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Listeriosis is a zoonotic disease caused by Listeria monocytogenes and Listeria ivanovii. The genus Listeria currently includes 27 recognized species and is found throughout the environment. The number of systematic studies on antimicrobial resistance in L. monocytogenes isolates from domestic farms using antimicrobial substances is limited. Importantly, dairy ruminant farms are reservoir of hypervirulent lineage I L. monocytogenes isolates, previously associated with human clinical cases. Considering that the classes of antibiotics used in food-producing domestic animals are frequently the same or closely related to those used in human medicine, studies about the impact of antibiotic use on the acquisition of antibiotic resistance in Listeria spp. in domestic animal farms are, therefore, of high importance. Here, susceptibility to 25 antibiotics was determined. Eighty-one animal-related, 35 food and 21 human pathogenic Listeria spp. isolates and 114 animal-related non-pathogenic Listeria spp. isolates were tested. Whole genome sequencing data was used for molecular characterization. Regarding L. monocytogenes , 2 strains from the clinical-associated linage I showed resistance to erythromycin, both related to dairy ruminants. Acquired resistance to one antibiotic was exhibited in 1.5% of L. monocytogenes isolates compared with 14% of non-pathogenic Listeria spp. isolates. Resistance to tetracycline (7.9%), doxycycline (7.9%), penicillin (4.4%), and ampicillin (4.4%) were the most frequently observed in non-pathogenic Listeria spp. While resistance to two or more antibiotics (5.6%) was most common in Listeria spp., isolates, resistance to one antibiotic was also observed (1.6%). The present results show that non-pathogenic Listeria spp. harbour antimicrobial resistance genes. • Antibiotic resistance in Listeria monocytogenes isolates is infrequent (1.5%). • Antibiotic-resistant L. monocytogenes were only detected in animal sources. • L. monocytogenes from food or human sources showed no antibiotic resistance. • Non-pathogenic Listeria spp. showed a higher prevalence of resistance (14%). • MIC values of relevant antibiotics differ between L. monocytogenes lineage I and II. [ABSTRACT FROM AUTHOR]

Microorganisms in processing environments significantly impact the quality and safety of food products and can serve as potential reservoirs for antibiotic-resistant genes, contributing to public health concerns about antimicrobial resistance (AMR). Fish processing plants represent an understudied environment for microbiome mapping. This study investigated the microbial composition, prevalence of Listeria spp., and resistome structures in three catfish processing facilities in the southeastern United States. The 16S rRNA gene sequencing revealed that the observed richness and Shannon diversity index increased significantly from fish to fillet. Beta diversity analysis showed distinct clustering of microbial communities between fish, environment, and fillet samples. Fast expectation-maximization microbial source tracking (FEAST) algorithm demonstrated that the microbiota presents in the processing environment contributed 48.2 %, 62.4 %, and 53.7 % to the microbiota present on fillet in Facility 1 (F1), F2, and F3, respectively. Food contact surfaces made larger contributions compared to the non-food contact surfaces. The linear discriminant analysis of effect size (LEfSe) identified specific microbial genera (e.g., Plesiomohas, Brochothrix , Chryseobacterium and Cetobacterium) that significantly varied between Listeria spp. positive and negative samples in all three processing plants. The metagenomic sequencing results identified 212 antimicrobial resistance genes (ARGs) belonging to 72 groups from the raw fish and fish fillet samples collected from three processing plants. Although there was a significant decrease in the overall diversity of ARGs from fish to fillet samples, the total abundance of ARGs did not change significantly (P > 0.05). ARGs associated with resistance to macrolide-lincosamide-streptogramin (MLS), cationic antimicrobial peptides, aminoglycosides, and beta-lactams were found to be enriched in the fillet samples when compared to fish samples. Results of this study highlight the profound impact of processing environment on shaping the microbial populations present on the final fish product and the need for additional strategies to mitigate AMR in fish products. • Microbiota in processing environment contributed up to 62.4 %, of fillet microbiota. • Food contact surfaces (FCS) impact the microbiota in fillets more than non-FCS. • Plesiomohas, and Brochothrix were more abundant in Listeria positive samples. • Chryseobacterium and Cetobacterium were more abundant in Listeria negative samples. • The richness of the AMR increased while the total abundance remained unchanged. [ABSTRACT FROM AUTHOR]

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 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]

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]

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]

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]

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]

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]

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]

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]

Listeria monocytogenes is an important foodborne pathogen. To effectively control this pathogen, it is necessary to have a method that can detect and differentiate L. monocytogenes from other Listeria species in food, environmental, and clinical samples. A new multiplex PCR method using new primers targeting the iap gene was developed to detect and differentiate L. monocytogenes and other Listeria species, and the method was applied to examine deli meat samples. Sixteen Listeria strains (8 L. monocytogenes , 2 Listeria innocua , 1 Listeria seeligeri , 3 Listeria welshimeri , 1 Listeria ivanovii , and 1 Listeria grayi ) from the American Type Culture Collection were tested using the new PCR method in comparison to 16S rRNA sequencing assay and a previously described PCR method based on the detection of iap gene with other primers. The new PCR method was able to differentiate L. monocytogenes from the other Listeria species, while the 16S rRNA sequencing assay could not distinguish L. welshimeri from L. monocytogenes and the previously published multiplex PCR assay was not able to distinguish L. monocytogenes from L. innocua or L. ivanovii . Furthermore, 150 deli meat samples were analyzed by the newly developed multiplex PCR in comparison to ISO11290-1 method and 16S rRNA sequencing assay to detect L. monocytogenes and differentiate it from the other 5 species of Listeria . The developed PCR provided the same results as the ISO method. Out of 150 samples, 16 (10.7%) samples and 5 (3.3%) samples were tested positive and confirmed for Listeria spp. and L. monocytogenes , respectively. The multiplex PCR method is capable of discriminating between L. monocytogenes and other Listeria species. The method is simple and specific when combined with simplified enrichment procedures. [ABSTRACT FROM AUTHOR]

Listeria contamination in processing plant environments is a major issue for the seafood industry worldwide; faster and more reliable results are therefore desired for early detection and monitoring of environmental Listeria spp. This study aimed to gain a better understanding of the prevalence and diversity of Listeria spp., and to evaluate a rapid detection method, the 3M Molecular Detection Assay (MDA) Listeria , for its ability to detect Listeria spp. in environmental samples from seafood processing plants. Duplicate environmental sponge samples ( n = 444) were collected from 152 different sites within three seafood processing plants, and analyzed for Listeria spp. by the MDA method (after 26 and 48 h of enrichment) and the U.S. Food and Drug Administration Bacteriological Analytical Manual method. Overall, detection of Listeria spp. by the two methods did not differ significantly ( p > 0.05); 11 (4.9%) and 13 (5.9%) samples were positive for Listeria spp. by the MDA and FDA-BAM method, respectively. The sensitivity of the MDS was 87.0% (95% CI: 77.4–96.6%), specificity was 97.6% (95% CI: 95.5–99.7%), accuracy was 95.3%, and the positive predictive value was 89.4% (95% CI: 80.5–98.2%). Classification of 19 Listeria isolates by partial SigB sequencing analysis identified three allelic types. Twelve of these isolates were ATs 58 and 60 which were classified as Listeria monocytogenes lineage I and serotypes 1/2b, 3b, 4b, 4d, 4e, by multiplex-PCR serotyping. Six Listeria isolates were classified as Listeria innocua (AT31). Our data show that the 3M Molecular Detection Assay Listeria provides rapid and reliable results for detection and monitoring of Listeria spp., which are important for seafood processing plants. Effective Listeria monitoring programs will allow for improved development of Listeria control measures in order to minimize cross-contamination in finished products. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to compare standard selective plating, conventional PCR (16S rRNA and species specific primers), MALDI-TOF MS and the 3M™ Molecular Detection System for the routine detection of the pathogens Listeria, Salmonella and Escherichia coli 0157:H7 in wastewater and river water samples. MALDI-TOF MS was able to positively identify 20/21 (95%) of the E. coli isolates obtained at genus and species level, while 16S rRNA sequencing only correctly identified 6/21 (28%) as E. coli strains. None of the presumptive positive Listeria spp. and Salmonella spp. isolates obtained by culturing on selective media were positively identified by MALDI-TOF and 16S rRNA analysis. The species-specific E. coli 0157:H7 PCR described in this present study, was not able to detect any E. coli 0157:H7 strains in the wastewater and river water samples analysed. However, E. coli strains, Listeria spp., L. monocytogenes and Salmonella spp. were detected using species specific PCR. Escherichia coli 0157:H7, Listeria spp. and Salmonella spp. were also sporadically detected throughout the sampling period in the wastewater and river water samples analysed by the 3M™ Molecular Detection System. MALDI-TOF MS, which is a simple, accurate and cost-effective detection method, efficiently identified the culturable organisms, while in the current study both species specific PCR (Listeria spp. and Salmonella spp.) and 3M™ Molecular Detection System could be utilised for the direct routine analysis of pathogens in water sources. [Copyright &y& Elsevier]

The aims of this study were to determine the prevalence and antimicrobial resistance of Listeria, Salmonella, and Yersinia spp. isolated from duck and goose intestinal contents. A total of 471 samples, including 291 duck and 180 goose intestinal contents, were purchased from wet markets between November 2008 and July 2010. Listeria, Salmonella, and Yersinia spp. were isolated from 58 (12.3%), 107 (22.7%), and 80 (17%) of the samples, respectively. It was concluded that Listeria ivanovii, Salmonella Thompson, and Yersinia enterocolitica were the predominant serovars among Listeria, Salmonella, and Yersinia spp., respectively. Moreover, resistance to tetracycline was common in Listeria (48.3%) and Salmonella spp. (63.6%), whereas 51.3% of the Yersinia spp. isolates were resistant to cephalothin. Therefore, continued surveillance of the prevalence of the pathogens and also of emerging antibiotic resistance is needed to render possible the recognition of foods that may represent risks and also ensure the effective treatment of listeriosis, salmonellosis, and yersiniosis. [ABSTRACT FROM AUTHOR]

Food processors face serious challenges due to the ubiquity and prevalence of Listeria monocytogenes in production and processing facilities. Environmental monitoring for Listeria within the industry is important and detection of Listeria spp. is often used as an indicator for the potential presence of L. monocytogenes in the food processing environment. Environmental monitoring data from the frozen food manufacturing industry was compiled and analyzed to evaluate the adequacy of current practices in mitigating risks of L. monocytogenes in the processing environment and to determine if there are trends that could be used to further refine industry practices. A method to collect anonymous data for analysis to build a strong aggregate data set from multiple facilities was used. Information included general descriptions of each facility and specific information about individual environmental monitoring test results from environmental zones 2–4, or nonfood contact surfaces. Information collected from facilities included the size of the facilities and how environmental monitoring samples were collected and analyzed. For each individual sample, information collected included the area or equipment sampled and the result of each sample. Descriptors were provided to allow for grouping of similar results. The data represents environmental monitoring samples that were collected between six months to a year prior to the beginning of this research. Twenty-seven facilities provided 42,799 environmental monitoring observations. Environmental zones 3 and 4 had a higher estimated marginal probability of Listeria positive results compared to zone two for routine environmental monitoring samples (p < 0.05). Pre-lethality and post-lethality production areas had a higher probability of Listeria positive results compared to lethality areas for all environmental samples (p < 0.05). Cold storage locations, i.e., coolers and freezers had a significantly higher probability for a Listeria positive result than noncold storage areas (p < 0.01). Applying statistical modeling and comparing estimated marginal probabilities of aggregate Listeria prevalence data from processing operations across the industry can provide information for guidance on focusing sanitation within processing operations to reduce risk related to L. monocytogenes. These data help to identify common themes in the industry and determine potential areas on which to focus when testing for prevalence of Listeria spp. within the food processing environment. This study serves as a useful baseline for continued improvement in environmental monitoring across all frozen food manufacturing facilities. • Environmental monitoring samples from frozen food facilities were collected. • Twenty-seven facilities provided 42,799 environmental monitoring observations. • Zones 3/4 had a higher probability of Listeria positive results compared to zone 2. [ABSTRACT FROM AUTHOR]

Listeria spp. is a kind of important food-borne pathogen with a high fatality rate and is widely distributed in food chain, posing a potential threat to the public health. It is urgently necessary to develop a pathogenic Listeria detection platform with high specificity, sensitivity, high-throughput, and user-friendliness to meet the requirements of on-line monitoring of food production. We therefore developed a one-step detection method (hMC-CRISPR) based on recombinase aided amplification (RAA) and CRISPR on a high-throughput microfluidic chip. This strategy coordinates the nucleic acid amplification and the cleavage efficiency of CRISPR/Cas13a through the transcription process, thereby preventing the complete cleavage of all genomic DNA and amplicons from being cleaved. The corresponding RAA-CRISPER/Cas13a system was designed based on the specific markers of Listeria spp., L. monocytogenes , L. innocua and L. ivanovii , and the reaction volume was limited to 5 µL to match the microfluidic chip. This strategy achieved sensitive and robust detection of pathogenic Listeria with a sample-to-answer time of ~60 min, and a detection limit of each index reached aM level. More importantly, hMC-CRISPR can detect pathogenic Listeria in eight samples at one time and avoid the influence of aerosol on the test results. It is practically validated by quantitatively determining four types of spiked samples and 24 natural samples. Collectively, this new strategy has great potential to improve the current rapid screening of pathogenic Listeria. • A one-step RAA-CRISPR/Cas13a is constructed by the coordination of transcriptase. • CRISPR/Cas13a is integrated into centrifugal microfluidic chip for the first time. • Favorable assay performance toward three types of Listeria are obtained. • Without enrichment culture, a detection limit of aM level is reported within 1 h. [ABSTRACT FROM AUTHOR]

Abstract: A total of 446 various raw milk samples were collected from numerous farm bulk milk tanks to examine the presence of Listeria species. These isolates were further characterised by biochemical tests and Polymerase Chain Reaction (PCR). Listeria spp. was isolated in 83 of the 446 samples (18.6%). The highest prevalence of Listeria spp. was detected in raw cow milk samples (22.5%), followed by raw sheep milk (16.4%) and raw goat milk (4.9%). The most common species isolated was Listeria innocua (57.8%); the remaining Listeria isolates were Listeria monocytogenes (21.7%), Listeria welshimeri (12%), and Listeria seeligeri (8.4%). Based on PCR serotyping, the 18 L. monocytogenes isolates were distributed into three serogroups “1/2a, 3a” (n = 11), “1/2c, 3c” (n = 5), and “4b, 4d, 4e” (n = 2). All the examined L. monocytogenes were positive for internalin genes (inlA, inlC, and inlJ). The Listeria spp. isolates were resistant to tetracycline (49.4%) and penicillin G (43.4%) but remained susceptible to gentamicin, vancomycin and rifampicin. The findings of this study show that consumption of raw milk could be a potential risk of human listeriosis. [Copyright &y& Elsevier]

The effect of different concentrations of carvacrol [0.1–0.25 μL/mL] and citral [0.25–1.5 μL/mL], at different storage temperatures [8–37 °C] was evaluated against Escherichia coli O157:H7 and Listeria monocytogenes surrogates. Results were integrated into a stochastic model to perform probabilistic predictions of the final load. The study takes into account the variability in growth conditions by means of maximum growth rate (μ max ) and lag time duration (λ) kinetic parameters, using the Monte Carlo simulation. Carvacrol showed a greater effectiveness against both bacteria than citral. A sensitivity analysis was carried out revealing that, at low temperatures [8–15 °C], carvacrol contributed to delaying the growth of the studied microorganisms. These results are important for food managers and industrial processors because they reveal the probability of being below a microbial threshold limit in presence of carvacrol and citral, even if a cold chain failure occurs. [ABSTRACT FROM AUTHOR]

Abstract: We report the detection of Listeria spp. and Listeria monocytogenes in 34 dairy plants. In total, 547 of food, product contact surface and floor drain samples were collected along the product lines. Nineteen cheese factories (55.8%) were contaminated by Listeria spp. Of these 20.6% were L. monocytogenes positive. Listeria spp. was found in 6.8% of food samples, 11.3% of product contact surfaces and 40.6% of floor drains. L. monocytogenes was found in 2.4% of food samples, 4.9% of product contact surfaces and 18.8% of floor drains. Twentyfive L. monocytogenes isolates were serotyped using commercial specific antisera and genotyped using Amplified Fragment Length Polymorphism (AFLP) analysis. AFLP genotyping discriminated the four species of Listeria isolated and different genotypes for each species, moreover it could identify persistent genotypes in some dairy facilities. Listeria spp. and L. monocytogenes are widely spread in the dairy sector and probably contaminate foods during the production process. Facility-based monitoring can identify possible routes of transmission and thus allow establishment of more effective strategies to prevent food contamination. [Copyright &y& Elsevier]

Abstract: In the present study, a total of 402 poultry product samples composed of raw, ready-to-cook (RTC) and ready-to-eat (RTE) products were examined for the presence of Listeria spp. The total contamination rate with Listeria spp. in poultry products was 33.3% with a higher rate of contamination in warm seasons than in cold seasons. The most species recovered was Listeria innocua (46.3%); the remaining isolates were Listeria monocytogenes (38.8%), Listeria ivanovii (9.7%) and Listeria seeligeri (5.22%). L. monocytogenes was detected in 14.1%, 12.2% and 11.4% of raw, RTC and RTE poultry products, respectively. Serotype 4b (44.9%) was the predominant serotype of L. monocytogenes isolates followed by 1/2a (40.8%), 1/2b (10.2%) and 1/2c (4.08%). Considering seasonal variability, 1/2a was the most prevalent serotype in warm seasons, while 4b was predominant in cold seasons. The Listeria spp. particularly L. monocytogenes isolates were highly resistant to ampicillin, penicillin, fluroquinolones and tetracycline. The results indicate that high prevalence of Listeria spp. especially L. monocytogenes in poultry products, and resistance of the isolates to the antimicrobials commonly used to treat human listeriosis could be a potential health hazard for consumers. In addition, prevalence of L. monocytogenes serotype 4b that involved in the majority of foodborne outbreaks of human listeriosis is a public health concern. [Copyright &y& Elsevier]

Abstract: Since the 1980s, an increase in outbreaks of human listeriosis linked to contaminated food has been a concern of health authorities. Intensively manipulated foods, such as Brazilian fresh sausage, are frequently responsible for food-borne diseases. In this work the occurrence of Listeria monocytogenes and the efficacy of bacteriophage P100 (LISTEX™) to control the microorganism was evaluated in Brazilian fresh sausage. Eighty samples were analyzed, 40 each of swine and chicken Brazilian fresh sausage. Listeria spp. were isolated from 12 samples (15%), of which three (3.75%) were positive for L. monocytogenes. L. monocytogenes strains isolated belonged to serotype 1/2a. L. monocytogenes 1/2a was inoculated in Brazilian fresh sausage (2.1×104 cfu/g) with the bacteriophage added thereafter (3.0×107 pfu/g). Samples were analysed immediately (day zero) and then stored at 4°C for 10 days. The bacteriophage P100 reduced L. monocytogenes counts by 2.5log units at both 0 and 10 days compared to controls without bacteriophage. In spite of this, the populations of L. moncytogenes increased over the 10 day storage. Our data demonstrate that in one of the samples the use of the bacteriophage dropped the bacteria count below the level of direct detection. This study demonstrates a new alternative for pathogen control in the food industry, especially in the processes used to produce Brazilian fresh sausage. [ABSTRACT FROM AUTHOR]

Abstract: Listeria monocytogenes is the causal agent of listeriosis, a disease that can be serious and is often fatal in susceptible individuals. The objective of the study was to determine the prevalence of Listeria spp. in raw chicken and ready-to-eat (RTE) chicken products in Amman, Jordan and the antimicrobial resistance of L. monocytogenes isolates. A total of 280 raw chicken and RTE chicken products (chicken-shawirma, chicken-burger, chicken-sausage and mortadella) were collected from Amman abattoir and local retail markets in Amman city. Listeria spp. were isolated by the conventional International Organization for Standardization (ISO) method and L. monocytogenes identified by biochemical and Polymerase Chain Reaction (PCR). Results of conventional method showed that out of total 280 samples, 141 (50%) were found to be contaminated with Listeria spp. [L. monocytogenes (18.2%), Listeria ivanovi (26.1%), Listeria grayi (3.5%), Listeria seeligeri (1.8), Listeria welshimeri (0.7%)]. The PCR confirmed all L. monocytogenes isolates (51 isolates: 15 from raw dressed broiler chicken, 23 from chicken-burger, 9 from chicken-sausage, and 4 from chicken-shawirma). Five of the tested L. monocytogenes isolates were resistance to two antibiotics (tilimicosin and tetracycline) among the ten tested antibiotics as determined by microbroth dilution method. The results presented in this study indicate the potential risk of contamination of RTE chicken products with L. monocytogenes. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to determine the prevalence of Listeria spp. in milk and dairy products in Isfahan province, Iran. From March 2007 to September 2009, a total of 594 samples of various milk and dairy products were obtained from randomly selected retail stores. Using conventional bacteriologic method, 55 samples (9.3%) were positive for Listeria spp. The highest prevalence of Listeria was found in raw sheep milk samples (22.6%), followed by cheese samples (18.9%). The most species recovered was Listeria innocua (58.2%); the remaining isolates were Listeria monocytogenes (32.7%) and Listeria seeligari (9.1%). Overall, 54 Listeria isolates (98.2%) were resistant to one or more antimicrobial agents. Resistance to nalidixic acid was the most common finding (96.4%). All Listeria isolates were susceptible to vancomycin. The results of this study indicate the potential risk of infection with Listeria in people consuming raw and unpasteurized milk and dairy products. [Copyright &y& Elsevier]

Abstract: Listeria and particularly Listeria monocytogenes is an important foodborne pathogen that can cause listeriosis with flu-like symptoms in healthy people, and severe complications in immunocompromised subjects, children, pregnant women and the elderly. A research survey was conducted to check the presence of Listeria spp. in raw meat and retail products and to analyse their antibiotic resistances. Total prevalence was 11.7%: in raw meat was 21.4%; in ham it was 5.2%; in fresh soft cheese it was 3.49%; in sandwiches it was 5.88%, while we found no isolates in smoked salmon and only two in ready salads (1.23%). The highest percentage of prevalence of L. monocytogenes was found in samples of ham (37.5%), lower percentages were in sandwiches (25.0%), in raw meat samples (23.6%), in fresh soft cheeses (20.0%), while ready salads and smoked salmons were not contaminated. The susceptibility of 168 strains of Listeria spp. was determined by disk diffusion method: we found 51 (30.4%) strains resistant to three or more antibiotics. All isolated strains, except one, are susceptible or at least to one of the first choice antibiotics (ampicillin and gentamycin) or to trimethoprim–sulfamethoxazole used as antibiotic of second choice in the treatment of human listeriosis. Strains isolated from ready-to-eat food show high level of resistance to ampicillin, gentamycin and meticillin. Meticillin is used normally, in treatment of Enterococcus spp. human infection; L. monocytogenes can transfer antibiotic resistance genes from plasmids and transposons to Enterococcus spp. in vitro and in vivo causing an increase of these bacteria resistant to meticillin. L. monocytogenes, in the last decades, is becoming resistant to a lot of antibiotics, a continued surveillance on its incidence on raw foods and on emerging resistances are important to identify food that can represent a risk of infection for the population, particularly for immunocompromised, children, pregnant women and the elderly to ensure effective treatment of human listeriosis with effective antibiotics. [Copyright &y& Elsevier]

Abstract: The aim of this work was to study survival of Listeria innocua and Listeria monocytogenes in muscle of cod during salt-curing and growth during chilled storage of the rehydrated product. Fresh cod was inoculated with L. innocua and L. monocytogenes at different levels before salt-curing. After salt-curing and rehydration, the levels were within 1 log10 CFU/g lower than prior to salt-curing in all experiments. During the first 5days of storage after rehydration, growth of L. innocua was observed in 1 out of 5 experiments at 4°C, but a 10–100-fold increase were observed in all experiments from day 5 to day 10. The growth started earlier and was more rapid when samples were stored at 7°C. Growth of L. monocytogenes at 4°C appeared to start earlier than for L. innocua, but a 10–100-fold increase was observed also for this bacterium. The lag phases in rehydrated products were longer than in experiments with cod muscle juice. The differences could be explained by a different level of salt stress. This work demonstrates that long term exposure to very high salt concentrations does not eliminate Listeria spp., and that Listeria being present in the fish prior to salt-curing can recover and grow in rehydrated salt-cured cod during chilled storage. [Copyright &y& Elsevier]

Abstract: Effectiveness of combined steam (10 and 60 s, 70 °C and 98 °C) and chemical treatments, using concentrated solutions of lactic acid (1 and 30 min, 5% and 10% lactic acid), on the inactivation of Listeria innocua inoculated on the surface of chicken skins have been studied. Surviving bacteria on the skin were enumerated immediately after treatment, and after 7 days of storage at 4 °C. The most effective treatment was the combination of steam of 98 °C and 10% lactic acid with its immediate efficacy being mainly attributed to the applied heat treatment. However, after  7-day storage, the treatment''s effectiveness was mainly due to the applied acid treatment, which prevented growth of the bacteria that survived the heat treatment. Milder treatments (70 °C steam, 5% lactic acid) revealed a genuine synergy between the heat and acid treatments, paving the way for an effective means of reducing bacterial load on the surface of poultry without affecting the product''s “raw” appearance. [Copyright &y& Elsevier]

Abstract: The incidence of Listeria species in the seafood of markets in Goa, India was studied. One hundred and fifteen raw/fresh seafoods bought at the fish markets were sampled and tested for presence of Listeria spp. using a two step enrichment procedure, followed by plating on two selective agars. The confirmation of the isolates was based on biochemical identification. Twenty eight seafood samples were positive for Listeria spp. and in 10 samples L. monocytogenes was detected. L. innocua was the most common Listeria species recovered and was detected in 18 samples. L. monocytogenes in raw seafood may pose a health risk in kitchen if contaminating ready-to-eat food. [Copyright &y& Elsevier]

Abstract: One hundred and forty-two homemade white cheese samples from various public bazaars were collected and tested for the occurrence of Listeria species. The overall incidence of Listeria spp. in cheese samples was 33.1%. Listeria monocytogenes was isolated from 13 (9.2%) out of 142 studied samples. Other species isolated were Listeria innocua (9.2%), Listeria seeligeri (5.6%), Listeria grayi (4.9%), Listeria ivanovii (2.1%), Listeria welshimeri (2.1%). Also, the antimicrobial susceptibility to various antimicrobial agents of 47 Listeria strains isolated from cheese was tested. Listeria spp. were resistant to penicillin (12.8%), chloramphenicol (8.5%), clarithromycin (6.4%), amikacin (4.3%), tetracycline (2.1%) and cefaclor (2.1%), but sensitive or displayed intermediate susceptibility to amoxicillin-clavulanic acid, vancomycin, gentamicin, ciprofloxacin, rifampin and trimethoprim-sulfamethoxazole. [Copyright &y& Elsevier]

This cross-sectional study determined the prevalence of Listeria spp. in bulk-tank milk on dairy farms in the region of Galicia in northwest Spain. The aim was to identify management practices associated with the presence ofListeria spp. and possible effects on milk hygienic quality. A total of 98 farms was randomly selected on the basis of an expected prevalence of 6.5% for Listeria monocytogenes from 20,107 dairy farms in the region. Bulk-tank milk samples were obtained from 98 farms, fecal samples from lactating cows from 97 farms, and silage samples from 83 farms. Listeria monocytogenes was detected in 6.1, 9.3, and 6.0% of these samples, respectively. Statistical analyses confirmed the relationship between low silage quality (as indicated by high pH) and presence ofListeria spp. in silage (29.5 vs. 6.2% for pH above or below 4.5, respectively). Only milking system [tie-stall systems (28.6%) vs. parlor milking (10%)] and inadequately controlled milking order [yes (32.0%) vs. no (10.7%)] had statistically significant effects on management practices for increasing the risk of Listeria contamination of bulk-tank milk. [ABSTRACT FROM AUTHOR]

Abstract: This study aimed to establish the occurrence of Listeria spp., especially L. monocytogenes and its main serotypes, in beef and processing plants. A total of 443 samples were obtained from equipment, installations and products from 11 meat processing establishments from Paraná state, Brazil. All samples were analyzed using USDA methodology for Listeria spp. detection, followed by species identification. The occurrence of Listeria spp. in the samples was 38.1% of which 51.4% were from equipment, 35.4% from installations and 30.2% from products. The identified species were: L. monocytogenes (12.6%), L. innocua (78.4%), L. seeligeri (1.2%), L. welshimeri (7.2%) and L. grayi (0.6%). The identified serotypes of L. monocytogenes were 1/2a and 4b. The results demonstrate the significance of equipment and installations as sources of contamination by Listeria spp. and L. monocytogenes in the processing of beef and meat products. [Copyright &y& Elsevier]

Abstract: The incidence of Listeria spp. in the salt-water edible fish and in the environment of fish markets in Thessaloniki, Northern Greece was studied. One hundred and twenty raw/fresh fish bought at the fish markets of Thessaloniki (Northern Greece), were sampled and tested for presence of Listeria species using a two step enrichment procedure, followed by plating on two selective agars and subsequent biochemical identification of the isolates. Five fish samples were positive for Listeria spp. and in only one sample L. monocytogenes was detected. Also, 100 samples of knives, hands, boxes etc were sampled and 18 samples were positive for Listeria spp. and five for L. monocytogenes. L. innocua was more common being detected in four fish samples and 13 environmental samples. L. seeligeri was detected only in one environmental sample. Our findings indicate that only a few fish were contaminated with Listeria spp., while the level of contamination of the environment of fish markets was higher. [Copyright &y& Elsevier]

Abstract: Eight dairies, located in two distant geographic regions of Portugal, were screened along the production cycle in order to evaluate the presence and distribution of Listeria spp. in their environment. Three dairies in each region were positive for the presence of listeriae and 213 isolates were obtained. Based on an integrated analysis of RAPD fingerprints with three primers, molecular identification and genomic typing of isolates was performed followed by spatial and temporal mapping on dairy plants. The occurrence of Listeria species by region was noticeable different. Listeria monocytogenes prevailed in South Portugal dairies and L. innocua presented the highest occurrence in Azores, whereas L. seeligeri and L. ivanovii were detected in distinct regions. Dairies were at risk of contamination, from more than one source, whatever the stage in the production cycle and the surface materials used. For the three prevalent species, most of the genomic types were dairy and sampling time specific. Nonetheless, more than one type could be found in each dairy at a particular site and, in a few cases, even for different species. Some dairies also shared types, mainly for L. innocua and usually at the same stage of the production cycle. For L. monocytogenes, PCR serotyping was applied and 52% of genomic types were serotype 4b. An equal frequency of genomic types (24%) was found for serotypes 1/2b or 3b and 1/2a or 3a. The global pattern of types within a dairy is not constant, suggesting cycles of elimination and recontamination along the production cycle. [Copyright &y& Elsevier]

Abstract: A total of 200 samples (muscles and viscera, 100 of each) of fresh water fish, walking catfish (Clarias batrachus) were screened for Listeria spp. All the samples were subjected to a two-step enrichment followed by plating on selective media. Confirmation of the isolates was on the basis of biochemical characters, haemolysis on blood agar and Christie, Atkins, Munch Petersen test. A total of 39 isolates of Listeria spp. were recovered. Of these 26 (67%), 8 (21%), 3 (8%) and 2 (5%) were Listeria monocytogenes, Listeria seeligeri, Listeria grayi and Listeria welshimeri, respectively. The isolates were subjected to a PCR assay for detection of the virulence-associated genes individually or together. The plcA, actA, hlyA and iap genes were detected in six strains, three genes (actA, hlyA and iap) in nine strains, the plcA, hlyA and iap in our strain, the hlyA and iap were in three strains, actA and hlyA in four strains, plcA and hlyA in our strain and hlyA in two strains. The hlyA and iap were also detected in L. seeligeri. [Copyright &y& Elsevier]

Abstract: In this study, the presence of Listeria spp. was investigated in a total of 157 raw milk and dairy product samples sold in Antakya (Antioch). The prevalence of Listeria spp. in raw milk and Turkish white cheese samples was found to be 2.12% and 8.23%, respectively. Listeria monocytogenes was not isolated from raw milk and found in only two cheese samples (2.35%). No Listeria spp. were isolated in any of the butter and yoghurt samples. [Copyright &y& Elsevier]

Abstract: This study was conducted to evaluate the efficacy of gaseous ozone exposure on Listeria innocua 2030c growth during cold-smoke processing of Oncorhynchus mykiss (salmon-trout). Three sets of experiments were performed: inoculation with L. innocua 2030c followed by a 20min ozone exposure were applied to (a) fresh salmon-trout after filleting, (b) to fresh whole fish, and (c) to fresh whole fish after removal of the fish slime. In sets (a) and (b) fillets were subsequently cold-smoked but not in set (c). The ozone concentration inside the exposure chamber after 20min reached 0.1×10−3 g/l. Counts of L. innocua 2030c were performed after treatment for sets (a), (b) and (c), after smoking and weekly during 21 days in vacuum packs at 5°C, for sets (a) and (b). Sampling for total Aerobic Plate Counts (APC) of non-inoculated samples was also performed in set (a). The percentage of salt in the water phase, peroxide values and the effect of treatment on sensory properties of cold-smoked salmon-trout fillets were also determined in the first and second set. In the first set, a decrease of less than 1log10 in L. innocua numbers occurred on ozone treated samples in all sampling occasions. APC was slightly lower on fresh fillets after treatment and on smoked fillets at 3 weeks of storage at 5°C (less than 1log10 CFU/g). In the second set, a reduction greater than 1log10 L. innocua/g occurred on smoked fillets at the end of the storage period. In the third set, the slime removal resulted in a 1log10 L. innocua/g reduction on fresh treated samples. Ozone treatment had no significant (p >0.05) effect on L. innocua counts on samples compared to those on untreated fish. In both sets, no significant differences among ozone treated/untreated samples were noticeable by sensory evaluation (p >0.05). [Copyright &y& Elsevier]

Abstract: The incidence of Salmonella spp., Listeria monocytogenes and Escherichia coli O157:H7 was determined in 100 Turkish sausage (soudjouck) samples collected from shops and markets in the Afyon province, Turkey. Salmonella spp. were detected in 7% of the samples. All of the isolates were S. enterica Paratyphi B. In addition, Listeria spp. were detected in 9% of the samples. Its distribution was 7% L. monocytogenes and 1% each of L. ivanovii and L. innocua. Serological study of the seven L. monocytogenes isolates showed that three of these were 1/2 ab, three were 5/6 ab and one was 1 ab. E. coli O157:H7 was not detected in any of the samples. The pH values of the samples ranged from 4.8 to 6.5. In conclusion, increasing number of listeriosis and salmonellosis cases in Turkey and the contamination levels found indicate that risk assessment and improved preventive measures are required for these sausages. [Copyright &y& Elsevier]

Abstract: The objectives of this study were to ascertain the efficacies of Carnobacterium divergens V41 and its supernatant V41 as treatments to control Listeria innocua 2030c during salmon-trout (Oncorhynchus mykiss) cold-smoking processes by treating the raw fish fillets. Fillets were dip-inoculated with 2% (v/v) culture of L. innocua 2030c and/or 2% (v/v) culture of C. divergens V41 culture and 2% or 5% (v/v) of culture supernatant V41. Fillets were dry-salted for 6 h and an average salt content of 5.3% (water phase salt) was obtained. Salted fillets were cold-smoked for 5 h (3 h of drying+2 h of smoking) and stored at 5 °C for 3 weeks in vacuum packs. The % of salt in the water phase was determined for all fillets. Sensorial analyses were performed in order to compare treated/untreated cold-smoked salmon-trout fillets to ascertain potential spoilage odours due to the treatments. All the treatments with C. divergens V41 or supernatant showed a significant inhibitory effect on L. innocua 2030c growth, but the 5% (v/v) C. divergens supernatant treatment, was by far the most effective against this species. No significant off-odours were found in the products with respect to the tested treatments. [Copyright &y& Elsevier]

Abstract: Ninety-six samples of bulk untreated goats¿ milk and 96 milk-filter samples, obtained monthly from eight farms in Valtellina and Valchiavenna, province of Sondrio, Lombardy Prealps, Italy, from October 2002 to October 2003, were subjected to exhaustive micro-biological analyses for the presence of Listeria spp. Two (2.1%) milk samples and six (6.3%) filter samples were positive for non-pathogenic Listeria species: L. innocua or L. ivanovii in milk; L. innocua, L. ivanovii or L. grayi in milk-filters. No strains pathogenic for humans (in particular L. monocytogenes) were present. This is a reassuring finding particularly as some of the farms are using their untreated milk to produce cheeses on the farm. [Copyright &y& Elsevier]

Detection of Listeria monocytogenes is generally performed in a two-step cultural enrichment process and takes on average 1 week until the biochemical identification of a L. monocytogenes suspicious colony is completed. However, food processing companies depend increasingly on test methods, which attempt to generate results comparable to standard methods but in reduced time-frame and which allow to release produced batches dependent on such results. In the present study, the vermicon identification technology (VIT®), a rapid commercial test system using fluorescently labelled gene probes, was compared to a cultural standard method. In total, 298 naturally contaminated samples were analysed. The sensitivity and the specificity of the VIT® system were 100% for the detection of L. monocytogenes and 97.1% and 100%, respectively, for the detection of the genus Listeria. [Copyright &y& Elsevier]

Lysozyme placed on the SiO2 surfaces that have previously been derivatized with C18 coating will capture both Escherichia coli and Listeria monocytogenes cells from PBS buffer at pH 7.2. This phenomenon is of significance for the design and fabrication of protein biochips that are designed to capture bacteria from buffer or water so that these can be further interrogated with respect to possible pathogenicity. Fluorescent microscopy shows that two types of bacteria (gram-negative E. coli and gram-positive Listeria spp.) will be adsorbed by lysozyme placed on the surface of the biochip but that strong adsorption of the bacteria is reduced but not eliminated when Tween 20 is present (at 0.5%) in the PBS buffer in which the cells are suspended. In comparison, Tween 20 and Bovine Serum Albumin (BSA) almost completely block adsorption of these bacteria on C18 coated surfaces. The combination of a lysozyme surface with Tween 20 gives a greater degree of adsorption of L. monocytogenes than E. coli, and hence suggests selectivity for the more hydrophobic E. coli may be reduced by the Tween 20. This paper presents protocols for preparing protein-coated, SiO2 surfaces and the effect of buffer containing Tween 20 on adsorption of bacteria by SiO2 surfaces coated with C18 to which BSA, lysozyme or C11E9 antibody is immobilized at pH 7.2 and ambient temperature. [Copyright &y& Elsevier]

Conventional isolation methods, including the Health Products and Food Branch (HPFB), Health Canada method used for the isolation and identification of Listeria species and Listeria monocytogenes from foods and environmental samples, can take a week or more to complete and are usually labor-intensive. This has led to the development of various rapid methods which attempt to generate results comparable to standard methods but in a reduced time-frame with less hands-on operation. Our previous work with rapid detection systems indicated that the recommended enrichment protocols failed to grow the Listeria to detectable levels in a reliable and consistent manner.In the present study, a novel enrichment protocol is described and consists of samples being pre-enriched in Palcam broth (incubated at 35 °C for 26 h), enriched in UVM 2 (30 °C for 26 h) and then plated and analysed by a rapid detection kit, with results being generated after 52 h of incubation.In total, 200 naturally contaminated samples were analysed by both the HPFB standard method and the Palcam method. The results showed that the Palcam method is comparable to the HPFB method. Further analysis involved a rapid detection system, which applies ELISA techniques and automation in an enzyme-linked fluorescent assay (ELFA) system. This system, referred to as the Vitek Immuno Diagnostic Assay System or VIDAS, can identify Listeria to the genus or species (L. monocytogenes) level.In this comparison, an additional 324 naturally contaminated samples were analysed by both the Palcam and ELFA methods. The sensitivity and specificity of the ELFA method were 98.1% and 97.0%, respectively, while the efficiency was 97.5%. False-negative and false-positive rates were 1.9% and 3.0%, respectively. These results show that the ELFA method (when using the Palcam method for pre- and secondary enrichment) was efficient and gave reliable results after 52 h of incubation, and met Health Canada''s criteria for approval as a rapid method. [Copyright &y& Elsevier]

Twelve lots of fresh unskinned fillets of rainbow trout (Oncorhynchus mykiss) and 10 lots of fresh sliced salmon (Salmo salar) prepacked in trays wrapped with an oxygen-permeable film were obtained immediately after packing from two supermarkets having in-plant facilities for packaging wet fish. During storage at 3 °C, Listeria innocua was detected in eight lots of trout fillets after 4 days storage. L. monocytogenes was recovered from a single lot also contaminated with L. innocua. Initial numbers of aeromonads were significantly (p<0.05) lower in trout fillets (3.35±0.62 log cfu g−1) than in salmon slices (4.20±0.89 log cfu g−1). In both fish products, these bacteria significantly (p<0.05) increased up until spoilage. Most Aeromonas spp. isolates from trout fillets were assigned to A. veronii biovar sobria HG8 (hybridisation group 8), A. caviae HG4, A. eucrenophila HG6, A. hydrophila HG1 and A. veronii biovar veronii HG10. Strains of HG12 (A. schubertii), HG4 and HG8 formed the majority of aeromonads recovered from salmon slices. [Copyright &y& Elsevier]

Abstract: The aim of this study was to establish the occurrence of Listeria spp., especially Listeria monocytogenes in ready to eat RTE food marketed in Algiers (Algeria). A total of 227 samples were collected from different producers and retailers. All samples were analyzed using a conventional cultivation method AFNOR V08-055. Out of 227 samples tested, 21 (9.3%) tested positive for Listeria spp. among them, 6 (2.6%) tested positive for L. monocytogenes. L. innocua was the most common Listeria species found being detected in 11 samples (4.8%), although both Listeria ivanovii and Listeria welshimeri were detected in 3 (1.3%) and 1 (0.4%) food samples respectively. The study of the antimicrobial sensitivity of Listeria monocytogenes strains showed no resistance. The study has enabled us to detect these contaminants in a wide range of RTE foods, to suggest that contamination likely occurs after heat treatment, and to assess the danger represented by this category of food for populations at risk. [Copyright &y& Elsevier]

Abstract: Listeria (L.) monocytogenes, a foodborne pathogen, is known to be a possible contaminant of foods during production and processing. Samples (n=985) of raw meat and by-products obtained from beef and pork were first screened by the VIDAS system for the presence of Listeria spp., followed by testing for the presence of L. monocytogenes. Positive L. monocytogenes results were confirmed by plating on selective agars: 14% of the samples were positive for Listeria and 4% tested positive for L. monocytogenes, of which 3% were confirmed on selective agars. In by-products (17%) the contamination with listeriae was higher than in meat cuts (10%). Only samples strongly positive for Listeria spp. by VIDAS were positive for L. monocytogenes. Overall, the prevalence of L. monocytogenes in beef and pork samples was rather low in comparison to most previous studies. The VIDAS system was shown to be a suitable method for screening out Listeria-negative samples; the main advantage being a markedly reduced assay time. [Copyright &y& Elsevier]

The aims of this study were to determine the prevalence, characteristics and antimicrobial resistance of Listeria spp. isolated from bovine clinical mastitis in Iran. Listeria spp. were detected in 21/207 bovine mastitic milk samples from dairy farms in Iran, comprising L. monocytogenes (n = 17), L innocua (n = 3) and L. ivanovii (n = 1). L monocytogenes isolates were grouped into serogroups '4b, 4d, 4e', 'l/2a, 3a', '1/ 2b, 3b, 7' and 'l/2c, 3c'; all harboured inlA, inIC and inlj virulence genes. Listeria spp. were most frequently resistant to penicillin G (14/21 isolates, 66.7%) and tetracyclines (11/21 isolates, 52.4%). [ABSTRACT FROM AUTHOR]