PA showed no significant difference (p < 0.05). For other treatments, significant reductions of 0.98, 1.51, and 1.17 log CFU/g were observed for nebulized PA, immersion, and LA fogging, respectively. Concerning the pH of the samples, neither of the acids used differed from the control. However, treatments with LA, and fogging with PA, reduced the pH compared to immersion in PA. As for color parameters, L* and a* values showed changes regardless of the acid or method used, resulting in an improved perception of fillet quality. These results indicate that fogging and immersion are alternatives for reducing S. Typhimurium, E. coli, and S. aureus in tilapia fillets.

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Posted in E.coli, Food Microbiology Research, Food Technology, Research, Salmonella, Staphylococcus aureus, Technology

Research – Outbreak of Listeria monocytogenes in hospital linked to a fava bean product, Finland, 2015 to 2019

Posted on May 18, 2024 | Leave a comment

Eurosurveillance

Listeriosis is a severe bacterial infection caused by  (), usually via consumption of food contaminated with the bacterium. However, other ways of transmission than food-borne have been reported [1].  species are ubiquitous in the environment and many animals shed  in their faeces. Infections are often associated with raw, chilled or ready-to-eat (RTE) foods. Symptoms develop within 1–70 days after eating food contaminated with  [2]. The disease can manifest as severe, invasive illness, more likely in elderly people, pregnant women, unborn or newborn babies and people with weakened immune systems [3]. In these persons, listeriosis may present as septicaemia or meningitis and lead to high hospitalisation and mortality rates.

In 2021, an incidence of 0.5 per 100,000 population was reported for listeriosis in the European Union/European Economic Area (EU/EEA), while the incidence in Finland was 1.3 per 100,000 [4].

Listeriosis cases have been reported in healthcare facilities [5–11]. Two healthcare-associated  outbreaks have been reported in Finland during the last three decades. In 1999, a large hospital outbreak occurred with six deaths in 25 cases of invasive listeriosis. The source of the outbreak was butter which may have been contaminated after pasteurisation [12]. In 2012, RTE meat jelly was suspected to be the source of a hospital outbreak affecting 25 people [9].

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Posted in food bourne outbreak, Food Illness, Food Microbiology Research, Foodborne Illness, foodborne outbreak, foodbourne outbreak, Illness, Listeria, Listeria monocytogenes, Research

Research – Decontamination of egg-associated pathogens by plasma-activated water and hydrogen peroxide

Posted on May 15, 2024 | Leave a comment

Wiley Online

Abstract

This study investigated the effectiveness of plasma-activated water (PAW) and plasma-activated hydrogen peroxide (PAHP) in reducing egg-associated pathogens. The antimicrobial activity of these solutions against Salmonella Enteritidis, Campylobacter jejuni, and Staphylococcus aureus on eggs was evaluated at different plasma treatment durations. The results demonstrated that increasing the duration of plasma treatment enhanced the antimicrobial efficacy of both PAW and PAHP. The bacterial counts of the egg-associated pathogens significantly decreased from 7.61, 7.59, and 7.54 log (CFU/egg) to 5.4 and 3.09, 5.36 and 3.11, and 5.08 and 3.73 log (CFU/egg) for PAW and PAHP, respectively. The characteristics of the plasma solutions, including electrical conductivity, pH, H2O2, NO3¯, and NO2¯, synergistically acted as antimicrobial agents in both PAW and PAHP treatments. The storage study revealed that PAHP treatment had no adverse effects on the eggs’ pH, albumen and yolk color, Haugh unit, and yolk index. However, it did result in reduced eggshell strength and compromised cuticle integrity. Overall, this study demonstrates the successful application of PAW and PAHP in effectively inhibiting egg-associated pathogens while preserving essential egg quality attributes. Further research is needed to optimize the treatment conditions and investigate the long-term effects of PAW and PAHP on eggs in larger-scale applications. This research contributes to developing innovative and sustainable approaches for enhancing the safety and quality of eggs in the food industry.

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Posted in Campylobacter, Campylobacter jejuni, Food Microbiology Research, Plasma Activated Water, Plasma-activated hydrogen peroxide (PAHP), Research, Salmonella

Research – Foodborne Pathogenic Bacteria: Prevalence and Control—Volume I

Posted on May 15, 2024 | Leave a comment

MDPI

1. Introduction

From the farm to the dining table, foodborne pathogenic bacteria can contaminate food at any stage of the food production, processing, delivery, preparation, and consumption chain, posing a critical threat to the safety of food systems worldwide [1]. Staphylococcus aureus, Escherichia coli, Salmonella, Listeria monocytogenes, Campylobacter, and Vibrio parahaemolyticus are some of the most common foodborne pathogenic bacteria, and food products contaminated by them traverse intricate global trade networks, posing many disease risks to millions of consumers annually [2]. Foodborne diseases can result from unsafe food storage, processing, preservation, and infected workers, as well as several forms of environmental contamination, including pollution in water, soil, air, infected livestock, and animal feces [3]. Some other factors that increase the incidence of foodborne diseases include the adaptation of pathogens to new environments, the formation of biofilms, the acquisition of virulence factors, and the development of antimicrobial resistance in foodborne pathogenic bacteria [4].
To enhance the safety of our food system, the first step is to know how the food system has been, and could still be, contaminated by common pathogenic bacteria, as well as other emerging and re-emerging pathogenic bacteria. On the other hand, we need to know how these bacteria could survive different storage, processing, and preservation processes in the food system. Biofilm formation and antimicrobial resistance could explain the mechanisms of bacterial survival. However, much is unknown. Once basic information is acquired, we can prevent and control the contamination of foodborne pathogenic bacteria to keep us far away from the pathogens’ attacks.
We are pleased to present this Special Issue on “Foodborne Pathogenic Bacteria: Prevalence and Control”, which contains eleven research articles and two review articles on the detection, prevalence, growth, survival and control. In addition, this Special Issue also covered topics related to rapid detection, persistence in food processing environment, antimicrobial resistance, stress adaptation, antibacterial and antibiofilm mechanisms, etc., as alternative and sustainable innovations to prevent and control the contamination of pathogenic bacteria in the food system. We present a brief overview of each contribution.

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Posted in Bio-Preservative, Campylobacter, escherichia coli, Food Microbiology Research, Listeria, Listeria monocytogenes, Research, Salmonella, Vibrio

Research – Microbial community structure of plant-based meat alternatives.

Posted on May 14, 2024 | Leave a comment

Nature

A reduction in animal-based diets has driven market demand for alternative meat products, currently raising a new generation of plant-based meat alternatives (PBMAs). It remains unclear whether these substitutes are a short-lived trend or become established in the long term. Over the last few years, the trend of increasing sales and diversifying product range has continued, but publication activities in this field are currently limited mainly to market research and food technology topics. As their popularity increases, questions emerge about the safety and nutritional risks of these novel products. Even though all the examined products must be heated before consumption, consumers lack experience with this type of product and thus further research into product safety, is desirable. To consider these issues, we examined 32 PBMAs from Austrian supermarkets. Based on 16S rRNA gene amplicon sequencing, the majority of the products were dominated by lactic acid bacteria (either Leuconostoc or Latilactobacillus), and generally had low alpha diversity. Pseudomonadota (like Pseudomonas and Shewanella) dominated the other part of the products. In addition to LABs, a high diversity of different Bacillus, but also some Enterobacteriaceae and potentially pathogenic species were isolated with the culturing approach. We assume that especially the dominance of heterofermentative LABs has high relevance for the product stability and quality with the potential to increase shelf life of the products. The number of isolated Enterobacteriaceae and potential pathogens were low, but they still demonstrated that these products are suitable for their presence.

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Posted in Bacillus, Bacillus cereus, Enterobacteriaceae, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Lactobacillus, Leuconostoc mesenteroides, microbial contamination, Microbial growth, Microbial Spoilage, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, Pseudomonas, Research, Shewanella

Research – Lysin and Lytic Phages Reduce Vibrio Counts in Live Feed and Fish Larvae

Posted on May 12, 2024 | Leave a comment

MDPI

Bacteriophage on colorful background

Abstract

Vibrio species are naturally found in estuarine and marine ecosystems, but are also recognized as significant human enteropathogens, often linked to seafood-related illnesses. In aquaculture settings, Vibrio poses a substantial risk of infectious diseases, resulting in considerable stock losses and prompting the use of antimicrobials. However, this practice contributes to the proliferation of antimicrobial-resistant (AMR) bacteria and resistance genes. Our investigation aimed to explore the potential of biological agents such as bacteriophage CH20 and endolysin LysVPp1 in reducing Vibrio bacterial loads in both rotifer and fish larvae. LysVPp1’s lytic activity was assessed by measuring absorbance reduction against various pathogenic Vibrio strains. Phage CH20 exhibited a limited host range, affecting only Vibrio alginolyticus GV09, a highly pathogenic strain. Both CH20 and LysVPp1 were evaluated for their effectiveness in reducing Vibrio load in rotifers or fish larvae through short-setting bioassays. Our results demonstrated the significant lytic effect of endolysin LysVPp1 on strains of Vibrio alginolyticus, Vibrio parahaemolyticus, and Vibrio splendidus. Furthermore, we have showcased the feasibility of reducing the load of pathogenic Vibrio in live feed and fish larvae by using a non-antibiotic-based approach, such as lytic phage and endolysin LysVPp1, thus contributing to the progress of a sustainable aquaculture from a One Health perspective

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Posted in antimicrobial resistance, Antimicrobials, Bacteriophage, Food Microbiology Research, Food Pathogen, Pathogen, pathogenic, Research, Vibrio