Recent advances in the microbial safety of fresh fruits and vegetables

A metagenomic assessment of bacterial community in spices sold open-air markets in Saint-Louis, Senegal

Natural spices play an essential role in human nutrition and well-being. However, their processing on different scales can expose them to potential sources of contamination. This study aimed to describe the bacterial community genomic footprint in spices sold in Senegal. Spice samples were collected in August 2022 in Saint-Louis, Senegal. The genomic region coding bacterial 16S rRNA was then amplified and sequenced using Oxford Nanopore Technology (ONT). Sequencing was carried out on two batches of samples, one containing part of the "Local Spices or Herbs" (n = 10), and the other, a mixture of 7 spices, Curcuma, Thyme and the other part of the "Local Spices or Herbs" (n = 39). Results showed high bacterial diversity and the predominance of Escherichia coli and Salmonella enterica in samples, with total reads of 65,744 and 165,325 for the two batches, respectively. The sample category "Homemade mixture of food condiments ", which includes all "Local Spices or Herbs" samples, showed remarkable bacterial diversity. These were followed by Curcuma, a blend of 7 spices and thyme. Also, the different categories of spices studied show similarities in their bacterial composition. These results highlight the microbial community's highly diverse genomic profile, including pathogenic bacteria, in spice samples.

Influence of the use of remediated soil and agricultural drainage water on the safety of tomato fruits

The objective of this study is to assess the effectiveness of different techniques employed in remediating contaminated soil and wastewater ecosystems to ensure the safety of tomato fruits (Solanum lycopersicum L. var. cerasiforme) cultivated in these environments. Three biochemical techniques T1-T3, besides two controls CCU and CCT, were used to remediate contaminated soil ecosystems using rock phosphate, elemental sulfur, bentonite, phosphate-dissolving bacteria, and Thiobacillus sp. The contaminated agricultural drainage water was remediated by a down-flow hanging sponge (DHS) system. Two experiments were conducted: a pot experiment took place in the greenhouse at the National Research Center of Cairo (Egypt) and a field experiment was carried out at the basin site in the village of El-Rahawy, applying the optimal treatment(s) identified from the greenhouse experiment. The health risk assessment for potentially toxic elements (PTEs) in the harvested tomato fruits was conducted by calculating estimated daily intake (EDI) and target risk quotient (THQ) values. Results from the greenhouse experiment indicated the high effectiveness of the DHS technique in remediating El-Rahawy agricultural drainage water. The content of PTEs after remediation was significantly reduced by 100%, 93.3%, 97.8, and 77.8% for cadmium, copper, manganese, and zinc, respectively. The application of treated drainage water in employed reclaimed soil ecosystems led to a remarkable decrease in PTE levels, especially under T3 treatment; the reduction reached 89.4%, 89.5%, and 78.4% for nickel, copper, and zinc, respectively. The bioremediation technique also reduced the content of PTEs in tomato fruits harvested from both greenhouse and field experiments; the cadmium content, for example, was below detection limits in all treatments. The T3 treatment applied in the greenhouse experiment caused the highest percentage decrease among the employed PTEs in tomato fruits grown in the greenhouse. The same trend was also reached in the field experiment. Microbiological analyses of tomato fruits revealed that E. coli, Salmonella, or S. aureus bacteria were identified on tomato fruits harvested from either greenhouses or field experiments, showing that the counted total bacteria were higher under the field experiment compared to the greenhouse experiment. The health risk assessment parameter THQ was below 1.0 for all tested metals under all treatments. This means that no potential health risk is expected from consuming tomato products produced under the different employed remediation treatments. In conclusion, the employed bioremediation techniques successfully reduced the PTE content and microbial load in both soil and drainage water ecosystems and in harvested tomato fruits. Henceforth, no health risks are expected from the consumption of this product.

Internalization of Salmonella in Leafy Vegetables during Postharvest Conditions

The consumption of fresh produce is increasing due to its role in promoting a healthy and balanced diet. However, this trend is accompanied by increased foodborne disease cases associated with pathogens such as Escherichia, Listeria, and Salmonella. Previous studies provided evidence that the internalization of foodborne pathogens in fresh produce may be a potential contamination route and may pose a public health risk. This study investigates the combination effects of storage temperature and humidity on Salmonella internalization in six types of leafy greens (iceberg lettuce, romaine lettuce, red lettuce, green onion, spinach, and kale) during the storage stage. The results indicated that temperature plays a critical role in Salmonella internalization, with higher concentrations observed in samples stored at 25 °C compared to those stored at 7 °C. The mean concentration of internalized Salmonella in the iceberg lettuce sample was the highest and that in the green onion sample was the lowest (iceberg lettuce > red lettuce > romaine lettuce > spinach > kale > green onion). Mist conditions also had an impact on internalization. The group treated with mist showed an increase in Salmonella internalization of about 10-30% rather than the group without mist treatment. This research emphasizes the importance of understanding the factors influencing bacterial internalization in fresh produce and highlights the need for proper storage conditions to minimize the risk of contamination and ensure food safety.

Efficacy of combined caprylic acid and thymol treatments for inactivation of Listeria monocytogenes on enoki mushrooms in household and food-service establishments

Raw enoki mushroom is a high-risk vector for listeriosis, which led to foodborne outbreaks resulting in four deaths in the United States in 2020. This study aimed to investigate the washing method for the inactivation of L. monocytogenes in enoki mushrooms for household and food service establishments. Five methods of washing fresh agricultural products without using disinfectants were selected: (1) rinsing under running water (2 L/min, 10 min), (2-3) dipping in water (200 ml/20 g) at 22 or 40 °C for 10 min, and using (4) 10% NaCl or (5) 5% vinegar at 22 °C for 10 min. The antibacterial efficacy of each washing method along with the final rinse was tested with enoki mushrooms inoculated with a 3-strain cocktail of L. monocytogenes (ATCC 19111, 19115, 19117; ca. 6 log CFU/g). The 5% vinegar showed a significant difference in antibacterial effect compared to the other treatments except 10% NaCl (P < 0.05), with the maximum elimination of L. monocytogenes by 1.23 log CFU/g. Therefore, a disinfectant for enoki mushrooms that can complement the commonly used washing method was developed using antimicrobials (caprylic acid, CA: 0, 0.20, 0.40%; thymol, TM: 0, 0.075, 0.15%). By combined treatment of 0.40% CA and 0.15% TM at 22 °C for 10 min, L. monocytogenes was completely inactivated (>5.55 log reduction CFU/g) and did not recover after enrichment, although individual treatments of antimicrobials showed low bactericidal effects of <1.50 log reduction CFU/g. The bacterial membrane disintegration induced by the disinfectant was analyzed through flow cytometry. Additionally, the sensory scores (odor and appearance) and color parameters (L*, a*, and b*) of enoki mushrooms treated with the disinfectant were not significantly different from those of enoki mushrooms washed with water (P > 0.05). Our findings suggest a washing disinfectant consisting of low concentrations of CA and TM with synergistic antibacterial effects without quality deterioration that can ensure the safe consumption of raw enoki mushrooms in homes and food service establishments.

Internalization of Salmonella in Leafy Greens and Impact on Acid Tolerance

Salmonella colonizes the surface or the inner part of leafy greens, while the ability of internalized bacteria to evade common disinfection practices may pose a considerable risk. Hereby, we aimed to assess how the colonization and internalization of Salmonella spp. (i) vary with the type of leafy green, the storage conditions (temperature, time), and Salmonella serovar at phenotypic and gene transcriptional level (regarding stress- and virulence- or type III secretion system [T3SS]-associated genes) and (ii) potentially impact the survival of the pathogen against subsequent exposure at lethal pH (2.7), mimicking the gastric acidity. Internalized Salmonella reached 3.0 to 5.0 log CFU/g depending on storage conditions and vegetable, with spinach and chicory allowing the highest (P < 0.05) internalization. Prolonged storage (48 h) at 20°C increased the recovery of internalized Salmonella in spinach and green amaranth by 1.0 to 1.5 log units. Colonization of Salmonella on/in leafy vegetables induced the transcription (maximum fold change [FCmax], ∼2,000) of T3SS-related genes. Interserovar variation regarding the internalization ability of Salmonella was observed only in lettuce and green amaranth in a time- and temperature-dependent manner. Attached cells exhibited higher survival rates against low pH than the internalized subpopulation; however, habituation at 20°C in lettuce and amaranth induced acid tolerance to internalized cells, manifested by the 1.5 to 2.0 log CFU/g survivors after 75 min at pH 2.7. Habituation of Salmonella in vegetable extracts sensitized it toward acid, while indigenous microbiota had limited impact on acid resistance of the organism. These findings reveal physiological aspects of Salmonella colonizing leafy vegetables that could be useful in fresh produce microbial risk assessment. IMPORTANCE Consumption of leafy greens has been increasingly associated with foodborne illnesses, and their contamination could occur at pre- and/or postharvest level. Human pathogens may become passively or actively internalized in plant tissues, thereby escaping decontamination procedures. Plant colonization may impact bacterial physiology such as stress resistance and virulence. In this study, it was demonstrated that internalization of Salmonella spp., at the postharvest level, varied with type of vegetable, serovar, and storage conditions. Attached and internalized subpopulations of Salmonella on/in leafy greens showed distinct physiological responses regarding transcriptional changes of stress- and virulence-associated genes, as well as survival capacity against subsequent exposure to lethal pH (2.7). These findings could contribute to a better understanding and potential (re)definition of the risk of enteric pathogens colonizing leafy greens, as well as to the design of intervention strategies aiming to improve the microbiological safety of fresh produce.

The Survival of Salmonella Senftenberg, Escherichia coli O157:H7, Listeria monocytogenes, Enterococcus faecalis and Clostridium sporogenes in Sandy and Clay Loam Textured Soils When Applied in Bovine Slurry or Unpasteurised Digestate and the Run-Off Rate for a Test Bacterium, Listeria innocua, When Applied to Grass in Slurry and Digestate

This study investigated the survival of Salmonella Senftenberg, Escherichia coli O157:H7, Listeria monocytogenes, Enterococcus faecalis and Clostridium sporogenes in sandy and clay loam textured soils when applied in bovine slurry or unpasteurised digestate, using laboratory based inoculation studies. The run-off rate for a test bacterium, Listeria innocua, when applied to grass in slurry and digestate, was also examined using field studies. Bovine slurry and digestate were inoculated with the target bacteria to a final concentration of 106 log10 cfu/g or spores/g, thoroughly mixed into soil samples and incubated at 4°C or 14°C. Samples were removed periodically and the surviving cells enumerated using AOAC or equivalent methods. The loss of viability/culturability phase followed first order kinetics and T90 values ranged from 11.9 to 166.7 d at 4°C and from 6.0 to 156 d at 14°C. With the exception of E. coli O157:H7 and E. faecalis in sandy loam textured soil at 14°C (T90 values were significantly (P &lt; 0.05) higher in slurry) the type of soil texture or application material (slurry or digestate) did not affect survival rates. In the field study, 12 grass covered micro-plots were prepared. L. innocua was applied in digestate and bovine slurry and rainfall was simulated at a target rate of ~11 mm per plot per h−1. Rainfall simulation (30 min) took place after 24, 48 h, 14 d and 30 d. Run-off samples were tested for the L. innocua strain using Brilliance Listeria agar supplemented with streptomycin sulphate (1,000 μg/ml) at 37°C for 48 h, as were soil samples after 30, 58, 86 and 112 d. Significantly (P &lt; 0.05) lower counts were obtained in the run-off from digestate after 1, 2 and 30 d as compared to slurry. It was concluded that the type of organic fertiliser does not affect the bacterial survival rates in sandy and clay soils, with the exception of E. coli O157:H7 and E. faecalis in sandy loam textured soil at 14°C. Furthermore, bacteria may be retained better in the soil-digestate matrices during rainfall although additional research is required to further validate and provide the scientific basis for this observation.

Listeria monocytogenes Survival on Peaches and Nectarines under Conditions Simulating Commercial Stone-Fruit Packinghouse Operations

Recent recalls of stone fruit due to potential Listeria contamination and associated foodborne outbreaks highlight the risk for pathogen transmission through stone-fruit consumption. Particularly, surface contamination of fruits increases the risk for cross-contamination of produce during processing and storage. This highlights the need for quality control in stone fruits intended for consumption. To develop effective food safety practices, it is essential to determine the critical factors during stone-fruit processing that influence Listeria survival. Therefore, this study evaluated the ability of Listeria to survive on peaches and nectarines under simulated stone-fruit loading and staging, waxing and fungicide application and storage conditions. The results of our study indicate that current stone-fruit handling conditions do not favor Listeria growth. However, once fruit is contaminated, Listeria can survive on the fruit surface in significant numbers under current processing conditions. Therefore, there is a need to develop and implement preventive controls at the stone-fruit packinghouse to prevent Listeria contamination and deter pathogen persistence.

Effects of Pre-Treatment Using Plasma on the Antibacterial Activity of Mushroom Surfaces

Although non-thermal atmospheric pressure plasma is an efficient tool for preventing post-harvest microbial contamination, many studies have focused on the post-treatment of infected or contaminated foods. In this study, we examined the antimicrobial quality of mushrooms pre-treated with a non-thermal atmospheric pressure plasma jet (NTAPPJ) or plasma-treated water (PTW). The CFU (Colony Forming Unit) number of Escherichia coli inoculated on surfaces of mushrooms pre-treated with NTAPPJ or PTW was significantly reduced (about 60-75% for NTAPPJ and about 35-85% for PTW), and the reduction rate was proportional to the treatment time. Bacterial attachment and viability of the attached bacteria were decreased on NTAPPJ-treated mushroom surfaces. This may be caused by the increased hydrophilicity and oxidizing capacity observed on NTAPPJ-treated mushroom surfaces. In PTW-treated mushrooms, bacterial attachment was not significantly changed, but death and lipid peroxidation of the attached bacteria were significantly increased. Analysis of mushroom quality showed that loss of water content was greater in mushrooms treated with NTAPPJ compared to that in those with no treatment (control) and PTW treatment during storage. Our results suggest that pre-treatment with NTAPPJ or PTW can improve the antibacterial quality of mushroom surfaces by decreasing bacterial attachment (for NTAPPJ) and increasing bacterial lipid peroxidation (for both NTAPPJ and PTW).

Parsimonious Mechanistic Modeling of Bacterial Runoff into Irrigation Ponds To Inform Food Safety Management of Agricultural Water Quality

Pond irrigation water comprises a major pathway of pathogenic bacteria to fresh produce. Current regulatory methods have been shown to be ineffective in assessing this risk when variability of bacterial concentrations is large. This paper proposes using mechanistic modeling of bacterial transport as a way to identify improved strategies for mitigating this risk pathway. If the mechanistic model is successfully tested against observed data, global sensitivity analysis (GSA) can identify important mechanisms to inform alternative, preventive bacterial control practices. Model development favored parsimony and prediction of peak bacterial concentration events. Data from two highly variable surface water irrigation ponds showed that the model performance was similar or superior to that of existing pathogen transport models, with a Nash-Sutcliffe efficiency of 0.48 and 0.18 for the two ponds. GSA quantified bacterial sourcing and hydrology as the most important processes driving pond bacterial contamination events. Model analysis has two main implications for improved regulatory methods: that peak concentration events are associated with runoff-producing rainfall events and that intercepting bacterial runoff transport may be the best option to prevent bacterial contamination of surface water irrigation ponds and thus fresh produce. This research suggests the need for temporal management strategies. IMPORTANCE Preventive management of agricultural waters requires understanding of the drivers of bacterial contamination events. We propose mechanistic modeling as a way forward to understand and predict such events and have developed and tested a parsimonious model for rain-driven surface runoff contributing to generic Escherichia coli contamination of irrigation ponds in Central Florida. While the model was able to predict the timing of peak events reasonably well, the highly variable magnitude of the peaks was less well predicted. This indicates the need to collect more data on the fecal contamination inputs of these ponds and the use of mechanistic modeling and global sensitivity analysis to identify the most important data needs.

Microbial Quality Assessment and Efficacy of Low-Cost Disinfectants on Fresh Fruits and Vegetables Collected from Urban Areas of Dhaka, Bangladesh

This study aimed to examine the total viable bacteria (TVBC); total coliform (TCC); fecal coliform (TFC); pathogenic Pseudomonas spp., Staphylococcus aureus, and total fungi (TF); and the effect of different low-cost disinfectants (sterile water, salt water, blanched, and vinegar) in decontamination of 12 types of fruit and 10 types of vegetables. In fruit samples, the lowest TVBC was enumerated at 3.18 ± 0.27 log CFU/g in Indian gooseberry and the highest at 6.47 ± 0.68 log CFU/g in guava. Staphylococci (2.04 ± 0.53-5.10 ± 0.02 log CFU/g), Pseudomonas (1.88 ± 0.03-5.38 ± 0.08 log CFU/g), and total fungi (2.60 ± 0.18-7.50 ± 0.15 log CFU/g) were found in all fruit samples; however, no Salmonella was detected in fruit samples. Similarly, the lowest TVBC recorded 5.67± 0.49 log CFU/g in cucumber and the highest 7.37 ± 0.06 log CFU/g in yard long bean. The Staphylococci (3.48 ± 0.13-4.81 ± 0.16 log CFU/g), Pseudomonas (3.57± 0.21- 4.75 ± 0.23 log CFU/g), TCC (1.85 ± 1.11-56.50 ± 37.14 MPN/g), TFC (1.76 ± 0.87- 3.78 ± 3.76 MPN/g), and TF (3.79 ± 0.18-4.40 ± 0.38 log CFU/g) were recorded in all vegetables samples, but no Salmonella was detected in yard long bean, pointed gourd, carrot, tomato, cucumber, or brinjal. However, vinegar showed the highest microbial load reduction of selected fruit and vegetables among the different treatments. With vinegar treatment, the highest reduction of TVBC (1.61-log) and TF (2.54-log) was observed for fruits, and TVBC (2.31-log) and TF (2.41-log) for vegetables. All the disinfectant treatments resulted in significant (p < 0.01) bacterial load reduction compared to control for the studied fruits and vegetable samples.

A Double-Edged Sword of Surfactant Effect on Hydrophobic Surface Broccoli Leaf as a Model Plant: Promotion of Pathogenic Microbial Contamination and Improvement to Disinfection Efficiency of Ozonated Water

Pathogenic microbial contamination is significantly influenced by the crop surface properties and surfactant use, which are crucial factors for the postharvest washing process. However, there is little information on the interaction between surfactant and food pathogens on food crops. Thus, this study (1) investigated whether the attachment of Salmonella increases as pesticides denature epicuticular wax crystals and (2) tested if the antibacterial effect of ozonated water can be improved on waxy produce surfaces by adding surfactant to ozonated water. As a result, significantly lower levels of Salmonella Typhimurium attached to waxy leaf surfaces than they did to glossy and pesticide-treated waxy leaf surfaces (3.28 as opposed to 4.10 and 4.32 Log colony forming units (CFU)/cm2, respectively), suggesting that the pesticide containing a surfactant application increased the attachment of S. Typhiumurium on waxy leaf surfaces. There was no significant washing effect on waxy leaf surfaces washed with ozonated water. On the other hand, S. Typhimurium were not detected on waxy leaf surfaces after washing with surfactant-added ozonated water.

Antibiogram Signatures of Some Enterobacteria Recovered from Irrigation Water and Agricultural Soil in two District Municipalities of South Africa

This study was undertaken to evaluate the antibiogram fingerprints of some Enterobacteria recovered from irrigation water and agricultural soil in two District Municipalities of the Eastern Cape Province, South Africa using standard culture-based and molecular methods. The prevalent resistance patterns in the isolates follow the order: Salmonella enterica serovar Typhimurium [tetracycline (92.3%), ampicillin (69.2%)]; Enterobacter cloacae [amoxicillin/clavulanic acid (77.6%), ampicillin (84.5%), cefuroxime (81.0%), nitrofurantoin (81%), and tetracycline (80.3%)]; Klebsiella pneumoniae [amoxicillin/clavulanic acid (80.6%), ampicillin (88.9%), and cefuroxime (61.1%)]; and Klebsiella oxytoca [chloramphenicol (52.4%), amoxicillin/clavulanic acid (61.9%), ampicillin (61.9%), and nitrofurantoin (61.9%)]. Antibiotic resistance genes detected include tetC (86%), sulII (86%), and bla_AmpC (29%) in Salmonella enterica serovar Typhimurium., tetA (23%), tetB (23%), tetC (12%), sulI (54%), sulII (54%), catII (71%), bla_AmpC (86%), bla_TEM (43%), and bla_PER (17%) in Enterobacter cloacae., tetA (20%), tetC (20%), tetD (10%), sulI (9%), sulII (18%), FOX (11%) and CIT (11%)-type plasmid-mediated AmpC, bla_TEM (11%), and bla_SHV (5%) in Klebsiella pneumoniae and bla_AmpC (18%) in Klebsiella oxytoca. Our findings document the occurrence of some antibiotic-resistant Enterobacteria in irrigation water and agricultural soil in Amathole and Chris Hani District Municipalities, Eastern Cape Province of South Africa, thus serving as a potential threat to food safety.

Environmental Drivers for Persistence of Escherichia coli and Salmonella in Manure-Amended Soils: A Meta-Analysis

ABSTRACT

Application of organic amendments to agricultural land improves soil quality and provides nutrients essential for plant growth; however, they are also a reservoir for zoonotic pathogens whose presence poses a significant risk to public health. The persistence of bacteria in manure-amended soil, and differences in manure handling practices, are important issues from a food safety perspective. The primary objective of this study was to quantitatively summarize the variations in the rate of decline of Escherichia coli and Salmonella spp. in manure-amended soil under laboratory and field conditions, and to assess the impact of environmental factors. Available literature data on persistence of E. coli and Salmonella spp. in manure-amended soil from 42 primary research studies were extracted and statistically analyzed using a mixed-effect regression model. The results indicated that temperature (soil and air combined) was the most prominent factor affecting persistence of both E. coli and Salmonella spp. under laboratory conditions (P < 0.001), and of E. coli under field conditions (P < 0.05). The time required for a log reduction of E. coli under field conditions was significantly higher at low temperature (0 to 10°C) than at high temperature (greater than 20°C) (P < 0.05). In addition, application method was identified as a significant factor, with manure incorporation to soil inducing longer survival compared with surface application by approximately 1.2 times. The significant variation observed among primary research studies of bacterial persistence has highlighted that mitigation strategies associated with the use of manures in fresh produce production need to be improved by addressing factors such as climate, soil management, application method, and initial microbial levels. These findings may be used to support guidelines establishing exclusion periods between manure fertilization and the grazing or harvesting of crops, and may be useful for the generation of quantitative microbial risk models for fresh produce.

HIGHLIGHTS

Fate of Salmonella enterica and Enterohemorrhagic Escherichia coli on Vegetable Seeds Contaminated by Direct Contact with Artificially Inoculated Soil during Germination

ABSTRACT

Contaminated vegetable seeds have been identified as a potential source of foodborne bacterial pathogens. This study was undertaken to observe the behavior of Salmonella and enterohemorrhagic Escherichia coli (EHEC) on vegetable seeds, contaminated by direct contact with artificially inoculated soil, during germination. Sterile sandy soil inoculated with lyophilized cells of four individual strains of Salmonella or EHEC (three O157:H7 strains and one O104:H4 strain) was mixed with sanitized seeds (2 g) of alfalfa, fenugreek, lettuce, and tomato at 20°C for 1 h. The contaminated seeds were germinated on 1% water agar at 25°C for 9 days in the dark. Populations of Salmonella and EHEC on various tissues (seed coat, root, cotyledon, and stem, etc.) of sprouts and seedlings were determined every other day over the germination period. Overall, 70.4 and 72.4% of collected tissue samples (n = 544) tested positive for Salmonella and EHEC, respectively. In general, the mean populations of Salmonella and EHEC on sprout and seedling tissues increased with the prolongation of germination time. Seed coats had the highest bacterial counts (4.00 to 4.06 log CFU/0.01 g), followed by the root (3.36 to 3.38 log CFU/0.01 g), cotyledon (3.13 to 3.38 log CFU/0.01 g), and stem tissues (2.67 to 2.84 log CFU/0.01 g). On average, tissue sections of fenugreek sprouts and lettuce seedlings had significantly higher (P < 0.05) numbers of Salmonella and EHEC cells than that of alfalfa sprouts and tomato seedlings. Data suggest that the growth and dissemination of Salmonella and EHEC cells on alfalfa, fenugreek, lettuce, and tomato sprout and seedling tissues are influenced by the type of vegetable seeds and sprout and seedling tissues involved. The study provides useful information on the fate of two important foodborne bacterial pathogens on selected vegetable seeds, contaminated by direct contact with inoculated soil, during the germination process.

HIGHLIGHTS

Survival of Salmonella enterica subsp. enterica serovar Javiana and Listeria monocytogenes is dependent on type of soil-free microgreen cultivation matrix

AIMS

This study measured the survival of Listeria monocytogenes and Salmonella enterica subsp. enterica serovar Javiana over a 10-day period on four soil-free cultivation matrix (SFCM) types in the absence of microgreens and fertilizers.

METHODS AND RESULTS

Coco coir (CC), a Sphagnum peat/vermiculite mix, Biostrate^® and hemp mat samples were inoculated with 3 × 10⁶  CFU per ml bacteria, incubated at room temperature, and analysed on day 0, 1, 3, 6, and 10. Statistically significant differences in pathogen survival were observed across multiple time points for hemp and Biostrate compared to CC, peat and bacteria in phosphate buffered saline (PBS) (P < 0·05). S. Javiana showed greater overall survival compared to Listeria (P < 0·0002). By day 10, S. Javiana persisted at the initial inoculum concentration for hemp and Biostrate while declining by 1-2 log CFU per ml in CC, peat and PBS. Listeria also persisted at the initial concentration in hemp and Biostrate but decreased to 1 log CFU per ml in peat and below the detection limit in CC and PBS.

CONCLUSIONS

Overall, there are survival differences between bacterial pathogens in SFCM used in microgreen production systems. To our knowledge, this is the first comparison of survival among SFCM involving a S. enterica serovar and L. monocytogenes, and the first study comparing CC, Biostrate and hemp.

SIGNIFICANCE AND IMPACT OF THE STUDY

Microgreens production systems predominantly utilize soil alternatives, and it is not well-understood how pathogen transmission risk may be affected by the type of SFCM. The results of this study impact the microgreen industry as media selection may be used to reduce the risk of bacterial pathogen proliferation and transmission to the plant potentially resulting in potential foodborne illness.

Sources of food contamination in a closed hydroponic system

This study investigated potential contamination sources in a commercial, closed hydroponic system. Water, substrate and lettuce (Lactuca sativa) samples were evaluated for microbiological indicator populations, including aerobic plate count (APC), coliform bacteria (CB) and yeast and mould (YM). Listeria spp. detection via cultural enrichment and agglutination was negative for all samples. Peat moss substrate (postharvest) had the highest counts for APC (6·8 log CFU per g), CB (4·5 log MPN per g) and YM (5·1 and 4·8 log CFU per g respectively). Roots embedded in plugs demonstrated counts for all populations nearly as high as the substrate. Among water samples, a seedling water reservoir housing germinated plants yielded the highest count for APC (5·1 log CFU per g) and CB (2·4 log MPN per g) likely due to the large numbers of plugs and their close proximity in the reservoir. Harvested lettuce leaves demonstrated higher APC (4·1 log CFU per g) than preharvest leaves (1·7 log CFU per g) due to the transfer of microbes from the root ball. These data suggest that substrates are a significant potential source of contamination in hydroponic systems and likely facilitate microbial transfer to harvested leaves. There is, therefore, the need to further investigate mitigation of potential contamination events. SIGNIFICANCE AND IMPACT OF THE STUDY: Hydroponic production is known to provide safe, clean produce. This study, however, suggests that the hydroponic substrate (peat moss plug) is a possible source of contamination in the hydroponic system. This finding is important as most harvested hydroponic lettuces are packaged and sold with substrate and root ball intact. This implies a high probability of microbial transfer from the root ball to edible harvested lettuce leaves.

Salmonella Survival in Soil and Transfer onto Produce via Splash Events

Nearly one-half of foodborne illnesses in the United States can be attributed to fresh produce consumption. The preharvest stage of production presents a critical opportunity to prevent produce contamination in the field from contaminating postharvest operations and exposing consumers to foodborne pathogens. One produce-contamination route that is not often explored is the transfer of pathogens in the soil to edible portions of crops via splash water. We report here on the results from multiple field and microcosm experiments examining the potential for Salmonella contamination of produce crops via splash water, and the effect of soil moisture content on Salmonella survival in soil and concentration in splash water. In field and microcosm experiments, we detected Salmonella for up to 8 to 10 days after inoculation in soil and on produce. Salmonella and suspended solids were detected in splash water at heights of up to 80 cm from the soil surface. Soil-moisture conditions before the splash event influenced the detection of Salmonella on crops after the splash events-Salmonella concentrations on produce after rainfall were significantly higher in wet plots than in dry plots (geometric mean difference = 0.43 CFU/g; P = 0.03). Similarly, concentrations of Salmonella in splash water in wet plots trended higher than concentrations from dry plots (geometric mean difference = 0.67 CFU/100 mL; P = 0.04). These results indicate that splash transfer of Salmonella from soil onto crops can occur and that antecedent soil-moisture content may mediate the efficiency of microbial transfer. Splash transfer of Salmonella may, therefore, pose a hazard to produce safety. The potential for the risk of splash should be further explored in agricultural regions in which Salmonella and other pathogens are present in soil. These results will help inform the assessment of produce safety risk and the development of management practices for the mitigation of produce contamination.

Efficacy of cold plasma functionalised water for improving microbiological safety of fresh produce and wash water recycling

Atmospheric cold plasma (ACP) is an effective method for microbiological decontamination. This study evaluated an alternative water-based decontamination approach for inactivation of bacterial population from fresh produce and in the wash water generated from fresh produce washing. The study characterised ACP inactivation of attached Listeria innocua and Pseudomonas fluorescens inoculated on lettuce in comparison to chlorine treatment. P. fluorescens was sensitive to ACP treatment and was reduced below detection limit within 3 min of treatment. L. innocua population was reduced by ∼2.4 Log10 CFU/g after 5 min of treatment; showing similar inactivation efficacy to chlorine treatment. The microbial load in wash water was continuously decreased and was below detection limits after 10 min of ACP treatment. Micro-bubbling along with agitation assisted the bacterial detachment and distribution of reactive species, thus increasing bacterial inactivation efficacy from fresh produce and wash water. A shift in pH of plasma functionalised water was observed along with high concentration of nitrate and ozone with a relative amount of nitrites which increased with plasma exposure time. Further, L. innocua treated at different independent pH conditions showed minimal or no effect of pH on ACP bacterial inactivation efficacy. Aqueous ACP treatment poses a promising alternative for decontamination of fresh produce and the associated wash-waters which could be applied in the food industry to replace continuous chlorine dosing of process waters.

Quantitative PCR-based identification of enteric viruses contaminating fresh produce and surface water used for irrigation in Egypt

Fresh produce irrigated with surface water that may contain pathogens such as enteric viruses can lead to outbreaks of foodborne viral illnesses. In the current study, we performed real-time PCR (qPCR) to monitor the presence of enteric viruses such as human adenoviruses (HAdVs), hepatitis A virus (HAV), rotavirus group A (RVA), and norovirus GI (NoV GI) in surface water and fresh produce that were grown using this surface water in Egypt. Samples were collected on four occasions from different sites located in the Delta and in Greater Cairo, Egypt. Of the 32 water samples and 128 fresh produce samples, 27/32 (84.3%) and 99/128 (77.3%), respectively, were positive for at least one virus. HAdV (30/32) with a mean viral load = 1.5 × 10⁷ genome copies/L (GC/L) was the most commonly detected virus in water, followed by RVA (16/32, with a mean viral load = 2.7 × 10⁵ GC/L), HAV (11/32, with a mean viral load = 1.2 × 10⁴ GC /L), and NoV GI (10/32, with a mean viral load = 3.5 × 10³ GC/L). Additionally, HAdV (71/128, with a mean viral load = 9.8 × 10⁵ GC/g) was also the most commonly detected virus in the fresh produce, followed by NoV GI (43/128, with a mean viral load = 4.5 × 10³ GC/g), HAV (33/128, with a mean viral load = 6.4 × 10³ GC/g), and RVA (25/128, with a mean viral load = 1.5 × 10⁴ GC/g). Our results indicate that fresh produce may be contaminated with a wide range of enteric viruses, and these viruses may originate from virus-contaminated irrigation water. Moreover, this fresh produce may serve as a potential vector for the transmission of viral foodborne illnesses. These findings are important for future risk assessment analysis related to water/foodborne viruses. Graphical abstract . Please provide caption for Graphical AbstractGraphical abstract showing sample collection and processing.

Decontamination Effect of the Spindle and 222-Nanometer Krypton-Chlorine Excimer Lamp Combination against Pathogens on Apples (Malus domestica Borkh.) and Bell Peppers (Capsicum annuum L.)

In this study, we developed a washing system capable of decontaminating fresh produce by combining the Spindle apparatus, which detaches microorganisms on sample surfaces, and a 222-nm krypton-chlorine excimer lamp (KrCl excilamp) (Sp-Ex) and investigated their decontamination effect against Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes on apple (Malus domestica Borkh.) and bell pepper (Capsicum annuum L.) surfaces. Initial levels of the three pathogens were approximately 108 CFU/sample. Both E. coli O157:H7 and S. Typhimurium were reduced to below the detection limit (2.0 log CFU/sample) after 5 and 7 min of treatment on apple and bell pepper surfaces, respectively. The amounts of L. monocytogenes on apple and bell pepper surfaces were reduced by 4.26 and 5.48 logs, respectively, after 7 min of treatment. The decontamination effect of the Sp-Ex was influenced by the hydrophobicity of the sample surface as well as the microbial cell surface, and the decontamination effect decreased as the two hydrophobicity values increased. To improve the decontamination effect of the Sp-Ex, Tween 20, a surfactant that weakens the hydrophobic interaction between the sample surface and pathogenic bacteria, was incorporated into Sp-Ex processing. It was found that its decontamination effect was significantly (P < 0.05) increased by the addition of 0.1% Tween 20. Sp-Ex did not cause significant quality changes in apple or bell pepper surfaces during 7 days storage following treatment (P > 0.05). Our results suggest that Sp-Ex could be applied as a system to control pathogens in place of chemical sanitizer washing by the fresh-produce industry.IMPORTANCE Although most fresh-produce processing currently controls pathogens by means of washing with sanitizers, there are still problems such as the generation of harmful substances and changes in product quality. A combination system composed of the Spindle and a 222-nm KrCl excilamp (Sp-Ex) developed in this study reduced pathogens on apple and bell pepper surfaces using sanitizer-free water without altering produce color and texture. This study demonstrates the potential of the Sp-Ex to replace conventional washing with sanitizers, and it can be used as baseline data for practical application by industry. In addition, implementation of the Sp-Ex developed in this study is expected not only to meet consumer preference for fresh, minimally processed produce but also to reduce human exposure to harmful chemicals while being beneficial to the environment.

Interactions of Carvacrol, Caprylic Acid, Habituation, and Mild Heat for Pressure-Based Inactivation of O157 and Non-O157 Serogroups of Shiga Toxin-Producing Escherichia coli in Acidic Environment

The current study investigated synergism of elevated hydrostatic pressure, habituation, mild heat, and antimicrobials for inactivation of O157 and non-O157 serogroups of Shiga toxin-producing Escherichia coli. Various times at a pressure intensity level of 450 MPa were investigated at 4 and 45 °C with and without carvacrol, and caprylic acid before and after three-day aerobic habituation in blueberry juice. Experiments were conducted in three biologically independent repetitions each consist of two replications and were statistically analyzed as a randomized complete block design study using ANOVA followed by Tukey- and Dunnett’s-adjusted mean separations. Under the condition of this experiment, habituation of the microbial pathogen played an influential (p < 0.05) role on inactivation rate of the pathogen. As an example, O157 and non-O157 serogroups were reduced (p < 0.05) by 1.4 and 1.6 Log CFU/mL after a 450 MPa treatment at 4 °C for seven min, respectively, before habituation. The corresponding log reductions (p < 0.05) after three-day aerobic habituation were: 2.6, and 3.3, respectively at 4 °C. Carvacrol and caprylic acid addition both augmented the pressure-based decontamination efficacy. As an example, Escherichia coli O157 were reduced (p < 0.05) by 2.6 and 4.2 log CFU/mL after a seven-min treatment at 450 MPa without, and with presence of 0.5% carvacrol, respectively, at 4 °C.

Polydimethylsiloxane Replicas Efficacy for Simulating Fresh Produce Surfaces and Application in Mechanistic Study of Colloid Retention

Foodborne illnesses associated with fresh produce have attracted increasing attention in the food industry, scientific and public health communities. Studies have shown that surface properties of fresh produce can affect bacterial attachment and colonization, yet the mechanisms involved remain poorly understood. In our previous work, using colloids as bacterial surrogates, we demonstrated that colloid retention on fresh produce was controlled by water retention/distribution on produce surfaces, which were in turn governed by produce surface properties. However, high variabilities among the natural samples and multiple factors that were simultaneously involved made it difficult for interpreting the results and in pinpointing the mechanisms responsible for the observed colloid retention behavior. To better evaluate the mechanisms, polydimethylsiloxane (PDMS) replicas of tomato, lettuce, and spinach were fabricated and compared with fresh produce surfaces in this study. The PDMS replicas thoroughly preserved the surface topographical features of their natural counterparts while having identical chemical properties (for example, hydrophobicity), thus, allowing for the separation of surface topography/roughness and hydrophobicity effects. We found that residual water retention/distribution and colloid retention on the PDMS replicas were consistent with the results observed on the corresponding fresh produce surfaces, but had smaller deviations from the respective means when compared to the natural surfaces. The use of PDMS replicas improved experimental reproducibility, and enabled differentiation on the effects of surface hydrophobicity and surface roughness on colloid retention, thus, allowed more rigorous elucidation of the underlying mechanisms. Therefore, PDMS replicas could be used as surrogates of fresh produce for mechanistic studies of surface-bacteria interactions. PRACTICAL APPLICATION: This work demonstrates the feasibility of using polydimethylsiloxane (PDMS) to simulate fresh produce surfaces for studying interactions between produce surfaces and colloids, including bacteria. Although it is more realistic to use fruit or vegetable surfaces, the difficulties of working with natural surfaces that are heterogeneous and variable hinder systematic and mechanistic studies. The use of PDMS replicas can eliminate these difficulties and improve experimental reproducibility. This study demonstrated that PDMS replicas could adequately represent the topographical features of natural produce surfaces; the results on colloid retention provided insight into fresh produce contamination and the development of effective decontamination strategies.

Predicting the Growth of Listeria monocytogenes and Salmonella Typhimurium in Diced Celery, Onions, and Tomatoes during Simulated Commercial Transport, Retail Storage, and Display

Temperature is arguably the most important factor affecting microbial proliferation in fresh-cut produce. In this study, growth of Listeria monocytogenes in diced onions and celery and Salmonella Typhimurium in diced tomatoes was determined in modified atmosphere packages and snap-fit containers using three fluctuating temperature scenarios for transport, retail storage, and display. As expected, L. monocytogenes growth in diced onions and celery varied depending on the extent of temperature abuse, with exposure to high and intermediate temperature-abuse scenarios generally being growth supportive. A Baranyi primary model with a square-root secondary model for maximum growth rate, and a linear model for maximum population density, were used to estimate Listeria growth under fluctuating temperature. Accuracy and acceptability of the model prediction were evaluated in terms of root mean square error (RMSE) and acceptable prediction zone (APZ), respectively. Overall, growth predictions for L. monocytogenes were more accurate for celery (RMSE, 0.28 to 0.47) than onions (RMSE, 0.42 to 1.53) under the fluctuating temperature scenarios tested. However, both predictions yielded APZ values that ranged from 82 to 100% for celery and 36 to 78% for onions. In contrast, Salmonella Typhimurium populations increased more than 1 log CFU/g in diced tomatoes under the three fluctuating temperature scenarios studied. Overall, these diced products packaged under a high-oxygen atmosphere showed decreased pathogen growth compared with product stored in a passive modified atmosphere. Findings from this study will be particularly useful in assessing the risk associated with consumption of diced celery, tomatoes, and onions and in designing effective packaging strategies to minimize pathogen growth in fresh-cut produce.

Associations of Salmonella hospitalizations with ambient temperature, humidity and rainfall in Hong Kong

BACKGROUND

Little is known about the relationship between Salmonella infection and meteorological parameters other than air temperature. This study aimed to explore associations of Salmonella hospitalizations with temperature, relative humidity (RH) and rainfall.

METHODS

With negative binomial distribution assumed, time-series regression model adjusting for season and time trend were constructed employing distributed lag non-linear models and generalized additive models. Meteorological variables including mean temperature, RH, and daily total rainfall as well as indicator variables including day of the week and public holiday were incorporated in the models.

RESULTS

Higher temperature was strongly associated with more hospitalizations over the entire range of temperatures observed. There was a net 6.13 (95%Confidence Interval (CI) 3.52-10.67) relative risk of hospitalization at a temperature of 30.5 °C, relative to 13 °C, lag 0-16 days. Positive associations were found for RH above 60% and rainfall between 0 and 0.14 mm. Extreme high humidity (96%) and trace rainfall (0.02 mm) were associated with 2.06 (95%CI 1.35-3.14), lag 0-17 day, and 1.30 (95%CI 1.01-1.67), lag 0-26 days, relative risks of hospitalizations, relative to 60% and no rain, respectively.

CONCLUSIONS

High temperatures, high RH and light rainfall are positively associated with Salmonella hospitalizations. The very strong association with temperatures implies that hotter days will lead to increases in Salmonella morbidity in the absence of other changes, and the public health implications of this could be exacerbated by global climate change.

Comparative persistence of Salmonella and Escherichia coli O157:H7 in loam or sandy loam soil amended with bovine or swine manure

The fate of Salmonella and Escherichia coli O157:H7 in swine or dairy manure amended into sandy loam or loam soil under field conditions was studied. Soil was amended with manure inoculated with a Salmonella or E. coli O157:H7 cocktail, then transferred to 0.22 μm pore size membrane walled vials. The vials were then placed on the surface or at 15 cm depth in the test plots. Pathogen numbers, soil moisture, rainfall, and temperature were measured throughout the three trials (20-47 weeks duration) representing spring or fall application. Survival curves were characterized by having an initial rapid decline in pathogen numbers followed by a slower inactivation phase with an occasional increase in culturable cells. The CT_99.9 values (time to reach a 3 log CFU reduction) varied from 2 to 120 days, with the most rapid decrease being observed on the surface of sandy loam soil. The persistence of pathogens is primarily governed by variations in moisture and temperature, although season of application along with manure and soil type also contribute. To generate more accurate predictive pathogen models, there is a need for laboratory-based trials to mirror the dynamic variation in temperature and soil moisture encountered within the natural environment.

Sources and contamination routes of microbial pathogens to fresh produce during field cultivation: A review

Foodborne illness resulting from the consumption of contaminated fresh produce is a common phenomenon and has severe effects on human health together with severe economic and social impacts. The implications of foodborne diseases associated with fresh produce have urged research into the numerous ways and mechanisms through which pathogens may gain access to produce, thereby compromising microbiological safety. This review provides a background on the various sources and pathways through which pathogenic bacteria contaminate fresh produce; the survival and proliferation of pathogens on fresh produce while growing and potential methods to reduce microbial contamination before harvest. Some of the established bacterial contamination sources include contaminated manure, irrigation water, soil, livestock/ wildlife, and numerous factors influence the incidence, fate, transport, survival and proliferation of pathogens in the wide variety of sources where they are found. Once pathogenic bacteria have been introduced into the growing environment, they can colonize and persist on fresh produce using a variety of mechanisms. Overall, microbiological hazards are significant; therefore, ways to reduce sources of contamination and a deeper understanding of pathogen survival and growth on fresh produce in the field are required to reduce risk to human health and the associated economic consequences.

Viral outbreaks linked to fresh produce consumption: a systematic review

AIMS

Α systematic review to investigate fresh produce-borne viral outbreaks, to record the outbreak distribution worldwide and to analyse the implication of different types of fresh produce and viral types as well.

METHODS AND RESULTS

Four databases (PubMed/Medline, Scopus, Eurosurveillance Journal and Spingerlink electronic journal) and a global electronic reporting system (ProMED-mail) were searched up to 2016. One hundred and fifty-two viral outbreaks linked to fresh produce consumption were identified. The majority of the reported outbreaks was reported in Europe, followed by North America, Asia, Australia, Africa and South America. A great number of the outbreaks was recorded in Denmark and Finland. The most common viral pathogens were norovirus (48·7%) and hepatitis A virus (46·1%). The most frequent type of fresh produce involved was frozen raspberries (23·7%). Differences in the reporting of outbreaks were recorded between the scientific literature and ProMED.

CONCLUSIONS

The number of reported illnesses linked to fresh produce has increased in several countries. Consumption of contaminated fresh produce represents a risk to public health in both developed and developing countries, but the impact will be disproportionate and likely to compound existing health disparities. For this reason, all countries should systematically collate and report such data through a disease surveillance system, in order to adopt risk management practices for reducing the likelihood of contamination.

Incorporating Phage Therapy into WPI Dip Coatings for Applications on Fresh Whole and Cut Fruit and Vegetable Surfaces

There is a significant unmet need to develop antimicrobial solutions to reduce the risk of contamination in fresh produce. Bacteriophages have been proposed as a potential approach for controlling foodborne pathogens. This study evaluated the combination of edible dip coatings with T7 bacteriophages on whole and cut produce. The evaluation includes an assessment of phage loading, phage storage stability, antimicrobial activity, and phage stability during simulated gastric digestion on sliced cucumbers, sliced apples, and whole cherry tomatoes. In this evaluation, phages coated on fresh produce using edible whey protein isolate (WPI) were compared with phages coated from an aqueous suspension (control coating). The results demonstrated that WPI coatings load more phages than the control and enhanced phage stability during cold storage (4 °C) for cut apples and whole cherry tomatoes. Phage stability decreased by 1 to 3 log(PFU) in a simulated gastric environment. Phage antimicrobial activity against Escherichia coli BL21 decreased 2 to 4 log(CFU) of bacteria on cut apples and whole cherry tomatoes, while no significant bacterial reduction was observed for sliced cucumbers. Overall, the results show that WPI dip coating provides phage loading, stability, and antimicrobial activity to produce surfaces compared to the control coating, and thus may be considered an effective approach for extending phage therapy on fresh produce.

PRACTICAL APPLICATION

The practical application is to prevent bacterial cross contamination of fresh produce by using a combination of edible coating with bacteriophages. The results demonstrate enhanced loading and stability of phages on fresh produce when used in combination with an edible coating.

Application of water-assisted ultraviolet light in combination of chlorine and hydrogen peroxide to inactivate Salmonella on fresh produce

With the demand for fresh produce increases in recent decades, concerns for microbiological safety of fresh produce are also raised. To identify effective ultraviolet (UV) light treatment for fresh produce decontamination, we first determined the effect of three forms of UV treatment, dry UV (samples were treated by UV directly), wet UV (samples were dipped in water briefly and then exposed to UV), and water-assisted UV (samples were treated by UV while being immersed in agitated water) on inactivation of Salmonella inoculated on tomatoes and fresh-cut lettuce. In general, the water-assisted UV treatment was found to be the most effective for both produce items. Chlorine and hydrogen peroxide were then tested to determine whether they could be used to enhance the decontamination efficacy of water-assisted UV treatment and prevent transfer of Salmonella via wash water by completely eliminating it. Neither of them significantly enhanced water-assisted UV inactivation of Salmonella on tomatoes. Chlorine significantly improved the decontamination effectiveness of the water-assisted UV treatment for baby-cut carrots and lettuce, but not for spinach. In general, the single water-assisted UV treatment and the combined treatment of water-assisted UV and chlorine were similar or more effective than the chlorine washing treatment. In most of the cases, no Salmonella was detected in the wash water when the single water-assisted UV treatment was used to decontaminate tomatoes. In a few cases when Salmonella was detected in the wash water, the populations were very low,≤2CFU/mL, and the wash water contained an extremely high level of organic load and soil level. Therefore, the single water-assisted UV treatment could potentially be used as an environmentally friendly and non-chemical alternative to chlorine washing for tomatoes after validation in industrial scale. For lettuce, spinach and baby-cut carrots, the combined treatment of water-assisted UV treatment and chlorine was needed to maintain a pathogen free environment in the wash water so that cross contamination could be prevented during fresh produce washing.

Comparative stability and efficacy of selected chlorine-based biocides against Escherichia coli in planktonic and biofilm states

Microbial contamination is an unavoidable problem in industrial processes. Sodium hypochlorite (SH) is the most common biocide used for industrial disinfection. However, in view of the current societal concerns on environmental and public health aspects, there is a trend to reduce the use of this biocide as it can lead to the formation of organochlorinated carcinogenic compounds. In this work the efficacy of SH was assessed against Escherichia coli in planktonic and biofilm states and compared with three alternative chlorine-based biocides: neutral electrolyzed oxidizing water (NEOW), chlorine dioxide (CD) and sodium dichloroisocyanurate (NaDCC). The planktonic tests revealed that SH had the fastest antimicrobial action, NaDCC exhibited the highest antimicrobial rate and NEOW caused the highest antimicrobial effects. Additionally, NEOW was the biocide that allowed the highest formation of reactive oxygen species (ROS). In biofilm control, NEOW and CD were the most efficient biocides causing 3.26 and 3.20 log CFU·cm^-2 reduction, respectively. In terms of stability for chlorine depletion, NEOW had the longest decay time for chlorine loss (70days at 5°C) and the lowest chlorine loss rate (0.013ppm·min^-1 at 5°C). CD and NaDCC had equivalent stability. The overall results demonstrated NEOW as a good alternative to SH due to its higher antimicrobial effects and lower chlorine depletion over time.

Reducing Foodborne Pathogen Persistence and Transmission in Animal Production Environments: Challenges and Opportunities

Preharvest strategies to reduce zoonotic pathogens in food animals are important components of the farm-to-table food safety continuum. The problem is complex; there are multiple pathogens of concern, multiple animal species under different production and management systems, and a variety of sources of pathogens, including other livestock and domestic animals, wild animals and birds, insects, water, and feed. Preharvest food safety research has identified a number of intervention strategies, including probiotics, direct-fed microbials, competitive exclusion cultures, vaccines, and bacteriophages, in addition to factors that can impact pathogens on-farm, such as seasonality, production systems, diet, and dietary additives. Moreover, this work has revealed both challenges and opportunities for reducing pathogens in food animals. Animals that shed high levels of pathogens and predominant pathogen strains that exhibit long-term persistence appear to play significant roles in maintaining the prevalence of pathogens in animals and their production environment. Continued investigation and advancements in sequencing and other technologies are expected to reveal the mechanisms that result in super-shedding and persistence, in addition to increasing the prospects for selection of pathogen-resistant food animals and understanding of the microbial ecology of the gastrointestinal tract with regard to zoonotic pathogen colonization. It is likely that this continued research will reveal other challenges, which may further indicate potential targets or critical control points for pathogen reduction in livestock. Additional benefits of the preharvest reduction of pathogens in food animals are the reduction of produce, water, and environmental contamination, and thereby lower risk for human illnesses linked to these sources.

Assessing the antimicrobial potential of aerosolised electrochemically activated solutions (ECAS) for reducing the microbial bio-burden on fresh food produce held under cooled or cold storage conditions

The main aim of this study was to assess the antimicrobial efficacy of electrochemically activated fog (ECAF) for reducing the microbial bio-burden on artificially inoculated fresh produce held under cooled (cucumber and vine tomatoes) or cold (rocket and broccoli) storage conditions. The ECAF treatment (1100 ± 5 mV ORP; 50 ± 5 mg L^-1 free chlorine; 2.7 ± 0.1 pH) resulted in a significant log reduction in the potential pathogen E. coli recovered from rocket (2.644 Log₁₀ CFU g^-1), broccoli (4.204 Log₁₀ CFU g^-1), cucumber (3.951 Log₁₀ CFU g^-1) and tomatoes (2.535 Log10 CFU g-1) after 5 days. ECAF treatment also resulted in a significant log reduction in potential spoilage organisms, whereby a 3.533 Log₁₀ CFU g^-1, 2.174 Log₁₀ CFU g^-1 and 1.430 Log₁₀ CFU g^-1 reduction in presumptive Pseudomonads was observed for rocket, broccoli and cucumber respectively, and a 3.527 Log₁₀ CFU g^-1 reduction in presumptive Penicillium spp. was observed for tomatoes (after 5 days). No adverse visual effects on produce were recorded. The results of this study will inform industrial scale-up trials within commercial facilities (assessing shelf-life, microbial quality and organoleptic assessment) to assess the developed ECAF technology platform within a real food processing environment.