Incidence of enterohemorrhagic Escherichia coli, Escherichia coli O157, Salmonella, and Listeria monocytogenes in retail fresh ground beef, sprouts, and mushrooms

Escherichia coli O157:H7, a Common Contaminant of Raw Milk from Ecuador: Isolation and Molecular Identification

Escherichia coli (E. coli), especially the Shiga toxin-producing O157:H7 strain, poses severe health risks. In rural Ecuador, raw milk consumption heightens contamination risks. This study analyzed 633 raw milk samples from Pichincha and Manabí to assess E. coli O157:H7 prevalence. The samples were enriched using BHI broth, and then specific culture media were used to isolate E. coli O157:H7. The pathogen in the enriched raw milk was identified, and the isolates were specifically confirmed through the application of a newly designed qPCR assay. The novel qPCR assay demonstrated remarkable sensitivity, capable of detecting up to one copy of genetic material, and specificity (no amplification of other bacteria). An extremely high E. coli O157:H7 prevalence of 0.63 (n = 401) was detected, where the province with the highest number of positive samples was Manabí with 72.8% (n = 225/309) and 54.3% (n = 179/324) for Pichincha. In both provinces, the presence of E. coli O157:H7 contamination exhibited a favorable correlation with small-scale farms and elevated temperatures. This research provides valuable data on the microbiological contamination of E. coli O157:H7 present in raw milk, in addition to an improved method that has been demonstrated to be faster, more sensitive, and more specific than conventional and previously published methods, highlighting the associated risk of food-borne infections and pointing out potential shortcomings in the regulation of agricultural practices and the need for periodic monitoring of bacterial contamination levels with updated methods.

Microbiological Assessment of White Button Mushrooms with an Edible Film Coating

The development of edible coatings incorporating bioextracts from mushrooms native to Portuguese forests aims to enhance the value of the endogenous forest and mycological resources by harnessing their potential as a source of antimicrobial and antioxidant compounds. Edible coatings represent an important pathway to decreasing food waste and contributing to implementing a circular bioeconomy. The coating should result in product valorization through improved preservation/conservation, increased shelf life, as well as enhancement of its antioxidant and enzymatic properties. To evaluate the effectiveness of an edible coating on fungal food matrices, a 14-day shelf-life study was conducted, wherein both coated and untreated mushrooms were examined under controlled storage temperatures of 4 °C and 9.3 °C. Agaricus bisporus was chosen as the food matrix for its bioeconomy significance, and Pleurotus eryngii was selected for the preparation of the food-based coating due to its profile of bioactive compounds. Microbiological analysis and physicochemical monitoring were conducted on the food matrices and the coating. Coated mushrooms had less mass loss and color change, and had better texture after 14 days. Microbiological analysis revealed that the coating had no antimicrobial activity. Overall, the coating improved the shelf life of the coated mushrooms but had less effect on the microbial community.

Bacterial microbiota profiling of oyster mushrooms (Pleurotus ostreatus) based on cultivation methods and distribution channels using high-throughput sequencing

The annual consumption and production of oyster mushrooms (Pleurotus ostreatus) have continued to rise due to its nutritive and health-promoting benefits. Cultivated mushrooms are mostly grown in small to medium-scaled scale production plants that present hygienic challenges which could, in turn, increase associated foodborne pathogenic outbreaks. The present study aimed to investigate the shift in microbial ecologies of oyster mushrooms from pre-distribution (cultivation in bottles or on shelves) to post-distribution at supermarkets and open-air markets. Aerobic plate counts and coliforms were quantified using traditional microbiological techniques, and the microbiome associated with oyster mushrooms (n = 70) was analyzed using 16S rRNA amplicon sequencing for an enhanced level of bacterial microbiota profiling. Overall, coliforms recovered from pre-distribution bottle-cultivated mushrooms were 1.9 log CFU/g higher (p < 0.05) than that of shelf-cultivated mushrooms. The mean aerobic plate counts of oyster mushrooms distributed to open-air markets was 1.2 log CFU/g higher (p < 0.05) than packaged mushrooms from supermarkets while there were no significant differences in coliform counts. The pattern of bacterial composition differed by post-distribution channels, with oyster mushrooms collected from the open-air markets demonstrating the richest microbiome diversity. An increase in the relative abundance of Enterobacteriaceae (55-68 %) and Pseudomonadaceae (27-35 %) was observed in pre- and post-distribution mushrooms, respectively. However, no distinct bacterial microbiota differences were observed for the different cultivation methods or different geographical locations for each market type. The current findings add to our understanding of the effects of cultivation methods and commercial distribution channels regarding the microbiome of oyster mushrooms and may inform potential intervention strategies for future production and distribution processes. Furthermore, the tandem analyses of culture-dependent and culture-independent methods can provide more comprehensive information than that obtained when using each approach independently.

Presence and Virulence Characteristics of Shiga Toxin Escherichia coli and Non-Shiga Toxin-Producing Escherichia coli O157 in Products from Animal Protein Supply Chain Enterprises in South Africa

Consumption of food that is contaminated with Shiga toxin-producing Escherichia coli (STEC) has been linked to serious foodborne disease outbreaks. Our aim was to provide a descriptive study on the presence and virulence factors of STEC and non-STEC O157 isolates recovered from 2017 diverse meat and meat product samples from all provinces of South Africa (n = 1758) and imported meat from South Africa's major ports of entry (n = 259). A cross-sectional study was undertaken to analyze raw intact meat, raw processed (nonintact) meat, and ready-to-eat (RTE) meat from cattle, game, sheep, pork, and poultry. Isolation was performed using International Organization for Standardization-based microbiological techniques, while detection and characterization were performed using real-time PCR (RT-PCR) and conventional PCR targeting the stx1, stx2, eae, and ehxA genes. A total of 28 of 1758 (1.59%; confidence interval [CI] 1.1-2) samples from the domestic market tested positive (n = 10 Escherichia coli O157:H7; n = 14 Escherichia coli O157: non-H7; and n = 4 non-O157 STEC), while 4/259 (1.54%; CI 0.4-4) samples from ports of entry tested positive for Escherichia coli O157:H7 based on RT-PCR. On average, diverse samples from domestic meat and meat products from cattle showed the highest number of positive samples (22/1758; 1.3%; CI 0.8-2). RT-PCR detected more positive samples (n = 32) compared with culture (n = 17). Sixteen different virulence factor combinations were observed. Our findings demonstrate a relatively low presence of diverse STEC strains along the meat value chain. To our knowledge, this is the first extensive report in South Africa to analyze STEC and non-STEC O157 from local and imported samples from many animal species. This is important as it reveals virulence factors in STEC strains circulating in meat and meat products in South Africa, which contribute to the risk of infection.

The pathogenic and spoilage bacteria associated with red meat and application of different approaches of high CO2 packaging to extend product shelf-life

With the fast-global development of packaging techniques, the potential antimicrobial effect of CO₂, as a safe, cheap and readily available gas, makes it the integral component for packaging of meat products. The associated spoilage and/or pathogenic bacteria on raw meat may respond in different ways to elevated CO₂ concentrations. The growth of some aerobic Gram-negative bacteria such as Pseudomonas spp. is significantly inhibited but some LAB bacteria may be allowed to grow faster and dominate the product. The antimicrobial efficacy of enriched CO₂ packaging is attributed to the rate of CO₂ solubility in the product which is itself affected by the level of headspace CO₂, product pH, temperature and the ratio of headspace gas to product (G:P). This review, first, explores the varied range of beef and sheep meat spoilage and pathogenic bacteria and the intrinsic and extrinsic parameters that may influence the pattern of microbial growth and meat spoilage rate during storage. Then, the antimicrobial mechanism of elevated CO₂ packaging will be discussed and the different approaches of achieving enriched CO₂ packaging i.e. the traditional technique of flushing a desired gas mixture and/or using the new commercially developed CO₂ emitters will then be compared in terms of their strengths, limitations and technical mode of action.

A Systematic Review of Listeria Species and Listeria monocytogenes Prevalence, Persistence, and Diversity throughout the Fresh Produce Supply Chain

Listeria monocytogenes is an increasing food safety concern throughout the produce supply chain as it has been linked to produce associated outbreaks and recalls. To our knowledge, this is the first systematic literature review to investigate Listeria species and L. monocytogenes prevalence, persistence, and diversity at each stage along the supply chain. This review identified 64 articles of 4863 candidate articles obtained from four Boolean search queries in six databases. Included studies examined naturally detected/isolated Listeria species and L. monocytogenes in fresh produce-related environments, and/or from past fresh produce associated outbreaks or from produce directly. Listeria species and L. monocytogenes were detected in each stage of the fresh produce supply chain. The greatest prevalence of Listeria species was observed in natural environments and outdoor production, with prevalence generally decreasing with each progression of the supply chain (e.g., packinghouse to distribution to retail). L. monocytogenes prevalence ranged from 61.1% to not detected (0.00%) across the entire supply chain for included studies. Listeria persistence and diversity were also investigated more in natural, production, and processing environments, compared to other supply chain environments (e.g., retail). Data gaps were identified for future produce safety research, for example, in the transportation and distribution center environment.

Microbiological Safety and Sensory Quality of Cultivated Mushrooms (Pleurotus eryngii, Pleurotus ostreatus and Lentinula edodes) at Retail Level and Post-Retail Storage

In this study, the microbiological and sensory quality of cultivated mushrooms (Pleurotus ostreatus and eryngii and Lentinula edodes) available at the Austrian retail level were determined. Aerobic mesophilic bacteria (AMC), Enterobacteriaceae (EB), Pseudomonadaceae (PS), lactic acid bacteria (LAB), yeast, moulds and presumptive Bacillus cereus were enumerated at the day of purchase and after storage at 4 °C for 7 or 12 days. Additionally, the presence of Salmonella spp. and Listeria monocytogenes was investigated. Isolates of presumptive spoilage bacteria were confirmed by partial 16S rRNA sequencing. At the day of purchase, 71.2% of the samples were of high microbiological quality and grouped into the low contamination category (AMC < 5.0 log cfu/g), while the sensory quality of 67.1% was categorized as “very good or good”. After storage, the number of samples with high microbial quality was 46.6%, and only 37.0% of the samples scored as “very good or good”. The most abundant species across all mushroom samples were the Pseudomonas fluorescens species complex (58.4%) and the potential mushroom pathogen Ewingella americana (28.3%). All mushroom samples tested negative for Salmonella spp., L. monocytogenes and Bacillus cereus. The microbiological and sensory quality of the analysed mushrooms at the day of purchase and after storage was considered to be good overall. Longer transport distances were found to have a significant influence on the microbiological and sensory quality.

Microbial ecology of alfalfa, radish, and rapeseed sprouts based on culture methods and 16S rRNA microbiome sequencing

Sprouts harbor high populations of bacteria and cause numerous foodborne disease outbreaks, yet little is known about their microbial composition. The present study aimed to define the microbiological ecology of sprouts using 16S rRNA microbiome sequencing and culture-dependent methods. Different types (radish, alfalfa, and rapeseed), brands (A, B, and C), and distribution routes (online and offline) of sprouts (n = 70) were considered for microbiome analysis, as well as quantitative (aerobic plate count and coliforms) and qualitative analyses (Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium). The aerobic plate count ranged from 7 to 8 CFU/g, and the coliforms ranged from 6 to 7 log CFU/g. Microbiome analysis revealed that Proteobacteria was the dominant phylum, accounting for 79.0% in alfalfa sprouts, 68.5% in rapeseed sprouts, and 61.9% in radish sprouts. Enterobacteriaceae was the dominant family in alfalfa sprouts (33.9%) and rapeseed sprouts (14.6%), while Moraxellaceae (11.9%) were prevalent on radish sprouts. The majority of the dominant genera were common in the environment, such as soil or water. Alfalfa sprouts yielded the lowest aerobic plate count but the highest relative abundance of Enterobacteriaceae compared to the other sprouts. These results could explain why alfalfa sprouts are a leading cause of sprout-related foodborne disease outbreaks. Alpha-diversity results (Chao1 and Shannon indices) suggested that species richness was greater on radish sprouts than the other sprout types. Beta-diversity results showed samples were clustered by types, indicating dissimilarity in microbial communities. However, the distribution route had a limited influence on microbial composition. The present study provides a comparative examination of the microbial profiles of sprouts. Microbiome analyses contribute to an in-depth understanding of the microbial ecology of sprouts, leading to potential control measures for ensuring food safety.

Identification of the gamma irradiation dose applied to ground beef that reduces Shiga toxin producing Escherichia coli but has no impact on consumer acceptance

The aims of the present study were: a) to estimate the minimal dose of gamma irradiation required to reduce 5 log CFU/g of native O157 and non-O157 Shiga toxin-producing Escherichia coli population in ground beef samples inoculated with high inoculum; b) to assess its effectiveness in samples with low inoculum and 3) to evaluate consumer acceptance. Based on the results, 1 kGy was estimated as the minimal dose of gamma irradiation required to reduce 5 log CFU/g of STEC in ground beef. However, when samples with low inoculum level were subjected to 1 kGy, 3.9% of the samples were positive for stx and eae genes after an enrichment step. Consumer acceptance analysis was carried out with samples subjected to 2.5 kGy and no significant differences were found between irradiated and control samples. Therefore, 2.5 kGy was identified as the gama irradiation dose that reduces STEC but has no impact on consumer acceptance of ground beef.

Microbiological safety of ready-to-eat fresh-cut fruits and vegetables sold on the Canadian retail market

Following implementation of Health Canada's Policy on Listeria monocytogenes in Ready-to-Eat Foods by Canadian food safety authorities in 2011, a four-year study (2012-2016) was carried out to gain baseline information on the occurrence of bacterial pathogens, notably the prevalence and levels of Listeria monocytogenes (L. monocytogenes) in various product types of ready-to-eat (RTE) fresh-cut fruits and fresh-cut vegetables sold at retail in Canada. A total of 10,070 pre-packaged samples, including 4691 fresh-cut fruit and 5379 fresh-cut vegetable samples were collected from retail stores across Canada and analyzed for bacterial pathogens and generic Escherichia coli (E. coli). Salmonella species (spp.), E. coli O157:H7, Shigella and Campylobacter were not detected in any of the tested samples. L. monocytogenes was identified in 0.51% (95% CI [0.34, 0.76]) of the fresh-cut fruit and in 0.24% (95% CI [0.14, 0.41]) of the fresh-cut vegetable samples. Of the 37 L. monocytogenes positive samples identified, levels of L. monocytogenes <5 CFU/g, 5-<100 CFU/g, and ≥100 CFU/g were found in 67.6% (25/37), 24.3% (9/37) and 8.1% (3/37) of the samples, respectively. The results of this study indicate that the vast majority of fresh-cut fruits and vegetables sold on the Canadian retail market are safe for consumption. However, contamination by L. monocytogenes can infrequently occur in fresh-cut fruits and vegetables, with certain types of fresh-cut fruits (i.e., melons, apples) and vegetables (i.e., mushrooms, cauliflower) being more likely to be contaminated than others. Safe handling practices are recommended for producers, retailers and consumers including storage at refrigerated temperatures.

Prevalence of Multidrug-Resistant Foodborne Pathogens and Indicator Bacteria from Edible Offal and Muscle Meats in Nashville, Tennessee

This study investigated the prevalence of antimicrobial-resistant bacteria in retail edible offal and muscle meats in Nashville, Tennessee. A total of 348 retail meats (160 edible offal and 188 muscle) were analyzed for Salmonella enterica serovar, Campylobacter, Escherichia coli, E. coli O157:H7, and enterococci. Bacteria was identified using biochemical and PCR methods. Salmonella enterica serovar (4.4% and 4.3%), Campylobacter (1.9% and 1.1%), E. coli (79.4% and 89.4%), and enterococci (88.1% and 95.7%) was detected in offal and muscle meats, respectively. Chicken liver (9.7%) was most frequently contaminated with Salmonella enterica serovar, followed by ground chicken (6.9%) and chicken wings (4.2%). No Salmonella enterica serovar was detected in beef liver, beef tripe, and ground beef. The prevalence of Campylobacter was 6.9%, 2.3%, and 1.4% in beef liver, ground beef, and ground chicken, respectively. None of the meats were positive for E. coli O157:H7. Resistance of isolates was significantly (p < 0.05) highest in erythromycin (98.3%; 99.1%), followed by tetracycline (94%; 98.3%), vancomycin (88.8%; 92.2%) as compared to chloramphenicol (43.1%; 53.9%), amoxicillin/clavulanic (43.5%; 45.7%), and ciprofloxacin (45.7%; 55.7%) in offal and muscle meats, respectively. Imipenem showed the lowest resistance (0%; 0.9%). A total of 41 multidrug-resistant patterns were displayed. Edible offal could be a source of antibiotic-resistant bacteria.

Identification and Characterization of Salmonella Serovars Isolated from Pig Farms in Benin City, Edo State, Nigeria: One Health Perspective

The present study was carried out to characterize Salmonella serovars from commercial pig farms in Benin City, Nigeria. A total of 81 samples were collected from the Agricultural Development Program farms between January and June 2017. Standard culture-based and polymerase chain reaction procedures were adopted in the isolation and identification of Salmonella serovars. Antibiotic susceptibility profiles of the isolates were conducted using the Kirby-Bauer disc diffusion method with prominent resistance determinants screened for using specific primer sets. The 84 identified Salmonella serovars include 15 Salmonella ser. Enteritidis, 11 Salmonella ser. Typhimurium, and 58 other Salmonella serovars. Phenotypic virulence factors include: hemolytic activity (51.7-100%), lipase activity (48.3-81.8%), protease activity (60.3-100%), gelatinase production (50-90.9%), DNA degrading activity (55.2-90.9%), and S-layer formation (63.8-100%). The biofilm formation profiles include nonbiofilm producers (0-12.1%), weak biofilm producers (0-20%), moderate biofilm producers (24.1-27.3%), and strong biofilm producers (48.3-72.7%). Salmonella serovars in this study harbored resistant determinants, such as tetA, tetC, ampC, sul1, sul2, sul3, floR, ermA, and ermC. The occurrence of resistance phenotype and determinants in pathogenic Salmonella serovars from pig farms is a significant public health concern, which could result in the dissemination of resistant elements within the environment.

Translocation of Orally Inoculated Salmonella Following Mild Immunosuppression in Holstein Calves and the Presence of the Salmonella in Ground Beef Samples

The objective of this study was to determine if immunosuppression through daily dexamethasone (DEX) infusion altered Salmonella translocation from the gastrointestinal tract. Weaned Holstein steers (n = 20; body weight [BW] = 102 ± 2.7 kg) received DEX (n = 10; 0.5 mg/kg BW) or saline (control [CON]; n = 10;) for 4 days (from day -1 to 2) before oral inoculation of naldixic acid-resistant Salmonella enterica Typhimurium (SAL; 3.4 × 10⁶ colony-forming units [CFU]/animal) on day 0. Fecal swabs were obtained daily, and blood was collected daily for hematology. At harvest (day 5), ileum, cecal fluid, lymph nodes (ileocecal, mandibular, popliteal, and subscapular), and synovial (stifle, coxofemoral, and shoulder) samples were collected for isolation of the inoculated strain of SAL. White blood cell (WBC) and neutrophil concentrations were elevated (p < 0.01) in DEX calves following each administration event. Following inoculation, 100% of DEX calves shed the experimental strain of SAL for all 5 days, 90% of CON calves shed from day 1 to 3, and 100% of CON calves shed from day 4 to 5. Greater (p < 0.01) concentrations of SAL were quantified from the cecum of DEX calves (3.86 ± 0.37 log CFU/g) compared with CON calves (1.37 ± 0.37 log CFU/g). There was no difference in SAL concentrations between DEX and CON calves in ileal tissue (p = 0.07) or ileocecal (p = 0.57), mandibular (p = 0.12), popliteal (p = 0.99), or subscapular (p = 0.83) lymph nodes. Of the stifle samples collected, 3.3% were positive for SAL, highlighting a contamination opportunity during hindquarter breakdown. While more research is needed to elucidate the interactions of immunosuppression and pathogen migration patterns, these data confirm that orally inoculated SAL can translocate from the gastrointestinal tract and be harbored in atypical locations representing a food safety risk.

Inactivation of Shiga Toxin-Producing Escherichia coli and Listeria monocytogenes within Plant versus Beef Burgers in Response to High Pressure Processing

ABSTRACT

We evaluated high pressure processing to lower levels of Shiga toxin-producing Escherichia coli (STEC) and Listeria monocytogenes inoculated into samples of plant or beef burgers. Multistrain cocktails of STEC and L. monocytogenes were separately inoculated (∼7.0 log CFU/g) into plant burgers or ground beef. Refrigerated (i.e., 4°C) or frozen (i.e., -20°C) samples (25 g each) were subsequently exposed to 350 MPa for up to 9 or 18 min or 600 MPa for up to 4.5 or 12 min. When refrigerated plant or beef burger samples were treated at 350 MPa for up to 9 min, levels of STEC were reduced by ca. 0.7 to 1.3 log CFU/g. However, when refrigerated plant or beef burger samples were treated at 350 MPa for up to 9 min, levels of L. monocytogenes remained relatively unchanged (ca. ≤0.3-log CFU/g decrease) in plant burger samples but were reduced by ca. 0.3 to 2.0 log CFU/g in ground beef. When refrigerated plant or beef burger samples were treated at 600 MPa for up to 4.5 min, levels of STEC and L. monocytogenes were reduced by ca. 0.7 to 4.1 and ca. 0.3 to 5.6 log CFU/g, respectively. Similarly, when frozen plant and beef burger samples were treated at 350 MPa up to 18 min, reductions of ca. 1.7 to 3.6 and ca. 0.6 to 3.6 log CFU/g in STEC and L. monocytogenes numbers, respectively, were observed. Exposure of frozen plant or beef burger samples to 600 MPa for up to 12 min resulted in reductions of ca. 2.4 to 4.4 and ca. 1.8 to 3.4 log CFU/g in levels of STEC and L. monocytogenes, respectively. Via empirical observation, pressurization did not adversely affect the color of plant burger samples, whereas appreciable changes in color were observed in pressurized ground beef. These data confirm that time and pressure levels already validated for control of STEC and L. monocytogenes in ground beef will likely be equally effective toward these same pathogens in plant burgers without causing untoward effects on product color.

HIGHLIGHTS

Shiga Toxin-Producing Escherichia coli Contamination of Raw Beef and Beef-Based Ready-to-Eat Products at Retail Outlets in Pretoria, South Africa

ABSTRACT

A cross-sectional study was conducted to determine the prevalence of and factors associated with Shiga toxin-producing Escherichia coli (STEC) in raw beef and ready-to-eat (RTE) beef products sold in 31 retail outlets in Pretoria, South Africa, and nearby areas. A total of 463 beef and RTE samples were screened for four STEC virulence genes (stx1, stx2, eaeA, and hlyA) and seven O-serogroups (O113, O157, O26, O91, O145, O111, and O103) with a multiplex PCR assay. The total aerobic plate count (TAPC) per gram was also determined. A total of 38 STEC isolates were recovered and characterized by conventional PCR assay and serotyping. The overall prevalence of STEC in the beef and RTE samples tested was 16.4% (76 of 463 samples; 95% confidence interval, 13 to 20%). The prevalence of STEC differed significantly by product type (P < 0.0001), with the highest prevalence (35%) detected in boerewors (spicy sausage). The STEC prevalences in minced beef, brisket, RTE cold beef, and biltong were 18, 13, 9, and 5%, respectively. The most frequently detected stx gene was stx2 (13%), and STEC serogroups from recovered isolates were detected at the following prevalences: O2, 15%; O8, 12%; O13, 15%; O20, 8%; O24, 3%; O39, 3%; O41, 8%; O71, 3%; O76, 3%; O150, 12%; and O174, 3%. A high proportion (77%) of the samples had TAPCs that exceeded the South African microbiological standards for meat export (5.0 log CFU/g). The prevalence of O157 STEC (16%) and the diversity of non-O157 STEC serogroups found in five common beef-based products from retail outlets in South Africa suggest exposure of raw beef and beef products to multiple contamination sources during carcass processing and/or cutting and handling at retail outlets. These data provide direct estimates of the potential health risk to consumers from undercooked contaminated products and indicate the need to improve sanitary practices during slaughter and processing of beef and beef-based RTE products. A risk-based surveillance system for STEC may be needed.

HIGHLIGHTS

Contamination Level of Hygiene Indicator and Prevalence of Foodborne Pathogens in Retail Beef in Parallel with Market Factor

In this study, the contamination levels of hygienic indicators and foodborne pathogens in retail meat products were investigated in relation to the various market factors including processing temperature, processing area, and market type. Ground beef samples (n=80) were purchased from 40 meat markets and investigated for microbiological quality. Beefs processed below 20℃ had significantly lower numbers of total coliforms (TC) than these processed over 20℃ (2.01 vs. 2.79 log CFU/g; p<0.05). Interestingly, separation of processing area did not affect the contamination levels. Remarkably, the contamination levels of hygienic indicator differ among market types, indicating that not only processing condition but distribution structure that is directly related with storage period could affect the final microbiological loads of the meat products. In addition, the prevalences of Listeria monocytogenes (a psychrotroph), Enterococcus faecium, and Enterococcus faecalis were 7.5% (6/80), 10.0% (8/80), and 20.0% (16/80), respectively, which is irrelevant to market factors except meat products from wholesale markets where no L. monocytogenes were found among 30 samples. The results of this study indicate that the contamination level of hygiene indicator and foodborne pathogens in retail beef is more related with processing temperature and storage period than other environmental factors.

Prevalence, Potential Virulence, and Genetic Diversity of Listeria monocytogenes Isolates From Edible Mushrooms in Chinese Markets

Listeria monocytogenes, an intracellular foodborne pathogen, is capable of causing listeriosis, such as meningitis, meningoencephalitis, and abortion. In recent years, the occurrence of Listeria monocytogenes in edible mushroom products has been reported in several countries. There are no guidelines for qualitative and quantitative detection of L. monocytogenes in mushroom products in China. Therefore, this study aimed to investigate the prevalence and contamination level of L. monocytogenes in edible mushrooms in Chinese markets and to determine the antibiotic resistance and sequence types (STs) of these isolates to provide data for risk assessments. Approximately 21.20% (141/665) of edible mushroom samples were positive for L. monocytogenes, while 57.44% (81/141) of positive samples contained contamination levels of less than 10 MPN/g. The 180 isolates derived from positive samples belonged to serogroup I.1 (1/2a-3a, n = 111), followed by serogroup II.2 (1/2b-3b-7, n = 66), and serogroup III (4a-4c, n = 3). Antibiotic susceptibility testing showed that over 95% of L. monocytogenes isolates were resistant to penicillin, ampicillin, oxacillin, and clindamycin, while over 90% were susceptible to 16 antibiotic agents, the mechanisms of resistance remain to be elucidated. According to multilocus sequencing typing, the 180 isolates represented 21 STs, one of which was identified for the first time. Interestingly, ST8 and ST87 were predominant in edible mushroom products, indicating that specific STs may have distinct ecological niches. Potential virulence profiles showed that most of the isolates contained full-length inlA genes, with novel premature stop codons found in isolate 2035-1LM (position 1380, TGG→TGA) and 3419-1LM (position 1474, CAG→TAG). Five isolates belonging to serogroup II.2 carried the llsX gene from Listeria pathogenicity island (LIPI)-3, present in ST224, ST3, and ST619; 53 (29.44%) harbored the ptsA gene from LIPI-4, presenting in ST3, ST5, ST87, ST310, ST1166, and ST619. Five potential hypervirulent isolates carrying all three of these virulence factors were identified, suggesting edible mushrooms may serve as possible transmission routes of potential hypervirulent L. monocytogenes, which may be of great public health concern to consumers. Based on our findings, the exploration of novel approaches to control L. monocytogenes contamination is necessary to ensure the microbiological safety of edible mushroom products.

Distinct fermentation and antibiotic sensitivity profiles exist in salmonellae of canine and human origin

Background

Salmonella enterica is a recognised cause of diarrhoea in dogs and humans, yet the potential for transfer of salmonellosis between dogs and their owners is unclear, with reported evidence both for and against Salmonella as a zoonotic pathogen. A collection of 174 S. enterica isolates from clinical infections in humans and dogs were analysed for serotype distribution, carbon source utilisation, chemical and antimicrobial sensitivity profiles. The aim of the study was to understand the degree of conservation in phenotypic characteristics of isolates across host species.

Results

Serovar distribution across human and canine isolates demonstrated nine serovars common to both host species, 24 serovars present in only the canine collection and 39 solely represented within the human collection. Significant differences in carbon source utilisation profiles and ampicillin, amoxicillin and chloramphenicol sensitivity profiles were detected in isolates of human and canine origin. Differences between the human and canine Salmonella collections were suggestive of evolutionary separation, with canine isolates better able to utilise several simple sugars than their human counterparts. Generally higher minimum inhibitory concentrations of three broad-spectrum antimicrobials, commonly used in veterinary medicine, were also observed in canine S. enterica isolates.

Conclusions

Differential carbon source utilisation and antimicrobial sensitivity profiles in pathogenic Salmonella isolated from humans and dogs are suggestive of distinct reservoirs of infection for these hosts. Although these findings do not preclude zoonotic or anthroponotic potential in salmonellae, the separation of carbon utilisation and antibiotic profiles with isolate source is indicative that infectious isolates are not part of a common reservoir shared frequently between these host species.

Prevalence and Phylogenetic Characterization of Escherichia coli and Hygiene Indicator Bacteria Isolated from Leafy Green Produce, Beef, and Pork Obtained from Farmers' Markets in Pennsylvania

The popularity of farmers' markets in the United States has led to over 8,400 farmers' markets being in operation in 2015. As farmers' markets have increased in size and complexity in the kinds of foods sold at these venues, so have the potential food safety risks. Since 2008, seven major foodborne illness outbreaks and two recalls associated with food products from farmers' markets have occurred, causing 80 known reported illnesses and one death. Various researchers also have observed vendors performing high-risk food safety retail behaviors, and others have identified microbiological hazards in foods sold at farmers' markets. In this study, the presence of hygiene indicators (coliforms, fecal coliforms, Listeria spp., and Escherichia coli ) was assessed in select samples of leafy green produce and meat obtained from farmers' markets in Pennsylvania. E. coli isolates were further characterized by phylogenetic profile and virulence potential. E. coli was present in 40% (20 of 50) and 18% (9 of 50) of beef and pork samples, respectively, and in 28% (15 of 54), 29% (15 of 52), and 17% (8 of 46) of kale, lettuce, and spinach samples, respectively. Listeria spp. was found in 8% (4 of 50) of beef samples, 2% (1 of 54) of kale samples, 4% (2 of 52) of lettuce samples, and 7% (3 of 46) of spinach samples. Among the 10 Listeria spp. isolates, 3 were identified as L. monocytogenes . E. coli isolated from meat samples mainly clustered into phylogroup B1 (66%; 19 of 29), whereas produce isolates clustered into phylogroups B2 (36%; 14 of 39) and B1 (33%; 13 of 39). These E. coli isolates possessed the fimH, iroN, hlyD, and eae genes associated with extraintestinal pathogenic E. coli and Shiga toxin-producing E. coli . The high prevalence but low levels of E. coli and Listeria spp. found on both produce and meat products obtained from farmers' markets in this study strongly indicate that farmers' market vendors would benefit greatly from food safety training and increased public health oversight.

Comprehensive Evaluation and Implementation of Improvement Actions in Butcher Shops

Foodborne pathogens can cause acute and chronic diseases and produce a wide range of symptoms. Since the consumption of ground beef is a risk factor for infections with some bacterial pathogens, we performed a comprehensive evaluation of butcher shops, implemented improvement actions for both butcher shops and consumers, and verified the impact of those actions implemented. A comprehensive evaluation was made and risk was quantified on a 1-100 scale as high-risk (1-40), moderate-risk (41-70) or low-risk (71-100). A total of 172 raw ground beef and 672 environmental samples were collected from 86 butcher shops during the evaluation (2010-2011) and verification (2013) stages of the study. Ground beef samples were analyzed for mesophilic aerobic organisms, Escherichia coli and coagulase-positive Staphylococcus aureus enumeration. Salmonella spp., E. coli O157:H7, non-O157 Shiga toxin-producing E. coli (STEC), and Listeria monocytogenes were detected and isolated from all samples. Risk quantification resulted in 43 (50.0%) high-risk, 34 (39.5%) moderate-risk, and nine (10.5%) low-risk butcher shops. Training sessions for 498 handlers and 4,506 consumers were held. Re-evaluation by risk quantification and microbiological analyses resulted in 19 (22.1%) high-risk, 42 (48.8%) moderate-risk and 25 (29.1%) low-risk butcher shops. The count of indicator microorganisms decreased with respect to the 2010-2011 period. After the implementation of improvement actions, the presence of L. monocytogenes, E. coli O157:H7 and stx genes in ground beef decreased. Salmonella spp. was isolated from 10 (11.6%) ground beef samples, without detecting statistically significant differences between both study periods (evaluation and verification). The percentage of pathogens in environmental samples was reduced in the verification period (Salmonella spp., 1.5%; L. monocytogenes, 10.7%; E. coli O157:H7, 0.6%; non-O157 STEC, 6.8%). Risk quantification was useful to identify those relevant facts in butcher shops. The reduction of contamination in ground beef and the environment was possible after training handlers based on the problems identified in their own butcher shops. Our results confirm the feasibility of implementing a comprehensive risk management program in butcher shops, and the importance of information campaigns targeting consumers. Further collaborative efforts would be necessary to improve foodstuffs safety at retail level and at home.

Enterococci as indicator of potential growth of Salmonella in fresh minced meat at retail

The present study had the purpose of demonstrating a positive correlation between enterococci and Salmonella in minced pork and beef. Data from 2001 to 2002 from retail minced pork and beef in Denmark were used and the association between concentration of enterococci and prevalence and concentration of Salmonella was examined. A total of 2187 and 2747 samples of minced pork and beef, respectively, were collected from butcher shops and supermarkets throughout the country. In pork, 2.1% of all samples were positive for Salmonella whereas 1.5% of beef samples were positive. Among samples with ≥100 CFU/g of enterococci, prevalence of Salmonella positive samples was 3.4%, which was significantly higher than 1.2% observed in minced meat with less than 100 CFU/g of enterococci (P < 0.001). A positive association between occurrence of enterococci and presence of Salmonella in retail minced meat was supported as both prevalence and concentration of Salmonella in positive samples increased with increasing concentrations of enterococci in minced meat. From our data, we suggest that minced meat containing more than 500 enterococci per gram is suspected of having been exposed to temperatures allowing growth of Salmonella. This is to our knowledge the first report, which links presence of an indicator to potential growth of Salmonella.

Evaluation of Microbial Loads on Dried and Fresh Shiitake Mushrooms (Lentinula edodes) as Obtained from Internet and Local Retail Markets, Respectively

Consumer demand for shiitake mushrooms is increasing. However, food safety information regarding the prevalence of microbial pathogens on the products sold via the Internet or at local retail markets is limited. The present study was conducted to assess the microbial load on shiitake mushrooms sold through the Internet and at local (central Virginia) retail markets. A total of 90 shiitake mushroom products, consisting of locally-purchased whole (LW) and sliced (LS) and Internet-procured whole (IW), sliced (IS), and powdered (IP) forms, were tested. High levels of aerobic mesophiles (6.9 ± 1.3 to 7.5 ± 1.1 log CFU/g), yeast and mold (5.8 ± 0.9 to 6.0 ± 0.3 log CFU/g), and coliforms (1.6 ± 1.0 to 1.9 ± 1.1 log MPN/g) were found in locally-acquired mushrooms. One LW sample and 2 of LS contained Listeria spp. Our findings suggest that shiitake mushroom producers and retailers need to be aware of potential microbial hazards associated with handling fresh shiitake mushrooms and consumers should take appropriate precautions when handling fresh shiitake mushrooms to prevent cross-contamination and possible foodborne illness in the home.

Predominance and Distribution of a Persistent Listeria monocytogenes Clone in a Commercial Fresh Mushroom Processing Environment

A longitudinal study was conducted to determine the prevalence of Listeria spp. in a commercial fresh mushroom slicing and packaging environment. Samples were collected at three different sampling periods within a 13-month time interval. Of the 255 environmental samples collected, 18.8% tested positive for L. monocytogenes, 4.3% for L. innocua, and 2.0% for L. grayi. L. monocytogenes was most often found on wet floors within the washing and slicing and packaging areas. Each of the 171 L. monocytogenes isolates found in the environment could be placed into one of three different serotypes; 1/2c was predominant (93.6%), followed by 1/2b (3.5%) and 1/2a (2.9%). Of 58 isolates subtyped using multi-virulence-locus sequence typing, all 1/2c isolates were identified as virulence type (VT) 11 (VT11), all 1/2b isolates were VT105, and 1/2a isolates were either VT107 or VT56. VT11 was designated as the predominant and persistent clone in the environment because it was isolated repeatedly at numerous locations throughout the study. The overall predominance and persistence of VT11 indicates that it likely colonized the mushroom processing environment. Areas adjacent to the trench drain in the washing and slicing area and a floor crack in the packaging area may represent primary harborage sites (reservoirs) for VT11. Improvements made to sanitation procedures by company management after period 2 coincided with a significant (P ≤ 0.001) reduction in the prevalence of L. monocytogenes from 17.8% in period 1 and 30.7% in period 2 to 8.5% in period 3. This suggests that targeted cleaning and sanitizing procedures can be effective in minimizing the occurrence of L. monocytogenes contamination in processing facilities. Additional research is needed to understand why VT11 was predominant and persistent in the mushroom processing environment.

Comparison of the Microbial Quality of Lamb and Goat Meat Acquired from Internet and Local Retail Markets

This study was conducted to evaluate the microbial quality of lamb and goat meat sold through local (Virginia) and Internet (U. S.) retail markets. A total of 134 frozen meat products consisting of locally purchased lamb ground (LLG) and lamb chops and Internet-procured lamb ground, goat ground, lamb chops (ILC), goat chops (IGC), lamb stew, and goat stew were tested. Significantly higher levels of aerobic mesophiles, psychrotrophs, and coliforms were found in the meat locally acquired than in the meat procured from the Internet. Similar average prevalence (27%) of Escherichia coli was observed regardless of market source. Ground meat had significantly high levels and prevalence of mesophiles, psychrotrophs, coliforms, and Listeria spp. One sample of LLG contained Campylobacter, and one sample of IGC contained Salmonella. Listeria spp. were present in 23 to 40% and 17 to 80% of samples from local and Internet markets, respectively. Pulsed-field gel electrophoresis (PFGE) of isolated E. coli strains revealed brand specificity and genomic diversity. No isolate from different brands and market sources had matching PFGE profiles. The average price of Internet meat ($23.4/kg) was about 1.2 times higher than the price of local meat, except for ILC, whose price was 2.7 times higher. This study revealed differences in microbial quality of lamb and goat meat based on market source; thus, meat products should be handled carefully regardless of market source because of the presence of high microbial levels and the high prevalence of pathogens.

Climate-sensitive health priorities in Nunatsiavut, Canada

BACKGROUND

This exploratory study used participatory methods to identify, characterize, and rank climate-sensitive health priorities in Nunatsiavut, Labrador, Canada.

METHODS

A mixed method study design was used and involved collecting both qualitative and quantitative data at regional, community, and individual levels. In-depth interviews with regional health representatives were conducted throughout Nunatsiavut (n = 11). In addition, three PhotoVoice workshops were held with Rigolet community members (n = 11), where participants took photos of areas, items, or concepts that expressed how climate change is impacting their health. The workshop groups shared their photographs, discussed the stories and messages behind them, and then grouped photos into re-occurring themes. Two community surveys were administered in Rigolet to capture data on observed climatic and environmental changes in the area, and perceived impacts on health, wellbeing, and lifestyles (n = 187).

RESULTS

Climate-sensitive health pathways were described in terms of inter-relationships between environmental and social determinants of Inuit health. The climate-sensitive health priorities for the region included food security, water security, mental health and wellbeing, new hazards and safety concerns, and health services and delivery.

CONCLUSIONS

The results highlight several climate-sensitive health priorities that are specific to the Nunatsiavut region, and suggest approaching health research and adaptation planning from an EcoHealth perspective.

Microbiological Safety and Food Handling Practices of Seed Sprout Products in the Australian State of Victoria

Seed sprouts have been implicated as vehicles for numerous foodborne outbreaks worldwide. Seed sprouts pose a unique food safety concern because of the ease of microbiological seed contamination, the inherent ability of the sprouting process to support microbial growth, and their consumption either raw or lightly cooked. To examine seed sprout safety in the Australian state of Victoria, a survey was conducted to detect specific microbes in seed sprout samples and to investigate food handling practices relating to seed sprouts. A total of 298 seed sprout samples were collected from across 33 local council areas. Escherichia coli was detected in 14.8%, Listeria spp. in 12.3%, and Listeria monocytogenes in 1.3% of samples analyzed. Salmonella spp. were not detected in any of the samples. A range of seed sprout handling practices were identified as potential food safety issues in some food businesses, including temperature control, washing practices, length of storage, and storage in proximity to unpackaged ready-to-eat potentially hazardous foods.

Magnetic bead based immuno-detection of Listeria monocytogenes and Listeria ivanovii from infant formula and leafy green vegetables using the Bio-Plex suspension array system

Listeriosis, a disease contracted via the consumption of foods contaminated with pathogenic Listeria species, can produce severe symptoms and high mortality in susceptible people and animals. The development of molecular methods and immuno-based techniques for detection of pathogenic Listeria in foods has been challenging due to the presence of assay inhibiting food components. In this study, we utilize a macrophage cell culture system for the isolation and enrichment of Listeria monocytogenes and Listeria ivanovii from infant formula and leafy green vegetables for subsequent identification using the Luminex xMAP technique. Macrophage monolayers were exposed to infant formula, lettuce and celery contaminated with L. monocytogenes or L. ivanovii. Magnetic microspheres conjugated to Listeria specific antibody were used to capture Listeria from infected macrophages and then analyzed using the Bio-Plex 200 analyzer. As few as 10 CFU/mL or g of L. monocytogenes was detected in all foods tested. The detection limit for L. ivanovii was 10 CFU/mL in infant formula and 100 CFU/g in leafy greens. Microsphere bound Listeria obtained from infected macrophage lysates could also be isolated on selective media for subsequent confirmatory identification. This method presumptively identifies L. monocytogenes and L. ivanovii from infant formula, lettuce and celery in less than 28 h with confirmatory identifications completed in less than 48 h.

Real-time PCR detection of Listeria monocytogenes in infant formula and lettuce following macrophage-based isolation and enrichment

AIMS

To develop a rapid detection procedure for Listeria monocytogenes in infant formula and lettuce using a macrophage-based enrichment protocol and real-time PCR.

METHODS AND RESULTS

A macrophage cell culture system was employed for the isolation and enrichment of L. monocytogenes from infant formula and lettuce for subsequent identification using real-time PCR. Macrophage monolayers were exposed to infant formula and lettuce contaminated with a serial dilution series of L. monocytogenes. As few as approx. 10 CFU ml(-1) or g(-1) of L. monocytogenes were detected in infant formula and lettuce after 16 h postinfection by real-time PCR. Internal positive PCR controls were utilized to eliminate the possibility of false-negative results. Co-inoculation with Listeria innocua did not reduce the L. monocytogenes detection sensitivity. Intracellular L. monocytogenes could also be isolated on Listeria selective media from infected macrophage lysates for subsequent confirmation.

CONCLUSIONS

The detection method is highly sensitive and specific for L. monocytogenes in infant formula and lettuce and establishes a rapid identification time of 20 and 48 h for presumptive and confirmatory identification, respectively.

SIGNIFICANCE AND IMPACT OF THE STUDY

The method is a promising alternative to many currently used q-PCR detection methods which employ traditional selective media for enrichment of contaminated food samples. Macrophage enrichment of L. monocytogenes eliminates PCR inhibitory food elements and contaminating food microflora which produce cleaner samples that increase the rapidity and sensitivity of detection.

Lived experience of acute gastrointestinal illness in Rigolet, Nunatsiavut: "just suffer through it"

Enteric illness associated with foodborne and waterborne disease is thought to be common in some Canadian Indigenous communities. This study aimed to understand the lived experience of acute gastrointestinal illness (AGI), including symptoms and severity, perceived causes, and healthcare seeking behaviors of AGI in the small Inuit community of Rigolet, Canada. A concurrent mixed quantitative and qualitative methods design was used. Two cross-sectional retrospective surveys provided quantitative data to examine self-reported AGI symptoms and the distribution of potential risk factors in the community. Qualitative data from in-depth interviews with one-third of AGI cases were analyzed using a constant-comparative method to describe symptoms and severity, identify perceived risk factors, and explore health seeking behavior of AGI in Rigolet. Of the survey respondents reporting AGI, most reported symptoms of diarrhea without vomiting, followed by diarrhea with vomiting, and vomiting without diarrhea. The most common secondary symptoms included stomach cramps and abdominal pain, nausea, and extreme tiredness. Community members identified potential risk factors for AGI that reflect the epidemiology triad (host, agent, and environmental factors), including hygiene, retail food, tap water, boil water advisories, and personal stress. Risk aversion and healthcare seeking behaviors reflected the core constructs of the Health Belief Model (perceived susceptibility, severity, and benefits and barriers to action). Understanding community experience, perspectives, and beliefs related to AGI is useful for public health practitioners and health care providers. This information is important especially considering the relatively high estimated burden of AGI and the relatively low healthcare seeking behaviors in some Indigenous communities compared to national estimates. Moreover, the mixed-methods approach used to understand the burden of AGI could be extended to other health research in Indigenous contexts.

Listeria spp. em carpaccio de carne bovina e perfil de resistência aos agentes antimicrobianos

O presente estudo foi conduzido com o objetivo de veri-ficar a ocorrência de Listeria spp. em 50 amostras de carpaccio de carne bovina comercializados em bares e restaurantes do município de Niterói, Rio de Janeiro, e avaliar o perfil de resistência dos isola-dos aos agentes antimicrobianos utilizados no tratamento de infec-ções. Constataram-se que 20% das amostras obtidas de restaurantes e 35% de bares estavam contaminadas com Listeria spp. Dentre as espécies, L. welshimeri foi isolada com maior frequência (81,82%), seguida de L. grayi, (13,66%) e L. monocytogenes(4,55%), sendo o ágar Oxford o meio de plaqueamento mais eficiente para isolamento. Foi verificada a ocorrência de resistência dos isolados frente a todos os agentes antimicrobianos testados, exceto à tetraciclina, diante da qual 95,5% dos isolados apresentaram sensibilidade. A multirresistência foi verificada em 68,75% das estirpes analisadas. Desta forma, concluiu-se que o consumo de carpaccio de carne bovina representa risco potencial, constituindo um grave problema de saúde coletiva, especialmente devido à confrmação de estirpes patogênicas e resistentes aos principais agentes antimicrobianos utilizados no tratamento de listeriose.

Comparison of conventional culture method and fluorescent in situ hybridization technique for detection of Listeria spp. in ground beef, turkey, and chicken breast fillets in İzmir, Turkey

The occurrence of Listeria species in refrigerated fresh chicken breast fillet, turkey breast fillet, and ground beef was evaluated, comparing the conventional culture method and fluorescent in situ hybridization (FISH). FISH uses hybridization of a nucleic acid sequence target of a microorganism with a specific DNA probe labeled with a fluorochrome and imaging by a fluorescence microscope. First, Listeria was inoculated in chicken breast fillet, turkey breast fillet, or ground beef, and the applicability of the FISH method was evaluated. Second, Listeria was detected in fresh chicken breast fillet, turkey breast fillet, and ground beef by culture and FISH methods. Listeria was isolated from 27 (37.4%) of 216 samples by the standard culture method, whereas FISH detected 25 (24.7%) preenriched samples. Of these isolates, 17 (63%) were L. innocua, 6 (22%) L. welshimeri, and 4 (14.8%) L. seeligeri. Overall, the prevalences of Listeria spp. found with the conventional culture method in chicken breast fillet, turkey breast fillet, and ground beef were 9.7, 6.9, and 20.8%, whereas with the FISH technique these values were 11.1, 6.9, and 16.7%, respectively. The molecular FISH technique appears to be a cheap, sensitive, and time-efficient procedure that could be used for routine detection of Listeria spp. in meat. This study showed that retail raw meats are potentially contaminated with Listeria spp. and are, thus, vehicles for transmitting diseases caused by foodborne pathogens, underlining the need for increased precautions, such as implementation of hazard analysis and critical control points and consumer food safety education.

Prevalence and contamination patterns of Listeria monocytogenes in Flammulina velutipes plants

Four mushroom (Flammulina velutipes) production plants were sampled to investigate the prevalence and contamination source of Listeria monocytogenes. Among 295 samples, the prevalence of L. monocytogenes was 18.6%; the contamination appeared to originate from the mycelium-scraping machinery, contaminating both the product and upstream packaging equipment. Of 55 L. monocytogenes isolates, lineages I.1 (1/2a-3a) and II.2 (1/2b-3b-7) accounted for 65.5% and 34.5%, respectively. In addition, lineage I.1 formed significantly thicker biofilms than those within lineage II.2, as determined by crystal violet staining and scanning electron microscopy. Genotype analyses of L. monocytogenes isolates using enterobacteria repetitive intergenic consensus-polymerase chain reaction, and random amplified polymorphic DNA revealed that the surfaces of mycelium-scraping machinery may serve as the main source of L. monocytogenes contamination in three of the four plants. This study was the first report to explore the potential contamination sources of L. monocytogenes in the mushroom production chain, thereby providing baseline information for adopting prophylactic measures for critical control points during production in mushroom plants to avoid L. monocytogenes contamination.