Trond Møretrø

• PhD
• Researcher at Nofima, Norwegian Institute of Food, Fisheries and Aquaculture Research, Ås, Norway

Listeria monocytogenes presents a significant concern for the food industry due to its ability to persist in the food processing environment. One of the factors contributing to its persistence is decreased sensitivity to disinfectants. Our objective was to assess the diversity of L. monocytogenes sensitivity to food industry disinfectants by testin...

Listeria monocytogenes (in the meat, fish and seafood, dairy and fruit and vegetable sectors), Salmonella enterica (in the feed, meat, egg and low moisture food sectors) and Cronobacter sakazakii (in the low moisture food sector) were identified as the bacterial food safety hazards most relevant to public health that are associated with persistence...

Listeria monocytogenes is a significant concern for the food industry due to its ability to persist in the food processing environment. Decreased susceptibility to disinfectants is one of the factors that contribute to the persistence of L. monocytogenes . The objective of this study was to explore the diversity of L. monocytogenes susceptibility t...

Inadequate cleaning and disinfection (C&D) in slaughterhouses can cause bacterial contamination of meat, resulting in foodborne disease and reduced meat quality. Different methods for monitoring the efficacy of C&D procedures are available, but few studies have assessed their reliability. This study examined C&D efficacy in slaughterhouses and eval...

The residential kitchen is often heavily colonized by microbes originating from different sources, including food and human contact. Although a few studies have reported the bacterial composition in cleaning utensils and surface samples there is limited knowledge of the bacterial diversity across different sample types, households, and countries. A...

This is the french translation of: Møretrø, T., Ferreira, V.B., Moen, B., Almli, V.L., Teixeira, P. & Kasbo, I.M. et al. (2022) Bacterial levels and diversity in kitchen sponges and dishwashing brushes used by consumers. Journal of Applied Microbiology, 133, 1378–1391. Available from: https://doi.org/10.1111/ jam.15621

Whole genome sequencing (WGS) of foodborne pathogens such as Listeria monocytogenes is globally on the rise in the food industry. It provides an improvement for proactive surveillance and source-tracking and allows in-depth genetic characterization of the pathogen. In the present study, the virulence gene profile including 99 virulence genes of 767...

Listeria monocytogenes can persist in food processing environments for months to decades and spread through the food system by, e.g., contaminated raw materials. Knowledge of the distribution and diversity of L. monocytogenes is important in outbreak investigations and is essential to effectively track and control this pathogen in the food system.

Food poisoning is a threat to health and economy across regions and living standards, with an estimated 600 million cases worldwide every year. In consumer households, water and electricity facilities are key to safe food preparation and storage. However, recreational home environments may be of lower standard and expose dwellers to higher risk of...

Kitchen cloths have an important role in maintaining kitchen surfaces hygienically clean but may also act as vehicles for cross contamination of pathogens from food spills to hands and other foods. The aim of the present study was to map consumer practices across Europe and identify main factors that may contribute to unsafe use of kitchen cloths,...

To investigate the diversity, distribution, persistence, and stress resistome of Listeria monocytogenes clones dominating in food processing environments in Norway, genome sequences from 769 L. monocytogenes isolates from food industry environments, foods, and raw materials (of which 512 were sequenced in the present study) were subjected to wgMLST...

Aims: The purpose of the work was to investigate bacterial levels and diversity as well as survival of Salmonella in used dish washing sponges and brushes and identify consumer practices that can potentially explain bacterial status of these items. Methods and results: Used washing up utensils were collected from consumers. The bacterial numbers...

Listeria monocytogenes is a ubiquitous environmental bacterium associated with a wide variety of natural and man-made environments, such as soil, vegetation, livestock, food processing environments, and urban areas. It is also among the deadliest foodborne pathogens, and knowledge about its presence and diversity in potential sources is crucial to...

Import of roughage to Norway may introduce novel plant pests, invasive plants and disease-causing pathogens to both animals and humans. However, there is a high level of uncertainty behind these conclusions.

The XyRex® formulations are antimicrobial agents with sodium chlorite as the active substance. The Norwegian Food Safety Authority has received a request to authorise XyRex® formulations for use in refrigerated sea-water (RSW) tanks on board fishing vessels for pelagic fish caught for production of fish meal/fish oil for use in animal feed. The use...

In this study we addressed different aspects regarding the implementation of quasimetagenomic sequencing as a hybrid surveillance method in combination with enrichment for early detection of Listeria monocytogenes in the food industry. Different experimental enrichment cultures were used, comprising seven L. monocytogenes strains of different seque...

Listeria monocytogenes is a ubiquitous environmental bacterium associated with a wide variety of natural and man-made environments, such as soil, vegetation, livestock, food processing environments, and urban areas. It is also among the deadliest foodborne pathogens, and knowledge about its presence and diversity in potential sources is crucial to...

The data presented here capture the structure of kitchen layouts belonging to consumers vulnerable to foodborne diseases and food risk-takers. Data were collected in the frame of the SafeConsume project by multidisciplinary research teams that visited consumers during preparing a meal and had the possibility to examine their cooking routines. Dista...

Our paper emphasizes the importance of the kitchen layout in facilitating consumers' food hygiene practices. A significant correlation was found between the sink placement (inside or outside the kitchen) and hygienic practices during food handling based on a survey performed on consumers from ten European countries, indicating that those who had th...

Providing risk managers with the information that they need for decision making is an important element in food-safety management. The present risk assessment was undertaken to establish a scientific basis that could be used to assist the Norwegian Food Safety Authority (NFSA) in implementing risk-based surveillance, monitoring, and control program...

Updated knowledge about the zoonotic potential of chronic wasting disease (CWD) associated with animal slaughter and consumption of meat.

Nontyphoidal salmonellae are among the most prevalent foodborne pathogens causing gastrointestinal infections worldwide. A high number of cases and outbreaks of salmonellosis are associated with the consumption of eggs and egg products, and several of these occur at the household level. The aim of the current study is to critically evaluate the cur...

The frequency of foodborne outbreaks epidemiologically associated with Listeria monocytogenes in fresh produce has increased in recent years. Although L. monocytogenes may be transferred from the environment to vegetables during farming, contamination of food products most commonly occurs in food processing facilities, where L. monocytogenes has th...

About 40% of foodborne infections are acquired in the home. The aim of the present study was to track contamination of pathogens during domestic food preparation and link the contamination to preparation practices. Research participants from 87 households in six European countries were observed and interviewed during shopping and preparation of a c...

Contamination of food products with the foodborne pathogen Listeria monocytogenes may occur in the food processing environment. Many bacterial species co-exist in this environment and can interact in multispecies biofilms. Recent studies have shed light on the composition of microbial communities present in the same ecological habitat as L. monocyt...

Sponges are frequently used in kitchens and have been shown to harbor large numbers of bacteria, occasionally also pathogens. Less is known about kitchen brushes regarding usage and presence of bacteria. In the present study, the use of sponges and brushes was studied in a survey among 9966 European consumers in ten countries, and growth and surviv...

The aim of the study was to evaluate the fungicidal effect of a H2O2 mist generating system for disinfection of spores of six food-related moulds (Alternaria alternata, Aspergillus flavus, Geotrichum candidum, Mucor plumbeus, Paecilomyces variotii, and Penicillium solitum) dried on stainless steel. Exposure to H2O2 mist for 2 or 4 h lead to >3 log...

Listeria monocytogenes is a pathogen mostly associated with the consumption of ready-to-eat foods and can cause severe disease and death. It can be introduced into food chains from raw materials, but often the contamination source is the food production environment, where certain clones can persist for years. In the meat chain, ST9 is one of the mo...

Sampling plans today tend not to be based on assessing the increased likelihood of contamination, and samples may be taken non-systematically and too seldom. Many of the analyses conducted to date have been performed by laboratories lacking accreditation for that particular analysis. Accreditation ensures the quality of the analyses performed. Our...

About one third of foodborne illness outbreaks in Europe are acquired in the home and eating undercooked poultry is among consumption practices associated with illness. The aim of this study was to investigate whether actual and recommended practices for monitoring chicken doneness are safe. Seventy-five European households from five European count...

Effective cleaning and disinfection (C&D) is pivotal for the control of Listeria monocytogenes in food processing environments. Bacteria in biofilms are protected from biocidal action, and effective strategies for the prevention and removal of biofilms are needed. In this study, different C&D biofilm control strategies on pre-formed L. monocytogene...

Cleaning is a method at the disposal of domestic cooks for curtailing the dispersal of foodborne pathogens in the process of preparing food. The observation of visible dirt/soil ‘in the wrong place’ operates as one of the stimuli for action. This paper makes a transdisciplinary contribution to understandings of cleaning as a practice for ensuring s...

A transdisciplinary observational study, coupled with a web-based survey, was conducted to investigate refrigerated storage of food, in five European countries. The investigated consumer groups in this study were: young families with small children and/or pregnant women, elderly people, persons with an immunodeficient system, and young single men....

An assessment of Listeria monocytognes in sushi and sashimi for vulnerable consumers. The assessment is prepared as decision support for the Norwegian Food Safety Authorities in their revision of advices to vulnerable consumers.

Aims To evaluate ATP bioluminescence‐based hygiene monitoring systems under conditions relevant for fish processing environments. Methods and Results The ATP bioluminescence of fish fractions that are potentially present after insufficient cleaning of fish processing environments was determined. Different fractions and interfering substances repre...

In spring 2018 the last wild reindeer in Zone 1 in Nordfjella wildlife area was shot. In total 2024 wild reindeer were killed, mostly through culling organized by the Norwegian Nature Inspectorate. The background for this measure, unparalleled in Norwegian game management, was the detection of the contagious and lethal Chronic Wasting Disease (CWD)...

Listeria monocytogenes surviving daily cleaning and disinfection is a challenge for many types of food industries. In this study, it was tested whether whole room disinfection (WRD) with H2O2 mist could kill L. monocytogenes under conditions relevant for the food industry. Survival of a mixture of four L. monocytogenes strains exposed to H2O2 mist...

Interactions and competition between resident bacteria in food processing environments could affect their ability to survive, grow and persist in microhabitats and niches in the food industry. In this study, the competitive ability of L. monocytogenes strains grown together in separate culture mixes with other L. monocytogenes (L. mono mix), L. inn...

Listeria monocytogenes is a foodborne pathogen that causes the often-fatal disease listeriosis. We present here the complete genome sequences of sixL. monocytogenesisolates of sequence type 9 (ST9) collected from two different meat processing facilities in Norway. The genomes were assembled using Illumina and Nanopore sequencing data.

Several guidelines for control of L. monocytogenes in food processing environments recommend the addition of citric acid powder to floors. However, documentation of the effect of this advice on L. monocytogenes in the food industry is not available in scientific literature. In the current study, the effect of addition of citric acid powder to five...

Surfaces of food processing premises are exposed to regular cleaning and disinfection (C & D) regimes, using biocides that are highly effective against bacteria growing as planktonic cells. However, bacteria growing in surface-associated communities (biofilms) are typically more tolerant toward C & D than their individual free-cell counterparts, an...

Surface hygiene is commonly measured as a part of the quality system of food processing plants, but as the bacteria present are commonly not identified, their roles for food quality and safety are not known. Here, we review the identity of residential bacteria and characteristics relevant for survival and growth in the food industry along with pote...

Significance and impact of the study: The source tracking of fungal contamination in the food industry is an important aspect of food safety. Currently, all available methods are time consuming and require the use of a reference library that may limit the accuracy of the identification. In this study, we report for the first time, a library-indepe...

The antibacterial effect of disinfectants is crucial for the control of Listeria monocytogenes in food processing environments. Tolerance of L. monocytogenes to sublethal levels of disinfectants based on quaternary ammonium compounds (QAC) is conferred by the resistance determinants qacH and bcrABC. The presence and distribution of these genes have...

The processing environment of salmon processing plants represents a potential major source of bacteria causing spoilage of fresh salmon. In this study, we have identified major contamination routes of important spoilage associated species within the genera Pseudomonas, Shewanella and Photobacterium in pre-rigor processing of salmon. Bacterial count...

Staphylococci are frequently isolated from food processing environments, and it has been speculated whether survival after cleaning and disinfection with benzalkonium chloride (BC)-containing disinfectants is due to biofilm formation, matrix composition, or BC efflux mechanisms. Out of 35 food associated staphylococci, eight produced biofilm in a mic...

Staphylococci are frequently isolated from food processing environments, and it has been speculated whether survival after cleaning and disinfection with benzalkonium chloride (BC)-containing disinfectants is due to biofilm formation, matrix composition, or BC efflux mechanisms. Out of 35 food associated staphylococci, eight produced biofilm in a m...

Listeria monocytogenes is an important foodborne pathogen responsible for the disease listeriosis, and can be found throughout the environment, in many foods and in food processing facilities. The main cause of listeriosis is consumption of food contaminated from sources in food processing environments. Persistence in food processing facilities has...

SNPs and indels detected in L. monocytogenes ST8 isolates. The allelic state for each SNP/indel is presented relative to that found in the neighbour L. monocytogenes strains 10304S, 08–5578, and 08–5923. Plasmid and prophage regions in L. monocytogenes isolates Lm_1823 and Lm_1889 are disregarded. (PDF)

Summary of SNPs and indels showing the distribution of nucleotide states in all analysed CC8 L. monocytogenes strains. (XLSX)

Accessory genome in ST8 isolates relative to L. monocytogenes strains EGD-e and 10403S. Genes in prophages and plasmids are disregarded. (PDF)

Stainless steel coupons are frequently used in biofilm studies in the laboratory, as this material is commonly used in the food industry. The coupons are attached to different surfaces to create a “natural” biofilm to be studied further in laboratory trials. However, little has been done to investigate how well the microbiota on such coupons repres...

Aims: The microbiota surviving sanitation of salmon processing conveyor belts was identified and its growth dynamics further investigated in a model mimicking processing surfaces in such plants. Methods and results: A diverse microbiota dominated by gram-negative bacteria was isolated after regular sanitation in three salmon processing plants. A...

Coaggregation, the specific recognition and adherence of different microbial species, is thought to enhance biofilm formation. To date, no studies have focused on the ability of microorganisms isolated from a broad range of environments to coaggregate with each other and it is unclear whether coaggregation promotes the transmission of micro-organis...

A community-based sessile life style is the normal mode of growth and survival for many bacterial species. Under such conditions, cell-to-cell interactions are inevitable and ultimately lead to the establishment of dense, complex and highly structured biofilm populations encapsulated in a self-produced extracellular matrix and capable of coordinate...

In this study, coaggregation interactions between Rhodococcus and Acinetobacter strains isolated from food-processing surfaces were characterized. Rhodococcus sp. strain MF3727 formed intrageneric coaggregates with Rhodococcus sp. strain MF3803 and intergeneric coaggregates with 2 strains of Acinetobacter calcoaceticus (MF3293, MF3627). Stronger co...

Few studies have compared the effectiveness of hygienic cleaning under simulated use conditions. This study compares commonly used and novel cleaning methods for food contact and hand contact surfaces in kitchens. We report results from two surveys on Norwegian consumers’ cleaning procedures. Laboratory models involving cutting boards, tap handles...

AimsFew studies have compared the effectiveness of hygienic cleaning under simulated use conditions. This study compares commonly used and novel cleaning methods for food contact and hand contact surfaces in kitchens.Methods and ResultsWe report results from two surveys on Norwegian consumers’ cleaning procedures. Laboratory models involving cuttin...

It is crucial for the quality and safety of ready-to-eat (RTE) foods to maintain the cold chain from production to consumption. The effect of temperature abuse related to daily meals and elevated refrigerator temperatures on the growth and toxin production of Bacillus cereus, Bacillus weihenstephanensis and Staphylococcus aureus and the growth of L...

Unlabelled: Although Salmonella persistence has been predominantly linked to biofilm formation, the physiological state of Salmonella should also be considered as a possible pathway for persistence and survival in the feed industry. Hence, the purpose of this study was to assess the extent of viability of Salmonella cells through long-term desicca...

The aim of the study was to investigate how the use of fresh cheese brines compared with used brines and various combinations of pH and NaCl concentrations affected the survival of Listeria monocytogenes. Cheese brines from five Norwegian small scale cheese producers were analysed and showed great variations in pH (4·54-6·01) and NaCl concentration...

The background microbiota of 5 Norwegian small-scale cheese production sites was examined and the effect of the isolated strains on the growth and survival of Listeria monocytogenes was investigated. Samples were taken from the air, food contact surfaces (storage surfaces, cheese molds, and brine) and noncontact surfaces (floor, drains, and doors)...

The application of Fourier Transform Infrared Spectroscopy for characterization of yeasts is growing rapidly. Since it is known that the phenotypic expression of yeast cells depends sensitively on the nutrients that are available in the growth medium, one standardized growth medium is usually used for identification and characterization purposes in...

The objective of the study was to evaluate a high-throughput liquid microcultivation protocol and FTIR spectroscopy for the differentiation of food spoilage filamentous fungi. For this study, fifty-nine food-related fungal strains were analysed. The cultivation of fungi was performed in liquid medium in the Bioscreen C microtitre plate system with...

In the present study the antibacterial effect of three commercially available cutting boards containing silver zeolites or nanosilver was studied. Mixtures of five strains of Staphylococcus aureus were added to coupons of cutting boards followed by incubation at 35–93% relative humidity on open surfaces or at 100% relative humidity in the Japanese...

Two commercially available all-in-one swab rapid detection systems for Listeria spp. (InSite Listeria Test and Path-Chek hygiene Listeria) were tested for performance in cheese production environments and salmon processing facilities. Sampling was conducted both on clean surfaces and during production. A total of 338 samples were taken using the sw...

Different bacteria that can grow and survive in food producing environments are discussed and how they are affected by control measures is revived. Pseudomonas dominates studies on seafood production and meat production, and dairies. Psychrotrophic Pseudomonas is found in water, soil and raw materials. Acinetobacter is ubiquitous in nature, exhibit...

Listeria monocytogenes, an important foodborne pathogen, commonly encounters organic acids in food-related environments. The transcriptome of L. monocytogenes L502 was analyzed after adaptation to pH 5 in the presence of acetic acid, lactic acid, or hydrochloric acid (HCl) at 25 °C, representing a condition encountered in mildly acidic ready-to-eat...

Salmonella may be transferred to food through cross-contamination during processing and preparation. To minimise the risk of cross-contamination, proper cleaning and disinfection is essential for the food industry. Recently, disinfection of areas for preparation and storage of food has also gained increased popularity in households. There is a rang...

Surfaces with microorganisms may transfer unwanted microorganisms to food through cross-contamination during processing and preparation. A high hygienic status of surfaces that come in contact with food is important in order to reduce the risk of cross-contamination. During the last decade, products containing antimicrobial compounds, such as cutti...

Several studies have shown that consumers may not clean cutting boards properly between preparation of raw and cooked meat. Cutting boards may therefore act as sources for contamination of cooked meat or other ready-to-eat foods with pathogenic and spoilage bacteria. The aim of the work was to investigate if cutting boards containing the antimicrob...

Total number of regulated genes grouped according to their biological role. Total number of (A) up-regulated and (B) down-regulated genes in different functional role categories according to the primary annotation in CMR-JCVI L. monocytogenes EGDe genome database in the L502-1 and L502-6 strains grown on mannose or cellobiose compared to the wild-t...

Validation of the microarray data by qRT-PCR analysis. Validation of microarray data (y-axis) by qRT-PCR analysis (x-axis) on six genes. The transcriptional studies for the sakacin P-resistant strains (L502-1 and L502-6) and the wild-type (L502) was performed during growth on mannose or cellobiose. (A) L502-1 grown on mannose (B) L502-1 grown on ce...

Transcript level of the mptA gene. Transcript level of the mptA gene extracted from qRT-PCR analysis in the sakacin P-resistant (L502-1 and L502-6) and the wild-type (L502) strain during growth on mannose or cellobiose. Error bar indicates the standard error of the mean of two independent experiments. (TIF)

Primer and probe sets used for qRT-PCR. a Taq probes, 6-FAM, 6-carboxyfluorescein (fluorophore); TAMRA, 6-carboxytetramethylrhodamine (quencher). (DOC)

List of all differentially regulated genes. a Description of genes according to the annotation of the Comprehensive Microbial Resource of the J. Craig Venter Institute (http://cmr.jcvi.org) and published literature resources. The functional role categories are also according to the primary annotation in CMR-JCVI L. monocytogenes EGDe genome databas...

Subclass IIa bacteriocins have strong antilisterial activity and can control the growth of Listeria monocytogenes in food. However, L. monocytogenes may develop resistance towards such bacteriocins. In this follow-up study, the transcriptomes of a high level (L502-1) and a low level (L502-6) spontaneous sakacin P-resistant mutant strain of L. monoc...