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Most Austrian dairies and cheese manufacturers participated in a Listeria monitoring program, which was established after the first reports of dairy product-associated listeriosis outbreaks more than thirty years ago. Within the Listeria monitoring program, up to 800 mL of product-associated liquids such as cheese smear or brine are processed in a semi-quantitative approach to increase epidemiological sensitivity. A sampling strategy within cheese production, which detects environmental contamination before it results in problematic food contamination, has benefits for food safety management. The liquid-based sampling strategy was implemented by both industrial cheese makers and small-scale dairies located in the mountainous region of Western Austria. This report considers more than 12,000 Listeria spp. examinations of liquid-based samples in the 2009 to 2018 timeframe. Overall, the occurrence of L. monocytogenes in smear liquid samples was 1.29% and 1.55% (n = 5043 and n = 7194 tested samples) for small and industrial cheese enterprises, respectively. The liquid-based sampling strategy for Listeria monitoring at the plant level appears to be superior to solid surface monitoring. Cheese smear liquids seem to have good utility as an index of the contamination of cheese up to that point in production. A modelling or validation process should be performed for the new semi-quantitative approach to estimate the true impact of the method in terms of reducing Listeria contamination at the cheese plant level.

Predictive models offer food scientists, farmers, and processors tools to help identify variables that lead to an increase in the food safety risk of a product. Foodborne pathogens, such as Listeria spp., pose a major problem for the pastured poultry industry. Currently, there is a lack of understanding of what farm practices lead to higher prevalence of Listeria spp. This study constructed random forest (RF) models to predict the prevalence of Listeria spp. in pastured poultry farming environments and the final broiler product based on major farm practices and variables. Feces, soil, and whole carcass rinse samples were collected from 11 farms in the southeastern United States and evaluated for Listeria spp. presence. The preharvest sample RF model identified the time of year and age of the broiler flock at time of sampling as factors of increased probability of Listeria spp. presence in feces and soil samples. The final product RF model identified brood feed and the presence of chlorine in processing rinse water as the two most important variables associated with an increased likelihood of Listeria spp. presence. Both the preharvest RF model and final sample RF model performed well on a held-out test set, with area under the receiver operating characteristic curve values of 0.876 and 0.887, respectively. The presented models showed the usefulness of RF models in a food safety context. Both RF models will help pastured poultry farmers and processors guide control strategies to manage Listeria contamination in pastured poultry farms and products.

Foodborne pathogens such as Listeria spp. contain the ability to survive and multiply in poultry farming environments, which provides a route of contamination for poultry processing environments and final poultry products. An understanding of the effect of meteorological variables on the prevalence of Listeria spp. in the farming environment is lacking. Soil and feces samples were collected from 11 pastured poultry farms from 2014 to 2017. Random forest (RF) and gradient boosting machine (GBM) predictive models were generated to describe and predict Listeria spp. prevalence in feces and soil samples based on meteorological factors at the farming location. This study attempted to demonstrate the use of GBM models in a food safety context and compare their use to RF models. Both feces models performed very well, with area under the curve (AUC) values of 0.905 and 0.855 for the RF and GBM models, respectively. The soil GBM model outperformed the RF model with AUCs of 0.873 and 0.700, respectively. The developed models can be used to predict the prevalence of Listeria spp. in pastured poultry farm environments and should be of great use to poultry farmers, producers, and risk managers. Unlabelled Image • Environmental samples were evaluated from poultry farms for Listeria prevalence. • Listeria prevalence can be predicted by machine learning models based on weather. • Wind speed, temperature, and humidity affect Listeria spp. prevalence. • This study provides a framework for future use of machine learning in food safety. [ABSTRACT FROM AUTHOR]

Abstract The aim of the study was to analyze the contamination of mold cheese (Brie, Camembert, Gorgonzola, Munster and Roquefort) with Listeria spp. and assessment of culturable cells number recovered from the biofilm formed on the surface of stainless steel by obtained strains. Identified isolates (MALDI TOF MS technique) were subjected to susceptibility testing (disk-diffusion method) and their genetic similarity (PFGE method), ability to form biofilm (quantitative method), biofilm dry weight, and biofilm survival on stainless steel were evaluated. Out of 250 samples of cheese 26 (10.4%) were Listeria spp. positive, including 15 isolates (6.0% of samples) of L. monocytogenes , 7 isolates of L. innocua (2.8% of samples) and 4 isolates of L. welshimeri species (1.6% of samples). Of the 26 isolates tested, 22 strains were genetically different. It was shown that L. innocua and L. welshimeri strains were sensitive to all antibiotics tested, while two (16.7%) L. monocytogenes strains were resistant to penicillin and one (8.3%) to erythromycin. L. monocytogenes formed biofilm most intensively on stainless steel, while L. welshimeri the least effectively. The median of bacteria number recovered from the biofilm for L. monocytogenes was 6.81 log CFU × cm−2, for L. innocua – 5.63 log CFU × cm−2, and for L. welshimeri – 4.93 log CFU × cm−2. The survival in the biofilm of Listeria spp. strains decreased along with the increase in a storage temperature of steel coupons. The longest survival time was reported at 4 °C, i.e. 47.58–124.41 days, with an elimination rate of 0.06–0.13 log CFU × day−1. Collectively, L. monocytogenes is the most prevalent species of Listeria genus in the mold cheese. The ability of L. monocytogenes strains to form biofilm on stainless steel and survive in the food processing environment increases chance of the secondary contamination of food posing risk to the consumer health. Highlights • Listeria spp. was detected in 26 (10.4%) from 250 cheese samples. • The L. monocytogenes species included 15 (57.7%) isolates, L. innocua - 7 (26.9%), and L. welshimeri - 4 isolates (15.4%). • Two (16.7%) L. monocytogenes strains were resistant to penicillin and one (8.3%) to erythromycin. • Theoretical survival time of Listeria spp. in the biofilm decreased with the increase in storage temperature of steel coupons. [ABSTRACT FROM AUTHOR]

Abstract Increasing demands for lightly processed seafood stresses the need for development of non-intensive processing methods that ensures a safe product. The limitation to the shelf life of seafood is often ascribed to microbial activity. An experiment was design to investigate the influence of heat-treatments in combination with packaging technologies (vacuum (VAC), modified atmosphere (MA) packaging, or soluble gas stabilization (SGS)) on the microbial survival of inoculated species. Fish patties were inoculated with either Brochothrix thermosphacta or Listeria innocua before heat-treatment, packaging, and storage at 2 ᵒC for 16 days. Increased heat-treatment lowered the bacterial load throughout the storage and type of packaging technology affected the bacterial load significantly. VAC-samples had a significantly higher bacterial load than MA- and SGS-packaged samples, regardless of heat-treatment (L. innocua : 8.7 ± 0.1, 8.3 ± 0.1, 8.2 ± 0.1 log CFU x g−1, B. thermosphacta : 9.9 ± 0.1, 9.2 ± 0.1, 8.6 ± 0.1 log CFU x g−1, respectively) at end of storage. Furthermore, use of SGS significantly increased the bacterial inhibition by heat (0.5–0.6 log CFUx −1) and extended the lag phase of B. thermosphacta , as well as decreasing the growth rate of both inoculum species. It is concluded that use of SGS can fulfill the consumers' demand of fresh, lightly processed seafood with a prolonged shelf life. Highlights • CO 2 present during heat treatment increases bacterial inhibition by heat. • Growth inhibitions were proportional to CO 2 levels in the product. • Packaging technology is more influential on bacterial growth than heat treatment. [ABSTRACT FROM AUTHOR]

Abstract The reference method for the detection and enumeration of L. monocytogenes in food (Standards EN ISO 11290-1&2) have been validated by inter-laboratory studies in the frame of the Mandate M381 from European Commission to CEN. In this paper, the inter-laboratory studies led in 2013 on 5 matrices (cold-smoked salmon, milk powdered infant food formula, vegetables, environment, and cheese) to validate Standard EN ISO 11290-2 are reported. According to the results obtained, the method of the revised Standard EN ISO 11290-2 can be considered as a good method for the enumeration of L. monocytogenes in foods and food processing environment, in particular for the matrices included in the study. Values of repeatability and reproducibility standard deviations can be considered satisfactory for this type of method with a confirmation stage, since most of them were below 0.3 log 10 , also at low levels, close to the regulatory limit of 100 CFU/g. [ABSTRACT FROM AUTHOR]

Fruit waste parts, particularly peel, are abundant sources of bioactive compounds. To be included in the formulation of value-added foods, peel needs to be transformed and subjected to a preservation process. Therefore, this study seeks to assess the effect of ozone on the quality and antilisterial indicators of cantaloupe melon peel paste, aiming at obtaining a product with the potential to be used as a food additive. Ozone was bubbled during 30 and 60 min, and some physicochemical characteristics (soluble solids content, pH and colour), bioactive compounds (total phenolics, chlorophylls and vitamin C) and antioxidant activity were analysed. Peel was also inoculated with Listeria innocua, used as a treatment efficiency indicator. The results indicated that, although ozone negatively affected antioxidant activity, it positively influenced all bioactive compounds analysed. An L. innocua reduction of 1.2 log cycle was achieved after ozone exposure. Ozone should be exploited as a promising technology to assure the quality/safety of cantaloupe melon peel. Indeed, if melon peel is conveniently converted into a suitable form that can be used as a food ingredient, this will promote the valorisation of waste materials with the consequent reduction of industrial by-products and new perspectives for market opportunities.

Lactic acid bacteria have been used since ancient times for food preparation and for bio-conservation by fermentation. Selected strains are capable of producing antimicrobial peptides - bacteriocins, which can be natural preservatives, especially in products with short shelf lives. The present study is focused on inhibitory effects of the bacteriocin-producing bacteria strains Enterococcus faecium, Pediococccus acidilactici and Lactobacillus plantarum against Listeria innocua as an indicator microorganism. Freeze-dried preparations of bacterial strains producing particular bacteriocins were tested by agar well-diffusion assay and by the traditional spread plate method. Plantaricin exhibited the highest anti-listerial effect among the tested bacteriocins. Pediocin also demonstrated a distinct inhibitory effect, but enterocin appeared to be heat labile and its efficiency was also suppressed under cold storage conditions. Plantaricin reduced Listeria innocua counts by 1 log in dairy spread made from cheese and quark. The formation of bacteriocins by various Lactobacillus plantarum strains were substantially influenced by the cultivation conditions of the mother culture and by the microbial preparation process before freeze-drying. Bacteriocins introduced into foodstuffs via protective cultures in situ offer new perspectives on enhancing food quality and safety.

L. monocytogenes contamination in processed food, especially fish-based snack, may results from contaminated raw materials, underprocessed or recontamination. The aims of this study were to identify the presence of Listeria spp. especially L. monocytogenes by PCR method and biochemical methods, as well as calculate the prevalence of Listeria spp. in fish-based snack food in Bogor. This study was conducted of 4 steps: (1) determination of L. monocytogenes’s DNA limit detection, (2) sample preparation, (3) identification of L. monocytogenes with real-time PCR, and (4) identification of Listeria spp. with biochemical methods. The results showed that DNA detection limits of L. monocytogenes in fish meatball and otak-otak were at 8.3x102 and 2.9x102 CFU/g, respectively. The study on 65 samples indicated that contamination of L. monocytogenes was not observed, but other species of Listeria spp., namely L. grayi and L. innocua, were found. The prevalence of L. grayi and L. innocua in siomay was at 5.9%, while the prevalence of L. grayi in shrimp meatballs, fish meat balls, fried meatballs was at 8.3, 9.1, and 50%, respectively. Furthermore, L. innocua from takoyaki samples with a prevalence of 20% was observed.

Listeriosis is one of the most notable foodborne diseases and is characterized by high rates of mortality. L. monocytogenes is the main cause of human listeriosis outbreaks, however, there are isolated cases of disease caused by other species of the genus Listeria. The aim of this study was to evaluate strains of L. monocytogenes (n = 7), L. innocua (n = 6), and L. welshimeri (n = 2) isolated from fish and shrimps for their virulence based on the presence of virulence genes and the in vivo Danio rerio (zebrafish) larvae models. A total of 15 strains were analyzed. The zebrafish larvae model showed that the larvae injected with L. monocytogenes strains were characterized by the lowest survival rate (46.5%), followed by L. innocua strains (64.2%) and L. welshimeri (83.0%) strains. Multiplex PCRs were used for detection of selected virulence genes (luxS, actA2, prfA, inlB, rrn, iap, sigB, plcB, actA, hlyA), the majority of which were present in L. monocytogenes. Only a few virulence-related genes were found in L. welshimeri, however, no correlation between the occurrence of these genes and larval survival was confirmed. This research highlights the importance of the potential impact that Listeria spp. strains isolated from fish and shrimps may have on consumers.

The present study evaluated the presence of Listeria spp. and L. monocytogenes in four plants producing PDO Taleggio cheese. A total of 360 environmental samples were collected from different areas during production. The sampling points were identified as Food Contact Surfaces (FCS), transfer-Non Food Contact Surfaces (tr-NFCS), and non-transfer-NFCS (non-tr-NFCS). Fifty-nine ingredients/products were also analyzed. Listeria spp. was found in all the plants with a mean prevalence of 23.1%; plants that included a ripening area showed significantly higher prevalence if compared to the other plants. The positivity rate detected on FCS was moderate (~12%), but significantly lower if compared to NFCS (about 1/4 of the samples, p < 0.01). Among the FCS, higher prevalence was revealed on ripening equipment. Listeria spp. was never detected in the ingredients or products. A total of 125 Listeria spp. isolates were identified, mostly as L. innocua (almost 80%). L. monocytogenes was detected only from two FCS samples, in an area dedicated to the cutting of ripened blue cheeses; strain characterization by whole genome sequencing (WGS) evidenced a low virulence of the isolates. The results of the present study stress the importance of Listeria spp. management in the dairy plants producing PDO Taleggio and similar cheeses, mainly by the application of strict hygienic practices.

This study evaluates the hazards posed by foodborne bacteria of the Listeria genus by analyzing the occurrence, diversity and virulence of Listeria spp.in food and food-manufacturing plants. Seventy-five isolates obtained from the routine analysis of 653 samples taken by three diagnostic laboratories in Northern Italy were genotypically differentiated by Repetitive Extragenic Palindrome (rep) PCR, with the GTG5 primer identified by sequencing the 16S rRNA gene and examined by specific PCR tests for the presence of L. monocytogenes virulence determinants occasionally found to occur in other species of the genus. Within this sample, 76% (n = 57) isolates were identified as L. innocua, 16% (n = 12) as L. monocytogenes, 6.6% (n = 5) as L. welshimeri and 1.3% (n = 1) as L. seeligeri. All L. monocytogenes isolates belonged to the serotype 1/2a and were predicted to be virulent for the presence of the inlJ internalin gene. Potentially virulent strains of L. innocua, L. seeligeri and L. welshimeri, carrying the L. monocytogenesinlA gene and/or hly gene, were identified, and most isolates were found to possess the toxin−antitoxin system mazEF for efficient adaptation to heat shock. Results indicated the need to reinforce food-contamination-prevention measures against all Listeria species by defining efficiently their environmental distribution.

Aim: The present study was undertaken with the prime objective of isolating and identifying Listeria spp. from various foods of animal origin sold at retail market outlets in the city of Navsari, Gujarat. Materials and Methods: Total 200 samples comprising of milk, milk products, meat, and fish (50 each) collected aseptically from local market which were subjected first to pre-enrichment in half strength Fraser broth followed by enrichment in full strength Fraser broth and subsequent plating on PALCAM agar. The growth with the typical colony characteristics were further identified up to species level on the basis of their morphological and biochemical characteristics. Cultures identified as Listeria monocytogenes were further subjected to in vitro pathogenicity tests and detection of different virulence associated genes viz. actA, hlyA, and iap using polymerase chain reaction. Results: Of the total 200 food samples of animal origin; 18 (9%) were found positive for Listeria spp. which were identified as Listeria seeligeri (6, 33.3%), Listeria innocua (5, 27.7%), Listeria welshimeri (4, 22.2%), and L. monocytogenes (3, 16.6%). The highest prevalence was observed in milk samples (8). Species wise, 6 isolates of L. seeligeri which included two each from cow milk, buffalo milk, and meat samples; 5 L. innocua isolates included four recovered from fish and one from meat sample; 4 L. welshimeri comprised of two isolates from ice cream and one each from buffalo milk and meat sample; and 3 isolates of L. monocytogenes recovered from milk (1 cow and 2 buffalo milk). All 3 L. monocytogenes isolates screened for the presence of virulence genes viz. actA, hlyA, and iap using the specific primers revealed the presence of all the genes suggesting the possibility of danger of foodborne listeriosis among raw milk consumers. Conclusion: Listeria spp. was isolated from 9% (18/200) of the animal origin food samples viz.; milk, milk products, meat, and fish with the highest prevalence in the milk samples. L. monocytogenes was isolated from 3 milk samples only. L. seeligeri was the predominant species isolated followed by L. innocua, L. welshimeri, and L. monocytogenes in this study. L. monocytogenes were found to carry virulence genes like actA, hly A, and iap genes suggesting the pathogenic potential of these isolates.

Mytilus galloprovincialis is called ‘‘black mussel’’ in Turkey and is mostly consumed as stuffed mussels and fried mussels. Mussels pump large quantities of water through their bodies, so they accumulate the toxic substances and microorganisms present in ambient water. In recent years, stuffed mussel sale increased in various foods consumption places (restaurants, supermarkets, etc.) in Turkey. The aim of this study was invastigated the microbiological quality of thirty stuffed mussels samples (270 stuffed mussels in total) collected from street sellers according to Turkish Food Codex (TFC) in Aydın and in İzmir provience. The microbiological analysis of stuffed mussel samples showed that the total viable counts were ranging between

The efficacy of “gaseous” ozone in reducing numbers and re-growth of food-borne pathogens, (Escherichia coli and Listeria spp.), on leafy salads was investigated using spinach. A preliminary in vivo study showed 1-log reduction in six strains of E. coli and two species of Listeria spp. on spinach exposed to 1 ppm ozone for 10 min. A range of ozone treatments were explored to deliver optimal bacterial inactivation while maintaining the visual appearance (color) of produce. Exposure to a higher ozone concentration for a shorter duration (10 ppm for 2 min) significantly reduced E. coli and Listeria spp. viable counts by 1-log and the pathogens did not re-grow following treatment (over a nine-day storage period). Impacts of 1 and 10 ppm ozone treatments were not significantly different. Approximately 10% of the pathogen population was resistant to ozone treatment. We hypothesized that cell age may be one of several factors responsible for variation in ozone resistance. E. coli cells from older colonies demonstrated higher ozone resistance in subsequent experiments. Overall, we speculate that gaseous ozone treatment constitutes the basis for an alternative customer-friendly method to reduce food pathogen contamination of leafy produce and is worth exploring on a pilot-scale in an industrial setting.

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The aim of the present study was to assess performance of waste stabilization ponds (WSPs) on the removal of Listeria spp. in Isfahan, Iran. A total of 104 samples were taken from eight sampling locations from influent and effluent of a wastewater treatment plant (WWTP). Sewage samples were analyzed for the presence of Listeria spp. using selective enrichment protocol. Listeria isolates were also identified by biochemical and polymerase chain reaction (PCR) amplification. Listeria spp. was enumerated by a three tube most probable number (MPN) for total coliform counts (TC), fecal coliform counts (FC), total suspended solids (TSS), and total dissolved solids (TDS). In total, 54/104 (51.92%), 49/104 (47.11%), 36/104 (34.61%), and 27/104 (25.95%) samples were positive for Listeria spp., L. monocytogenes, L. innocua, and L. seeligeri, respectively. The mean MPN/100 mL enumeration of L. monocytogenes for influent, anaerobic, facultative ponds 1, 2, 3, 4 and maturation ponds 1 and 2 were 21.54, 10.61, 8, 5.77, 4, 2.54, 1.38, and 0.46, respectively. The removal percentage of Listeria spp. in the anaerobic, facultative, and maturation ponds were 44.71, 76.5, and 81.4%, respectively. Results showed that the WSPs were able to decrease the Listeria spp. levels significantly, although unable to remove them completely. [ABSTRACT FROM AUTHOR]

In this study, the presence of Listeria monocytogenes in raw milk and milk products produced from raw milk by traditional method, such as cheese and butter using cultural and molecular techniques and the antibiotic resistances were investigated. Isolation was performed using the FDA technique. Microbact 12L test kit was used for biochemical identification. Genotyping of isolates was done by traditional PCR method. Antibiotic resistance of isolates was determined by standard disk diffusion method. Listeria spp. was detected in 16 (5.3%) of the total 300 food samples according to the biochemical identification results. The highest prevalence of Listeria spp. was in raw milk samples (10%), followed by cheese samples (4%) and butter samples (2%). All 36 Listeria spp. isolates which were obtained from biochemical identification were tested for L. monocytogenes by PCR, and 15 (41.6%) of them were confirmed as L. monocytogenes. According to the antibiotic resistance test results of L. monocytogenes strains, four (26.7%) isolates were resistant to at least one antibiotic while only one (6.7%) had multiple antibiotic resistance. The highest resistance was found against trimethoprim-sulfamethoxazole. It has been determined that L. monocytogenes isolates had the same degree resistance against penicillin G, meropenem, amikacin and vancomycin. In conclusion, the presence of L. monocytogenes which has been detected in dairy products made from raw milk and in raw milk itself may constitute a potential risk for public health. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes can cause circling disease, encephalitis, meningitis, septicemia, and mastitis in dairy cattle. Contamination from the environment can contaminate foods with Listeria spp. Consumption of foods containing L . monocytogenes can lead to listeriosis in susceptible people (adults with a compromised immune system), pregnant women, and infants. The objective of this study was to determine the prevalence of Listeria spp. and L. monocytogenes in various foods in Iran. We searched PubMed, Science direct, Scopus, Google scholar, and Iranian local databases including Iranian scientific information database and Magiran for relevant studies up to May 2015 using related keywords. In our preliminary search, we retrieved 1344 articles. After removing duplicates and reviewing titles/abstracts, 117 articles were considered, out of which, 75 articles had sufficient quality for inclusion in this meta-analysis. The prevalence of Listeria spp. contamination was about 18.3% in poultry, 8.5% in raw meat, 14.6% in ready-to-eat (RTE) foods, 10% in sea foods, 7.3% in traditional dairy, 3.2% in commercial dairy, and 0.1% in eggs. The findings showed that L. monocytogenes was most prevalent in ready to eat (9.2%), seafood (5.1%), poultry (5%), traditional dairy (4%), raw meat (2.6%), commercial dairy (1.4%), and egg (0.2%), respectively. Furthermore, the presence of L. monocytogenes particularly in RTE foods (that are consumed without further heat processing) and under-cooked products could be a potential risk for public health. So, contamination should be controlled at all levels of the food chain. [ABSTRACT FROM AUTHOR]

Listeria spp. are ubiquitous in nature and can be found in various environmental niches such as soil, sewage, river water, plants, and foods, but the most frequently isolated species are Listeria monocytogenes and Listeria innocua. In this study, the presence of Listeria spp. in raw chicken meat and chicken-related products sold in local markets in Klang Valley, Malaysia was investigated. A total of 44 Listeria strains (42 L. innocua and 2 L. welshimeri) were isolated from 106 samples. Antibiotic susceptibility tests of the L. innocua strains revealed a high prevalence of resistance to clindamycin (92.9%), ceftriaxone (76.2%), ampicillin (73.8%), tetracycline (69%), and penicillin G (66.7%). Overall, 31 L. innocua and 1 L. welshimeri strain were multidrug resistant, i.e., nonsusceptible to at least one antimicrobial agent in three or more antibiotic classes. The majority of the L. innocua strains were placed into five AscI pulsogroups, and overall 26 distinct AscI pulsotypes were identified. The detection of multidrug-resistant Listeria strains from different food sources and locations warrants attention because these strains could serve as reservoirs for antimicrobial resistance genes and may facilitate the spread and emergence of other drug-resistant strains. [ABSTRACT FROM AUTHOR]

Cilj ovog rada je bio da se utvrdi preživljavanje Listeria spp. u toku proizvodnje i zrenja tradicionalne srpske kobasice (Petrovačka kobasica) kao i da se okarakterišu izolati dobijeni umnožavanjem hlyA gena. Rezultati dobijeni standardnim mikrobiološkim i molekularnim metodama su pokazali da je tokom fermentacije, sušenja, zrenja i skladištenja Petrovačke kobasice, 17 od ukupno 99 uzoraka bilo pozitivno na prisustvo Listeria spp. Među njima, otkriven je hemolitični, atipični nepatogeni soj L. innocua FSL J1-023, čija je genomska sekvenca važna u rezumevanju uloge horizontalnog genskog transfera i rekombinacije tokom evolucije patogenosti. Najvažnije karakteristike proizvoda koje su uticale na preživljavanje i rast Listeria spp. tokom proizvodnje i zrenja Petrovačke kobasice bili su pH, aktivnost vode, temperature i starter kultura.

Controlled environment agriculture (CEA) is a growing industry for the production of leafy vegetables and fresh produce in general. Moreover, CEA is a potentially desirable alternative production system, as well as a risk management solution for the food safety challenges within the fresh produce industry. Here, we will focus on hydroponic leafy vegetable production (including lettuce, spinach, microgreens, and herbs), which can be categorized into six types: (1) nutrient film technique (NFT), (2) deep water raft culture (DWC), (3) flood and drain, (4) continuous drip systems, (5) the wick method, and (6) aeroponics. The first five are the most commonly used in the production of leafy vegetables. Each of these systems may confer different risks and advantages in the production of leafy vegetables. This review aims to (i) address the differences in current hydroponic system designs with respect to human pathogen internalization risk, and (ii) identify the preventive control points for reducing risks related to pathogen contamination in leafy greens and related fresh produce products.

The purpose of this study was to detect the prevalence of Listeria spp. in retail yoghurts in Şanlıurfa, Turkey. A total of 62 yoghurt samples were analyzed for the presence of Listeria spp. using a two-step selective enrichment method recommended by ISO 11290-1/A1-2004. L. monocytogenes strains were identified by real-time polymerase chain reaction (PCR) amplification. The prevalence of Listeria spp. in yoghurt was 3.2% (2 samples). All strains of L. monocytogenes was identified by biochemical tests and by real-time PCR. Yoghurt samples were stored at 4oC for 10 days and pH measurements, isolation and identification procedures were carried out again in first, third and tenth days for positive samples. The study shows the prevalence of Listeria species in yoghurt sold in the bazaars and local markets. This work demonstrates that efficient heat-treated milk and the consumption of raw produced dairy products can cause serious health problems so that manufacturers need to indicate the implementation of food safety training program. [ABSTRACT FROM AUTHOR]

The aims of the present study were to evaluate the prevalence of Arcobacter spp., Campylobacter spp., Listeria spp., and Salmonella spp. in heat-processed ready-to-eat (RTE) chicken products manufactured by various companies using bacterial culture methods and to perform virulence gene analysis, serotyping, genotyping, and antibacterial susceptibility tests on the isolated strains. For this purpose, 50 packages of chicken convenience products were used as the study material. Phenotypic tests and a molecular method (Polymerase Chain Reaction, PCR) were used to identify the isolated bacteria. All samples examined were negative for Arcobacter spp., Campylobacter spp., and Salmonella species. Listeria species were isolated from 12 (24%) of the examined samples. Among the Listeria species isolated, 9 were identified as L. monocytogenes , 2 were identified as L. innocua , and one was identified as L. welshimeri . All isolates were susceptible to the antibiotics tested. A detailed molecular analysis of the Listeria spp. revealed that the examined food products posed a significant public health hazard. Considering the presence of different genotypes of L. monocytogenes in RTE food production facilities, all the steps of food production must be reviewed in terms of conformity with sanitation and hygiene rules, and necessary measures must be set in place. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes is a Gram-positive bacterium and an opportunistic food-borne pathogen which poses significant risk to the immune-compromised and pregnant due to the increased likelihood of acquiring infection and potential transmission of infection to the unborn child. Conventional methods of analysis suffer from either long turn-around times or lack the ability to discriminate between Listeria spp. reliably. This paper investigates an alternative method of detecting Listeria spp. using two novel enzyme substrates that liberate exogenous volatile organic compounds in the presence of α-mannosidase and d-alanyl aminopeptidase. The discriminating capabilities of this approach for identifying L. monocytogenes from other species of Listeria are investigated. The liberated volatile organic compounds (VOCs) are detected using an automated analytical technique based on static headspace-multi-capillary column-gas chromatography-ion mobility spectrometry (SHS-MCC-GC-IMS). The results obtained by SHS-MCC-GC-IMS are compared with those obtained by the more conventional analytical technique of headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results found that it was possible to differentiate between L. monocytogenes and L. ivanovii, based on their VOC response from α-mannosidase activity. [ABSTRACT FROM AUTHOR]

The present study aimed at evaluating the growth of Escherichia coli , Salmonella enterica , and Listeria spp. and studying the efficacy of Ultraviolet-C (UV-C) irradiation, acidic electrolyzed (AEW) and neutral electrolyzed (NEW) waters in the reduction of these bacteria on ‘Rocha’ pear. Fresh-cut pieces were inoculated and incubated at 4–20 °C for 8 days. Inoculated pears were treated with UV-C (2.5–10 kJ/m 2 ), AEW, NEW and sodium hypochlorite (SH) and microbiological and quality parameters were evaluated. The three bacteria, inoculated at 6.1–6.2 log cfu/g, grew on the pear at high growth rates at 12 and 20 °C reaching populations of 8.1–8.6 log cfu/g, in 24 h. At 8 °C the microorganisms increased their populations by at least 1 log cfu/g in three days. At 4 °C adaptation phases of less than 24 h for Listeria spp. were measured before exponential growth occurred and the enterobacteria did not grow despite having survived for 8 days. AEW and NEW caused microbial reductions similar to SH, of approximately 1 log cfu/g, while the best UV-C dose (7.5 kJ/m 2 ) of at least 2.4 log cfu/g. Fresh-cut pears were a good substrate for foodborne bacteria emphasizing the importance of preventing contaminations and cross contaminations. The UV-C was more effective than the chemical decontaminations, as it provided superior microbial reductions without greatly affecting the quality of pears. [ABSTRACT FROM AUTHOR]

The goal of our study was to characterize the proportions and seasonal prevalence of Escherichia coli (E. coli) O157:H7, Listeria spp. and Salmonella spp. in fermented sausages, sosis and salami. A total of 192 samples consisting of sausage (n=96), sosis (n=48) and salami (n=48) purchased from different butcher shops and markets in the Elazig Province of eastern Turkey for one year duration were processed and tested by culture and polymerase chain reaction (PCR) for the presence of E. coli O157:H7, Listeria spp. and Salmonella spp. L. innocua was found to be the most predominant Listeria spp. in fermented sausages and sosis whereas, L. monocytogenes (1.04%) and Salmonella spp. (1.04%) were detected at much lower prevalence in fermented sausage. No L. monocytogenes and Salmonella spp. were determined in salami samples. In addition, no Salmonella spp. was detected in sosis samples. L. welshimeri (12.5%) was observed most frequently on salami samples. No E. coli O157:H7 was isolated in any samples of fermented sausage, sosis and salami. Seasonal prevalence of Listeria spp. in fermented sausages, sosis and salami was highest in July, with no L. monocytogenes and Salmonella spp. being isolated during autumn, winter and spring months of the year. Although the proportion of L. monocytogenes in fermented sausages and sosis is much lower in the current study, the presence of L. monocytogenes in these samples in the Elazig Province of eastern Turkey could still present a major public health threat. [ABSTRACT FROM AUTHOR]

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Listeria monocytogenes is one of the major foodborne pathogen found in a large set of foodstuff. With the aim of decreasing listeriosis occurrence, the early detection of this pathogen in food products is of tremendous interest. So far, the reference method and all the alternative methods require a pre-enrichment step lasting 24 h to several days. Then, an aliquot of the enriched sample is collected and characterized according different methods including genetic analysis, or beads immuno-agglutination. With the aim of significantly decreasing the overall processing time, we propose an approach involving the detection of alive bacteria during their growing phase via the use of an immuno-chip SPR imaging process. Listeria specific antibodies were also produced and chemically grafted on the biochip before being selected for their ability to distinguish different Listeria strains. Finally, this approach allows the detection of a very low number of L. monocytogenes present in foodstuff. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate the prevalence of Listeria spp. in some dairy products. A total of 240 samples of fresh cream, ice cream, butter milk cheese, Kareish cheese, Talaga cheese and yoghurt (40 of each) were collected randomly from different supermarkets, retail outlets and other markets outlets in Beni-Suef Governorate, Egypt. Out of 240 samples, 24(10%) were positive for Listeria species. The occurrence of Listeria spp. in fresh cream, ice cream, butter milk cheese and Kareish cheese was 6(15%), 8 (20%), 5 (12.5%) and 5(12.5%) respectively, while Listeria species couldn ׳t be detected in any of Talaga cheese and yoghurt samples. The most prevalent species was L.grayii (45.83%), followed by L.monocytogenes (33.33%), and L.welshimeri (12.51%) and L. innocua 2(8.33%). All 8 L.monocytogenes isolates showed the presence of the hly A gene suggesting the possibility of danger of food borne listeriosis among dairy products consumers. In conclusion, the results of this study emphasize the need forapplying more strict hygienic control measures especially during processing, storage and marketing of dairy products. [ABSTRACT FROM AUTHOR]

Two species of Listeria are pathogenic, Listeria monocytogenes and Listeria ivanovii. Although studies have shown that dairy ruminants shed Listeria spp. in feces, there is little information about ruminants that do not shed Listeria spp. in their feces but asymptomatically carry them in organs. We evidence that ruminants can asymptomatically carry L. ivanovii in udders and L. monocytogenes and L. ivanovii in tonsils without fecal shedding. Whole-genome sequence of L. monocytogenes and L. ivanovii contained known core genes involved in virulence and antibiotic resistance. This work highlights tonsils and udders as a Listeria intra-host site of colonization. [ABSTRACT FROM AUTHOR]

Commercial extracts of three spices (lemon, caraway and basil) against Listeria monocytogenes, L. innocua and L. welshimeri were investigated using disc diffusion method. Lemon and basil extracts inhibited all the organisms at the level of ≥ 5 μl (lemon) and 20 μl (basil). These extracts produced inhibitory zones of 9-19 mm (lemon) and 8-11.5 mm (basil). The extract of caraway showed activity only against L. innocua at the highest level (20 μl), producing an inhibitory zone of 14.7 mm. Generally, the lemon extract was the most effective. This extract exhibited greater inhibitory activity against L. monocytogenes, while the basil extract had the strongest effect on L. welshimeri. [Projekat Ministarstva nauke Republike Srbije, br. TR 31017]

The present research was conducted to check the presence of Listeria spp. in some meat and chicken products purchased from retail supermarkets in Assiut (Egypt). A total of 100 samples including 25 samples each of minced frozen beef, luncheon, frozen chicken legs and frozen chicken breast fillets were collected over a 7-month period between January and July 2009 and analyzed for the presence of Listeria spp. In addition, 28 stool cultures examined for Listeria spp. from hospitalized children resident in Assiut Pediatric University Hospital with diarrhea or fever. Out of the total 100 meat samples examined, Listeria spp. were detected in 8 (32%) of minced frozen beef, 8 (32%) of luncheon, 13 (52%) of frozen chicken leg and 14 (56%) of frozen chicken fillet samples analyzed, respectively. Regarding the examined 28 stool cultures from hospitalized children with underlying disease in Assiut Univ. hospital, 2 (7.14%) were found positive for Listeria spp. For identification of L. monocytogenes using polymerase chain reaction (PCR), two primers were selected to detect 217-pb fragment ofthe prfA (transcriptional activator of the virulence factor) gene for L. monocytogenes. 13 selected Listeria isolates displayed beta-haemolysis on sheep blood agar and positive CAMP test were further identified using PCR. PCR results showed that L. monocytogenes were confirmed in one of minced imported frozen meat examined, two of luncheon samples and two of frozen chicken legs with the total incidence of 5 isolates (5%) from the total 100 examined food samples. This suggests the presence of a significant public health hazard linked to the consumption of these meat and chicken products sold in Assiut city contaminated with L. monocytogenes. The public health significance of these pathogens as well as recommended sanitary measures was discussed. [Veterinary World 2010; 3(8.000): 353-359]

Listeria spp. are Gram positive, short, non-sporing rods, microaerophilic. Of the six species currently recognized, Listeria monocytogenes is the most important as it causes a range of infections in humans and animals. The organism can be found in a wide variety of habitats including the soil, food processing environments and raw foods. The ability of the organism to grow at refrigeration temperatures is of major importance in food production. This study examines the presence of Listeria species in fresh meat. 29 samples (chicken, pork and beef) meat. This bacteria was found in 82.7% of analyzed samples; 7 L. innocua, 8 L. monocytogenes and 9 L. welshimeri (of all isolates). L. innocua prevailed in pork meat (40%), L. monocytogenes in chicken and pork meat (30%), and L. welshimeri in beef meat (44.4%).

Listeria monocytogenes contamination of the environment and surfaces of the equipment was examined in seven meat processing facilities. Up to date prevalence of this foodborn pathogen in meat processing facilities facilities in Republic of Macedonia was unknown. Biofilms are composed from food spoilage microorganisms and food born pathogens. They are located on the surfaces of the equipment that come in contact with food and in facilities environment. Microorganisms in biofilm presenting micro eco system and are source of dissemination and contamination of food born pathogens in final meat products. During the preparation of this study we have covered a 7 meat processing facilities and we took a total of 39 swabs from surfaces that come in direct or indirect contact with food. Listeria monocytogenes was discovered in 10 (25,64%) swabs (locations). Prevalence of other Listeria spp. compared with total number of taken samples was 15 (38,46%) Listeria innocua, 3 (7,69%) Listeria welshimeri and 1 (2,65%) isolate Listeria seeligeri.

Listeriosis is a foodborne disease caused by Listeria monocytogenes and is considered as a serious health problem, due to the severity of symptoms and the high mortality rate. Recently, other Listeria species have been associated with disease in human and animals. The aim of this study was to develop a multiplex polymerase chain reaction (PCR) in order to simultaneously detect six Listeria species (L. grayi, L. welshimeri, L. ivanovii, L. monocytogenes, L. seeligeri, L. innocua) in a single reaction. One hundred eighteen Listeria spp. strains, isolated from meat products (sausages) and processing plants (surfaces in contact and not in contact with meat), were included in the study. All the strains were submitted to biochemical identification using the API Listeria system. A multiplex PCR was developed with the aim to identify the six species of Listeria. PCR allowed to uniquely identify strains that had expressed a doubtful profile with API Listeria The results suggest that the multiplex PCR could represent a rapid and sensitive screening test, a reliable method for the detection of all Listeria species, both in contaminated food and in clinical samples, and also a tool that could be used for epidemiological purposes in food-borne outbreaks. A further application could be the development of a PCR that can be directly applied to the pre-enrichment broth.

During the past six years, new species of the genus Listeria have been isolated from foods and other environmental niches worldwide. The Standard method EN ISO 11290-1 that is currently under revision will include in its scope all Listeria species in addition to L. monocytogenes . The objective of this project was to evaluate the ability of the Standard EN ISO 11290-1 method to detect and identify the newly discovered Listeria spp., and to assess potential over-growth effects of the new species in mixed cultures with L. monocytogenes during each step of the enrichment process. This objective was addressed by the generation of necessary data on the behavior of the new species during the pre-enrichment and the enrichment steps of the reference method as well as data on their phenotypic characteristics on rich and selective media used for isolation and identification. Most of the new Listeria species developed well on selective agar media for Listeria , however the recovery of some species was difficult due to poor growth in Half Fraser and Fraser broth. Good results (consistently positive) were obtained for confirmation at the genus level via the catalase test, the Gram test and the blueish appearance test on non-selective medium, but not with the VP test, as most of the new species yielded a negative result. In the light of results obtained in co-culture experiments and inhibition tests, and considering the growth rates in Half Fraser and Fraser broths, the new species do not seem to interfere with the detection of L. monocytogenes . [ABSTRACT FROM AUTHOR]

ISOPOL – for “International Symposium on Problems of Listeria and Listeriosis” – meetings gather every three years since 1957 participants from all over the world and allow exchange and update on a wide array of topics concerning Listeria and listeriosis, ranging from epidemiology, diagnostic and typing methods, to genomics, post-genomics, fundamental microbiology, cell biology and pathogenesis. The XIXth ISOPOL meeting took place in Paris from June 14th to 17th, 2016 at Institut Pasteur. We provide here a report of the talks that were given during the meeting, which represents an up-to-date overview of ongoing research on this important pathogen and biological model. [ABSTRACT FROM AUTHOR]

In the retail food service industry, small countertop sinks, or dipper wells, are utilized to rinse and store serving utensils between uses. These dipper wells are designed to operate under a constant flow of water, which serves both to prevent the accumulation of microorganisms and to aid in the cleanliness of the dipper well itself. Here, a recirculating dipper well ozone sanitation system (DWOSS) was evaluated for the control and inactivation of Escherichia coli, Listeria innocua, PRD1 bacteriophage, and Staphylococcus aureus present on a stainless steel disher. In a low ozone (0 3) demand medium, the DWOSS achieved over a 5-log reduction for E. coli, L. innocua, and PRD1 at 30 s when exposed to 0.45 to 0.55 ppm of residual 0 3. A greater than 5-log total CFU reduction was achieved for S. aureus at a 600-s exposure time and 0.50 ppm of residual 0 3. When evaluated in the presence of high 0 3 demand medium (10% skim milk), the DWOSS performed significantly better (P < 0.05) for all microbe-exposure time combinations compared with a conventional dipper well with respect to the reduction of microbes on the stainless steel disher. For example, at 30 s, the DWOSS achieved 4.37, 2.48, 1.38, and 1.31 greater log (CFU or PFU) reduction of E. coli, L. innocua, PRD 1, and S. aureus, respectively, than a conventional dipper well. In addition, the DWOSS was evaluated under two neglect scenarios to determine its ability to control microbes in 10% skim milk medium on the stainless steel disher and within the dipper well basin itself over an extended period of use (2 h of use per day over 5 days). Considering the efficacy of the DWOSS unit against the microbes evaluated here, the integration of ozone into a dipper well could be a potential critical control point to reduce the incidence of microbial contamination during retail food service. To our knowledge, a dipper well with a cleaning-in-place sanitizing system is not currently available for use in the food service industry; and, thus, this is the first study to evaluate the efficacy of a cleaning-in-place dipper well. [ABSTRACT FROM AUTHOR]

L. monocytogenes contamination in processed food, especially fish-based snack, may results from contaminated raw materials, underprocessed or recontamination. The aims of this study were to identify the presence of Listeria spp. especially L. monocytogenes by PCR method and biochemical methods, as well as calculate the prevalence of Listeria spp. in fish-based snack food in Bogor. This study was conducted of 4 steps: (1) determination of L. monocytogenes's DNA limit detection, (2) sample preparation, (3) identification of L. monocytogenes with real-time PCR, and (4) identification of Listeria spp. with biochemical methods. The results showed that DNA detection limits of L. monocytogenes in fish meatball and otak-otak were at 8.3x102 and 2.9x102 CFU/g, respectively. The study on 65 samples indicated that contamination of L. monocytogenes was not observed, but other species of Listeria spp., namely L. grayi and L. innocua, were found. The prevalence of L. grayi and L. innocua in siomay was at 5.9%, while the prevalence of L. grayi in shrimp meatballs, fish meat balls, fried meatballs was at 8.3, 9.1, and 50%, respectively. Furthermore, L. innocua from takoyaki samples with a prevalence of 20% was observed. [ABSTRACT FROM AUTHOR]

Backyard poultry has become increasingly popular in industrialized countries. In addition to keeping chickens for eggs and meat, owners often treat the birds as pets. However, several pathogenic enteric bacteria have the potential for zoonotic transmission from poultry to humans but very little is known about the occurrence of zoonotic pathogens in backyard flocks. The occurrence and the antimicrobial resistance of Salmonella enterica, Campylobacter spp., Listeria monocytogenes and enteropathogenic Yersinia spp. was studied in 51 voluntary backyard chicken farms in Finland during October 2012 and January 2013. Campylobacter isolates were further characterized by pulsed-field gel electrophoresis (PFGE), and the occurrence of ESBL/AmpC-producing E. coli was investigated. The findings from this study indicate that backyard chickens are a reservoir of Campylobacter jejuni strains and a potential source of C. jejuni infection for humans. Backyard chickens can also carry L. monocytogenes, although their role as a primary reservoir is questionable. Campylobacter coli, Yersinia pseudotuberculosis and Salmonella enterica were only found sporadically in the faecal and environmental samples of backyard poultry in Finland. No Yersinia enterocolitica carrying the virulence plasmid was isolated. All pathogens were highly susceptible to most of the antimicrobials studied. Only a few AmpC- and no ESBL-producing E. coli were found. [ABSTRACT FROM AUTHOR]

Consumer's refrigeration practice plays a significant role on food safety and quality. To determine the prevalence and identity of Listeria species in domestic refrigerators in student hostels, swab samples were obtained from vegetable drawers and shelves of 100 domestic refrigerators located in university student hostels in Lagos, Nigeria. The swabs were enriched in Listeria enrichment broth containing antibiotic supplement and then inoculated on Listeria selective agar medium containing antibiotic supplement too. Standard procedures including API Listeria were used to characterise and identify the isolates. Count of Listeria species ranged from 1.48 - 59.2 log10 cfu/ml /100cm2 with a cumulative frequency range of 0.16% - 59.17% in the vegetable drawers and count of 11.3 - 41.95 log10 cfu/ml / 100cm2 with a cumulative frequency range of 16.40% - 50.41% in the shelves. It was found that Listeria monocytogenes and Listeria seeligeri were each present in one of the 100 domestic refrigerators investigated. Listeria innocua was present in 13, Listeria ivanovii in 21, Listeria welshimeri in 25. Also 68% of the refrigerators investigated were operating at high temperature of 8.1 - 10oC while others were at 2 -8oC, 73% of the respondent cleaned their refrigerators less than a month interval, 16% monthly and 11% of the respondent every 2 - 2 V months. Although some of the respondent used proper cleaning agents for their refrigerators such as liquid wash (32%), detergent (27%) and antiseptic (8%), however 25% used water only and 5% used tissue paper. Overall, the findings obtained from the survey indicates poor standard of consumer refrigerator management and hygiene which can pose risk to consumer's health. Therefore there is great need for consumer education regarding appropriate refrigerator temperature control, proper refrigerator cleaning and safe food handling practices. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria have been used since ancient times for food preparation and for bio-conservation by fermentation. Selected strains are capable of producing antimicrobial peptides - bacteriocins, which can be natural preservatives, especially in products with short shelf lives. The present study is focused on inhibitory effects of the bacteriocin-producing bacteria strains Enterococcus faecium, Pediococccus acidilactici and Lactobacillus plantarum against Listeria innocua as an indicator microorganism. Freeze-dried preparations of bacterial strains producing particular bacteriocins were tested by agar well-diffusion assay and by the traditional spread plate method. Plantaricin exhibited the highest anti-listerial effect among the tested bacteriocins. Pediocin also demonstrated a distinct inhibitory effect, but enterocin appeared to be heat labile and its efficiency was also suppressed under cold storage conditions. Plantaricin reduced Listeria innocua counts by 1 log in dairy spread made from cheese and quark. The formation of bacteriocins by various Lactobacillus plantarum strains were substantially influenced by the cultivation conditions of the mother culture and by the microbial preparation process before freeze-drying. Bacteriocins introduced into foodstuffs via protective cultures in situ offer new perspectives on enhancing food quality and safety. [ABSTRACT FROM AUTHOR]

Considering the specific biochemical composition of buffalo ( Bubalus bubalis ) meat (high iron content, high biological value proteins and essential fatty acids, low amounts of fat and cholesterol), we evaluated the influence of cutting and deboning operations on the microbiological quality and shelf-life of vacuum-packed buffalo meat stored under refrigeration. On the processing day, samples were collected from carcass, deboning room surfaces and meat cuts. Samples from meat cuts were evaluated weekly for two months. On the processing day, higher counts of Pseudomonas spp. were observed in samples from meat cuts compared with the hindquarters and the processing surfaces. For thermotolerant coliform scores, the averages were − 0.5 log MPN·cm − 2 , − 0.4 log MPN·cm − 2 and 0.9 log MPN·g − 1 , respectively. Higher counts of Pseudomonas spp. and LAB in meat cuts were observed on the processing day and after the first week of storage, respectively, remaining constant during shelf life. Listeria grayi was identified in two samples of hindquarters and meat cuts during storage. Listeria innocua was identified in one meat cut. In conclusion, cutting and deboning operations influence the microbiological quality and shelf life of vacuum-packed buffalo meat stored under refrigeration. [ABSTRACT FROM AUTHOR]

Polymyxin Ceftazidime Oxford Medium (PCOM), a novel selective and differential plating medium for Listeria monocytogenes was compared with Modified Oxford Agar (MOX) for efficacy to isolate L. monocytogenes and other Listeria spp. naturally present in non-pasteurized Mexican-style cheese (n = 50), non-pasteurized fresh squeezed orange juice (n = 50), raw beef chunks (n = 36), and fresh cabbage (n = 125). Samples were collected from retail markets and farms in Mexico and tested following the US Department of Agriculture enrichment technique. Listeria spp. were isolated from 23.4% of analyzed samples, and from those, 75.0% corresponded to raw beef chunks, 38.0% to non-pasteurized Mexican-style cheese, and 30.0% to fresh squeezed orange juice. No Listeria spp. were isolated from fresh cabbage samples. L. monocytogenes was recovered from 15.3% of food samples analyzed. Non-pasteurized Mexican-style cheese showed the highest proportion of L. monocytogenes positive samples (36.0%), followed by orange juice (26.0%) and raw beef (25.0%). The frequency of isolation of Listeria spp. and L. monocytogenes was not different (P > 0.05) between PCOM and MOX. The advantages of using PCOM when comparing to MOX, include the easier way to identify Listeria species, the lower cost per plate and the availability of its ingredients for Latin-American countries. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes can grow and multiply in various food matrices and cause severe human illness. Apart from the influence on consumer health, L. monocytogenes contamination of ready-to-eat (RTE) food products causes major economic losses due to product recalls. Control of foodborne pathogens in RTE food products is a challenge, specifically in foods that cannot undergo a heat-treatment during processing. The aim of this study was to develop control strategies for the management of L. monocytogenes in an avocado processing facility, additional to a quality control system. An in-house monitoring system (IMS) was established to test specifically for Listeria spp. in the final products and processing environment, including floors, equipment, work areas and personnel. Guacamole and environmental samples were collected and tested on-site for Listeria with the ISO 11290-1 method. Based on the prevalence of Listeria , the facility introduced new strategies in processing to counter cross contamination. Results from the 2014 guacamole production season showed almost complete eradication of Listeria spp. in final products (0.17%, n = 1170) and the processing facility (0.79%, n = 1520). This is a major achievement since the highest incidence of Listeria spp. over a period of five years was measured at 11.39% (n = 948) in the final product during the 2013 season and 13.44% (n = 1927) in the processing facility in 2011. These results indicate that successful management of Listeria spp. in an avocado processing facility can be accomplished with in-house monitoring of the listerial population and subsequent adjustments to the processing system. [ABSTRACT FROM AUTHOR]

In this study, a total of 24 Listeria spp. strains were analyzed. Twenty-two isolates were obtained in San Luis (Argentina) from human, animal, and food samples. Two types of strains, Listeria monocytogenes CLIP 22762 and Listeria innocua CLIP 74915, were included as reference strains. All isolates were biochemically identified and characterized by serotyping, phage typing, and amplification of the flaA gene by polymerase chain reaction (PCR). Repetitive intergenic consensus (ERIC) sequence-based PCR was used to generate DNA fingerprints. On the basis of ERIC-PCR fingerprints, Listeria spp. strains were divided into three major clusters matching origin of isolation. ERIC-PCR fingerprints of human and animal isolates were different from those of food isolates. In addition, groups I and II included ten L. monocytogenes strains, and only one Listeria seeligeri strain. Group III included nine L. innocua strains and four L. monocytogenes strains. Computer evaluation of ERIC-PCR fingerprints allowed discrimination between the tested serotypes 1/2b, 4b, 6a, and 6b within each major cluster. The index of discrimination calculated was 0.94. This study suggests that the ERIC-PCR technique provides an alternative method for the identification of Listeria species and the discrimination of strains within one species.En este estudio se analizaron 24 cepas de Listeria spp. De ellas, 22 fueron obtenidas en San Luis (Argentina), a partir de muestras humanas, de animales y alimentos. Se incluyeron 2 cepas de referencia Listeria monocytogenes CLIP 22762 y Listeria innocua CLIP 74915. Todos los aislamientos fueron identificados bioquímicamente y caracterizados por serotipificación, fagotipificación y detección del gen flaA por reacción en cadena de la polimerasa (PCR). Se generaron perfiles de bandas de ADN mediante la amplificación de secuencias repetitivas de consenso intergénico de enterobacterias (ERIC-PCR). De acuerdo a los resultados obtenidos por ERIC-PCR, las cepas de Listeria spp. fueron divididas en 3 grupos según su origen. Los perfiles de los aislamientos humanos y animales fueron distintos de los correspondientes a alimentos. Por otra parte, dentro de los grupos I y II se incluyeron 10 cepas de L. monocytogenes y solamente una de Listeria seeligeri. Dentro del grupo III no sólo estuvieron incluidas las 9 cepas de L. innocua sino también 4 de L. monocytogenes. La evaluación de los perfiles de bandas obtenidos por ERIC-PCR permitió la discriminación entre los serotipos ensayados 1/2b, 4b, 6a y 6b dentro de cada grupo. El índice de discriminación calculado para ERIC-PCR fue de 0,94. Los resultados sugieren que la técnica de ERIC-PCR provee un método alternativo válido para la identificación de especies de Listeria y, asimismo, permite la diferenciación de cepas dentro de una misma especie.

Listeria monocytogenes, a foodborne pathogen, and other Listeria spp. are present in natural environments. Isolating and characterizing strains from natural reservoirs can provide insight into the prevalence and diversity of Listeria spp. in these environments, elucidate their contribution to contamination of agricultural and food processing environments and food products, and lead to the discovery of novel species. In this study, we evaluated the diversity of Listeria spp. isolated from soil in a small region of the Great Smoky Mountains National Park, the most biodiverse national park in the U.S. National Park system. Of the 17 Listeria isolates recovered, whole-genome sequencing revealed that 14 were distinct strains. The strains represented a diversity of Listeria species (L. monocytogenes [ n  = 9], L. cossartiae subsp. cossartiae [ n  = 1], L. marthii [ n  = 1], L. booriae [ n  = 1], and a potentially novel Listeria sp. [ n  = 2]), as well as a diversity of sequence types based on multilocus sequence typing (MLST) and core genome MLST, including many novel designations. The isolates were not closely related (≥99.99% average nucleotide identity) to any isolates in public databases (NCBI, PATRIC), which also indicated novelty. The Listeria samples isolated in this study were collected from high-elevation sites near a creek that ultimately leads to the Mississippi River; thus, Listeria present in this natural environment could potentially travel downstream to a large region that includes portions of nine southeastern and midwestern U.S. states. This study provides insight into the diversity of Listeria spp. in the Great Smoky Mountains and indicates that this environment is a reservoir of novel Listeria spp. IMPORTANCE Listeria monocytogenes is a foodborne pathogen that can cause serious systemic illness that, although rare, usually results in hospitalization and has a relatively high mortality rate compared to other foodborne pathogens. Identification of novel and diverse Listeria spp. can provide insights into the genomic evolution, ecology, and evolution and variance of pathogenicity of this genus, especially in natural environments. Comparing L. monocytogenes and Listeria spp. isolates from natural environments, such as those recovered in this study, to contamination and/or outbreak strains may provide more information about the original natural sources of these strains and the pathways and mechanisms that lead to contamination of food products and agricultural or food processing environments.