Listeria Monocytogenes In Foods Research Articles

Development of a fluorescence aptasensor for rapid and sensitive detection of Listeria monocytogenes in food

In this study, a simple fluorescence aptasensor was developed for rapid and sensitive detection of Listeria monocytogenes in food. The aptasensor was comprised of two parts. Aptamer-functionalized upconversion nanoparticles (UCNPs) recognized and adhered to the L. monocytogenes cells and provided strong fluorescent signals. Aptamer-functionalized magnetic nanoparticles (MNPs), which also recognized and adhered to the cells, were used to concentrate the aptamer-UCNP/L. monocytogenes/aptamer-MNP complex. The fluorescence intensity was measured and calibrated to a concentration series of L. monocytogenes. A low limit of detection of 8 cfu mL−1 was estimated from the range of 68 to 68 × 106 cfu mL−1. Compared with other methods currently available, the proposed method had wider detection range and higher sensitivity. Furthermore, the selectivity and functionality when used to detect L. monocytogenes in real food samples suggest it may be useful for practical applications.

A fluorescence immunoassay for a rapid detection of Listeria monocytogenes on working surfaces

Listeria monocytogenes is a foodborne pathogen responsible for human listeriosis. The increasing incidence of listeriosis induced governments and food manufacturing enterprises to act to diminish the problem. Several methods for the detection of Listeria monocytogenes in food industries were developed. However, they are time-consuming and require the use of specialized equipment. To reduce the detection time of Listeria monocytogenes in food, in this work we developed a fluorescence sandwich immunoassay based on the use of an innovative chitosan-cellulose nanocrystal (CNC) membrane that improves the antigen capture during bacterial growth. The combined use of CNC film for the capture of p60 protein-specific antigen together with the use of fluorescence detection reduced the time of analysis from 24 to 12 h with a limit of detection (LOD) of the assay of 102 CFU/mL (2 Log). In addition, the use of monoclonal anti-PepD covalently immobilized to a CNC membrane assured a high specificity of the assay. Interestingly, the obtained results show no cross-reactivity with the five most diffused pathogen bacteria strains tested.

Effectiveness of Phage-Based Inhibition of Listeria monocytogenes in Food Products and Food Processing Environments.

Providing safe products and compliance of legal requirements is still a great challenge for food manufacturers regarding microbiological safety, especially in the context of Listeria monocytogenes food contamination. L. monocytogenes is a human pathogen, which, due to the ability of survival and proliferation in preservation conditions such as high salinity, acidity and refrigeration temperatures, is a significant threat to the food industry. Novel methods of elimination of the bacterial pathogen in food products and food processing environments are required. Among emerging technologies, one of the very promising solutions is using bacteriophages as natural control agents. This review focus on the major aspects of phage-based inhibition of L. monocytogenes in aspects of food safety. We describe an overview of foods and technological factors influencing the efficacy of phage use in biocontrol of L. monocytogenes. The most noteworthy are food matrix properties, phage concentration and stability, the time of phage application and product storage temperature. The combined methods, phage immobilization (active packing), pathogen resistance to phages and legislation aspects of antilisterial bacteriophage use in the food industry are also discussed.

The Determination of Listeria monocytogenes in Foods with Optical Biosensors

Listeria monocytogenes is a food-borne intracellular pathogen that is resistant to adverse conditions of food processing and is a causative agent of high mortality listeriosis disease. Analysis of large food lots is limited by culture methods. Nowadays, although the conventional culture methods have been adopted as the gold standard method, they can be insufficient to control food parties that reach very large quantities. Biosensors with on-site detection potential and their characterizing with high accuracy and precision offers many opportunities for real-time estimation of industrial contamination. As the most promising technique for rapid detection of L.monocytogenes, ones based on surface plasmon resonance (SPR) and fiber optic biosensors (FOBs) where direct or indirect detections can be made by detecting the interaction of the biomarker element with the optical field without marking or labeling, have come to the fore. SPR and FOBs can be detected directly in the range of 102-106 cfu/ml and ≤101-103 cfu/ml, respectively.

Potential Ad Hoc Markers of Persistence and Virulence in Canadian Listeria monocytogenes Food and Clinical Isolates

The Listeria monocytogenes gene inlA, encoding a surface virulence protein, was examined for the presence of premature stop codon (PMSC) mutations in 82 isolates obtained by the Canadian Food Inspection Agency (CFIA) from foods and food contact surfaces. These mutations were coanalyzed for the presence of stress survival islet 1 (SSI-1) and for the abilities of the isolates to invade Caco-2 intestinal epithelial cells and form biofilms on polystyrene. PMSC mutations were present in one-third of the isolates (predominantly those of serogroup 1/2a), and their presence was correlated with a noninvasive phenotype. The presence of SSI-1 and the ability to form biofilms were also linked to the 1/2a serogroup. Serogroup 4b isolates lacked inlA PMSC mutations and were invasive, but neither formed biofilms nor carried SSI-1. To expand upon these experimental findings, an in silico analysis was performed on L. monocytogenes genomes from Canadian databases of 278 food isolates and 607 clinical isolates. The prevalence of inlA PMSC mutations in genomes of food isolates was significantly higher (P < 0.0001) than that in clinical isolates. Also, a three-codon deletion in inlA associated with a hyperinvasive phenotype was more prevalent in genomes from clinical isolates (primarily of clonal complex 6, serogroup 4b) than in those from food isolates (P < 0.001). In contrast, SSI-1 was significantly overrepresented (P < 0.001) in genomes from food isolates. We propose the hypothesis that SSI-1 and inlA play a role in the evolution of Canadian L. monocytogenes strains into either a virulent (represented by serogroup 4b clinical isolates) or an environmentally persistent (represented by serogroup 1/2a food isolates) phenotype. The combined presence of SSI-1 and inlA PMSC mutations have potential for use as genetic markers for risk assessment when L. monocytogenes is recovered from foods, indicating low potential for pathogenesis.

A review on Listeria monocytogenes in food: prevalence, pathogenicity, survivability and antibiotic resistance

A review on Listeria monocytogenes in food: prevalence, pathogenicity, survivability and antibiotic resistance

Food Safety Management Systems, Certified Food Protection Managers, and Compliance with Food Safety Practices Associated with the Control of Listeria monocytogenes in Foods at Restaurants

Proper cold holding and date marking practices help control Lm growth in foods. Most restaurants had ≥1 instance of improper cold holding. Less than 50% of all cold holding observations were found to be out of compliance. Restaurants in areas requiring date marking of food were more likely to date mark. CFPM did not predict out-of-compliance observations when FSMS effects were considered.

Cross-resistance to phage infection in Listeria monocytogenes serotype 1/2a mutants

Bacteriophage-based biocontrols are one of several tools available to control Listeria monocytogenes in food and food processing environments. The objective of this study was to determine if phage-resistance that has been characterized with a select few Listeria phages would also confer resistance to a diverse collection of over 100 other Listeria phages. We show that some mutations that are likely to emerge in bacteriophage-treated populations of serotype 1/2a L. monocytogenes can lead to cross-resistance against almost all types of characterized Listeria phages. Out of the 120 phages that showed activity against the parental strain, only one could form visible plaques on the mutant strain of L. monocytogenes lacking rhamnose in its wall teichoic acids. An additional two phages showed signs of lytic activity against this mutant strain; although no visible plaques were observed. The findings presented here are consistent with other studies showing mutations conferring phage resistance through loss of rhamnose likely pose the greatest challenge for phage-based biocontrol in serotype 1/2a strains.

Cost estimation of listeriosis (Listeria monocytogenes) occurrence in South Africa in 2017 and its food safety implications

Periodic outbreaks of foodborne pathogens have resulted in food safety concerns, due to health implications and cost consequences. Occurrence of Listeria monocytogenes in foods and listeriosis have been reported in developed countries; however, documentation of listeriosis in South Africa is limited. In 2017–2018, Listeria was reported on polony (processed deli meat) and listeriosis was observed in South Africa (L. monocytogenes sequence type 6 (ST-6) was identified as the causal agent for listeriosis). Due to its potential effects, we conducted cost estimates to assess the implications of listeriosis outbreak with respect to illnesses, hospitalizations and deaths, and productivity losses. Cost estimates were computed on publicly available data by using USDA-ERS cost computation model for Listeria. Listeriosis had significant impacts, as mortality of 204 individuals with confirmed listeriosis cases was reported, with infants having the highest percent of fatalities (42%). The cost valuation of fatality cases was over US$ 260 million. Hospitalization costs associated with one-month recovery from listeriosis were estimated at US$ 10.4 million. Productivity losses attributed to listeriosis for humans and export value losses for food processors were in excess of US$ 15 million. Increase of food safety measures in South Africa could reduce foodborne disease outbreaks. Pre-emptive pathogen detection, sanitary procedures and bacterial inactivation can enhance control of L. monocytogenes in food processing environments.

Listeria monocytogenes Isolated from Illegally Imported Food Products into the European Union Harbor Different Virulence Factor Variants.

Unregulated international flow of foods poses a danger to human health, as it may be contaminated with pathogens. Recent studies have investigated neglected routes of pathogen transmission and reported the occurrence of Listeria monocytogenes in food illegally imported into the European Union (EU), either confiscated at four international airports or sold illegally on the Romanian black market. In this study we investigated the genotype diversity and the amino acid sequence variability of three main virulence factors of 57 L. monocytogenes isolates. These isolates were derived from 1474 food samples illegally imported into the EU and originated from 17 different countries. Multilocus sequence typing revealed 16 different sequence types (STs) indicating moderate genotype diversity. The most prevalent STs were ST2, ST9, and ST121. The pulsed-field gel electrophoresis (PFGE) analysis resulted in 34 unique pulsotypes. PFGE types assigned to the most prevalent STs (ST2, ST9, and ST121) were highly related in their genetic fingerprint. Internalin A (InlA) was present in 20 variants, including six truncated InlA variants, all harbored by isolates of ST9 and ST121. We detected eight ST-specific listeriolysin O (LLO) variants, and among them, one truncated form. The actin-assembly-inducing protein ActA was present in 15 different ST-specific variants, including four ActA variants with an internal truncation. In conclusion, this study shows that L. monocytogenes, isolated from illegally imported food, have moderate genotype diversity, but diverse virulence factors variants, mainly of InlA.

The protective effect of food matrices on Listeria lytic bacteriophage P100 application towards high pressure processing

The application of lytic phages as biocontrol agents is emerging as a promising strategy towards elimination or reduction of foodborne pathogens in a variety of food products. This technology is particularly advantageous for minimally processed and ready-to-eat (RTE) foods. In this study, the potential use of Listex™ P100 combined with high hydrostatic pressure (HPP), to enhance the control of Listeria monocytogenes in food was evaluated. For that, the effect of three pressures (200, 300 or 400 MPa; 5 min, 10 °C) on phage P100 stability was tested when inoculated in six different matrices: phosphate buffered saline (PBS, pH 7.4); apple juice (pH 3.41); orange/carrot nectar (pH 3.54); UHT whole milk (pH 6.73); and, two traditional Portuguese fermented products, “Serra da Estrela” cheese (pH 5.66) and “Alheira”, a meat sausage (pH 6.07). The results showed that treatment at 400 MPa reduced phage titres to below the detection level in all matrices, whereas at milder pressures the survival of the phage was matrix dependent. “Alheira”, “Serra da Estrela” cheese and UHT whole milk were shown to be baroprotective matrices that support phage P100 application in HHP up to 300 MPa; however, an accentuated phage inactivation was observed in apple and orange/carrot nectar, which may be related to the acidic pH values of these matrices. The initial phage load did not affect the inactivation rate during HHP processing (300 MPa, 5 min, 10 °C) in PBS, cheese, sausage or milk matrices, and the phage titres were stable in these matrices during storage at 4 °C for 28 days for milk and 60 days for “Alheira” and “Serra da Estrela” cheese. In addition, a baroprotective effect on phage stability was observed when PBS was supplemented with reducing sugars, dextrin, casein, and tween 80. In conclusion, at mild HHP treatment, phage P100 remained active in specific matrices and seems to present potential to be added in non-thermal inactivation of L. monocytogenes.

A new single-tube platform of melting temperature curve analysis based on multiplex real-time PCR using EvaGreen for simultaneous screening detection of Shiga toxin-producing Escherichia coli, Salmonella spp. and Listeria monocytogenes in food

Shiga toxin-producing Escherichia coli (STEC), Salmonella spp. and Listeria monocytogenes are continuously reported as causative agents of great concern regarding food safety and widespread contamination in many food varieties. Therefore, their simultaneous detection may be advantageous in terms of cost, time and labor savings and simplicity. This study developed a new, simple platform of multiplex real-time polymerase chain reaction (mRT-PCR) for specific, sensitive and rapid detection of STEC, Salmonella spp. and L. monocytogenes in food. The single-tube mRT-PCR format was developed by combining an 18 h enrichment step in simultaneous enrichment broth, boiling based on DNA extraction assay and a mRT-PCR detection system based on melting curve analysis using a fluorescent dye (EvaGreen) for detection of the presence or absence of the three target bacterial pathogens in food samples. Three specific peaks were clearly detected with average melting temperatures of 84.52 ± 0.90 °C, 87.51 ± 0.54 °C and 79.32 °C ± 0.48 °C for STEC, Salmonella spp. and L. monocytogenes, respectively. The sensitivity and specificity of these newly developed mRT-PCR platforms were further investigated using artificially and naturally contaminated food samples. The relative sensitivity, relative specificity and relative accuracy were all 100%, with a detection limit of 1 cfu for each target pathogen in 25 g of food sample. The developed platform of EvaGreen-based single-tube mRT-PCR for detection of the three target pathogenic bacteria in food samples provided results of absence or presence within 20 h. The newly developed mRT-PCR platform in this study offers a promising approach for simple, rapid, sensitive, specific and accurate detection of the three target bacterial pathogens in food.

Development of DNAzyme-based PCR signal cascade amplification for visual detection of Listeria monocytogenes in food

Listeria monocytogenes is an important foodborne pathogen, and it can cause severe diseases. Rapid detection of L. monocytogenes is crucial to control this pathogen. A simple and robust strategy based on the cascade of PCR and G-quadruplex DNAzyme catalyzed reaction was used to detect L. monocytogenes. In the presence of hemin and the aptamer formed during PCR, the catalytic horseradish peroxidase-mimicking G-quadruplex DNAzymes allow the colorimetric responses of target DNA from L. monocytogenes. This assay can detect genomic DNA of L. monocytogenes specifically with as low as 50 pg/reaction with the naked eye. Through 20 pork samples assay, visual detection assay had the same results as conventional detection methods, and had a good performance. This is a powerful demonstration of the ability of G-quadruplex DNAzyme to be used for PCR-based assay with significant advantages of high sensitivity, low cost and simple manipulation over existing approaches and offers the opportunity for application in pathogen detection.

Ready-to-eat meat products as a source of Listeria monocytogenes

Abstract In 2015 in the European Union member states listeriosis caused 270 deaths. Food is the route of transmission in 99% of all human infection cases. Several studies from different countries have shown that the presence of Listeria monocytogenes in food can be as high as 58.3%. One of the most important ways to protect food from these microorganisms is to prevent the spread of the bacteria at processing plants at different stages of food production chain. The ability of L. monocytogenes to survive in extreme conditions and to form biofilms on various surfaces is a significant challenge for food safety. Removal of these bacteria from niches in processing plants is difficult and requires the use of sanitisers and precise equipment cleaning. The presence of L. monocytogenes in processing environment at slaughterhouses, deli meat factories or in retail may be a reason of cross-contamination. Proper hygienic systems applied by workers in food preparing places and knowledge about different routes of spreading of these bacteria may effectively decrease the risk of food contamination. Standardised legal regulations and control of meat product manufacture should be a fundamental way to protect food from L. monocytogenes contamination.

Ready-to-eat Meat Products As a Source of Listeria Monocytogenes

In 2015 in the European Union member states listeriosis caused 270 deaths. Food is the route of transmission in 99% of all human infection cases. Several studies from different countries have shown that the presence of Listeria monocytogenes in food can be as high as 58.3%. One of the most important ways to protect food from these microorganisms is to prevent the spread of the bacteria at processing plants at different stages of food production chain. The ability of L. monocytogenes to survive in extreme conditions and to form biofilms on various surfaces is a significant challenge for food safety. Removal of these bacteria from niches in processing plants is difficult and requires the use of sanitisers and precise equipment cleaning. The presence of L. monocytogenes in processing environment at slaughterhouses, deli meat factories or in retail may be a reason of cross-contamination. Proper hygienic systems applied by workers in food preparing places and knowledge about different routes of spreading of these bacteria may effectively decrease the risk of food contamination. Standardised legal regulations and control of meat product manufacture should be a fundamental way to protect food from L. monocytogenes contamination.

Listeria monocytogenes in Foods.

Listeria monocytogenes causes listeriosis, a rare foodborne disease with a mortality rate of 20%-30%. The elderly and immunocompromised are particularly susceptible to listeriosis. L. monocytogenes is ubiquitous in nature and can contaminate food-processing environments, posing a threat to the food chain. This is particularly important for ready-to-eat foods as there is no heat treatment or other antimicrobial step between production and consumption. Thus, occurrence and control of L. monocytogenes are important for industry and public health. Advances in whole-genome sequence technology are facilitating the investigation of disease outbreaks, linking sporadic cases to outbreaks, and linking outbreaks internationally. Novel control methods, such as bacteriophage and bacteriocins, can contribute to a reduction in the occurrence of L. monocytogenes in the food-processing environment, thereby reducing the risk of food contamination and contributing to a reduction in public health issues.

Prevalence and serotype distribution of Listeria monocytogenes isolated from foods in Montevideo-Uruguay.

The aim of this work was to study the prevalence of Listeria monocytogenes in foods obtained in retail shops and food industries located in Montevideo-Uruguay, and to identify the serogroups of the obtained isolates. Three-thousand one-hundred and seventy-five food samples (frozen, deli meats, ready-to-eat and cheese) were analyzed. The obtained isolates were serogrouped by multiplex PCR and serotyped by conventional procedure. Genetic comparisons were performed using pulsed-field gel electrophoresis on a sub-set of isolates belonging to the same serotype successively recovered from the same establishment. L. monocytogenes was isolated from 11.2% of samples. The highest prevalence was observed in frozen foods (38%), followed by cheese (10%). 1/2b and 4b were the most frequently identified serotypes. In six of 236 analyzed establishments we successively recovered L. monocytogenes isolates belonging to the same serotype. Most of them corresponded to serotype 1/2b. Pulsed-field gel electrophoresis profiles suggest that at least 33% of L. monocytogenes 1/2b isolates are genetically related and that may remain viable for prolonged periods. The observed prevalence of L. monocytogenes was lower than reported in neighboring countries. Our findings highlight the role that frozen foods may play in the spread of this pathogen, and the relevance of serotypes 1/2b and 4b.

Synthesis, chemical characterization, and economical feasibility of poly‐phenolic‐branched‐chain fatty acids

New poly‐phenolic branched‐chain fatty acid (poly‐PBC‐FA) products were synthesized from a combination of soybean fatty acids and phenolic materials through a highly efficient zeolite catalyzed arylation method. These poly‐PBC‐FAs are liquid at room temperature and do not have the unpleasant odor like the parent phenol reagent. They were found to be comprised of various numbers of phenol rings on the fatty acid chain, and this is important because compounds with a higher number of hydroxyl groups are expected to have better antimicrobial activities. Detailed characterization using gas chromatography and high performance liquid chromatography coupled to a quadrupole‐time of flight mass spectrometer techniques were used to measure the number of phenol groups on the alkyl fatty acid chains. A cost process modeling technique was used to determine the economic feasibility of this arylation process to make these important poly‐PBC‐FA products.Practical applications: The continued outbreaks of Listeria monocytogenes in foods imply that current antimicrobial products are not sufficient to control pathogen contamination. These new phenolic branched‐chain fatty acid products contain hydrophobic and hydrophilic properties. They are found to bear close resemblance to antimicrobial compounds that are receiving a great deal of attention for biomedical and/or materials applications. This finding is highly encouraging because the phenolic products are odorless which should make them appealing for possible food applications to kill the harmful Listeria monocytogenes.New poly‐phenolic branched‐chain fatty acid products were synthesized from a combination of soybean fatty acids and phenol materials through a highly efficient zeolite catalyzed arylation method. These isolated phenolic fatty acid materials are liquid at room temperature and do not have the unpleasant odor like the parent phenol reagent. Mass spectroscopy results confirmed more than one phenol group is on the alkyl chain due to the polyunsaturated fatty acid materials used. The cost model indicated that the process is feasible at the industrial scale.

Comparative evaluation of direct plating and most probable number for enumeration of low levels of Listeria monocytogenes in naturally contaminated ice cream products

A precise and accurate method for enumeration of low level of Listeria monocytogenes in foods is critical to a variety of studies. In this study, paired comparison of most probable number (MPN) and direct plating enumeration of L. monocytogenes was conducted on a total of 1730 outbreak-associated ice cream samples that were naturally contaminated with low level of L. monocytogenes. MPN was performed on all 1730 samples. Direct plating was performed on all samples using the RAPID'L.mono (RLM) agar (1600 samples) and agar Listeria Ottaviani and Agosti (ALOA; 130 samples). Probabilistic analysis with Bayesian inference model was used to compare paired direct plating and MPN estimates of L. monocytogenes in ice cream samples because assumptions implicit in ordinary least squares (OLS) linear regression analyses were not met for such a comparison. The probabilistic analysis revealed good agreement between the MPN and direct plating estimates, and this agreement showed that the MPN schemes and direct plating schemes using ALOA or RLM evaluated in the present study were suitable for enumerating low levels of L. monocytogenes in these ice cream samples. The statistical analysis further revealed that OLS linear regression analyses of direct plating and MPN data did introduce bias that incorrectly characterized systematic differences between estimates from the two methods.

Genome Sequence of the Listeria monocytogenes Food Isolate HPB913, Collected in Canada in 1993.

Listeria monocytogenes is a pathogenic bacterium of importance to public health and food safety agencies. We present the genome sequence of the serotype 1/2a L. monocytogenes food isolate HPB913, which was collected in Canada in 1993 as part of an investigation into a sporadic case of foodborne illness.