A note on challenge trials to determine the growth of Listeria monocytogenes on mushrooms (Agaricus bisporus)

peer-reviewedIn the EU, food is considered safe with regard to Listeria monocytogenes if the number of micro-organisms does not exceed 100 colony forming units (cfu)/g throughout its shelf-life. Therefore, it is important to determine if a food supports growth of L. monocytogenes. Guidelines for conducting challenge tests for growth assessment of L. monocytogenes on foods were published by the European Union Reference Laboratory (EURL) in 2014. The aim of this study was to use these guidelines to determine if refrigerated, fresh, whole, closed-cap, prepackaged mushrooms (Agaricus bisporus) support the growth of L. monocytogenes. Three batches of mushrooms were artificially inoculated at approximately 100 cfu/g with a three-strain mix of L. monocytogenes and incubated for 2 days at 8°C followed by 4 days at 12°C. L. monocytogenes numbers were determined (in triplicate for each batch) on days 0, 2 and 6. Water activity, pH and total bacterial counts were also determined. There was no increase in the number of L. monocytogenes above the threshold of 0.5 log cfu/g in any of the replicates. In 8 of 9 replicates, the numbers decreased indicating that A. bisporus do not support the growth of L. monocytogenes. As the EU regulations allow < 100 cfu/g if the food cannot support growth of L. monocytogenes, the significance of this study is that mushrooms with < 100 cfu/g may be within the regulations and therefore, quantitative rather than qualitative determination may be required.Safefoo

Monitoring, understanding and controlling listeria in food processing

The objective of this study was to monitor, understand and help control Listeria monocytogenes and L. ivanovii in the food processing environment. As foodborne transmission has been identified as the primary route of human infection of L. monocytogenes, the contamination of foods during production poses a serious threat to public health. Although the incidence of listeriosis is relatively low, the mortality rate can be extremely high, especially in the immunocompromised. This work aimed to examine the prevalence of L. monocytogenes and ivanovii at the primary production stage and, through the typing of isolates, identify and subsequently examine persistent strains. A three year monitoring programme was conducted in 54 processing facilities which identified 86 distinguishable PFGE pulsotypes, 17 of which were seen to be persistent. The effect of management practices on the occurrence of L. monocytogenes was also examined. Separation of personal protective equipment in high and low risk areas, training being performed by management and the use of a power hose were seen to have an effect on L. monocytogenes occurrence and persistence. Challenge tests were also performed using varying methodologies on several types of food in order to establish whether the growth of L. monocytogenes was supported by these foods. Different methodologies were seen to affect the results in challenge tests performed in mushrooms while smoked salmon was seen to support L. monocytogenes growth regardless of methodology used. Finally, two closely related 1/2a L. monocytogenes strains isolated from smoked salmon were subjected to whole genome sequencing and their genomes were compared. The monitoring and examination of L. monocytogenes and L. ivanovii has been seen to reduce the occurrence in the food processing environment and therefore reduce the risk to public health

Draft Genome Sequences of Listeria monocytogenes Serotype 4b Strains 944 and 2993 and Serotype 1/2c Strains 198 and 2932

Listeria monocytogenes is a foodborne pathogen and the causative agent of listeriosis among humans and animals. The draft genome sequences of L. monocytogenes serotype 4b strains 944 and 2993 and serotype 1/2c strains 198 and 2932 are reported here

Detection of presumptive Bacillus cereus in the Irish dairy farm environment

peer-reviewedThe objective of the study was to isolate potential Bacillus cereus sensu lato (B. cereus s.l.) from a range of farm environments. Samples of tap water, milking equipment rinse water, milk sediment filter, grass, soil and bulk tank milk were collected from 63 farms. In addition, milk liners were swabbed at the start and the end of milking, and swabs were taken from cows’ teats prior to milking. The samples were plated on mannitol egg yolk polymyxin agar (MYP) and presumptive B. cereus s.l. colonies were isolated and stored in nutrient broth with 20% glycerol and frozen at -80 °C. These isolates were then plated on chromogenic medium (BACARA) and colonies identified as presumptive B. cereus s.l. on this medium were subjected to 16S ribosomal RNA (rRNA) sequencing. Of the 507 isolates presumed to be B. cereus s.l. on the basis of growth on MYP, only 177 showed growth typical of B. cereus s.l. on BACARA agar. The use of 16S rRNA sequencing to identify isolates that grew on BACARA confirmed that the majority of isolates belonged to B. cereus s.l. A total of 81 of the 98 isolates sequenced were tentatively identified as presumptive B. cereus s.l. Pulsed-field gel electrophoresis was carried out on milk and soil isolates from seven farms that were identified as having presumptive B. cereus s.l. No pulsotype was shared by isolates from soil and milk on the same farm. Presumptive B. cereus s.l. was widely distributed within the dairy farm environment

Draft genome sequences of 25 Listeria monocytogenes isolates associated with human clinical Listeriosis in Ireland

Listeria monocytogenes is a Gram-positive opportunistic pathogen that is the causative agent of listeriosis. Here, we report the draft genome sequences of 25 L. monocytogenes strains isolated from patients with clinical listeriosis in the Republic of Ireland between 2013 and 201

Network governance for large‐scale natural resource conservation and the challenge of capture

Large‐scale natural resource conservation initiatives are increasingly adopting a network governance framework to respond to the ecological, social, and political challenges of contemporary environmental governance. A network approach offers new modes of management that allow resource managers and others to transcend a single institution, organization, resource, or landscape and engage in conservation that is multi‐species and multi‐jurisdictional. However, there are challenges to network governance in large‐scale conservation efforts, which we address by focusing on how special interests can capture networks and shape the goals, objectives, and outcomes of initiatives. The term “network capture” is used here to describe an array of strategies that direct the processes and outcomes of large‐scale initiatives in ways that advance a group's positions, concerns, or economic interests. We outline how new stakeholders emerge from these management processes, and how the ease of information sharing can blur stakeholder positions and lead to competing knowledge claims. We conclude by reasserting the benefits of network governance while acknowledging the unique challenges that networks present.Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.</p

Reviewed by:

Monitoring occurrence and persistence of Listeri

Occurrence, Persistence, and Virulence Potential of Listeria ivanovii in Foods and Food Processing Environments in the Republic of Ireland

The aim of this study was to assess the occurrence of L. ivanovii in foods and food processing environments in Ireland, to track persistence, and to characterize the disease causing potential of the isolated strains. A total of 2,006 samples (432 food samples and 1,574 environmental swabs) were collected between March 2013 and March 2014 from 48 food business operators (FBOs) belonging to different production sectors (dairy, fish, meat, and fresh-cut vegetable). Six of the forty-eight FBOs had samples positive for L. ivanovii on at least one sampling occasion. L. ivanovii was present in fifteen samples (fourteen environmental samples and one food sample). All but one of those positive samples derived from the dairy sector, where L. ivanovii prevalence was 1.7%. Six distinguishable pulsotypes were obtained by PFGE analysis, with one pulsotype being persistent in the environment of a dairy food business. Sequence analysis of the sigB gene showed that fourteen isolates belonged to L. ivanovii subsp. londoniensis, while only one isolate was L. ivanovii subsp. ivanovii. Cell invasion assays demonstrated that the majority of L. ivanovii strains were comparable to L. monocytogenes EGDe in their ability to invade CACO-2 epithelial cells whilst four isolates had significantly higher invasion efficiencies

Genomic Characterization of Listeria monocytogenes Isolates Associated with Clinical Listeriosis and the Food Production Environment in Ireland

Listeria monocytogenes is a major human foodborne pathogen that is prevalent in the natural environment and has a high case fatality rate. Whole genome sequencing (WGS) analysis has emerged as a valuable methodology for the classification of L. monocytogenes isolates and the identification of virulence islands that may influence infectivity. In this study, WGS was used to provide an insight into 25 L. monocytogenes isolates from cases of clinical infection in Ireland between 2013 and 2015. Clinical strains were either lineage I (14 isolates) or lineage II (11 isolates), with 12 clonal complexes (CC) represented, of which CC1 (6) and CC101 (4) were the most common. Single nucleotide polymorphism (SNP) analysis demonstrated that clinical isolates from mother–infant pairs (one isolate from the mother and one from the infant) were highly related (3 SNP differences in each) and also identified close similarities between isolates from otherwise distinct cases (1 SNP difference). Clinical strains were positive for common virulence-associated loci and 13 isolates harbour the LIPI-3 locus. Pulsed-field gel electrophoresis (PFGE) was used to compare strains to a database of 1300 Irish food and food processing environment isolates and determined that 64% of clinical pulsotypes were previously encountered in the food or food processing environment. Five of the matching food and food processing environment isolates were sequenced and results demonstrated a correlation between pulsotype and genotype. Overall, the work provides insights into the nature of L. monocytogenes strains currently causing clinical disease in Ireland and indicates that similar isolates can be found in the food or food processing environment