Food Production Environments Research Articles

Antimicrobial resistance of Listeria monocytogenes serogroups IIa and IVb from food and food-production environments in Poland.

Listeria monocytogenes is an important foodborne pathogen responsible for human listeriosis, which is a disease with high hospitalisation and mortality rates. The bacteria are usually susceptible to most antibacterial substances, but resistance to some of them has been recently observed. The present study introduces the evidence on the emergence of antibiotic resistance among L. monocytogenes strains isolated from food and food-production environments in Poland. A total of 283 L. monocytogenes isolates classified into serogroups IIa and IVb which had been recovered from food and food production environments were tested with 17 antimicrobials. These included those that are recommended for treatment of severe listeriosis cases in humans. A multiplex PCR was used to identify serogroups, and a microbroth dilution method was applied for the determination of antibiotic resistance among the isolates tested. Only 34 (12.0%) strains were susceptible to all the antimicrobials used in the study. The remaining 249 (88.0%) strains displayed different instances of resistance to the antimicrobials tested, from insusceptibility to one (112 strains; 39.6%) to resistance to four antibacterial substances (6 strains; 2.1%). Among them, there were 38 strains (13.4%) with multiresistance patterns. Polish food and its processing environments may be a potential source of antimicrobial-resistant L. monocytogenes, which may pose a potential health risk to consumers in the country.

Evaluating the effect of various types of disinfectants on bacterial biofilms

Biofilm formation on equipment surfaces is a potential food safety hazard, providing increased resistance and persistence of pathogens and spoilage microorganisms in food production environments. The issue of preventing the biofilm formation is extremely important, since a wide range of disinfectants does not always provide the proper effect. The article discusses the antimicrobial effectiveness of disinfectants with various active ingredients (based on active chlorine, peracetic acid and quaternary ammonium compounds (QAC) with enzymatic substances) on binary biofilms. The objects of the study were the strains of pathogenic and opportunistic microorganisms isolated from abiotic surfaces of food production environments and food products. Different effects of disinfectants on biofilms formed by bacteria have been established. Disinfectant based on peracetic acid and chlorine had the greatest effect on binary biofilms of Brochothrix thermosphacta/Salmonella spp. and Staphylococcus equorum/Salmonella spp. The greatest antimicrobial effect on biofilm of Listeria monocytogenes 12/Pseudomonas azotoformans 6 was shown by a chlorine-based disinfectant. Disinfectants based on chlorine and QAC with enzymatic substances were most effective against the binary biofilm of L. monocytogenes 12/Salmonella spp. 14. However, none of the disinfectants had absolute antimicrobial effectiveness against the studied binary biofilms. Biofilm-forming microorganisms have shown resistance to the recommended concentrations of disinfectants. Therefore, currently, it is extremely important to revise approaches to hygiene at enterprises by finding working concentrations of new antimicrobial agents and new procedure that are effective for destroying biofilms.

Biofilm formation in food processing plants and novel control strategies to combat resistant biofilms: the case of Salmonella spp.

Salmonella is one of the pathogens that cause many foodborne outbreaks throughout the world, representing an important global public health problem. Salmonella strains with biofilm-forming abilities have been frequently isolated from different food processing plants, especially in poultry industry. Biofilm formation of Salmonella on various surfaces can increase their viability, contributing to their persistence in food processing environments and cross-contamination of food products. In recent years, increasing concerns arise about the antimicrobial resistant and disinfectant tolerant Salmonella, while adaptation of Salmonella in biofilms to disinfectants exacerbate this problem. Facing difficulties to inhibit or remove Salmonella biofilms in food industry, eco-friendly and effective strategies based on chemical, biotechnological and physical methods are in urgent need. This review discusses biofilm formation of Salmonella in food industries, with emphasis on the current available knowledge related to antimicrobial resistance, together with an overview of promising antibiofilm strategies for controlling Salmonella in food production environments.

Cronobacter Species in the Built Food Production Environment: A Review on Persistence, Pathogenicity, Regulation and Detection Methods.

The powdered formula market is large and growing, with sales and manufacturing increasing by 120% between 2012 and 2021. With this growing market, there must come an increasing emphasis on maintaining a high standard of hygiene to ensure a safe product. In particular, Cronobacter species pose a risk to public health through their potential to cause severe illness in susceptible infants who consume contaminated powdered infant formula (PIF). Assessment of this risk is dependent on determining prevalence in PIF-producing factories, which can be challenging to measure with the heterogeneity observed in the design of built process facilities. There is also a potential risk of bacterial growth occurring during rehydration, given the observed persistence of Cronobacter in desiccated conditions. In addition, novel detection methods are emerging to effectively track and monitor Cronobacter species across the food chain. This review will explore the different vehicles that lead to Cronobacter species' environmental persistence in the food production environment, as well as their pathogenicity, detection methods and the regulatory framework surrounding PIF manufacturing that ensures a safe product for the global consumer.

The grain Food-Energy-Water nexus in China: Benchmarking sustainability with generalized data envelopment analysis

Food insecurity can be considered as a significant cause to instability in some regions around the world. Grain production utilizes a multiple of inputs, such as: water resources, fertilizers, pesticides, energy, machinery, and labor. In China, grain production has led to huge irrigation water use, non-point source pollution, and greenhouse gas emissions. It is necessary to emphasize the synergy between food production and ecological environment. In this study, a grain Food-Energy-Water nexus is delivered and an eco-efficiency sustainability evaluation metric is introduced, Sustainability of Grain Inputs (SGI), for investigating the sustainability of water and energy use in grain production across China. SGI is constructed by using generalized data envelopment analysis to comprehensively incorporate differences of water and energy inputs (including indirect energy use contained in agricultural chemicals such as fertilizers, pesticides, agricultural film, and direct energy use such as the electricity and diesel used for irrigation and agricultural machinery) in different regions across China. Both water and energy are considered by the new metric at the same time, which is built on the single resources metrices that are often used in the sustainability literature. This study evaluates the water and energy use of wheat and corn production in China. Wheat production uses water and energy sustainably in Sichuan, Shandong, and Henan; Corn production has the highest combined sustainability index in Shandong, Jilin, Liaoning, and Henan. In these areas, the grain sown area could be increased. However, wheat production in Inner Mongolia and corn production in Xinjiang rely on unsustainable water and energy inputs, and their grain sown areas could be reduced. The SGI is a tool that researchers and policy makers can use to better quantify the sustainability of water and energy inputs to grain production. It facilitates formulating policies about water saving and carbon emission reduce of grain production.

Pseudomonas fragi biofilm on stainless steel (at low temperatures) affects the survival of Campylobacter jejuni and Listeria monocytogenes and their control by a polymer molybdenum oxide nanocomposite coating

Pseudomonas spp. are widely distributed bacteria on surfaces in the food production and processing environment, where they form extracellular polymeric substance rich biofilms that interact with other bacteria. In this study, the influence of biofilm of Pseudomonas fragi ATCC 4973 on Listeria monocytogenes ATCC 19115 and Campylobacter jejuni NCTC 11168 was investigated at 5 °C and 15 °C on stainless steel in broth and food homogenates (fish or chicken meat). Stainless steel was then coated with PVDF-HFP/PVP/MoO3 nanocomposite and examined for surface changes (scanning electron microscope, static contact angle, Vickers hardness and elastic modulus). The effect of the prepared nanocomposite coating on P. fragi and on L. monocytogenes and C. jejuni was evaluated in mono- and co-culture. P. fragi produced more biofilm at 15 °C than at 5 °C, especially when food homogenates were used as growth media. Co-cultivation with pathogens did not affect biofilm production by P. fragi, but significant changes were observed in L. monocytogenes and C. jejuni, resulting in a decrease and increase, respectively, in the determined number of culturable biofilm cells. The first change was probably due to competition for the surface, and the second to the oxygen gradient. Stainless steel was then coated with a PVDF-HFP/PVP/MoO3 nanocomposite, which was characterised by lower roughness and higher wettability, but lower hardness compared to uncoated stainless steel. The prepared nanocoating showed bactericidal activity when tested in phosphate buffered saline. When used in food homogenates, a reduction of over 95 % in bacterial counts was observed. An abundant biofilm of P. fragi proved protective to L. monocytogenes and C. jejuni against the functionalised nanocomposite surface when tested in food homogenates. The control of spoilage Pseudomonas spp., which are common in the food production and processing environment, is important for reducing the contamination of food with spoilage bacteria and with pathogens such as L. monocytogenes and C. jejuni, which may be present in the same environment. The PVDF-HFP/PVP/MoO3 nanocomposite showed good potential for use as a coating for food contact surfaces, but possible migration of nanoparticles from the nanocomposite coating to food should be evaluated before its commercial use.

Presence and Persistence of Listeria monocytogenes in the Danish Ready-to-Eat Food Production Environment

Listeria monocytogenes is an ubiquitously occurring foodborne bacterial pathogen known to contaminate foods during the production processes. To assess the presence and persistence of L. monocytogenes in Danish ready-to-eat (RTE) food production companies in response to a Listeria awareness campaign, the production environment of selected companies were sampled in 2016 and in 2020. Whole genome sequencing (WGS) was performed to characterize the isolates (n = 50, plus 35 isolates obtained from the routine surveillance during 2016–2020), including investigation of the presence of virulence, persistence and resistance genes. The number of companies that tested positive by culture was 17/39 (43.6%) in 2016 and 11/34 (32.4%) in 2020, indicating a limited effect of the campaign. WGS analyses of the 85 isolates showed that the most common sequence types (STs) were ST8 and ST121. The single nucleotide polymorphism (SNP) analysis showed that isolates coming from the same company and belonging to the same ST exhibited <10 SNP differences regardless of the sampling year and whether the samples came from the environment or products, indicating the persistence of the specific STs. Several prevalent STs were found in clinical cases concurrently, including genetically similar isolates. This highlights the issue of persistent L. monocytogenes in the food production environment and the need for improved risk communication and mitigation strategies.

Variability in growth and biofilm formation of Listeria monocytogenes in Agaricus bisporus mushroom products

Foods and food production environments can be contaminated with Listeria monocytogenes and may support growth of this foodborne pathogen. This study aims to characterize the growth and biofilm formation of sixteen L. monocytogenes strains, isolated from mushroom production and processing environments, in filter-sterilized mushroom medium. Strain performance was compared to twelve L. monocytogenes strains isolated from other sources including food and human isolates. All twenty-eight L. monocytogenes strains showed rather similar growth performance at 20 °C in mushroom medium, and also significant biofilm formation was observed for all strains. HPLC analysis revealed the presence of mannitol, trehalose, glucose, fructose and glycerol, that were all metabolized by L. monocytogenes, except mannitol, in line with the inability of L. monocytogenes to metabolize this carbohydrate. Additionally, the growing behavior of L. monocytogenes was tested on whole, sliced and smashed mushroom products to quantify performance in the presence of product-associated microbiota. A significant increase of L. monocytogenes was observed with higher increase of counts when the mushroom products were more damaged, even with the presence of high background microbiota counts. This study demonstrated that L. monocytogenes grows well in mushroom products, even when the background microbiota is high, highlighting the importance to control (re)contamination of mushrooms.

Infant food production environments: A potential reservoir for vancomycin-resistant enterococci non-nosocomial infections

Enterococcus has been considered one of the most important nosocomial pathogens for human infections, and the hospital environment is an important reservoir for vancomycin-resistant enterococci (VRE) that leads to antimicrobial therapeutic failure. However, infant foods and their production environments could pose risks for the immature population, while this question remains unaddressed. This study conducted an extensive and thorough Enterococcus isolation, VRE risk assessment of the Chinese infant food production chains and additional online-marketing infant foods, including powdered infant formula (PIF) and infant complementary food (ICF). To investigate the prevalence of Enterococcus along infant food chains and commodities, a total of 482 strains of Enterococcus, including E. faecium (n = 363), E. faecalis (n = 84), E. casseliflavus (n = 13), E. mundtii (n = 12), E. gallinarum (n = 4), E. hirae (n = 4), and E. durans (n = 2) were recovered from 459 samples collected from infant food production chains (71/254) and food commodities (67/205). A decreasing trend for Enterococcus detection rate was found in the PIF production chain (PIF-PC), particularly during the preparation of the PIF base powder (From 100 % in raw milk to 8.70 % in end products), while an increasing trend was observed in the ICF production chain (ICF-PC) mainly during the initial processing of farm crops and the further processing of the product (20 % at farm crops increasing to 76.92 % at end products). The result indicated that the PIF-PC process effectively reduced Enterococcus contamination, while the ICF-PC showed the opposite trend. Importantly, eleven VRE isolates were recovered from the infant food production chain, including seven E. casseliflavus isolates carrying vanC2/C3 and four E. gallinarum isolates carrying vanC1. Ten VRE isolates were from food production environments. Collectively, our study demonstrated that infant food production environments represent potential reservoirs for VRE non-nosocomial infections in vulnerable populations.

Identification of microbial airborne contamination routes in a food production environment and development of a tailored protection concept using computational fluid dynamics (CFD) simulation

Airborne microbial re-contaminations are among the most frequent causes of food spoilage, contributing to food waste and economic losses. Cleanrooms can help to avoid bioaerosol re-contaminations, but are not suitable for open food processing environments. The present study assessed airborne microbial levels and their contamination routes within bakery production. Current airborne mold and total viable counts (TVCs) were evaluated over 8 months, indicating mold and TVCs ranging from 20 to 960 CFU/m 3 and from 20 to 1600 CFU/m 3 , respectively. The relative contamination level of each source point towards the cooling zone was virtually reproduced. The overall aim of this study was to develop a tailored cost-effective and easy-to-apply partial protection strategy, based on filter fan units (FFUs). The FFU concept with an air velocity of 0.3 m/s resulted in a significant reduction of the relative contamination (99.94%). Hence, this study suggests an alternative FFU-based control strategy for airborne contaminations within open food processing areas. • Evaluation of microbial counts in a bakery production facility. • Investigation of airborne microbial transmission routes through numerical simulation. • Identification of (bio)aerosol carryover by passive scalar transport functions with computational fluid dynamics. • Reduction of airborne contamination (≤99.94%) by targeted filter fan unit protection strategy.

Norovirus attribution study: Detection of norovirus from the commercial food preparation environment in outbreak and non-outbreak premises.

Norovirus remains the most significant virological risk that is transmitted via food and the environment to cause acute gastroenteritis. This study aimed to investigate the hypothesis that the contamination of the commercial food production environment with norovirus will be higher in premises that have recently reported a foodborne norovirus outbreak than those that have not. Sampling of commercial food production environments was carried out across a 16-month period between January 2015 and April 2016 in the South East and the North West of England by local authority environmental health departments as part of routine surveillance visits to premises. A total of 2982 samples, 2038 virological and 944 bacteriological, were collected from 256 premises. Sixteen of these premises, six from South East and ten from North West England, were sampled as part of a public health outbreak investigation. Overall, 2038 swabs were submitted for norovirus testing, with an average of eight swabs per premises (range 4 to 23) and a median of seven. Of the premises sampled, 11.7% (30/256) yielded at least one norovirus-positive sample (environmental, and/or food handler hand swab), and 2.5% of the swabs were positive for norovirus. A peak in the positivity rate was seen in the South East in April 2016. No associations were found between norovirus positivity and bacteriology indicators, or between bacteriology indicators and hygiene ratings. This study demonstrates that food premises and food handlers remain a potential source of norovirus transmission and outbreaks.

Antimicrobial and antibiofilm activity of silver nanoparticles against Salmonella Enteritidis.

Salmonella enterica serotype Enteritidis is one of the main pathogens associated with foodborne illnesses worldwide. Biofilm formation plays a significant role in the persistence of pathogens in food production environments. Owing to an increase in antimicrobial resistance, there is a growing need to identify alternative methods to control pathogenic microorganisms in poultry environments. Thus, this study aimed to synthesize silver nanoparticles (AgNPs) and evaluate their antibiofilm activity against poultry-origin Salmonella Enteritidis in comparison to a chemical disinfectant. AgNPs were synthesized, characterized, and tested for their minimum inhibitory concentration, minimum bactericidal concentration, and antibiofilm activity against S. Enteritidis strains on polyethylene surfaces. The synthesized AgNPs, dispersed in a liquid medium, were spherical in shape with a mean diameter of 6.2nm. AgNPs exhibited concentration-dependent bactericidal action. The bacterial reduction was significantly higher with AgNPs (3.91 log10 CFU [Formula: see text] cm-2) than that with sanitizer (2.57 log10 CFU∙cm-2). Regarding the time of contact, the bacterial count after a contact time of 30min was significantly lower than that after 10min. The AgNPs exhibited antimicrobial and antibiofilm activity for the removal of biofilms produced by S. Enteritidis, demonstrating its potential as an alternative antimicrobial agent. The bactericidal mechanisms of AgNPs are complex; hence, the risk of bacterial resistance is minimal, making nanoparticles a potential alternative for microbial control in the poultry chain.

Near-infrared spectroscopy and machine learning for classification of food powders during a continuous process

In food production environments, the wrong powder material is occasionally loaded onto a production line which impacts food safety, product quality, and production economics. The aim of this study was to assess the potential of using Near Infrared (NIR) spectroscopy combined with Machine Learning to classify food powders under motion conditions. Two NIR sensors with different wavelength ranges were compared and the ML models were tasked with classifying between 25 food powder materials. Eleven different spectra pre-processing methods, three feature selection methods, and five algorithms were investigated to find the optimal ML pipeline. It was found that pre-processing the spectra using autoencoders followed by using support vector machines with the all spectral wavelengths from both sensors was most accurate. The results were improved further using under-sampling and boosting. Overall, this method achieved 99.52, 97.12, 94.08, and 91.68% accuracy for the static, 0.017, 0.036 and 0.068 m s-1 sample speeds. The models were also validated using an independent test sets.

Barriers to the implementation, uptake and scaling up of the healthy plate model among regular street food consumers: a qualitative inquiry in Dar-es-Salaam city, Tanzania

IntroductionThe healthy plate model is considered one of the practical approaches to reduce the average portion of staple food in main meals, consequently reducing the risks associated with diabetes and other Non-communicable Diseases (NCDs). Despite its potential benefits, studies on the implementation of the healthy plate model are limited in Africa. An inquiry explored barriers to implementation, uptake, and scaling up of the healthy plate model among street food vendors and consumers in three districts of Dar-es-Salaam city in Tanzania.MethodsA qualitative research design was adopted. Qualitative data collection techniques were employed including; Key Informant Interviews (KIIs) with purposefully selected food and nutrition stakeholders at the National, Regional, District and Ward levels. Focus Group Discussions (FGDs) were conducted with purposefully selected street food consumers and vendors. A total of (13) KIIs were conducted as well as (6) FGDs with street food vendors (2 FGDs) and consumers (4 FGDs). Interview data was managed using Nvivo 12 Software and analyzed thematically.ResultsThree key themes emerged from participants’ accounts: (i) strategic policy barriers, (ii) food production and preparation environment barriers (producers and vendors), and (iii) individual barriers (consumers and vendors). The strategic policy barriers included absence of guidelines and regulations that focus on NCDs linked to nutrition and lack of education guidance for vendors and consumers. The food production and preparation environment barriers included safety and risks concerns regarding the quality of water used for irrigation and washing fruits and vegetables and the areas where vegetables and fruits are grown and prepared. Individual barriers included low consumer income, knowledge on nutrition, unhealthy eating practices and; low vendors’ knowledge as well as low investment capital.ConclusionImplementation, uptake and scaling up of the healthy plate model for street food consumers in Dar es Salaam City continues to be constrained by barriers in policy, food production and preparation environment, and individual obstacles. Strengthening of food and nutrition policies, ensuring safety of the food production and preparation environment and, consumer and vendor awareness creation and income generation efforts, provide useful entry points for the successful scaling up of a healthy plate model. This could consequently contribute towards prevention of diet related NCDs, including diabetes.

Antimicrobial Resistance in Aquaculture Environments: Unravelling the Complexity and Connectivity of the Underlying Societal Drivers.

Food production environments in low- and middle-income countries (LMICs) are recognized as posing significant and increasing risks to antimicrobial resistance (AMR), one of the greatest threats to global public health and food security systems. In order to maximize and expedite action in mitigating AMR, the World Bank and AMR Global Leaders Group have recommended that AMR is integrated into wider sustainable development strategies. Thus, there is an urgent need for tools to support decision makers in unravelling the complex social and environmental factors driving AMR in LMIC food-producing environments and in demonstrating meaningful connectivity with other sustainable development issues. Here, we applied the Driver-Pressure-State-Impact-Response (DPSIR) conceptual framework to an aquaculture case study site in rural Bangladesh, through the analysis of distinct social, microbiological, and metagenomic data sets. We show how the DPSIR framework supports the integration of these diverse data sets, first to systematically characterize the complex network of societal drivers of AMR in these environments and second to delineate the connectivity between AMR and wider sustainable development issues. Our study illustrates the complexity and challenges of addressing AMR in rural aquaculture environments and supports efforts to implement global policy aimed at mitigating AMR in aquaculture and other rural LMIC food-producing environments.

Transient and resident pathogens: Intra-facility genetic diversity of Listeria monocytogenes and Salmonella from food production environments

Food production facilities are often routinely tested over time for the presence of foodborne pathogens (e.g., Listeria monocytogenes or Salmonella enterica subsp. enterica). Strains detected in a single sampling event can be classified as transient; positive findings of the same strain across multiple sampling events can be classified as resident pathogens. We analyzed whole-genome sequence (WGS) data from 4,758 isolates (L. monocytogenes = 3,685; Salmonella = 1,073) from environmental samples taken by FDA from 536 U.S. facilities. Our primary objective was to determine the frequency of transient or resident pathogens within food production facilities. Strains were defined as isolates from the same facility that are less than 50 SNP (single-nucleotide polymorphisms) different from one another. Resident pathogens were defined as strains that had more than one isolate collected >59 days apart and from the same facility. We found 1,076 strains (median = 1 and maximum = 21 strains per facility); 180 were resident pathogens, 659 were transient, and 237 came from facilities that had only been sampled once. As a result, 21% of strains (180/ 839) from facilities with positive findings and that were sampled multiple times were found to be resident pathogens; nearly 1 in 4 (23%) of L. monocytogenes strains were found to be resident pathogens compared to 1 in 6 (16%) of Salmonella strains. Our results emphasize the critical importance of preventing the colonization of food production environments by foodborne pathogens, since when colonization does occur, there is an appreciable chance it will become a resident pathogen that presents an ongoing potential to contaminate product.

Co-culture with Acinetobacter johnsonii enhances benzalkonium chloride resistance in Salmonella enterica via triggering lipid A modifications

Salmonella enterica is one of the leading causes of foodborne gastroenteritis worldwide. In the food production environment, many bacterial species co-exist on surfaces in biofilm structures, which can act as reservoirs of microbial contamination of food products. Polymicrobial biofilms have been shown to have greater tolerance to antimicrobials, such as disinfectants, however the mechanistic basis of this is poorly understood. In this study, S. enterica subsp. enterica serovar Liverpool was co-cultured in mixed-species biofilms with bacteria isolated from the food production environment and challenged with the cationic biocide disinfectant, benzalkonium chloride (BC). Co-culture with the common environmental bacterium Acinetobacter johnsonii resulted in >200-fold higher resistance of S. Liverpool to BC, compared to mono-culture biofilms. The transcriptional response of S. enterica to biofilm co-culture was determined using a dual RNA-seq strategy. Genes controlled by the PhoPQ and PmrAB two-component systems, involved in lipid A modification and associated with cationic antimicrobial peptide resistance (CAMP) of S. Liverpool, were significantly upregulated. Deletion of either the phoP or pmrA genes resulted in an increase in susceptibility to BC, suggesting that activation of their regulons during co-culture enhances BC resistance. S. Liverpool lipid A profiles changed significantly upon co-culturing, with greater incorporation of both phosphoethanolamine and palmitate, which was dependent upon activation of PhoPQ and PmrAB. We conclude that when grown in the presence of A. johnsonii, S. Liverpool increases its tolerance to cationic BC disinfection by remodelling its cell envelope including reducing the net negative charge of lipid A and increasing lipid A acyl density.

Virulence Characteristics and Distribution of the Pathogen Listeria ivanovii in the Environment and in Food

Listeria ivanovii and L. monocytogenes, are the only pathogenic species of the genus Listeria and share many virulence factors and mechanisms of pathogenicity. L. ivanovii shows host tropism towards small ruminants and rodents and much lower virulence for humans compared to L. monocytogenes. However, severe infections caused by L. ivanovii, resulting in bacteremia, abortion and stillbirth, occasionally occurred in immunocompromised persons and in pregnant women, while in immunocompetent hosts L. ivanovii can cause gastroenteritis. In this review, the updated knowledge on virulence aspects and distribution of L. ivanovii in the environment and in food is summarized. Recent research on its virulence characters at genome level gave indications on how pathogenicity evolved in this bacterial species. As for L. monocytogenes, L. ivanovii infections occurred after the ingestion of contaminated food, so an overview of reports regarding its distribution in food products was carried out to obtain indications on the categories of foods exposed to contamination by L. ivanovii. It was found that a wide variety of food products can be a source of this microorganism and that, like L. monocytogenes, L. ivanovii is able to persist in the food production environment. Studies on its ability to grow in enrichment and isolation media suggested that its occurrence in nature might be underestimated. Moreover, virulence varies among strains for differences in virulence character regulation, presence/absence of genetic regions and the possible instability of a Listeria pathogenicity genomic island, LIPI-2, which is unique to L. ivanovii. We can conclude that L. ivanovii, as a possible pathogen for animals and humans, requires more focused investigations regarding its occurrence in the environment and in food and on intra-species variability of pathogenic potential.

Genomic characterization of polyextremotolerant black yeasts isolated from food and food production environments.

Black yeasts have been isolated from acidic, low water activity, and thermally processed foods as well as from surfaces in food manufacturing plants. The genomic basis for their relative tolerance to food-relevant environmental stresses has not been well defined. In this study, we performed whole genome sequencing (WGS) on seven black yeast strains including Aureobasidium (n=5) and Exophiala (n=2) which were isolated from food or food production environments. These strains were previously characterized for their tolerance to heat, hyperosmotic pressure, high pressure processing, hypochlorite sanitizers, and ultraviolet light. Based on the WGS data, three of the strains previously identified as A. pullulans were reassigned as A. melanogenum. Both haploid and diploid A. melanogenum strains were identified in this collection. Single-locus phylogenies based on beta tubulin, RNA polymerase II, or translation elongation factor protein sequences were compared to the phylogeny produced through SNP analysis, revealing that duplication of the fungal genome in diploid strains complicates the use of single-locus phylogenetics. There was not a strong association between phylogeny and either environmental source or stress tolerance phenotype, nor were trends in the copy numbers of stress-related genes associated with extremotolerance within this collection. While there were obvious differences between the genera, the heterogenous distribution of stress tolerance phenotypes and genotypes suggests that food-relevant black yeasts may be ubiquitous rather than specialists associated with particular ecological niches. However, further evaluation of additional strains and the potential impact of gene sequence modification is necessary to confirm these findings.

Genomic analysis of Listeria monocytogenes from US food processing environments reveals a high prevalence of QAC efflux genes but limited evidence of their contribution to environmental persistence

BackgroundQuaternary ammonium compound (QAC) efflux genes increase the minimum inhibitory concentration of Listeria monocytogenes (Lm) to benzalkonium chloride sanitizer, but the contribution of these genes to persistence in food processing environments is unclear. The goal of this study was to leverage genomic data and associated metadata for 4969 Lm isolates collected between 1999 and 2019 to: (1) evaluate the prevalence of QAC efflux genes among Lm isolates from diverse US food processors, (2) use comparative genomic analyses to assess confounding factors, such as clonal complex identity and stress tolerance genotypes, and (3) identify patterns in QAC efflux gene gain and loss among persistent clones within specific facilities over time.ResultsThe QAC efflux gene cassette bcrABC was present in nearly half (46%) of all isolates. QAC efflux gene prevalence among isolates was associated with clonal complex (\U0001d6d82 < 0.001) and clonal complex was associated with the facility type (\U0001d6d82 < 0.001). Consequently, changes in the prevalence of QAC efflux genes within individual facilities were generally attributable to changes in the prevalence of specific clonal complexes. Additionally, a GWAS and targeted BLAST search revealed that clonal complexes with a high prevalence of QAC efflux genes commonly possessed other stress tolerance genes. For example, a high prevalence of bcrABC in a clonal complex was significantly associated with the presence of the SSI-1 gene cluster (p < 0.05). QAC efflux gene gain and loss were both observed among persistent populations of Lm in individual facilities, suggesting a limited direct role for QAC efflux genes as predictors of persistence.ConclusionThis study suggests that although there is evidence that QAC efflux genes are part of a suite of adaptations common among Lm isolated from some food production environments, these genes may be neither sufficient nor necessary to enhance persistence. This is a crucial distinction for decision making in the food industry. For example, changes to sanitizer regimen targeting QAC tolerance would not address other contributing genetic or non-genetic factors, such as equipment hygienic design which physically mediates sanitizer exposure.