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Thomas GA, Paradell Gil T, Müller CT, Rogers HJ, Berger CN. From field to plate: How do bacterial enteric pathogens interact with ready-to-eat fruit and vegetables, causing disease outbreaks? Food Microbiol 2024; 117:104389. [PMID: 37919001 DOI: 10.1016/j.fm.2023.104389] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 09/11/2023] [Accepted: 09/17/2023] [Indexed: 11/04/2023]
Abstract
Ready-to-eat fruit and vegetables are a convenient source of nutrients and fibre for consumers, and are generally safe to eat, but are vulnerable to contamination with human enteric bacterial pathogens. Over the last decade, Salmonella spp., pathogenic Escherichia coli, and Listeria monocytogenes have been linked to most of the bacterial outbreaks of foodborne illness associated with fresh produce. The origins of these outbreaks have been traced to multiple sources of contamination from pre-harvest (soil, seeds, irrigation water, domestic and wild animal faecal matter) or post-harvest operations (storage, preparation and packaging). These pathogens have developed multiple processes for successful attachment, survival and colonization conferring them the ability to adapt to multiple environments. However, these processes differ across bacterial strains from the same species, and across different plant species or cultivars. In a competitive environment, additional risk factors are the plant microbiome phyllosphere and the plant responses; both factors directly modulate the survival of the pathogens on the leaf's surface. Understanding the mechanisms involved in bacterial attachment to, colonization of, and proliferation, on fresh produce and the role of the plant in resisting bacterial contamination is therefore crucial to reducing future outbreaks.
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Affiliation(s)
- Gareth A Thomas
- School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff, CF10 3AX, UK
| | - Teresa Paradell Gil
- School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff, CF10 3AX, UK
| | - Carsten T Müller
- School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff, CF10 3AX, UK
| | - Hilary J Rogers
- School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff, CF10 3AX, UK
| | - Cedric N Berger
- School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff, CF10 3AX, UK.
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2
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A Plasma-Based Decontamination Process Reveals Potential for an in-Process Surface-Sanitation Method. PLASMA 2022. [DOI: 10.3390/plasma5030027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Methods, which use an indirect plasma treatment for the inactivation of microorganisms in foods, claim a vastly growing field of research. This paper presents a method that uses plasma-processed air (PPA) as a sanitizer. In addition to a sanitation concept for the decontamination of produce in the value chain, the presented method offers a possible application as an “in-process” surface sanitation. PPA provides antimicrobial-potent species, which are predominantly reactive nitrogen species (RNS); this has an outstanding groove penetration property. In an experimental approach, surfaces, made from materials, which are frequently used for the construction of food-processing plants, were inoculated with different microorganisms. Listeria monocytogenes (ATCC 15313), Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 10538), Salmonella enterica subsp. enterica serovar Typhimurium (ATCC 43971), and Salmonella enterica subsp. enterica serovar Enteritidis (ATCC 13076) are all microorganisms that frequently appear in foods and possess the risk for cross-contamination from the plant to the produce or vice versa. The contaminated samples were treated for various treatment times (1–5 min) with PPA of different antimicrobial potencies. Subsequently, the microbial load on the specimens was determined and compared with the load of untreated samples. As a result, reduction factors (RF) up to several log10-steps were obtained. Although surface and the bacterial strain showed an influence on the RF, the major influence was seen by a prolongation of the treatment time and an increase in the potency of the PPA.
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3
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Grivokostopoulos NC, Makariti IP, Tsadaris S, Skandamis PN. Impact of population density and stress adaptation on the internalization of Salmonella in leafy greens. Food Microbiol 2022; 106:104053. [PMID: 35690446 DOI: 10.1016/j.fm.2022.104053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 04/26/2022] [Accepted: 04/26/2022] [Indexed: 11/17/2022]
Abstract
Salmonella enterica is capable of entering the interior of leafy greens and establishing in the apoplastic area, a phenomenon known as internalization. The ability of internalized bacteria to evade common disinfection practices poses a well-established risk. Our aim was to study the effect of: i) inoculum size and ii) prior adaptation of Salmonella to sublethal stresses, on the internalization of the pathogen in four leafy vegetables. Spinach, lettuce, arugula and chicory were inoculated, by immersion for 2 min at room temperature with: i) Salmonella Enteritidis at 3.0, 4.0, 5.0, 6.0, 7.0 log CFU/mL and ii) non-adapted or adapted S. Enteritidis to acid (in TSB with 1% glucose, incubated for 24 h at 37 °C), cold (in TSB for 7 days at 4 °C), starvation (0.85% NaCl of pH 6.6, 48 h at 37 °C) or desiccation (1.5 h at 42 °C, 4 days at 21 °C) stress at appx 3.5 log CFU/mL). Inoculated leafy greens were subsequently stored at 5 °C and 20 °C for 2 h and 48 h (n = 2 × 2). Population of internalized Salmonella, after surface decontamination with 1% w/v AgNO3, was assessed on selective media. Even the lowest initial bacterial inoculum was adequate for internalization of Salmonella to occur in leafy vegetables. Non-adapted Salmonella inoculum of 7.0 (maximum) and 3.0 log CFU/mL (lowest inoculation level tested) after short storage (2 h) resulted in 3.7-4.3 and 1.3-1.5 log CFU/g internalized bacterial population, respectively. Colonization (including both attachment and internalization processes), as well as internalization process, were positively correlated to initial inoculum level. These processes reached a different plateau beyond which, no further increase in internalization was observed. Adaptation of the pathogen to mild stresses enhanced internalization (P < 0.05), with desiccation- and acid-adapted Salmonella demonstrating the highest internalization capacity, regardless of the vegetable and storage temperature. These findings could contribute to further elucidation of colonization capacity of Salmonella in leafy vegetables and assist in selecting the proper conditions that contribute to the prevention of fresh produce contamination with Salmonella.
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Affiliation(s)
- N C Grivokostopoulos
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece
| | - I P Makariti
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece
| | - S Tsadaris
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece
| | - P N Skandamis
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece.
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4
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Grivokostopoulos NC, Makariti IP, Hilaj N, Apostolidou Z, Skandamis PN. Internalization of Salmonella in Leafy Greens and Impact on Acid Tolerance. Appl Environ Microbiol 2022; 88:e0224921. [PMID: 35108086 PMCID: PMC8939352 DOI: 10.1128/aem.02249-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 01/26/2022] [Indexed: 11/20/2022] Open
Abstract
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.
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Affiliation(s)
- N. C. Grivokostopoulos
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
| | - I. P. Makariti
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
| | - N. Hilaj
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
| | - Z. Apostolidou
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
| | - P. N. Skandamis
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
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5
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Rhodes G, Chuang YH, Hammerschmidt R, Zhang W, Boyd SA, Li H. Uptake of cephalexin by lettuce, celery, and radish from water. CHEMOSPHERE 2021; 263:127916. [PMID: 33297013 DOI: 10.1016/j.chemosphere.2020.127916] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 07/26/2020] [Accepted: 08/03/2020] [Indexed: 06/12/2023]
Abstract
The introduction of pharmaceuticals into agricultural lands from the application of biosolids and animal manure, and irrigation with treated wastewater has led to concern for animal and human health after the ingestion of pharmaceutical-tainted agricultural products. In this study, the uptake and accumulation of cephalexin, a commonly prescribed antibiotic, was compared in three common vegetables (lettuce, celery, and radish) grown in nutrient solution for 144 h. During the uptake experiments, cephalexin concentration in the nutrient solution decreased in the order of radish > celery > lettuce, while the accumulation of cephalexin in vegetable roots followed the rank of lettuce > celery > radish. The accumulation of cephalexin was below the limit of detection in radish roots. No accumulation of cephalexin was observed in the shoots of all three vegetables. The behaviors of cephalexin in vivo were further elucidated using in vitro measurements of cephalexin sorption by vegetable roots and transformation in plant enzyme extracts. The affinity of cephalexin to lettuce > celery > radish roots, and the respective sorption coefficients of 687, 303, and 161 mL g-1, coupled to the transformation of cephalexin in root enzyme extracts with estimated reaction rate constants of 0.020, 0.027 and 0.024 hr-1 for lettuce, celery and radish, could help elucidate the accumulation observed in the in vivo experiments. Overall, sorption by plant roots (affinity) and reaction with plant enzymes could collectively influence the uptake and accumulation of cephalexin in vegetables.
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Affiliation(s)
- Geoff Rhodes
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, 48824, USA; Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, 48824, USA
| | - Ya-Hui Chuang
- Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung, 402, Taiwan
| | - Raymond Hammerschmidt
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, 48824, USA
| | - Wei Zhang
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, 48824, USA; Environmental Science and Policy Program, Michigan State University, East Lansing, MI, 48824, USA
| | - Stephen A Boyd
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, 48824, USA
| | - Hui Li
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI, 48824, USA.
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6
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Cui Y, Liu DA, Chen J. Fate of Salmonella enterica and Enterohemorrhagic Escherichia coli on Vegetable Seeds Contaminated by Direct Contact with Artificially Inoculated Soil during Germination. J Food Prot 2020; 83:1218-1226. [PMID: 32221551 DOI: 10.4315/jfp-20-021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 03/17/2020] [Indexed: 11/11/2022]
Abstract
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
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Affiliation(s)
- Yue Cui
- Department of Food Science and Technology, The University of Georgia, Griffin, Georgia 30223-1797, USA.,College of Biological Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, 050081, People's Republic of China
| | - D A Liu
- Department of Food Science and Technology, The University of Georgia, Griffin, Georgia 30223-1797, USA
| | - Jinru Chen
- Department of Food Science and Technology, The University of Georgia, Griffin, Georgia 30223-1797, USA
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7
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Madikonda AK, Shaikh A, Khanra S, Yakkala H, Yellaboina S, Lin-Chao S, Siddavattam D. Metabolic remodeling in Escherichia coli MG1655. A prophage e14-encoded small RNA, co293, post-transcriptionally regulates transcription factors HcaR and FadR. FEBS J 2020; 287:4767-4782. [PMID: 32061118 DOI: 10.1111/febs.15247] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 10/10/2019] [Accepted: 02/12/2020] [Indexed: 11/26/2022]
Abstract
In previous studies, we have shown the existence of metabolic remodeling in glucose-grown Escherichia coli MG1655 cells expressing the esterase Orf306 from the opd island of Sphingobium fuliginis. We now show that Orf306-dependent metabolic remodeling is due to regulation of a novel small RNA (sRNA). Endogenous propionate, produced due to the esterase/lipase activity of Orf306, repressed expression of a novel E. coli sRNA, co293. This sRNA post-transcriptionally regulates expression of the transcription factors HcaR and FadR either by inhibiting translation or by destabilizing their transcripts. Hence, repression of co293 expression elevates the levels of HcaR and FadR with consequent activation of alternative carbon catabolic pathways. HcaR activates the hca and MHP operons leading to upregulation of the phenyl propionate and hydroxy phenyl propionate (HPP) degradation pathways. Similarly, FadR stimulates the expression of the transcription factor IclR which negatively regulates the glyoxylate bypass pathway genes, aceBAK.
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Affiliation(s)
- Ashok Kumar Madikonda
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, India
| | - Akbarpasha Shaikh
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, India
| | - Sonali Khanra
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, India
| | - Harshita Yakkala
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, India
| | - Sailu Yellaboina
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, India
| | - Sue Lin-Chao
- Institute of Molecular Biology, Academia Sinica, Nangang, Taiwan
| | - Dayananda Siddavattam
- Department of Animal Biology, School of Life Sciences, University of Hyderabad, India
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8
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The Role of Pathogenic E. coli in Fresh Vegetables: Behavior, Contamination Factors, and Preventive Measures. Int J Microbiol 2019; 2019:2894328. [PMID: 31885595 PMCID: PMC6899298 DOI: 10.1155/2019/2894328] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 11/11/2019] [Indexed: 12/31/2022] Open
Abstract
Many raw vegetables, such as tomato, chili, onion, lettuce, arugula, spinach, and cilantro, are incorporated into fresh dishes including ready-to-eat salads and sauces. The consumption of these foods confers a high nutritional value to the human diet. However, the number of foodborne outbreaks associated with fresh produce has been increasing, with Escherichia coli being the most common pathogen associated with them. In humans, pathogenic E. coli strains cause diarrhea, hemorrhagic colitis, hemolytic uremic syndrome, and other indications. Vegetables can be contaminated with E. coli at any point from pre- to postharvest. This bacterium is able to survive in many environmental conditions due to a variety of mechanisms, such as adhesion to surfaces and internalization in fresh products, thereby limiting the usefulness of conventional processing and chemical sanitizing methods used by the food industry. The aim of this review is to provide a general description of the behavior and importance of pathogenic E. coli in ready-to-eat vegetable dishes. This information can contribute to the development of effective control measures for enhancing food safety.
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9
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Adhikari A, Chhetri VS, Bhattacharya D, Cason C, Luu P, Suazo A. Effectiveness of daily rinsing of alfalfa sprouts with aqueous chlorine dioxide and ozonated water on the growth of Listeria monocytogenes during sprouting. Lett Appl Microbiol 2019; 69:252-257. [PMID: 31429475 DOI: 10.1111/lam.13209] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 08/13/2019] [Accepted: 08/13/2019] [Indexed: 11/30/2022]
Abstract
Alfalfa sprouts have been implicated in multiple foodborne disease outbreaks. This study evaluated the growth of Listeria monocytogenes during sprouting of alfalfa seeds and the effectiveness of daily chlorine dioxide & ozone rinsing in controlling the growth. Alfalfa seeds inoculated with L. monocytogenes were sprouted for 5 days (25°C) with a daily aqueous ClO2 (3 ppm, 10 min) or ozone water (2 ppm, 5 min) rinse. Neither treatment significantly reduced the growth of L. monocytogenes on sprouting alfalfa seeds. The initial level of L. monocytogenes was 3·44 ± 0·27, which increased to c. 7·0 log CFU per g following 3 days of sprouting. There was no significant difference in the bacterial population between the treatment schemes. Bacterial distribution in roots (7·63 ± 0·511 log CFU per g), stems (7·51 ± 0·511 log CFU per g) and leaves (7·41 ± 0·511 log CFU per g) were similar after 5 days. Spent sanitizers had significantly lower levels of bacterial populations compared to the spent distilled water control. The results indicated that sprouting process provides a favourable condition for the growth of L. monocytogenes and the sanitizer treatment alone may not be able to reduce food safety risks. SIGNIFICANCE AND IMPACT OF THE STUDY: Sprouts are high-risk foods. Consumption of raw sprouts is frequently associated with foodborne disease outbreaks. Optimum sprouting procedure involves soaking seeds in water followed by daily water rinsing to maintain a moist environment that is also favourable for the growth of pathogenic micro-organisms. The present study emphasized the potential food safety risks during sprouting and the effect of applying daily sanitizer rinsing in the place of water rinsing to reduce those risks. The finding of this study may be useful in the development of pre-harvest and post-harvest risk management strategies.
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Affiliation(s)
- A Adhikari
- School of Nutrition and Food Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, USA
| | - V S Chhetri
- School of Nutrition and Food Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, USA
| | - D Bhattacharya
- School of Nutrition and Food Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, USA
| | - C Cason
- School of Nutrition and Food Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, USA
| | - P Luu
- School of Nutrition and Food Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, USA
| | - A Suazo
- School of Nutrition and Food Sciences, Louisiana State University Agricultural Center, Baton Rouge, LA, USA
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10
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Schnabel U, Andrasch M, Stachowiak J, Weit C, Weihe T, Schmidt C, Muranyi P, Schlüter O, Ehlbeck J. Sanitation of fresh-cut endive lettuce by plasma processed tap water (PPtW) – Up-scaling to industrial level. INNOV FOOD SCI EMERG 2019. [DOI: 10.1016/j.ifset.2017.11.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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11
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Kroupitski Y, Gollop R, Belausov E, Pinto R, Sela Saldinger S. Salmonella enterica Growth Conditions Influence Lettuce Leaf Internalization. Front Microbiol 2019; 10:639. [PMID: 31057491 PMCID: PMC6482241 DOI: 10.3389/fmicb.2019.00639] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 03/13/2019] [Indexed: 11/21/2022] Open
Abstract
Human pathogens on plants (HPOP) have evolved complex interactions with their plant host. Stomatal internalization is one such mode of interaction, where bacteria are attracted to stomata and penetrate into the substomatal cavity by a process mediated by chemotaxis. Internalization enables HPOP to evade the hostile environment of the leaf surface and find a protected, nutrient-rich niche within the leaf. Numerous studies have documented attachment and entry of the foodborne pathogens, Salmonella enterica and Escherichia coli into stomata. Internalization, however, varies considerably among different pathogens and in different plants, and both bacterial and plant’s factors were reported to influence HPOP attachment and internalization. Here we have studied the effect of laboratory growth conditions, on the internalization of Salmonella enterica serovar Typhimurium (STm) into lettuce leaf. We have further tested the potential involvement of universal stress-proteins in leaf internalization. We found that STm grown in Luria Bertani broth devoid of NaCl (LBNS), or in diluted LB (0.5×LB) internalized lettuce leaf better (62 ± 5% and 59 ± 7%, respectively) compared to bacteria grown in LB (15 ± 7%). Growth under non-aerated conditions also enhanced STm internalization compared to growth under aerated conditions. Growth temperature of 25 and 37°C did not affect STm internalization, however, growth at 42°C, significantly augmented leaf internalization. Since, the tested growth conditions represent moderate stresses, we further investigated the involvement of five universal-stress genes in STm leaf internalization following growth in LBNS medium. Knockout mutations in ydaA, yecG, ybdQ, and uspAB, but not in ynaF, significantly reduced STm internalization compared to the wild-type (wt) strain, without affecting bacterial attachment and motility. Transduction of the mutations back to the parent strain confirmed the linkage between the mutations and the internalization phenotype. These findings support a specific role of the universal-stress genes in leaf internalization. The present study highlights the complexity of bacterial internalization process and may provide partial explanation for the variable, sometimes-contrasting results reported in the literature regarding stomatal internalization by HPOP. Characterization of the regulatory networks that mediate the involvement of usp genes and the tested growth factors in STm internalization should contribute to our understanding of human pathogens-plant interactions.
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Affiliation(s)
- Yulia Kroupitski
- Microbial Food-Safety Research Unit, Department of Food Science, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel
| | - Rachel Gollop
- Microbial Food-Safety Research Unit, Department of Food Science, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel
| | - Eduard Belausov
- Confocal Microscopy Unit, Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel
| | - Riky Pinto
- Microbial Food-Safety Research Unit, Department of Food Science, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel
| | - Shlomo Sela Saldinger
- Microbial Food-Safety Research Unit, Department of Food Science, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel
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12
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Risk of Human Pathogen Internalization in Leafy Vegetables During Lab-Scale Hydroponic Cultivation. HORTICULTURAE 2019. [DOI: 10.3390/horticulturae5010025] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Controlled environment agriculture (CEA) is a growing industry for the production of leafy vegetables and fresh produce in general. Moreover, CEA is a potentially desirable alternative production system, as well as a risk management solution for the food safety challenges within the fresh produce industry. Here, we will focus on hydroponic leafy vegetable production (including lettuce, spinach, microgreens, and herbs), which can be categorized into six types: (1) nutrient film technique (NFT), (2) deep water raft culture (DWC), (3) flood and drain, (4) continuous drip systems, (5) the wick method, and (6) aeroponics. The first five are the most commonly used in the production of leafy vegetables. Each of these systems may confer different risks and advantages in the production of leafy vegetables. This review aims to (i) address the differences in current hydroponic system designs with respect to human pathogen internalization risk, and (ii) identify the preventive control points for reducing risks related to pathogen contamination in leafy greens and related fresh produce products.
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13
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Rossi F, Lathrop A. Effects of Lactobacillus plantarum, Pediococcus acidilactici, and Pediococcus pentosaceus on the Growth of Listeria monocytogenes and Salmonella on Alfalfa Sprouts. J Food Prot 2019; 82:522-527. [PMID: 30810377 DOI: 10.4315/0362-028x.jfp-18-391] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The germination conditions of sprouted vegetables consisting of relatively high temperatures and humidity, low light, and abundance of nutrients are ideal for pathogen survival and growth. The continual occurrence of outbreaks and recalls associated with sprout vegetables indicate additional measures are needed to improve product safety. The objective of this study was to evaluate the efficacy of a mixture of Lactobacillus plantarum, Pediococcus acidilactici, and Pediococcus pentosaceus (LPP) against Listeria monocytogenes and Salmonella on alfalfa sprouts during 5 days of sprouting at 20°C and its influence on sprout quality. Alfalfa seeds were inoculated with L. monocytogenes or Salmonella (each at 1 and 3 log CFU/g) and LPP (7 log CFU/g). Populations of LPP were maintained at 7.5 to 8.0 log CFU/g throughout sprouting. LPP had a significant effect on the growth of L. monocytogenes and Salmonella ( P < 0.05). After 5 days of sprouting, populations of L. monocytogenes at an initial concentration of 1 and 3 log CFU/g of seeds treated with LPP were approximately 4.5 and 1.0 log CFU/g less than the untreated seeds, respectively. Populations of Salmonella at an initial concentration of 1 and 3 log CFU/g were 1.0 log CFU/g less than the control. LPP did not compromise the yield, seedling length, or pH of the sprouts.
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Affiliation(s)
- Franca Rossi
- Department of Food Science and Nutrition, California Polytechnic State University, San Luis Obispo, California 93407, USA
| | - Amanda Lathrop
- Department of Food Science and Nutrition, California Polytechnic State University, San Luis Obispo, California 93407, USA
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14
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Adegoke AA, Amoah ID, Stenström TA, Verbyla ME, Mihelcic JR. Epidemiological Evidence and Health Risks Associated With Agricultural Reuse of Partially Treated and Untreated Wastewater: A Review. Front Public Health 2018; 6:337. [PMID: 30574474 PMCID: PMC6292135 DOI: 10.3389/fpubh.2018.00337] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 11/01/2018] [Indexed: 01/25/2023] Open
Abstract
The use of partially treated and untreated wastewater for irrigation is beneficial in agriculture but may be associated with human health risks. Reports from different locations globally have linked microbial outbreaks with agricultural reuse of wastewater. This article reviews the epidemiological evidence and health risks associated with this practice, aiming toward evidence-based conclusions. Exposure pathways that were addressed in this review included those relevant to agricultural workers and their families, consumers of crops, and residents close to areas irrigated with wastewater (partially treated or untreated). A meta-analysis gave an overall odds ratio of 1.65 (95% CI: 1.31, 2.06) for diarrheal disease and 5.49 (95% CI: 2.49, 12.10) for helminth infections for exposed agricultural workers and family members. The risks were higher among children and immunocompromised individuals than in immunocompetent adults. Predominantly skin and intestinal infections were prevalent among individuals infected mainly via occupational exposure and ingestion. Food-borne outbreaks as a result of crops (fruits and vegetables) irrigated with partially or untreated wastewater have been widely reported. Contamination of crops with enteric viruses, fecal coliforms, and bacterial pathogens, parasites including soil-transmitted helminthes (STHs), as well as occurrence of antibiotic residues and antibiotic resistance genes (ARGs) have also been evidenced. The antibiotic residues and ARGs may get internalized in crops along with pathogens and may select for antibiotic resistance, exert ecotoxicity, and lead to bioaccumulation in aquatic organisms with high risk quotient (RQ). Appropriate mitigation lies in adhering to existing guidelines such as the World Health Organization wastewater reuse guidelines and to Sanitation Safety Plans (SSPs). Additionally, improvement in hygiene practices will also provide measures against adverse health impacts.
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Affiliation(s)
- Anthony A. Adegoke
- SARChI, Institute for Water and Wastewater Technology, Durban University of Technology, Durban, South Africa
- Department of Microbiology, Faculty of Science, University of Uyo, Uyo, Nigeria
| | - Isaac D. Amoah
- SARChI, Institute for Water and Wastewater Technology, Durban University of Technology, Durban, South Africa
| | - Thor A. Stenström
- SARChI, Institute for Water and Wastewater Technology, Durban University of Technology, Durban, South Africa
| | - Matthew E. Verbyla
- Department of Civil, Construction, and Environmental Engineering, San Diego State University, San Diego, CA, United States
| | - James R. Mihelcic
- Department of Civil & Environmental Engineering, University of South Florida, Tampa, FL, United States
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15
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Riggio GM, Wang Q, Kniel KE, Gibson KE. Microgreens-A review of food safety considerations along the farm to fork continuum. Int J Food Microbiol 2018; 290:76-85. [PMID: 30308448 DOI: 10.1016/j.ijfoodmicro.2018.09.027] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Revised: 09/17/2018] [Accepted: 09/28/2018] [Indexed: 01/24/2023]
Abstract
The food safety implications of microgreens, an emerging salad crop, have been studied only minimally. The farm to fork continuum of microgreens and sprouts has some overlap in terms of production, physical characteristics, and consumption. This review describes the food safety risk of microgreens as compared to sprouts, potential control points for microgreen production, what is known to date about pathogen transfer in the microgreen production environment, and where microgreens differ from sprouts and their mature vegetable counterparts. The synthesis of published research to date may help to inform Good Agricultural Practices (GAPs) and Good Handling Practices (GHPs) for the emerging microgreen industry.
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Affiliation(s)
- Gina M Riggio
- University of Arkansas, Dept. of Food Science, 2650 Young Ave, Fayetteville, AR 72704, United States of America.
| | - Qing Wang
- University of Delaware, College of Agriculture and Natural Resources, Newark, DE 19711, United States of America.
| | - Kalmia E Kniel
- University of Delaware, College of Agriculture and Natural Resources, Newark, DE 19711, United States of America.
| | - Kristen E Gibson
- University of Arkansas, Dept. of Food Science, 2650 Young Ave, Fayetteville, AR 72704, United States of America.
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16
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Alegbeleye OO, Singleton I, Sant'Ana AS. Sources and contamination routes of microbial pathogens to fresh produce during field cultivation: A review. Food Microbiol 2018; 73:177-208. [PMID: 29526204 PMCID: PMC7127387 DOI: 10.1016/j.fm.2018.01.003] [Citation(s) in RCA: 257] [Impact Index Per Article: 42.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 12/31/2017] [Accepted: 01/02/2018] [Indexed: 12/17/2022]
Abstract
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.
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Affiliation(s)
| | - Ian Singleton
- School of Applied Sciences, Sighthill Campus, Edinburgh Napier University, Edinburgh, UK
| | - Anderson S Sant'Ana
- Department of Food Science, Faculty of Food Engineering, University of Campinas, Campinas, São Paulo, Brazil.
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17
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Washington-Hughes CL, Ford GT, Jones AD, McRae K, Outten FW. Nickel exposure reduces enterobactin production in Escherichia coli. Microbiologyopen 2018; 8:e00691. [PMID: 30062714 PMCID: PMC6460284 DOI: 10.1002/mbo3.691] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 06/18/2018] [Accepted: 06/19/2018] [Indexed: 12/26/2022] Open
Abstract
Escherichia coli is a well‐studied bacterium that can be found in many niches, such as industrial wastewater, where the concentration of nickel can rise to low‐millimolar levels. Recent studies show that nickel exposure can repress pyochelin or induce pyoverdine siderophore production in Pseudomonas aueroginosa. Understanding the molecular cross‐talk between siderophore production, metal homeostasis, and metal toxicity in microorganisms is critical for designing bioremediation strategies for metal‐contaminated sites. Here, we show that high‐nickel exposure prolongs lag phase duration as a result of low‐intracellular iron levels in E. coli. Although E. coli cells respond to low‐intracellular iron during nickel stress by maintaining high expression of iron uptake systems such as fepA, the demand for iron is not met due to a lack of siderophores in the extracellular medium during nickel stress. Taken together, these results indicate that nickel inhibits iron accumulation in E. coli by reducing the presence of enterobactin in the extracellular medium.
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Affiliation(s)
| | - Geoffrey T Ford
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina
| | - Alsten D Jones
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina
| | - Kimberly McRae
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina
| | - F Wayne Outten
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina
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18
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Yun J, Wu C, Li X, Fan X. Improving the Microbial Food Safety of Fresh Fruits and Vegetables with Aqueous and Vaporous Essential Oils. NATURAL AND BIO-BASED ANTIMICROBIALS FOR FOOD APPLICATIONS 2018. [DOI: 10.1021/bk-2018-1287.ch005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Juan Yun
- Key Laboratory of Food Nutrition and Safety (Tianjin University of Science and Technology), Ministry of Education, Tianjin 300457, China
| | - Changqing Wu
- Department of Animal and Food Science, University of Delaware, Newark, Delaware 19716, United States
| | - Xihong Li
- Key Laboratory of Food Nutrition and Safety (Tianjin University of Science and Technology), Ministry of Education, Tianjin 300457, China
| | - Xuetong Fan
- Eastern Regional Research Center, ARS, USDA, Wyndmoor, Pennsylvania 19038, United States
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19
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Andrasch M, Stachowiak J, Schlüter O, Schnabel U, Ehlbeck J. Scale-up to pilot plant dimensions of plasma processed water generation for fresh-cut lettuce treatment. Food Packag Shelf Life 2017. [DOI: 10.1016/j.fpsl.2017.08.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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20
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Potential Dissemination of ARB and ARGs into Soil Through the Use of Treated Wastewater for Agricultural Irrigation: Is It a True Cause for Concern? ACTA ACUST UNITED AC 2017. [DOI: 10.1007/978-3-319-66260-2_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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21
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Shen Z, Mustapha A, Lin M, Zheng G. Biocontrol of the internalization of Salmonella enterica and Enterohaemorrhagic Escherichia coli in mung bean sprouts with an endophytic Bacillus subtilis. Int J Food Microbiol 2017; 250:37-44. [DOI: 10.1016/j.ijfoodmicro.2017.03.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 03/07/2017] [Accepted: 03/22/2017] [Indexed: 01/09/2023]
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22
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Wright KM, Crozier L, Marshall J, Merget B, Holmes A, Holden NJ. Differences in internalization and growth of Escherichia coli O157:H7 within the apoplast of edible plants, spinach and lettuce, compared with the model species Nicotiana benthamiana. Microb Biotechnol 2017; 10:555-569. [PMID: 28169510 PMCID: PMC5404196 DOI: 10.1111/1751-7915.12596] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 12/14/2016] [Indexed: 11/30/2022] Open
Abstract
Internalization of food-borne bacteria into edible parts of fresh produce plants represents a serious health risk. Therefore, internalization of verocytotoxigenic E. coli O157:H7 isolate Sakai was assessed in two species associated with outbreaks, spinach (Spinacia oleracea) and lettuce (Lactuca sativa) and compared to the model species Nicotiana benthamiana. Internalization occurred in the leaves and roots of spinach and lettuce throughout a 10 day time-course. The plant species, tissue type and inoculum dose all impacted the outcome. A combination of low inoculum dose (~102 CFU) together with light microscopy imaging highlighted marked differences in the fate of endophytic E. coli O157:H7 Sakai. In the fresh produce species, bacterial growth was restricted but viable cells persisted over 20 days, whereas there was > 400-fold (~2.5 Log10 ) increase in growth in N. benthamiana. Colony formation occurred adjacent to epidermal cells and mesophyll cells or close to vascular bundles of N. benthamiana and contained components of a biofilm matrix, including curli expression and elicitation, extracellular DNA and a limited presence of cellulose. Together the data show that internalization is a relevant issue in crop production and that crop species and tissue need to be considered as food safety risk parameters.
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Affiliation(s)
| | - Louise Crozier
- Cell and Molecular SciencesThe James Hutton InstituteDundeeUK
| | | | - Bernhard Merget
- Cell and Molecular SciencesThe James Hutton InstituteDundeeUK
| | - Ashleigh Holmes
- Cell and Molecular SciencesThe James Hutton InstituteDundeeUK
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23
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Shenoy AG, Oliver HF, Deering AJ. Listeria monocytogenes Internalizes in Romaine Lettuce Grown in Greenhouse Conditions. J Food Prot 2017; 80:573-581. [PMID: 28271926 DOI: 10.4315/0362-028x.jfp-16-095] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Listeria monocytogenes has been implicated in a number of outbreaks involving fresh produce, including an outbreak in 2016 resulting from contaminated packaged salads. The persistence and internalization potential of L. monocytogenes in romaine lettuce was evaluated, and the persistence of two L. monocytogenes strains was assessed on three romaine lettuce cultivars. Seeds were germinated, and plants grown in three soil types (i.e., standard potting mix, autoclaved potting mix, and top soil) and sterile soft-top agar for up to 21 days. Average CFU per gram of L. monocytogenes on seeds and plants was calculated from five replicates per harvest day. Up to 8.2 log CFU/g L. monocytogenes persisted on romaine lettuce plants (Braveheart cultivar) grown in soft-top agar, while those grown in commercial potting mix (initial soil aerobic plate count of 4.0 × 104 CFU/g) had a final concentration of 5.4 log CFU/g, and autoclaved commercial potting mix had a final concentration of 3.8 ± 0.2 log CFU/g after a 21-day period. Pathogen levels dropped below the limit of detection (2 log CFU/g) by day 18 in 75% topsoil (initial soil aerobic plate count of 4.0 × 101 CFU/g); this did not occur in sterile media. Although L. monocytogenes strain differences and presence of a clay coating on seeds did not affect persistence, differences were observed in L. monocytogenes growth and survival among cultivars. To assess internalization, seeds were inoculated with L. monocytogenes expressing green fluorescent protein. Three plants were fixed, paraffin embedded, and sectioned; localization was studied by using standard immunohistochemistry techniques. A total of 539 internalized L. monocytogenes cells were visualized among three 20-day seedlings. L. monocytogenes cells were located in all major tissue types (pith followed by cortex, xylem, phloem, and epidermis). The presence of L. monocytogenes in the plant vasculature suggests potential for transport throughout the plant into edible tissue.
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Affiliation(s)
- Archana G Shenoy
- Department of Food Science, Purdue University, 745 Agriculture Mall Drive, West Lafayette, Indiana 47907, USA
| | - Haley F Oliver
- Department of Food Science, Purdue University, 745 Agriculture Mall Drive, West Lafayette, Indiana 47907, USA
| | - Amanda J Deering
- Department of Food Science, Purdue University, 745 Agriculture Mall Drive, West Lafayette, Indiana 47907, USA
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24
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Stein R, Chirilã M. Routes of Transmission in the Food Chain. FOODBORNE DISEASES 2017. [PMCID: PMC7148622 DOI: 10.1016/b978-0-12-385007-2.00003-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
More than 250 different foodborne diseases have been described to date, annually affecting about one-third of the world's population. The incidence of foodborne diseases has been underreported and underestimated, and the asymptomatic presentation of some of the illnesses, worldwide heterogeneities in reporting, and the alternative transmission routes of certain pathogens are among the factors that contribute to this. Globalization, centralization of the food supply, transportation of food products progressively farther from their places of origin, and the multitude of steps where contamination may occur have made it increasingly challenging to investigate foodborne and waterborne outbreaks. Certain foodborne pathogens may be transmitted directly from animals to humans, while others are transmitted through vectors, such as insects, or through food handlers, contaminated food products or food-processing surfaces, or transfer from sponges, cloths, or utensils. Additionally, the airborne route may contribute to the transmission of certain foodborne pathogens. Complicating epidemiological investigations, multiple transmission routes have been described for some foodborne pathogens. Two types of transmission barriers, primary and secondary, have been described for foodborne pathogens, each of them providing opportunities for preventing and controlling outbreaks. Primary barriers, the most effective sites of prophylactic intervention, prevent pathogen entry into the environment, while secondary barriers prevent the multiplication and dissemination of pathogens that have already entered the environment. Understanding pathogen dynamics, monitoring transmission, and implementing preventive measures are complicated by the phenomenon of superspreading, which refers to the concept that, at the level of populations, a minority of hosts is responsible for the majority of transmission events.
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25
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Butscher D, Van Loon H, Waskow A, Rudolf von Rohr P, Schuppler M. Plasma inactivation of microorganisms on sprout seeds in a dielectric barrier discharge. Int J Food Microbiol 2016; 238:222-232. [PMID: 27668570 DOI: 10.1016/j.ijfoodmicro.2016.09.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 08/31/2016] [Accepted: 09/11/2016] [Indexed: 11/29/2022]
Abstract
Fresh produce is frequently contaminated by microorganisms, which may lead to spoilage or even pose a threat to human health. In particular sprouts are considered to be among the most risky foods sold at retail since they are grown in an environment practically ideal for growth of bacteria and usually consumed raw. Because heat treatment has a detrimental effect on the germination abilities of sprout seeds, alternative treatment technologies need to be developed for microbial inactivation purposes. In this study, non-thermal plasma decontamination of sprout seeds is evaluated as a promising option to enhance food safety while maintaining the seed germination capabilities. In detail, investigations focus on understanding the efficiency of non-thermal plasma inactivation of microorganisms as influenced by the type of microbial contamination, substrate surface properties and moisture content, as well as variations in the power input to the plasma device. To evaluate the impact of these parameters, we studied the reduction of native microbiota or artificially applied E. coli on alfalfa, onion, radish and cress seeds exposed to non-thermal plasma in an atmospheric pressure pulsed dielectric barrier discharge streamed with argon. Plasma treatment resulted in a maximum reduction of 3.4 logarithmic units for E. coli on cress seeds. A major challenge in plasma decontamination of granular food products turned out to be the complex surface topology, where the rough surface with cracks and crevices can shield microorganisms from plasma-generated reactive species, thus reducing the treatment efficiency. However, improvement of the inactivation efficiency was possible by optimizing substrate characteristics such as the moisture level and by tuning the power supply settings (voltage, frequency) to increase the production of reactive species. While the germination ability of alfalfa seeds was considerably decreased by harsh plasma treatment, enhanced germination was observed under mild conditions. In conclusion, the results from this study indicate that cold plasma treatment represents a promising technology for inactivation of bacteria on seeds used for sprout production while preserving their germination properties.
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Affiliation(s)
- Denis Butscher
- ETH Zurich, Institute of Process Engineering, Sonneggstrasse 3, 8092 Zurich, Switzerland
| | - Hanne Van Loon
- ETH Zurich, Institute of Process Engineering, Sonneggstrasse 3, 8092 Zurich, Switzerland; ETH Zurich, Institute of Food Science and Nutrition, Schmelzbergstrasse 7, 8092 Zurich, Switzerland
| | - Alexandra Waskow
- ETH Zurich, Institute of Process Engineering, Sonneggstrasse 3, 8092 Zurich, Switzerland; ETH Zurich, Institute of Food Science and Nutrition, Schmelzbergstrasse 7, 8092 Zurich, Switzerland
| | | | - Markus Schuppler
- ETH Zurich, Institute of Food Science and Nutrition, Schmelzbergstrasse 7, 8092 Zurich, Switzerland.
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26
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Karabiyikli Ş, Değırmencı H, Karapinar M. Inactivation ofListeria monocytogenesin Black Mulberry (Morus nigra) Juice. J FOOD PROCESS PRES 2016. [DOI: 10.1111/jfpp.12840] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Şenız Karabiyikli
- Gaziosmanpasa University, Faculty of Engineering and Natural Science, Food Engineering Department; 60000 Tokat Turkey
| | - Hüseyın Değırmencı
- Ege University, Faculty of Engineering, Food Engineering Department; 35100 Bornova Izmir Turkey
| | - Mehmet Karapinar
- Ege University, Faculty of Engineering, Food Engineering Department; 35100 Bornova Izmir Turkey
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27
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Predictive Modeling for Estimation of Bacterial Behavior from Farm to Table. Food Saf (Tokyo) 2016; 4:33-44. [PMID: 32231903 DOI: 10.14252/foodsafetyfscj.2016006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 05/20/2016] [Indexed: 11/21/2022] Open
Abstract
Microbial contamination is inevitable for raw and/or minimally processed ready-to-eat foods. As a consequence of the pathogenic bacterial contamination, the risk of food-borne illness increases during distribution and storage until consumption. Prediction of microbial growth and/or inactivation in/on those foods provides important information for ensuring the microbial food safety. Although numerous predictive models for bacterial growth have been proposed for various microorganisms, this review focuses on the modeling of pathogenic bacterial growth in raw and minimally processed ready-to-eat foods such as fresh-cut produce and raw minced-tuna, a common ingredient for sushi. The growth models described here take into account both the environment temperature and microbial competition in the food matrix. Microbial competition plays a key role in real food environments. Food-based predictive models enable not only to directly estimate the microbial growth on those foods, but also to apply to validation of culture-medium-based predictive models. Furthermore, toward a development of accurate and/or realistic bacterial dose-response models, a model for inactivation of pathogenic bacteria during simulated gastric fluid is also introduced.
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28
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Real-time bacterial microcolony counting using on-chip microscopy. Sci Rep 2016; 6:21473. [PMID: 26902822 PMCID: PMC4763285 DOI: 10.1038/srep21473] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 01/25/2016] [Indexed: 11/15/2022] Open
Abstract
Observing microbial colonies is the standard method for determining the microbe titer and investigating the behaviors of microbes. Here, we report an automated, real-time bacterial microcolony-counting system implemented on a wide field-of-view (FOV), on-chip microscopy platform, termed ePetri. Using sub-pixel sweeping microscopy (SPSM) with a super-resolution algorithm, this system offers the ability to dynamically track individual bacterial microcolonies over a wide FOV of 5.7 mm × 4.3 mm without requiring a moving stage or lens. As a demonstration, we obtained high-resolution time-series images of S. epidermidis at 20-min intervals. We implemented an image-processing algorithm to analyze the spatiotemporal distribution of microcolonies, the development of which could be observed from a single bacterial cell. Test bacterial colonies with a minimum diameter of 20 μm could be enumerated within 6 h. We showed that our approach not only provides results that are comparable to conventional colony-counting assays but also can be used to monitor the dynamics of colony formation and growth. This microcolony-counting system using on-chip microscopy represents a new platform that substantially reduces the detection time for bacterial colony counting. It uses chip-scale image acquisition and is a simple and compact solution for the automation of colony-counting assays and microbe behavior analysis with applications in antibacterial drug discovery.
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29
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Lone A, Anany H, Hakeem M, Aguis L, Avdjian AC, Bouget M, Atashi A, Brovko L, Rochefort D, Griffiths MW. Development of prototypes of bioactive packaging materials based on immobilized bacteriophages for control of growth of bacterial pathogens in foods. Int J Food Microbiol 2015; 217:49-58. [PMID: 26490649 DOI: 10.1016/j.ijfoodmicro.2015.10.011] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Revised: 10/09/2015] [Accepted: 10/11/2015] [Indexed: 11/17/2022]
Abstract
Due to lack of adequate control methods to prevent contamination in fresh produce and growing consumer demand for natural products, the use of bacteriophages has emerged as a promising approach to enhance safety of these foods. This study sought to control Listeria monocytogenes in cantaloupes and RTE meat and Escherichia coli O104:H4 in alfalfa seeds and sprouts under different storage conditions by using specific lytic bacteriophage cocktails applied either free or immobilized. Bacteriophage cocktails were introduced into prototypes of packaging materials using different techniques: i) immobilizing on positively charged modified cellulose membranes, ii) impregnating paper with bacteriophage suspension, and iii) encapsulating in alginate beads followed by application of beads onto the paper. Phage-treated and non-treated samples were stored for various times and at temperatures of 4°C, 12°C or 25°C. In cantaloupe, when free phage cocktail was added, L. monocytogenes counts dropped below the detection limit of the plating technique (<1 log CFU/g) after 5 days of storage at both 4°C and 12°C. However, at 25°C, counts below the detection limit were observed after 3 and 6h and a 2-log CFU/g reduction in cell numbers was seen after 24h. For the immobilized Listeria phage cocktail, around 1-log CFU/g reduction in the Listeria count was observed by the end of the storage period for all tested storage temperatures. For the alfalfa seeds and sprouts, regardless of the type of phage application technique (spraying of free phage suspension, bringing in contact with bacteriophage-based materials (paper coated with encapsulated bacteriophage or impregnated with bacteriophage suspension)), the count of E. coli O104:H4 was below the detection limit (<1 log CFU/g) after 1h in seeds and about a 1-log cycle reduction in E. coli count was observed on the germinated sprouts by day 5. In ready-to-eat (RTE) meat, LISTEX™ P100, a commercial phage product, was able to significantly reduce the growth of L. monocytogenes at both storage temperatures, 4°C and 10°C, for 25 days regardless of bacteriophage application format (immobilized or non-immobilized (free)). In conclusion, the developed phage-based materials demonstrated significant antimicrobial effect, when applied to the artificially contaminated foods, and can be used as prototypes for developing bioactive antimicrobial packaging materials capable of enhancing the safety of fresh produce and RTE meat.
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Affiliation(s)
- Ayesha Lone
- Canadian Research Institute for Food Safety, Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Hany Anany
- Canadian Research Institute for Food Safety, Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada; Department of Microbiology, Faculty of Science, Ain Shams University, Egypt.
| | - Mohammed Hakeem
- Canadian Research Institute for Food Safety, Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Louise Aguis
- Canadian Research Institute for Food Safety, Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Anne-Claire Avdjian
- Canadian Research Institute for Food Safety, Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Marina Bouget
- Canadian Research Institute for Food Safety, Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Arash Atashi
- Département de chimie, Université de Montréal, CP6128 Succ. Centre-Ville, Montréal, Québec H3C 3J7, Canada
| | - Luba Brovko
- Canadian Research Institute for Food Safety, Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Dominic Rochefort
- Département de chimie, Université de Montréal, CP6128 Succ. Centre-Ville, Montréal, Québec H3C 3J7, Canada
| | - Mansel W Griffiths
- Canadian Research Institute for Food Safety, Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada
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30
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Symes S, Goldsmith P, Haines H. Microbiological Safety and Food Handling Practices of Seed Sprout Products in the Australian State of Victoria. J Food Prot 2015; 78:1387-91. [PMID: 26197293 DOI: 10.4315/0362-028x.jfp-14-566] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
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.
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Affiliation(s)
- Sally Symes
- Department of Health and Human Services, 50 Lonsdale Street, Melbourne, 3000, Victoria, Australia.
| | - Paul Goldsmith
- Department of Health and Human Services, 50 Lonsdale Street, Melbourne, 3000, Victoria, Australia
| | - Heather Haines
- Department of Health and Human Services, 50 Lonsdale Street, Melbourne, 3000, Victoria, Australia
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31
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Dechet AM, Herman KM, Chen Parker C, Taormina P, Johanson J, Tauxe RV, Mahon BE. Outbreaks caused by sprouts, United States, 1998-2010: lessons learned and solutions needed. Foodborne Pathog Dis 2015; 11:635-44. [PMID: 25076040 DOI: 10.1089/fpd.2013.1705] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
After a series of outbreaks associated with sprouts in the mid-1990s, the U.S. Food and Drug Administration (FDA) published guidelines in 1999 for sprouts producers to reduce the risk of contamination. The recommendations included treating seeds with an antimicrobial agent such as calcium hypochlorite solution and testing spent irrigation water for pathogens. From 1998 through 2010, 33 outbreaks from seed and bean sprouts were documented in the United States, affecting 1330 reported persons. Twenty-eight outbreaks were caused by Salmonella, four by Shiga toxin-producing Escherichia coli, and one by Listeria. In 15 of the 18 outbreaks with information available, growers had not followed key FDA guidelines. In three outbreaks, however, the implicated sprouts were produced by firms that appeared to have implemented key FDA guidelines. Although seed chlorination, if consistently applied, reduces pathogen burden on sprouts, it does not eliminate the risk of human infection. Further seed and sprouts disinfection technologies, some recently developed, will be needed to enhance sprouts safety and reduce human disease. Improved seed production practices could also decrease pathogen burden but, because seeds are a globally distributed commodity, will require international cooperation.
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Affiliation(s)
- Amy M Dechet
- 1 Medical Education, Portland Providence Medical Center , Portland, Oregon
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32
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Martinez B, Stratton J, Bianchini A, Wegulo S, Weaver G. Transmission of Escherichia coli O157:H7 to internal tissues and its survival on flowering heads of wheat. J Food Prot 2015; 78:518-24. [PMID: 25719875 DOI: 10.4315/0362-028x.jfp-14-298] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Escherichia coli O157:H7 is a human pathogen that can cause bloody diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. E. coli O157:H7 illnesses are mainly associated with undercooked beef; however, in recent years, outbreaks have been linked to fresh produce, such as spinach, lettuce, and sprouts. In 2009, flour was implicated as the contamination source in an outbreak involving consumption of raw cookie dough that resulted in 77 illnesses. The objectives of this research were to determine (i) whether E. coli O157:H7 could be translocated into the internal tissues of wheat (Triticum aestivum) seedlings from contaminated seed, soil, or irrigation water and (ii) whether the bacterium could survive on flowering wheat heads. The levels of contamination of kanamycin-resistant E. coli O157:H7 strains in seed, soil, and irrigation water were 6.88 log CFU/g, 6.60 log CFU/g, and 6.76 log CFU/ml, respectively. One hundred plants per treatment were sown in pot trays with 50 g of autoclaved soil or purposely contaminated soil, watered every day with 5 ml of water, and harvested 9 days postinoculation. In a fourth experiment, flowering wheat heads were spray inoculated with water containing 4.19 log CFU/ml E. coli O157:H7 and analyzed for survival after 15 days, near the harvest period. To detect low levels of internalization, enrichment procedures were performed and Biotecon real-time PCR detection assays were used to determine the presence of E. coli O157:H7 in the wheat, using a Roche Applied Science LightCycler 2.0 instrument. The results showed that internalization was possible using contaminated seed, soil, and irrigation water in wheat seedlings, with internalization rates of 2, 5, and 10%, respectively. Even though the rates were low, to our knowledge this is the first study to demonstrate the ability of this strain to reach the phylloplane in wheat. In the head contamination experiment, all samples tested positive, showing the ability of E. coli O157:H7 to survive on the wheat head.
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Affiliation(s)
- Bismarck Martinez
- Department of Food Science and Technology, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - Jayne Stratton
- Department of Food Science and Technology, The Food Processing Center, University of Nebraska, Lincoln, Nebraska 68588, USA.
| | - Andréia Bianchini
- Department of Food Science and Technology, The Food Processing Center, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - Stephen Wegulo
- Department of Plant Pathology, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - Glen Weaver
- ConAgra Foods, 11-340 ConAgra Drive, Omaha, Nebraska 68137, USA
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33
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Chiang PJ, Tseng MJ, He ZS, Li CH. Automated counting of bacterial colonies by image analysis. J Microbiol Methods 2014; 108:74-82. [PMID: 25451456 DOI: 10.1016/j.mimet.2014.11.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 11/14/2014] [Accepted: 11/14/2014] [Indexed: 11/16/2022]
Abstract
Research on microorganisms often involves culturing as a means to determine the survival and proliferation of bacteria. The number of colonies in a culture is counted to calculate the concentration of bacteria in the original broth; however, manual counting can be time-consuming and imprecise. To save time and prevent inconsistencies, this study proposes a fully automated counting system using image processing methods. To accurately estimate the number of viable bacteria in a known volume of suspension, colonies distributing over the whole surface area of a plate, including the central and rim areas of a Petri dish are taken into account. The performance of the proposed system is compared with verified manual counts, as well as with two freely available counting software programs. Comparisons show that the proposed system is an effective method with excellent accuracy with mean value of absolute percentage error of 3.37%. A user-friendly graphical user interface is also developed and freely available for download, providing researchers in biomedicine with a more convenient instrument for the enumeration of bacterial colonies.
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Affiliation(s)
- Pei-Ju Chiang
- Department of Mechanical Engineering, National Chung Cheng University, Chia-Yi, Taiwan; Advanced Institute of Manufacturing with High-Tech Innovations, National Chung Cheng University, Chia-Yi, Taiwan
| | - Min-Jen Tseng
- Department of Life Science, National Chung Cheng University, Chia-Yi, Taiwan
| | - Zong-Sian He
- Department of Mechanical Engineering, National Chung Cheng University, Chia-Yi, Taiwan; Advanced Institute of Manufacturing with High-Tech Innovations, National Chung Cheng University, Chia-Yi, Taiwan
| | - Chia-Hsun Li
- Department of Mechanical Engineering, National Chung Cheng University, Chia-Yi, Taiwan; Advanced Institute of Manufacturing with High-Tech Innovations, National Chung Cheng University, Chia-Yi, Taiwan
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34
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Szabó S, Németh Z, Polyák É, Bátai I, Kerényi M, Figler M. Antibacterial effect of sprouts against human pathogens in vitro. ACTA ALIMENTARIA 2014. [DOI: 10.1556/aalim.43.2014.3.18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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35
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Melotto M, Panchal S, Roy D. Plant innate immunity against human bacterial pathogens. Front Microbiol 2014; 5:411. [PMID: 25157245 PMCID: PMC4127659 DOI: 10.3389/fmicb.2014.00411] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 07/21/2014] [Indexed: 11/13/2022] Open
Abstract
Certain human bacterial pathogens such as the enterohemorrhagic Escherichia coli and Salmonella enterica are not proven to be plant pathogens yet. Nonetheless, under certain conditions they can survive on, penetrate into, and colonize internal plant tissues causing serious food borne disease outbreaks. In this review, we highlight current understanding on the molecular mechanisms of plant responses against human bacterial pathogens and discuss salient common and contrasting themes of plant interactions with phytopathogens or human pathogens.
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Affiliation(s)
- Maeli Melotto
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
| | - Shweta Panchal
- Department of Biology, University of TexasArlington, TX, USA
| | - Debanjana Roy
- Department of Biology, University of TexasArlington, TX, USA
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36
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Kim SR, Yoon Y, Seo MK, Kim WI, Shim WB, Chung DH, Yun JC, Ryu KY, Kim BS. Modification of methods for detection of Escherichia coli O157:H7 on produce. Food Sci Biotechnol 2014. [DOI: 10.1007/s10068-014-0185-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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37
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Comparison of the growth of Escherichia coli O157: H7 and O104: H4 during sprouting and microgreen production from contaminated radish seeds. Food Microbiol 2014; 44:60-3. [PMID: 25084646 DOI: 10.1016/j.fm.2014.05.015] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 05/07/2014] [Accepted: 05/25/2014] [Indexed: 11/20/2022]
Abstract
Both sprouts and microgreens are popular tender produce items, typically grown and harvested in indoor facilities which allow a higher degree of control compared to open field production. While sprouts, which have frequently been implicated in foodborne illness outbreaks, are the subject of numerous national and international standards for their production and distribution, there is a lack of data pertaining to the microbiological safety of microgreens. In this study, sprouts and microgreens were produced from radish seeds inoculated with Escherichia coli O157: H7 or O104: H4 and E. coli populations on the harvested products compared to assess the potentials of product contamination from contaminated seeds during sprouting and microgreen production. Both E. coli O157:H7 and O104:H4 grew rapidly during sprouting, reaching levels of 5.8-8.1 log cfu/g and 5.2-7.3 log cfu/g, respectively, depending on the initial inoculation levels of the seeds (1.5-4.6 log cfu/g and 0.8-4.3 log cfu/g on radish seeds, respectively). In comparison, E. coli O157:H7 and O104:H4 populations on harvested microgreens ranged from 0.8 to 4.5 log cfu/g and from 0.6 to 4.0 log cfu/g, respectively. Although harvested microgreens carried significantly less (P < 0.001) E. coli than sprouts germinated from seeds inoculated at the same levels, proliferation of E. coli O157:H7 and O104:H4 occurred during both sprouting and microgreen growth.
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38
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Schnabel U, Niquet R, Schlüter O, Gniffke H, Ehlbeck J. Decontamination and Sensory Properties of Microbiologically Contaminated Fresh Fruits and Vegetables by Microwave Plasma Processed Air (PPA). J FOOD PROCESS PRES 2014. [DOI: 10.1111/jfpp.12273] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Uta Schnabel
- Leibniz Institute for Plasma Science and Technology; Felix-Hausdorff-Straße 2 17489 Greifswald Germany
| | - Rijana Niquet
- Leibniz Institute for Plasma Science and Technology; Felix-Hausdorff-Straße 2 17489 Greifswald Germany
| | - Oliver Schlüter
- Leibniz Institute for Agricultural Engineering Potsdam-Bornim; Max-Eyth-Allee 100 14469 Potsdam Germany
| | - Holger Gniffke
- neu.zlt - Zentrum für Lebensmitteltechnologie Mecklenburg-Vorpommern GmbH; Seestraße 7 17033 Neubrandenburg Germany
| | - Jörg Ehlbeck
- Leibniz Institute for Plasma Science and Technology; Felix-Hausdorff-Straße 2 17489 Greifswald Germany
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39
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Ge C, Rymut S, Lee C, Lee J. Salmonella internalization in mung bean sprouts and pre- and postharvest intervention methods in a hydroponic system. J Food Prot 2014; 77:752-7. [PMID: 24780329 DOI: 10.4315/0362-028x.jfp-13-370] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Mung bean sprouts, typically consumed raw or minimally cooked, are often contaminated with pathogens. Internalized pathogens pose a high risk because conventional sanitization methods are ineffective for their inactivation. The studies were performed (i) to understand the potential of internalization of Salmonella in mung bean sprouts under conditions where the irrigation water was contaminated and (ii) to determine if pre- and postharvest intervention methods are effective in inactivating the internalized pathogen. Mung bean sprouts were grown hydroponically and exposed to green fluorescence protein-tagged Salmonella Typhimurium through maturity. One experimental set received contaminated water daily, while other sets received contaminated water on a single day at different times. For preharvest intervention, irrigation water was exposed to UV, and for postharvest intervention-contaminated sprouts were subjected to a chlorine wash and UV light. Harvested samples were disinfected with ethanol and AgNO3 to differentiate surface-associate pathogens from the internalized ones. The internalized Salmonella Typhimurium in each set was quantified using the plate count method. Internalized Salmonella Typhimurium was detected at levels of 2.0 to 5.1 log CFU/g under all conditions. Continuous exposure to contaminated water during the entire period generated significantly higher levels of Salmonella Typhimurium internalization than sets receiving contaminated water for only a single day (P < 0.05). Preintervention methods lowered the level of internalized Salmonella by 1.84 log CFU/g (P < 0.05), whereas postintervention methods were ineffective in eliminating internalized pathogens. Preintervention did not completely inactivate bacteria in sprouts and demonstrated that the remaining Salmonella Typhimurium in water became more resistant to UV. Because postharvest intervention methods are ineffective, proper procedures for maintaining clean irrigation water must be followed throughout production in a hydroponic system.
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Affiliation(s)
- Chongtao Ge
- Department of Food Science and Technology, The Ohio State University, Columbus, Ohio 43210, USA
| | - Susan Rymut
- Department of Food Science and Technology, The Ohio State University, Columbus, Ohio 43210, USA
| | - Cheonghoon Lee
- College of Public Health, Division of Environmental Health Sciences, The Ohio State University, Columbus, Ohio 43210, USA
| | - Jiyoung Lee
- Department of Food Science and Technology, The Ohio State University, Columbus, Ohio 43210, USA; College of Public Health, Division of Environmental Health Sciences, The Ohio State University, Columbus, Ohio 43210, USA.
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40
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Enterobacteriaceae resistant to third-generation cephalosporins and quinolones in fresh culinary herbs imported from Southeast Asia. Int J Food Microbiol 2014; 177:72-7. [DOI: 10.1016/j.ijfoodmicro.2014.02.014] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 02/07/2014] [Accepted: 02/18/2014] [Indexed: 01/08/2023]
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41
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Crossing Over. Food Saf (Tokyo) 2014. [DOI: 10.1128/9781555816186.ch8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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42
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Role of curli and plant cultivation conditions on Escherichia coli O157:H7 internalization into spinach grown on hydroponics and in soil. Int J Food Microbiol 2014; 173:48-53. [DOI: 10.1016/j.ijfoodmicro.2013.12.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 11/26/2013] [Accepted: 12/01/2013] [Indexed: 02/08/2023]
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43
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Erickson MC, Webb CC, Díaz-Pérez JC, Davey LE, Payton AS, Flitcroft ID, Phatak SC, Doyle MP. Absence of internalization of Escherichia coli O157:H7 into germinating tissue of field-grown leafy greens. J Food Prot 2014; 77:189-96. [PMID: 24490912 DOI: 10.4315/0362-028x.jfp-13-216] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Both growth chamber and field studies were conducted to investigate the potential for Escherichia coli O157:H7 to be internalized into leafy green tissue when seeds were germinated in contaminated soil. Internalized E. coli O157:H7 was detected by enrichment in both spinach (Spinacia oleracea L.) and lettuce (Lactuca sativa L.) seedlings when seeds were germinated within the growth chamber in autoclaved and nonautoclaved soil, respectively, contaminated with E. coli O157:H7 at 2.0 and 3.8 log CFU/g, respectively. Internalized E. coli O157:H7 populations could be detected by enumeration within leafy green tissues either by increasing the pathogen levels in the soil or by autoclaving the soil. Attempts to maximize the exposure of seed to E. coli O157:H7 by increasing the mobility of the microbe either through soil with a higher moisture content or through directly soaking the seeds in an E. coli O157:H7 inoculum did not increase the degree of internalization. Based on responses obtained in growth chamber studies, internalization of E. coli O157:H7 surrogates (natural isolates of Shiga toxin-negative E. coli O157:H7 or recombinant [stx- and eae-negative] outbreak strains of E. coli O157:H7) occurred to a slightly lesser degree than did internalization of the virulent outbreak strains of E. coli O157:H7. The apparent lack of internalized E. coli O157:H7 when spinach and lettuce were germinated from seed in contaminated soil (ca. 3 to 5 log CFU/g) in the field and the limited occurrence of surface contamination on the seedlings suggest that competition from indigenous soil bacteria and environmental stresses were greater in the field than in the growth chamber. On the rare occasion that soil contamination with E. coli O157:H7 exceeded 5 log CFU/g in a commercial field, this pathogen probably would not be internalized into germinating leafy greens and/or would not still be present at the time of harvest.
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Affiliation(s)
- Marilyn C Erickson
- Center for Food Safety, Department of Food Science and Technology, University of Georgia, Griffin, Georgia 30223-1797, USA.
| | - Cathy C Webb
- Center for Food Safety, Department of Food Science and Technology, University of Georgia, Griffin, Georgia 30223-1797, USA
| | - Juan Carlos Díaz-Pérez
- Department of Horticulture, 4604 Research Way, University of Georgia, Tifton, Georgia 31793-0748, USA
| | - Lindsey E Davey
- Center for Food Safety, Department of Food Science and Technology, University of Georgia, Griffin, Georgia 30223-1797, USA
| | - Alison S Payton
- Center for Food Safety, Department of Food Science and Technology, University of Georgia, Griffin, Georgia 30223-1797, USA
| | - Ian D Flitcroft
- Department of Crops and Soil Science, 1109 Experiment Street, University of Georgia, Griffin, Georgia 30223-1797, USA
| | - Sharad C Phatak
- Department of Horticulture, 4604 Research Way, University of Georgia, Tifton, Georgia 31793-0748, USA
| | - Michael P Doyle
- Center for Food Safety, Department of Food Science and Technology, University of Georgia, Griffin, Georgia 30223-1797, USA
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44
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Sikin AM, Zoellner C, Rizvi SSH. Current intervention strategies for the microbial safety of sprouts. J Food Prot 2013; 76:2099-123. [PMID: 24290689 DOI: 10.4315/0362-028x.jfp-12-437] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Sprouts have gained popularity worldwide due to their nutritional values and health benefits. The fact that their consumption has been associated with numerous outbreaks of foodborne illness threatens the $250 million market that this industry has established in the United States. Therefore, sprout manufacturers have utilized the U.S. Food and Drug Administration recommended application of 20,000 ppm of calcium hypochlorite solution to seeds before germination as a preventative method. Concentrations of up to 200 ppm of chlorine wash are also commonly used on sprouts. However, chlorine-based treatment achieves on average only 1- to 3-log reductions in bacteria and is associated with negative health and environmental issues. The search for alternative strategies has been widespread, involving chemical, biological, physical, and hurdle processes that can achieve up to 7-log reductions in bacteria in some cases. The compilation here of the current scientific data related to these techniques is used to compare their efficacy for ensuring the microbial safety of sprouts and their practicality for commercial producers. Of specific importance for alternative seed and sprout treatments is maintaining the industry-accepted germination rate of 95% and the sensorial attributes of the final product. This review provides an evaluation of suggested decontamination technologies for seeds and sprouts before, during, and after germination and concludes that thermal inactivation of seeds and irradiation of sprouts are the most practical stand-alone microbial safety interventions for sprout production.
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Affiliation(s)
- Adi Md Sikin
- Institute of Food Science, Cornell University, Stocking Hall, Ithaca, New York 14853-7201, USA; Universiti Teknologi MARA, Shah Alam, Selangor, Malaysia.
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45
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Wang Q, Hirneisen KA, Markland SM, Kniel KE. Survival of murine norovirus, Tulane virus, and hepatitis A virus on alfalfa seeds and sprouts during storage and germination. Appl Environ Microbiol 2013; 79:7021-7. [PMID: 24014537 PMCID: PMC3811553 DOI: 10.1128/aem.01704-13] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 09/01/2013] [Indexed: 02/02/2023] Open
Abstract
Human norovirus (huNoV) and hepatitis A virus (HAV) have been involved in several produce-associated outbreaks and identified as major food-borne viral etiologies. In this study, the survival of huNoV surrogates (murine norovirus [MNV] and Tulane virus [TV]) and HAV was investigated on alfalfa seeds during storage and postgermination. Alfalfa seeds were inoculated with MNV, TV, or HAV with titers of 6.46 ± 0.06 log PFU/g, 3.87 ± 0.38 log PFU/g, or 7.01 ± 0.07 log 50% tissue culture infectious doses (TCID50)/g, respectively. Inoculated seeds were stored for up to 50 days at 22°C and sampled during that storage period on days 0, 2, 5, 10, and 15. Following storage, virus presence was monitored over a 1-week germination period. Viruses remained infectious after 50 days, with titers of 1.61 ± 0.19 log PFU/g, 0.85 ± 0.21 log PFU/g, and 3.43 ± 0.21 log TCID50/g for MNV, TV, and HAV, respectively. HAV demonstrated greater persistence than MNV and TV, without a statistically significant reduction over 20 days (<1 log TCID50/g); however, relatively high levels of genomic copies of all viruses persisted over the testing time period. Low titers of viruses were found on sprouts and were located in all tissues as well as in sprout-spent water sampled on days 1, 3, and 6 following seed planting. Results revealed the persistence of viruses in seeds for a prolonged period of time, and perhaps of greater importance these data suggest the ease of which virus may transfer from seeds to sprouts and spent water during germination. These findings highlight the importance of sanitation and prevention procedures before and during germination.
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Affiliation(s)
- Qing Wang
- Department of Animal and Food Sciences, University of Delaware, Newark, Delaware, USA
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46
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Ongeng D, Geeraerd AH, Springael D, Ryckeboer J, Muyanja C, Mauriello G. Fate ofEscherichia coliO157:H7 andSalmonella entericain the manure-amended soil-plant ecosystem of fresh vegetable crops: A review. Crit Rev Microbiol 2013; 41:273-94. [DOI: 10.3109/1040841x.2013.829415] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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47
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Studer P, Heller WE, Hummerjohann J, Drissner D. Evaluation of aerated steam treatment of alfalfa and mung bean seeds to eliminate high levels of Escherichia coli O157:H7 and O178:H12, Salmonella enterica, and Listeria monocytogenes. Appl Environ Microbiol 2013; 79:4613-9. [PMID: 23709507 PMCID: PMC3719507 DOI: 10.1128/aem.00443-13] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2013] [Accepted: 05/19/2013] [Indexed: 11/20/2022] Open
Abstract
Sprouts contaminated with human pathogens are able to cause food-borne diseases due to the favorable growth conditions for bacteria during germination and because of minimal processing steps prior to consumption. We have investigated the potential of hot humid air, i.e., aerated steam, to treat alfalfa and mung bean seeds which have been artificially contaminated with Escherichia coli O157:H7, Salmonella enterica subsp. enterica serovar Weltevreden, and Listeria monocytogenes Scott A. In addition, a recently collected E. coli O178:H12 isolate, characterized by a reduced heat sensitivity, was exposed to the treatment described. Populations of E. coli O157:H7 and S. enterica on alfalfa and mung bean seeds could be completely eliminated by a 300-s treatment with steam at 70 ± 1°C as revealed by enrichment studies. L. monocytogenes and E. coli O178:H12 could not be completely eliminated from artificially inoculated seeds. However, bacterial populations were reduced by more than 5 log CFU/g on alfalfa and by more than 4 log CFU/g on mung bean seeds. The germination rate of mung beans was not affected by the 300-s treatment compared to the germination rate of untreated seeds whereas that of alfalfa seeds was significantly lower by 11.9%. This chemical-free method is an effective alternative to the 20,000-ppm hypochlorite treatment presently recommended by the U.S. Food and Drug Administration (FDA).
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Affiliation(s)
- Patrick Studer
- Research Station Agroscope Changins-Wädenswil (ACW), Wädenswil, Switzerland
| | - Werner E. Heller
- Research Station Agroscope Changins-Wädenswil (ACW), Wädenswil, Switzerland
| | - Jörg Hummerjohann
- Research Station Agroscope Liebefeld-Posieux (ALP), Bern, Switzerland
| | - David Drissner
- Research Station Agroscope Changins-Wädenswil (ACW), Wädenswil, Switzerland
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Benjamin L, Atwill ER, Jay-Russell M, Cooley M, Carychao D, Gorski L, Mandrell RE. Occurrence of generic Escherichia coli, E. coli O157 and Salmonella spp. in water and sediment from leafy green produce farms and streams on the Central California coast. Int J Food Microbiol 2013; 165:65-76. [DOI: 10.1016/j.ijfoodmicro.2013.04.003] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 03/27/2013] [Accepted: 04/01/2013] [Indexed: 10/26/2022]
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Roy D, Panchal S, Rosa BA, Melotto M. Escherichia coli O157:H7 induces stronger plant immunity than Salmonella enterica Typhimurium SL1344. PHYTOPATHOLOGY 2013; 103:326-32. [PMID: 23301812 PMCID: PMC3982233 DOI: 10.1094/phyto-09-12-0230-fi] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Consumption of fresh produce contaminated with bacterial human pathogens has resulted in various, sometimes deadly, disease outbreaks. In this study, we assessed plant defense responses induced by the fully pathogenic bacteria Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium SL1344 in both Arabidopsis thaliana and lettuce (Lactuca sativa). Unlike SL1344, O157:H7 induced strong plant immunity at both pre-invasion and post-invasion steps of infection. For instance, O157:H7 triggered stomatal closure even under high relative humidity, an environmental condition that generally weakens plant defenses against bacteria in the field and laboratory conditions. SL1344 instead induced a transient stomatal immunity. We also observed that PR1 gene expression was significantly higher in Arabidopsis leaves infected with O157:H7 compared with SL1344. These results suggest that plants may recognize and respond to some human pathogens more effectively than others. Furthermore, stomatal immunity can diminish the penetration of human pathogens through the leaf epidermis, resulting in low bacterial titers in the plant apoplast and suggesting that additional control measures can be employed to prevent food contamination. The understanding of how plant responses can diminish bacterial contamination is paramount in preventing outbreaks and improving the safety of food supplies.
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Affiliation(s)
- Debanjana Roy
- Department of Biology, University of Texas, Arlington, Texas, 76019, USA
| | - Shweta Panchal
- Department of Biology, University of Texas, Arlington, Texas, 76019, USA
| | - Bruce A Rosa
- The Genome Institute, Washington University School of Medicine, St. Louis, Missouri, 63102, USA
| | - Maeli Melotto
- Department of Biology, University of Texas, Arlington, Texas, 76019, USA
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Fletcher J, Leach JE, Eversole K, Tauxe R. Human pathogens on plants: designing a multidisciplinary strategy for research. PHYTOPATHOLOGY 2013; 103:306-315. [PMID: 23406434 DOI: 10.1094/phyto-09-12-0236-ia] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Recent efforts to address concerns about microbial contamination of food plants and resulting foodborne illness have prompted new collaboration and interactions between the scientific communities of plant pathology and food safety. This article provides perspectives from scientists of both disciplines and presents selected research results and concepts that highlight existing and possible future synergisms for audiences of both disciplines. Plant pathology is a complex discipline that encompasses studies of the dissemination, colonization, and infection of plants by microbes such as bacteria, viruses, fungi, and oomycetes. Plant pathologists study plant diseases as well as host plant defense responses and disease management strategies with the goal of minimizing disease occurrences and impacts. Repeated outbreaks of human illness attributed to the contamination of fresh produce, nuts and seeds, and other plant-derived foods by human enteric pathogens such as Shiga toxin-producing Escherichia coli and Salmonella spp. have led some plant pathologists to broaden the application of their science in the past two decades, to address problems of human pathogens on plants (HPOPs). Food microbiology, which began with the study of microbes that spoil foods and those that are critical to produce food, now also focuses study on how foods become contaminated with pathogens and how this can be controlled or prevented. Thus, at the same time, public health researchers and food microbiologists have become more concerned about plant-microbe interactions before and after harvest. New collaborations are forming between members of the plant pathology and food safety communities, leading to enhanced research capacity and greater understanding of the issues for which research is needed. The two communities use somewhat different vocabularies and conceptual models. For example, traditional plant pathology concepts such as the disease triangle and the disease cycle can help to define cross-over issues that pertain also to HPOP research, and can suggest logical strategies for minimizing the risk of microbial contamination. Continued interactions and communication among these two disciplinary communities is essential and can be achieved by the creation of an interdisciplinary research coordination network. We hope that this article, an introduction to the multidisciplinary HPOP arena, will be useful to researchers in many related fields.
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Affiliation(s)
- Jacqueline Fletcher
- Department of Entomology & Plant Pathology, Oklahoma State University, Stillwater, OK, USA.
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