scholarly journals Variability in growth responses of non-O157 EHEC isolates in leafy vegetables, sprouted seeds and soil extracts occurs at the isolate level

2020 ◽  
Vol 367 (1) ◽  
Author(s):  
Bernhard Merget ◽  
Ulrich Dobrindt ◽  
Ken J Forbes ◽  
Norval J C Strachan ◽  
Fiona Brennan ◽  
...  
Keyword(s):  
Foodborne Pathogens ◽  
Growth Rates ◽  
Fresh Produce ◽  
Leafy Vegetables ◽  
Dependent Manner ◽  
Growth Responses ◽  
Soil Extracts ◽  
E Coli ◽  
Sprouted Seeds ◽  
Rates Of Growth

ABSTRACT Foods of plant origin are recognised as a major source of foodborne pathogens, in particular for Shigatoxigenic Escherichia coli (STEC). Most work for STEC and plant-based fresh produce has focused on the most prevalent outbreak serogroup, O157. However, non-O157 STEC is an emerging hazard, and as such it is important to characterise aspects within this group that reflect their ability to colonise alternative hosts and habitats relevant to horticultural production. Growth kinetics were quantified for a diverse set of clinical enterohaemorrhagic E. coli isolates in extracts made from different tissues of spinach, lettuce or sprouted seeds, or from soil, to represent association with ready-to-eat fresh produce production. For leafy vegetables, spinach apoplast supported the fastest rates of growth and lettuce root extracts generated the slowest growth rates. Growth rates were similar for the majority of isolates in fenugreek or alfalfa sprouted seed extracts. Monosaccharides were the major driver of bacterial growth. No correlations were found for growth rates between different serotypes or for Shigatoxin gene carriage. Thus, growth rates varied in a plant-dependent and isolate-dependent manner, for all plant or soil extracts tested, indicative of isolate-specific differences in metabolic flexibility. These findings are relevant for risk assessment of non-O157 STEC.

Salmonella and Escherichia coli Prevalence in Meat and Produce Sold at Farmers' Markets in Northern California

2020 ◽  
Vol 83 (11) ◽  
pp. 1934-1940
Author(s):  
ALDA F. A. PIRES ◽  
JAMES STOVER ◽  
ESTHER KUKIELKA ◽  
VIKTORIA HAGHANI ◽  
PEIMAN AMINABADI ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Foodborne Pathogens ◽  
Fresh Produce ◽  
Mitigation Strategies ◽  
Farmers Markets ◽  
Most Probable Number ◽  
Northern California ◽  
Animal Products ◽  
Probable Number ◽  
E Coli

ABSTRACT As the number of farmers' markets and other direct-to-consumer marketing channels increases, it is crucial to understand the potential risks associated with consuming directly marketed animal products and fresh produce. The overall aim of this project was to assess the prevalence of Salmonella and Escherichia coli in animal products and produce sold at farmers' markets in Northern California and to evaluate the food safety risks associated with consuming meat (e.g., beef, pork, and poultry) and fresh produce purchased from farmers' markets. Animal products and produce were purchased from a total of 44 certified farmers' markets in Northern California. Salmonella was found in 6 (1.8%) of 338 animal products and in 0 (0%) of 128 produce samples; E. coli was found in 40 (31.3%) of 128 fresh produce samples. E. coli concentration in produce ranged from 0 to 2.96, with an overall average of 0.13 log (most probable number + 1)/100 mL. Salmonella isolates were resistant to nalidixic acid and tetracycline. The results from this study highlight the need for further training on mitigation strategies to reduce contamination of animal products and fresh produce by foodborne pathogens. HIGHLIGHTS

Factors Affecting Compost Tea as a Potential Source of Escherichia coli and Salmonella on Fresh Produce†

2007 ◽  
Vol 70 (4) ◽  
pp. 828-834 ◽  
Author(s):  
D. T. INGRAM ◽  
P. D. MILLNER
Keyword(s):  
Escherichia Coli ◽  
Foodborne Pathogens ◽  
Salmonella Enteritidis ◽  
Fresh Produce ◽  
Fecal Coliforms ◽  
Compost Tea ◽  
Human Pathogens ◽  
Growth And Survival ◽  
E Coli ◽  
Nutrient Supplements

Compost tea (CT) is an unheated on-farm infusion of compost used as a spray or soil drench to promote plant growth and control foliar and root diseases. Because food safety involves all aspects from farm to fork, CT should meet basic microbiological criteria for water quality. This report describes the effects of two CT production processes, aerated and nonaerated, on growth and survival of foodborne pathogens and fecal coliforms. Seven commercially available nutrients used to supplement CT were tested individually and in combination for their effects on the growth of Escherichia coli and Salmonella. Compost containing 101 to 103 CFU/g initial concentrations of E. coli O157:H7 and Salmonella Enteritidis were used to assess growth and survival responses to aerated CT (36-h preparations) and nonaerated CT (8.5-day preparations). Pathogen and fecal coliform populations were undetectable by 8.5 days in nonaerated CT without nutrient supplements. E. coli O157:H7 decreased to below detection levels in aerated CT at 36 h without the use of supplements. In contrast, the addition of commercially formulated mixtures or combinations of nutrient supplements resulted in growth of E. coli O157: H7, Salmonella, and fecal coliforms by 1 to 4 log CFU/g in both aerated and nonaerated CT. When nutrient supplements were added, aerated CT sustained higher concentrations of E. coli O157:H7, Salmonella, and fecal coliforms than did nonaerated CT. Thus, addition of supplements supports growth of human pathogens from very low initial concentrations in both aerated and nonaerated CT and should be avoided when CT is used on fresh produce.

The growth responses of Locusta migratoria migratorioides (R. & F.) to fluctuating temperature regimes

1967 ◽  
Vol 57 (2) ◽  
pp. 259-270 ◽  
Author(s):  
Kenneth U. Clarke
Keyword(s):  
Weight Loss ◽  
Growth Rates ◽  
Locusta Migratoria ◽  
The Other ◽  
Wave Form ◽  
Growth Responses ◽  
Locusta Migratoria Migratorioides ◽  
Temperature Regimes ◽  
Resistance Thermometers ◽  
Rates Of Growth

Fourth- and fifth-instar hoppers and adults of Locusta migratoria migratorioides (R. & F.) were expected to three fluctuating remperature regimes in Weyco climatic cabinets and weighed daily. The regimes were 30 ± 0.25, 30 ± 10 and 30 ± 15°C., the change from one extreme to the other in the last two being made every two hours. Temperatures were accurately determined, by plantinum-resistance thermometers whose dimensions approximated to those of adult locusts, and were automatically recorded. The three thermorhythms were analysed by methods based on Fourier’s theorem, whereby a given wave form can be described in terms of a basic sine weve and a series of superimposed harmonics.The rates of growth (weight increase) in the 4th-instar and adult at 30 ± 10°C/ were higher than at 30 ± 0.25°C. and were within 10 per cent. of the means of the rates at constant temperatures of 20 and 40°C., whereas the frowth rate in the 5th instar, and the pre-copulation and pre-oviposition periods of adults and their rate of weight loss when starved, were the same under both regime. At 30 ± 15°C., 5th-instar hoppers did not survive and, in comparison with the other regimes, the growth rates of 4th-instar hoppers and adults were very much lower, the pre-copulation period of adults was the same but the pre-oviposition period was much longer and their rate of weight loss when starved was doubled. Adults locusts were also tested at 30 ± 17.5°C., but most of them died within 24 hours and all within three days.

scholarly journals Responses of Escherichia coli and Listeria monocytogenes to ozone treatment on non-host tomato: Efficacy of intervention and evidence of induced acclimation

2021 ◽  
Author(s):  
Benildo G de los Reyes ◽  
Xiaomei Shu ◽  
Manavi Singh ◽  
Naga Bhushana Rao Karampudi ◽  
David F Bridges ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Fresh Produce ◽  
Defense Responses ◽  
Ozone Treatment ◽  
High Dose ◽  
Dependent Manner ◽  
Moderate Dose ◽  
E Coli ◽  
Dose Time

Because of the continuous rise of foodborne illnesses caused by the consumption of raw fruits and vegetables, effective post-harvest anti-microbial strategies are needed. This study evaluated the dose × time effects on the anti-microbial action of ozone (O 3 ) gas against the Gram-negative Escherichia coli O157:H7 and Gram-positive Listeria monocytogenes, which are common contaminants in fresh produce . The study on non-host tomato environment correlated the dose × time aspects of xenobiosis by examining the correlation between bacterial survival in terms of log-reduction and defense responses at the level of gene expression. In E. coli , low (1 µg O 3 /g of fruit) and moderate (2 µg O 3 /g of fruit) doses caused insignificant reduction in survival, while high dose (3 µg/g of fruit) caused significant reduction in survival in a time-dependent manner. In L. monocytogenes , moderate dose caused significant reduction even with short-duration exposure. Distinct responses to O 3 xenobiosis between E. coli and L. monocytogenes are likely related to differences in membrane and cytoplasmic structure and components. Transcriptome profiling by RNA-Seq showed that primary defenses in E. coli were attenuated after exposure to a low dose, while the responses at moderate dose were characterized by massive upregulation of pathogenesis and stress-related genes, which implied the activation of defense responses. More genes were downregulated during the first hour at high dose, with a large number of such genes getting significantly upregulated after 2 hr and 3 hr. This trend suggests that prolonged exposure led to potential adaptation. In contrast, massive downregulation of genes was observed in L. monocytogenes regardless of dose and exposure duration, implying a mechanism of defense distinct from that of E. coli .  The nature of bacterial responses revealed by this study should guide the selection of xenobiotic agents for eliminating bacterial contamination on fresh produce without overlooking the potential risks of adaptation.

scholarly journals A Microbiological Survey of Selected Alberta-Grown Fresh Produce from Farmers' Markets in Alberta, Canada

2009 ◽  
Vol 72 (2) ◽  
pp. 415-420 ◽  
Author(s):  
V. M. BOHAYCHUK ◽  
R. W. BRADBURY ◽  
R. DIMOCK ◽  
M. FEHR ◽  
G. E. GENSLER ◽  
...  
Keyword(s):  
Foodborne Pathogens ◽  
Fresh Produce ◽  
Farmers Markets ◽  
Most Probable Number ◽  
Urban Centers ◽  
Probable Number ◽  
Public Markets ◽  
E Coli ◽  
Surrounding Areas ◽  
Campylobacter Spp

Previously there was no available information on the levels of indicator bacteria and the prevalence of pathogens in fresh produce grown in Alberta, Canada. Baseline information on the occurrence and levels of Escherichia coli and the prevalence of foodborne pathogens in selected produce items available to consumers from farmers' and public markets in two large urban centers and surrounding areas in Alberta was obtained. A total of 10 large markets with between 1 and 12 produce vendors and 26 small markets with between 1 and 6 produce vendors were sampled from 21 June to 7 October 2007. Lettuce (128 samples), spinach (59 samples), tomatoes (120 samples), carrots (206 samples), green onions (129 samples), and strawberries (31 samples) were analyzed for E. coli, Salmonella, E. coli O157:H7, and Campylobacter spp. Lettuce, spinach, green onion, and strawberry samples were also tested for the presence of Cryptosporidium spp. Information on whether produce was grown using organic or conventional practices was obtained from the produce vendors. E. coli was isolated from 8.2% of the samples that included lettuce, spinach, carrots, and green onions. The bacterial counts ranged from <0.48 to >3.04 Log most probable number per g. E. coli was not isolated from tomatoes or strawberries. The percentage of positive samples ranged from 4.4% for carrots to 27.1% for spinach. Salmonella, E. coli O157:H7, and Campylobacter spp. were not isolated from any of the samples. Cryptosporidium was identified by PCR in one sample of spinach (0.6% of the samples).

scholarly journals Survival and Persistence of Foodborne Pathogens in Manure-Amended Soils and Prevalence on Fresh Produce in Certified Organic Farms: A Multi-Regional Baseline Analysis

2021 ◽  
Vol 5 ◽  
Author(s):  
Thais De Melo Ramos ◽  
Michele T. Jay-Russell ◽  
Patricia D. Millner ◽  
Jerome Nicholas Baron ◽  
James Stover ◽  
...  
Keyword(s):  
Foodborne Pathogens ◽  
Crop Production ◽  
Fresh Produce ◽  
Soil Samples ◽  
Animal Origin ◽  
Treated Animal ◽  
Organic Farms ◽  
E Coli ◽  
Certified Organic ◽  
Regional Baseline

Biological soil amendments of animal origin (BSAAOs), including untreated (e.g., raw or aged manure, or incompletely composted manure) and treated animal products (e.g., compost), are used for crop production and as part of soil health management. Application of BSAAO's must be done cautiously, as raw manure commonly contains enteric foodborne pathogens that can potentially contaminate edible produce that may be consumed without cooking. USDA National Organic Program (NOP) certified production systems follow the 90-or 120-day interval standards between applications of untreated BSAAOs and crop harvest, depending on whether the edible portions of the crops are in indirect or direct contact with the soil, respectively. This study was conducted to evaluate the survival of four foodborne pathogens in soils amended with BSAAOs and to examine the potential for bacterial transfer to fresh produce harvested from USDA NOP certified organic farms (19) from four states. Only 0.4% (2/527) of produce samples were positive for L. monocytogenes. Among the untreated manure and compost samples, 18.0% (42/233) were positive for at least one of the tested and culturable bacterial foodborne pathogens. The prevalence of non-O157 STEC and Salmonella in untreated manure was substantially > that of E. coli O157:H7 and L. monocytogenes. Of the 2,461 soil samples analyzed in this study, 12.9% (318) were positive for at least one pathogen. In soil amended with untreated manure, the prevalence of non-O157 STEC [7.7% (190) and L. monocytogenes (5.0% (122), was > that of Salmonella (1.1% (26)] or E. coli O157 [0.04% (1)]. Foodborne pathogen prevalence in the soil peaked after manure application and decreased significantly 30 days post-application (dpa). However, non-O157 STEC and L. monocytogenes were recovered from soil samples after 90 and 120 dpa. Results indicate that produce contamination by tested foodborne pathogens was infrequent, but these data should not be generalized outside of the specific wait-time regulations for organic crop production and the farms studied. Moreover, other sources of contamination, e.g., irrigation, wildlife, environmental conditions, cropping and management practices, should be considered. This study also provides multi-regional baseline data relating to current NOP application intervals and development of potential risk mitigation strategies to reduce pathogen persistence in soils amended with BSAAOs. These findings contribute to filling critical data gaps concerning occurrence of fecal pathogens in NOP-certified farming systems used for production of fresh produce in different US regions.

Prevalence of Multidrug-Resistant Bacteria from U.S.-Grown and Imported Fresh Produce Retailed in Chain Supermarkets and Ethnic Stores of Davidson County, Tennessee

2017 ◽  
Vol 80 (3) ◽  
pp. 506-514 ◽  
Author(s):  
Siqin Liu ◽  
Agnes Kilonzo-Nthenge
Keyword(s):  
Pathogenic Bacteria ◽  
Fresh Produce ◽  
Agricultural Practices ◽  
Multidrug Resistant ◽  
Leafy Vegetables ◽  
Resistant Bacteria ◽  
Antibiotic Resistant Bacteria ◽  
Antibiotic Resistant ◽  
E Coli ◽  
Public Health Hazards

ABSTRACTThe aim of this study was to determine whether U.S.-grown and imported fresh produce retailed in ethnic stores and chain supermarkets was a reservoir of antibiotic-resistant bacteria. A total of 360 (129 imported and 231 U.S.-grown) samples of fresh produce were purchased from retail stores and analyzed for Enterobacteriaceae, including three pathogenic bacteria (Escherichia coli O157:H7, Shigella, and Salmonella), using standard methods. Presumptive pathogenic isolates were confirmed using PCR. The mean Enterobacteriaceae counts for imported produce were 6.87 ± 0.15 log CFU/g and 7.16 ± 0.11 log CFU/g in ethnic stores and chain supermarkets, respectively. For U.S.-grown produce, the contamination levels were at 8.35 ± 0.17 log CFU/g and 7.52 ± 0.13 log CFU/g in ethnic stores and chain supermarkets, respectively. Salmonella (0 and 0.3%), Shigella (1.7 and 0.6%), E. coli (3.1 and 1.4%), Enterobacter (9.4 and 8.6%), Klebsiella (6.7 and 0.6%), and Serratia (5.8 and 1.4%) were detected in produce from ethnic stores and chain supermarkets, respectively. None of the samples were positive for E. coli O157:H7. Regarding distribution by produce type, leafy vegetables had a significantly (P < 0.05) higher prevalence of Enterobacteriaceae (19.2%) than the other types, followed by root vegetables (6.4%), tomatoes (5.6%), and fruits (3.9%). Antibiotic-resistant Salmonella, Shigella, E. coli, Enterobacter, Klebsiella, and Erwinia bacteria were also isolated from fresh produce. The frequencies of vancomycin resistance (98.1 and 100%) were significantly higher (P < 0.05) than the frequencies of ampicillin resistance (42.3 and 72.9%) for imported and U.S.-grown produce, respectively. Despite the increased attention to the role of imported produce as a source of antimicrobial resistance, this study indicates that U.S.-grown produce is also contaminated with antibiotic-resistant bacteria. Good agricultural practices on the farms and washing of fresh produce before consumption are greatly recommended to avoid possible public health hazards.

Photocatalytically Enhanced Inactivation of Internalized Pathogenic Bacteria in Fresh Produce using Ultraviolet Irradiation with Nano-titanium Dioxide

2020 ◽  
Author(s):  
Seungjun Lee ◽  
Chulkyoon Mok ◽  
Jiyoung Lee
Keyword(s):  
Public Health ◽  
Titanium Dioxide ◽  
Food Safety ◽  
Uv Irradiation ◽  
Foodborne Pathogens ◽  
Pathogenic Bacteria ◽  
Safety Issue ◽  
Fresh Produce ◽  
Future Research ◽  
E Coli

Once pathogens are internalized in fresh produce, they pose a challenging food safety issue since they are not effectively inactivated by conventional rinsing or sanitization. To protect food safety and public health, the objectives were to examine internalized levels of foodborne pathogens in different types of fresh produce and to investigate the effectiveness of photocatalytically enhanced inactivation of internalized pathogens in fresh produce using UV irradiation with titanium dioxide (TiO 2 ). For this, green fluorescent protein-labeled S. Typhimurium and E. coli O157:H7 were inoculated on the leaf surface of four types of fresh produce (~10 8 CFU (colony-forming unit)/leaf) and varying concentrations of TiO 2 suspension (0.50, 0.75, 1.00, 1.25, and 1.50 µg/ml)) were applied to the surface of contaminated leaves. Depending on the nature of each vegetable, the internalized bacterial level differed (log 2 – 5 CFU/g of leaf). When UV irradiation (6,000 J/m 2 ) was applied, the internalized S. Typhimurium and E. coli levels were reduced by 0.8 – 2.4 log CFU/leaf and was with TiO 2 , the reduction was 1.1 – 3.7 log CFU/leaf. The inactivation efficiency increased as the TiO 2 concentration (up to 1.50 μg/leaf). These results indicate that the TiO 2 application enhanced the photocatalytic inactivation of internalized foodborne pathogens. The application of TiO2 would be most practical before UV irradiation and before distributing the produce. This study established a platform for future research on the inactivation of various internalized pathogens for protecting public health and scaling up fresh produce treatments by the food industry.

scholarly journals Influence of Plant Species, Tissue Type, and Temperature on the Capacity of Shiga-ToxigenicEscherichia coliTo Colonize, Grow, and Be Internalized by Plants

2019 ◽  
Vol 85 (11) ◽  
Author(s):  
Bernhard Merget ◽  
Ken J. Forbes ◽  
Fiona Brennan ◽  
Sean McAteer ◽  
Tom Shepherd ◽  
...  
Keyword(s):  
Plant Species ◽  
Growth Kinetics ◽  
Plant Extracts ◽  
Biofilm Formation ◽  
Leafy Vegetables ◽  
Tissue Type ◽  
In Planta ◽  
Content Type ◽  
E Coli ◽  
Sprouted Seeds

ABSTRACTContamination of fresh produce with pathogenicEscherichia coli, including Shiga-toxigenicE. coli(STEC), represents a serious risk to human health. Colonization is governed by multiple bacterial and plant factors that can impact the probability and suitability of bacterial growth. Thus, we aimed to determine whether the growth potential of STEC for plants associated with foodborne outbreaks (two leafy vegetables and two sprouted seed species) is predictive of the colonization of living plants, as assessed from growth kinetics and biofilm formation in plant extracts. The fitness of STEC isolates was compared to that of environmentalE. coliisolates at temperatures relevant to plant growth. Growth kinetics in plant extracts varied in a plant-dependent and isolate-dependent manner for all isolates, with spinach leaf lysates supporting the highest rates of growth. Spinach extracts also supported the highest levels of biofilm formation. Saccharides were identified to be the major driver of bacterial growth, although no single metabolite could be correlated with growth kinetics. The highest level ofin plantacolonization occurred on alfalfa sprouts, though internalization was 10 times more prevalent in the leafy vegetables than in sprouted seeds. Marked differences inin plantagrowth meant that the growth potential of STEC could be inferred only for sprouted seeds. In contrast, biofilm formation in extracts related to spinach colonization. Overall, the capacity ofE. colito colonize, grow, and be internalized within plants or plant-derived matrices was influenced by the isolate type, plant species, plant tissue type, and temperature, complicating any straightforward relationship betweenin vitroandin plantabehaviors.IMPORTANCEFresh produce is an important vehicle for STEC transmission, and experimental evidence shows that STEC can colonize plants as secondary hosts, but differences in the capacity to colonize occur between different plant species and tissues. Therefore, an understanding of the impact that these plant factors have on the ability of STEC to grow and establish is required for food safety considerations and risk assessment. Here, we determined whether growth and the ability of STEC to form biofilms in plant extracts could be related to specific plant metabolites or could predict the ability of the bacteria to colonize living plants. Growth rates for sprouted seeds (alfalfa and fenugreek) but not those for leafy vegetables (lettuce and spinach) exhibited a positive relationship between plant extracts and living plants. Therefore, the detailed variations at the level of the bacterial isolate, plant species, and tissue type all need to be considered in risk assessment.

scholarly journals Relating growth potential and biofilm formation of Shigatoxigenic Escherichia coli to in planta colonisation and the metabolome of ready-to-eat crops

2019 ◽  
Author(s):  
Bernhard Merget ◽  
Ken J. Forbes ◽  
Fiona Brennan ◽  
Sean McAteer ◽  
Tom Shepherd ◽  
...  
Keyword(s):  
Plant Species ◽  
Growth Kinetics ◽  
Plant Extracts ◽  
Biofilm Formation ◽  
Growth Potential ◽  
Leafy Vegetables ◽  
Tissue Type ◽  
In Planta ◽  
E Coli ◽  
Sprouted Seeds

AbstractContamination of fresh produce with pathogenic Escherichia coli, including Shigatoxigenic E. coli (STEC), represents a serious risk to human health. Colonisation is governed by multiple bacterial and plant factors that can impact on the probability and suitability of bacterial growth. Thus, we aimed to determine whether the growth potential of STEC for plants associated with foodborne outbreaks (two leafy vegetables and two sprouted seed species), is predictive for colonisation of living plants as assessed from growth kinetics and biofilm formation in plant extracts. Fitness of STEC was compared to environmental E. coli, at temperatures relevant to plant growth. Growth kinetics in plant extracts varied in a plant-dependent and isolate-dependent manner for all isolates, with spinach leaf lysates supporting the fastest rates of growth. Spinach extracts also supported the highest levels of biofilm formation. Saccharides were identified as the major driver of bacterial growth, although no single metabolite could be correlated with growth kinetics. The highest level of in planta colonisation occurred on alfalfa sprouts, though internalisation was 10-times more prevalent in the leafy vegetables than in sprouted seeds. Marked differences in in planta growth meant that growth potential could only be inferred for STEC for sprouted seeds. In contrast, biofilm formation in extracts related to spinach colonisation. Overall, the capacity of E. coli to colonise, grow and internalise within plants or plant-derived matrices were influenced by the isolate type, plant species, plant tissue type and temperature, complicating any straight-forward relationship between in vitro and in planta behaviours.ImportanceFresh produce is an important vehicle for STEC transmission and experimental evidence shows that STEC can colonise plants as secondary hosts, but differences in the capacity to colonise occur between different plant species and tissues. Therefore, an understanding of the impact of these plant factors have on the ability of STEC to grow and establish is required for food safety considerations and risk assessment. Here, we determined whether growth and the ability of STEC to form biofilms in plants extracts could be related to specific plant metabolites or could predict the ability of the bacteria to colonise living plants. Growth rates for sprouted seeds (alfalfa and fenugreek) exhibited a positive relationship between plant extracts and living plants, but not for leafy vegetables (lettuce and spinach). Therefore, the detailed variations at the level of the bacterial isolate, plant species and tissue type all need to be considered in risk assessment.

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