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Rangel LI, Leveau JHJ. Applied microbiology of the phyllosphere. Appl Microbiol Biotechnol 2024; 108:211. [PMID: 38358509 PMCID: PMC10869387 DOI: 10.1007/s00253-024-13042-4] [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: 10/16/2023] [Revised: 01/24/2024] [Accepted: 01/29/2024] [Indexed: 02/16/2024]
Abstract
The phyllosphere, or plant leaf surface, represents a microbial ecosystem of considerable size, holding extraordinary biodiversity and enormous potential for the discovery of new products, tools, and applications in biotechnology, agriculture, medicine, and elsewhere. This mini-review highlights the applied microbiology of the phyllosphere as an original field of study concerning itself with the genes, gene products, natural compounds, and traits that underlie phyllosphere-specific adaptations and services that have commercial and economic value for current or future innovation. Examples include plant-growth-promoting and disease-suppressive phyllobacteria, probiotics and fermented foods that support human health, as well as microbials that remedy foliar contamination with airborne pollutants, residual pesticides, or plastics. Phyllosphere microbes promote plant biomass conversion into compost, renewable energy, animal feed, or fiber. They produce foodstuffs such as thickening agents and sugar substitutes, industrial-grade biosurfactants, novel antibiotics and cancer drugs, as well as enzymes used as food additives or freezing agents. Furthermore, new developments in DNA sequence-based profiling of leaf-associated microbial communities allow for surveillance approaches in the context of food safety and security, for example, to detect enteric human pathogens on leafy greens, predict plant disease outbreaks, and intercept plant pathogens and pests on internationally traded goods. KEY POINTS: • Applied phyllosphere microbiology concerns leaf-specific adaptations for economic value • Phyllobioprospecting searches the phyllosphere microbiome for product development • Phyllobiomonitoring tracks phyllosphere microbial profiles for early risk detection.
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Affiliation(s)
- Lorena I Rangel
- Cell & Molecular Sciences, The James Hutton Institute, Dundee, Scotland, UK.
- Department of Plant Pathology, University of California, Davis, CA, USA.
| | - Johan H J Leveau
- Department of Plant Pathology, University of California, Davis, CA, USA.
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2
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Dhulappanavar GR, Gibson KE. Persistence of Salmonella enterica subsp. enterica ser. Javiana, Listeria monocytogenes, and Listeria innocua in Hydroponic Nutrient Solution. J Food Prot 2023; 86:100154. [PMID: 37640157 DOI: 10.1016/j.jfp.2023.100154] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2023] [Revised: 08/22/2023] [Accepted: 08/23/2023] [Indexed: 08/31/2023]
Abstract
This study aimed to determine the persistence of Salmonella Javiana, Listeria monocytogenes, and Listeria innocua in nonsterile, hydroponic nutrient solution (NS) at 15, 25, 30, and 37°C over a 21-day period to mimic time from seedling to mature lettuce. Bacteria were inoculated in modified Hoagland's NS at 106 CFU/mL and maintained at 15, 25, 30, and 37°C. Samples were collected at various time points, and bacteria were quantified. A mixed model was used to determine the effect of bacteria type, time (day), and temperature on bacteria concentration (log CFU/mL). The least-squares means were calculated to compare the mean log CFU/mL, and the mean values were compared with Tukey-Kramer honest significant difference test with a significance level of P = 0.05. Statistical analysis indicated that a 3-way interaction effect between temperature, time, and bacteria type had a significant impact on bacterial persistence in NS (P < 0.0001). At all temperatures, S. Javiana persisted in NS throughout the 21-day study period, compared to L. innocua and L. monocytogenes where persistence was limited to between 1 and 14 days. Similarly, decimal reduction values (D-values) of S. Javiana indicated longer persistence in NS than L. innocua and L. monocytogenes at most temperatures. For instance, at 15°C and 25°C, D-values for S. Javiana were estimated at 82 and 26 d, respectively, compared to D-values of 3.6 and ∼3 d for L. monocytogenes. Data indicate that the temperature of NS has a differential effect on the persistence of S. Javiana and Listeria spp. This study furthers the understanding of potential food safety risks associated with hydroponic systems and will contribute to the refinement of further studies to aid in the development of operation-specific risk profiles.
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Affiliation(s)
- Gayatri R Dhulappanavar
- Department of Food Science, Center for Food Safety, University of Arkansas System Division of Agriculture, Fayetteville, AR 72704, USA
| | - Kristen E Gibson
- Department of Food Science, Center for Food Safety, University of Arkansas System Division of Agriculture, Fayetteville, AR 72704, USA.
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3
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Sousa M, Mulaosmanovic E, Erdei AL, Bengtsson M, Witzgall P, Alsanius BW. Volatilomes reveal specific signatures for contamination of leafy vegetables with Escherichia coli O157:H7. Food Control 2022. [DOI: 10.1016/j.foodcont.2022.109513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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4
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Elnemr I, Mushtaha M, Sundararaju S, Hasan MR, Tsui KM, Goktepe I. Monitoring the effect of environmental conditions on safety of fresh produce sold in Qatar's wholesale market. INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 2022; 32:1986-2004. [PMID: 34085573 DOI: 10.1080/09603123.2021.1931050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 05/12/2021] [Indexed: 06/12/2023]
Abstract
Fresh produce imported by Qatar are mostly sold at the wholesale produce market (WPM) located in open-air and near major animal markets and slaughterhouses. This study was the first in Qatar to monitor the effect of environmental conditions on the microbial quality and safety of fresh produce sold at the WPM over 1 year. The monitoring involved the collection of 540 produce samples along with samples of air, soil, and surface swabs. Samples were analyzed for total aerobic bacteria (TAB); generic Listeria spp., Staphylococcus spp., Salmonella spp.; total coliforms and total fungi. Bacterial and fungal isolates were identified using 16S rRNA/ITS rRNA markers. Environmental/sanitary factors significantly impacted the prevalence of microorganisms in all samples tested. Produce quality was rated 'poor' during the months of November-February or May-August, with TAB and coliform counts exceeding 6 and 4 log10 CFU/g, respectively. Bacillus subtilus, Enterobacter cloacae, E. faecium, P. expansium, P. aurantiocandidum, and A. niger were the most abundant species with prevalence rate of 11-30%. The high microbial load of environmental samples indicates that the location of the WPM near livestock markets is likely impacting the microbial quality of fresh produce. Therefore, effective control measures need to be implemented at WPM to improve produce safety yearlong.
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Affiliation(s)
- I Elnemr
- Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Doha, Qatar
| | - M Mushtaha
- Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Doha, Qatar
| | | | - Mohammad Rubayet Hasan
- Department of Pathology, Sidra Medicine, Doha, Qatar
- Department of Clinical Pathology and Laboratory Medicine, Weill Cornell Medical College in Qatar, Doha, Qatar
| | - Kin-Ming Tsui
- Department of Pathology, Sidra Medicine, Doha, Qatar
- Department of Clinical Pathology and Laboratory Medicine, Weill Cornell Medical College in Qatar, Doha, Qatar
| | - I Goktepe
- Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Doha, Qatar
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5
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Yin HB, Chen CH, Colorado-Suarez S, Patel J. Biocontrol of Listeria monocytogenes and Salmonella enterica on Fresh Strawberries with Lactic Acid Bacteria During Refrigerated Storage. Foodborne Pathog Dis 2022; 19:324-331. [PMID: 35290741 DOI: 10.1089/fpd.2021.0091] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Small fruits such as strawberries have been increasingly implicated in outbreaks of foodborne illnesses. Salmonella enterica and Listeria monocytogenes may contaminate strawberries leading to potential public health concern. The objective of this study was to investigate the efficacy of a combined lactic acid bacteria (LAB) treatment of Lactobacillus plantarum and Pediococcus pentosaceus for controlling S. enterica and L. monocytogenes on fresh strawberries during storage at 4°C and 10°C. Strawberries purchased from a local grocery store were separately dip inoculated with Salmonella Newport, Salmonella Tennessee, Salmonella Thompson, or a three-strain cocktail of L. monocytogenes at ∼9 log colony-forming unit (CFU)/mL and allowed to air-dry for 1 h. Inoculated strawberries were then divided into three groups: (1) Control (pathogen alone), (2) Man, Rogosa, Sharpe (MRS) control (dipping in MRS broth), and (3) LAB treatment (dipping in a LAB cocktail of L. plantarum and P. pentosaceus). After treatment, strawberries were stored at 4°C or 10°C for 7 d in vented clamshell containers. Surviving Listeria, Salmonella, and LAB populations on strawberries were determined on 0, 1, 3, and 7 d post-treatment by plating on selective agars. At both 4°C and 10°C, LAB treatment significantly decreased Listeria populations by up to 2 log CFU/g compared to controls after 3 d of storage (p < 0.05). When strawberries were stored at 4°C, LAB treatment reduced ∼2.5 log, ∼2.7 log, and ∼2.9 log CFU/g in Salmonella Newport, Salmonella Tennessee, and Salmonella Thompson populations, respectively, compared to control on day 7. Similarly, ∼2.5 log CFU/g reductions of Salmonella populations were observed with LAB treatment at 10°C on day 7. LAB populations remained at ∼7.5 log CFU/g levels on strawberries at both temperatures throughout the entire study. Results of this study suggest that a combined LAB treatment can be potentially used as biocontrol agents against Salmonella and L. monocytogenes on strawberries at postharvest level.
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Affiliation(s)
- Hsin-Bai Yin
- Environmental Microbial & Food Safety Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland, USA
| | - Chi-Hung Chen
- Environmental Microbial & Food Safety Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland, USA
| | - Stephanie Colorado-Suarez
- Environmental Microbial & Food Safety Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland, USA
| | - Jitendra Patel
- Environmental Microbial & Food Safety Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland, USA
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Cabrera-Díaz E, Martínez-Chávez L, Gutiérrez-González P, Pérez-Montaño JA, Rodríguez-García MO, Martínez-Gonzáles NE. Effect of storage temperature and time on the behavior of Salmonella, Listeria monocytogenes, and background microbiota on whole fresh avocados (Persea americana var Hass). Int J Food Microbiol 2022; 369:109614. [DOI: 10.1016/j.ijfoodmicro.2022.109614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 12/30/2021] [Accepted: 03/04/2022] [Indexed: 11/27/2022]
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7
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Jongman M, Carmichael P, Loeto D, Gomba A. Advances in the use of biocontrol applications in preharvest and postharvest environments: A food safety milestone. J Food Saf 2021. [DOI: 10.1111/jfs.12957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | - Patricia Carmichael
- Department of Agricultural Research and Specialists Services Malkerns Eswatini
| | - Daniel Loeto
- Department of Biological Sciences University of Botswana Gaborone Botswana
| | - Annancietar Gomba
- National Institute for Occupational Health National Health Laboratory Service Johannesburg South Africa
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Lee KS, Jeong YJ, Lee MS. Escherichia coli Shiga Toxins and Gut Microbiota Interactions. Toxins (Basel) 2021; 13:toxins13060416. [PMID: 34208170 PMCID: PMC8230793 DOI: 10.3390/toxins13060416] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 06/03/2021] [Accepted: 06/08/2021] [Indexed: 12/19/2022] Open
Abstract
Escherichia coli (EHEC) and Shigella dysenteriae serotype 1 are enterohemorrhagic bacteria that induce hemorrhagic colitis. This, in turn, may result in potentially lethal complications, such as hemolytic uremic syndrome (HUS), which is characterized by thrombocytopenia, acute renal failure, and neurological abnormalities. Both species of bacteria produce Shiga toxins (Stxs), a phage-encoded exotoxin inhibiting protein synthesis in host cells that are primarily responsible for bacterial virulence. Although most studies have focused on the pathogenic roles of Stxs as harmful substances capable of inducing cell death and as proinflammatory factors that sensitize the host target organs to damage, less is known about the interface between the commensalism of bacterial communities and the pathogenicity of the toxins. The gut contains more species of bacteria than any other organ, providing pathogenic bacteria that colonize the gut with a greater number of opportunities to encounter other bacterial species. Notably, the presence in the intestines of pathogenic EHEC producing Stxs associated with severe illness may have compounding effects on the diversity of the indigenous bacteria and bacterial communities in the gut. The present review focuses on studies describing the roles of Stxs in the complex interactions between pathogenic Shiga toxin-producing E. coli, the resident microbiome, and host tissues. The determination of these interactions may provide insights into the unresolved issues regarding these pathogens.
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Affiliation(s)
- Kyung-Soo Lee
- Environmental Diseases Research Center, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahak-ro, Daejeon 34141, Korea;
- Department of Biomolecular Science, KRIBB School of Bioscience, Korea University of Science and Technology (UST), 127 Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea
| | - Yu-Jin Jeong
- Environmental Diseases Research Center, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahak-ro, Daejeon 34141, Korea;
- Correspondence: (Y.-J.J.); (M.-S.L.)
| | - Moo-Seung Lee
- Environmental Diseases Research Center, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahak-ro, Daejeon 34141, Korea;
- Department of Biomolecular Science, KRIBB School of Bioscience, Korea University of Science and Technology (UST), 127 Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea
- Correspondence: (Y.-J.J.); (M.-S.L.)
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Dorick J, Hayden M, Smith M, Blanchard C, Monu E, Wells D, Huang TS. Evaluation of Escherichia coli and coliforms in aquaponic water for produce irrigation. Food Microbiol 2021; 99:103801. [PMID: 34119095 DOI: 10.1016/j.fm.2021.103801] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 03/22/2021] [Accepted: 03/23/2021] [Indexed: 11/17/2022]
Abstract
The FDA Produce Safety Rule states that water used for irrigation purposes, likely to come into contact with the edible portion of fruit and vegetables, must not exceed a defined limit of Escherichia coli populations. Although aquaponics has not been included in this guideline, it is worth investigating to establish a baseline for facilities to reference in produce production. Two microbial assays were performed, one a decoupled media-based aquaponics system over one year and another on a decoupled nutrient film technique (NFT) aquaponics system over 16 days. Water was sampled from each system over time to analyze changes of E. coli and coliforms. The geometric mean (GM) and statistical threshold variable (STV) were calculated based on E. coli populations from the irrigation source in each system. From the first experiment, it was determined, based on the FDA Produce Safety Rule, that E. coli must be monitored more closely from June to January as they were above the advised limit. The second experiment determined that E. coli and coliforms in the water significantly decreased over 16 days. Water should be held for 8 d and up to 16 d to reduce the likelihood of foodborne pathogens to contaminate produce.
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Affiliation(s)
- Jennifer Dorick
- Department of Poultry Science, Auburn University, Auburn, AL, 36849, USA
| | - Michelle Hayden
- Department of Poultry Science, Auburn University, Auburn, AL, 36849, USA
| | - Mollie Smith
- School of Fisheries, Aquaculture and Aquatic Science, Auburn University, Auburn, AL, 36849, USA
| | | | - Emefa Monu
- Department of Poultry Science, Auburn University, Auburn, AL, 36849, USA
| | - Daniel Wells
- Department of Horticulture, Auburn University, Auburn, AL, 36849, USA
| | - Tung-Shi Huang
- Department of Poultry Science, Auburn University, Auburn, AL, 36849, USA.
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10
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Influence of Bacterial Competitors on Salmonella enterica and Enterohemorrhagic Escherichia coli Growth in Microbiological Media and Attachment to Vegetable Seeds. Foods 2021; 10:foods10020285. [PMID: 33572548 PMCID: PMC7912496 DOI: 10.3390/foods10020285] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 01/19/2021] [Accepted: 01/26/2021] [Indexed: 12/28/2022] Open
Abstract
Interests in using biological agents for control of human pathogens on vegetable seeds are rising. This study evaluated whether probiotic bacterium Lactobacillus rhamnosus GG, bacterial strains previously used as biocontrol agents in plant science, as well as a selected plant pathogen could compete with foodborne human pathogens, such as Salmonella enterica and enterohemorrhagic Escherichia coli (EHEC), for growth in microbiological media and attachment to vegetable seeds; and to determine whether the metabolites in cell-free supernatants of competitive bacterial spent cultures could inhibit the growth of the two pathogens. The results suggest that the co-presence of competitive bacteria, especially L. rhamnosus GG, significantly (p < 0.05) inhibited the growth of Salmonella and EHEC. Cell-free supernatants of L. rhamnosus GG cultures significantly reduced the pathogen populations in microbiological media. Although not as effective as L. rhamnosus GG in inhibiting the growth of Salmonella and EHEC, the biocontrol agents were more effective in competing for attachment to vegetable seeds. The study observed the inhibition of human bacterial pathogens by competitive bacteria or their metabolites and the competitive attachment to sprout seeds among all bacteria involved. The results will help strategize interventions to produce vegetable seeds and seed sprouts free of foodborne pathogens.
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Clairmont LK, Coristine A, Stevens KJ, Slawson RM. Factors influencing the persistence of enteropathogenic bacteria in wetland habitats and implications for water quality. J Appl Microbiol 2020; 131:513-526. [PMID: 33274572 DOI: 10.1111/jam.14955] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 11/12/2020] [Accepted: 11/29/2020] [Indexed: 11/28/2022]
Abstract
AIMS To better understand the persistence dynamics of enteropathogenic bacteria in freshwater wetland habitats, we constructed lab-scale mesocosms planted with two different wetland plant species using a subsurface flow wetland design. Mesocosms were treated with either a high-quality or a poor-quality water source to examine the effects of water quality exposure and plant species on Escherichia coli, Salmonella spp. and Enterococcus spp. in the rhizoplane, rhizosphere and water of wetland habitats. METHODS AND RESULTS Quantities of study micro-organisms were detected using real-time PCR in wetland mesocosms. A combination of molecular and culture-based methods was also used to enumerate these organisms from surface water and plant material at high, medium and poor water quality sites in the field. We found that all three enteropathogenic micro-organisms were influenced by microhabitat type and plant species. Organisms differed with respect to their predominant microhabitat and the extent of persistence associated with wetland plant species in the mesocosm study. Of the monitored pathogens, only E. coli was influenced by both water quality treatment and plant species. Salmonella spp. quantities in the rhizoplane consistently increased in all treatments over the course of the mesocosm experiment. CONCLUSIONS Plant species selection appears to be an overlooked aspect of constructed wetland design with respect to the removal of enteropathogenic micro-organisms. Escherichia coli and Enterococcus concentrations in wetland outflow were significantly different between the two plant species tested, with Enterococcus concentrations being significantly higher in mesocosms planted with Phalaris arundinaceae and E. coli concentrations being higher in mesocosms planted with Veronica anagallis-aquatica. Furthermore, there is evidence that the rhizoplane is a significant reservoir for Salmonella spp. within wetland habitats. SIGNIFICANCE AND IMPACT OF THE STUDY This is the first time that Salmonella spp. has been shown to proliferate under natural conditions within the rhizoplane. This will contribute to our understanding of wetland removal mechanisms for enteropathogenic bacteria. This study identifies the rhizoplane as a potentially important reservoir for human pathogenic micro-organisms and warrants additional study to establish whether this finding is applicable in non-wetland habitats.
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Affiliation(s)
| | - A Coristine
- Wilfrid Laurier University, Waterloo, ON, Canada
| | - K J Stevens
- Wilfrid Laurier University, Waterloo, ON, Canada
| | - R M Slawson
- Wilfrid Laurier University, Waterloo, ON, Canada
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12
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Belias AM, Sbodio A, Truchado P, Weller D, Pinzon J, Skots M, Allende A, Munther D, Suslow T, Wiedmann M, Ivanek R. Effect of Weather on the Die-Off of Escherichia coli and Attenuated Salmonella enterica Serovar Typhimurium on Preharvest Leafy Greens following Irrigation with Contaminated Water. Appl Environ Microbiol 2020; 86:e00899-20. [PMID: 32591379 PMCID: PMC7440809 DOI: 10.1128/aem.00899-20] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 06/21/2020] [Indexed: 11/25/2022] Open
Abstract
The Food Safety Modernization Act (FSMA) includes a time-to-harvest interval following the application of noncompliant water to preharvest produce to allow for microbial die-off. However, additional scientific evidence is needed to support this rule. This study aimed to determine the impact of weather on the die-off rate of Escherichia coli and Salmonella on spinach and lettuce under field conditions. Standardized, replicated field trials were conducted in California, New York, and Spain over 2 years. Baby spinach and lettuce were grown and inoculated with an ∼104-CFU/ml cocktail of E. coli and attenuated Salmonella Leaf samples were collected at 7 time points (0 to 96 h) following inoculation; E. coli and Salmonella were enumerated. The associations of die-off with study design factors (location, produce type, and bacteria) and weather were assessed using log-linear and biphasic segmented log-linear regression. A segmented log-linear model best fit die-off on inoculated leaves in most cases, with a greater variation in the segment 1 die-off rate across trials (-0.46 [95% confidence interval {95% CI}, -0.52, -0.41] to -6.99 [95% CI, -7.38, -6.59] log10 die-off/day) than in the segment 2 die-off rate (0.28 [95% CI, -0.20, 0.77] to -1.00 [95% CI, -1.16, -0.85] log10 die-off/day). A lower relative humidity was associated with a faster segment 1 die-off and an earlier breakpoint (the time when segment 1 die-off rate switches to the segment 2 rate). Relative humidity was also found to be associated with whether die-off would comply with FSMA's specified die-off rate of -0.5 log10 die-off/day.IMPORTANCE The log-linear die-off rate proposed by FSMA is not always appropriate, as the die-off rates of foodborne bacterial pathogens and specified agricultural water quality indicator organisms appear to commonly follow a biphasic pattern with an initial rapid decline followed by a period of tailing. While we observed substantial variation in the net culturable population levels of Salmonella and E. coli at each time point, die-off rate and FSMA compliance (i.e., at least a 2 log10 die-off over 4 days) appear to be impacted by produce type, bacteria, and weather; die-off on lettuce tended to be faster than that on spinach, die-off of E. coli tended to be faster than that of attenuated Salmonella, and die-off tended to become faster as relative humidity decreased. Thus, the use of a single die-off rate for estimating time-to-harvest intervals across different weather conditions, produce types, and bacteria should be revised.
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Affiliation(s)
| | - Adrian Sbodio
- Department of Plant Sciences, University of California, Davis, California, USA
| | - Pilar Truchado
- Department of Food Science and Technology, CEBAS-CSIC (Spanish National Research Council), Murcia, Spain
| | - Daniel Weller
- Department of Food Science, Cornell University, Ithaca, New York, USA
- Department of Biostatistics and Computational Biology, University of Rochester, Rochester, New York, USA
| | - Janneth Pinzon
- Department of Plant Sciences, University of California, Davis, California, USA
| | - Mariya Skots
- Department of Plant Sciences, University of California, Davis, California, USA
| | - Ana Allende
- Department of Food Science and Technology, CEBAS-CSIC (Spanish National Research Council), Murcia, Spain
| | - Daniel Munther
- Department of Mathematics, Cleveland State University, Cleveland, Ohio, USA
| | - Trevor Suslow
- Department of Plant Sciences, University of California, Davis, California, USA
- Produce Marketing Association, Newark, Delaware, USA
| | - Martin Wiedmann
- Department of Food Science, Cornell University, Ithaca, New York, USA
| | - Renata Ivanek
- Department of Population Medicine and Diagnostic Sciences, Cornell University, New York, USA
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Doan HK, Antequera-Gómez ML, Parikh AN, Leveau JHJ. Leaf Surface Topography Contributes to the Ability of Escherichia coli on Leafy Greens to Resist Removal by Washing, Escape Disinfection With Chlorine, and Disperse Through Splash. Front Microbiol 2020; 11:1485. [PMID: 32765440 PMCID: PMC7380079 DOI: 10.3389/fmicb.2020.01485] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Accepted: 06/08/2020] [Indexed: 12/25/2022] Open
Abstract
The attachment of foodborne pathogens to leaf surfaces is a complex process that involves multiple physical, chemical, and biological factors. Here, we report the results from a study designed to specifically determine the contribution of spinach leaf surface topography as it relates to leaf axis (abaxial and adaxial) and leaf age (15, 45, and 75 days old) to the ability of Escherichia coli to resist removal by surface wash, to avoid inactivation by chlorine, and to disperse through splash impact. We used fresh spinach leaves, as well as so-called "replicasts" of spinach leaf surfaces in the elastomer polydimethylsiloxane to show that leaf vein density correlated positively with the failure to recover E. coli from surfaces, not only using a simple water wash and rinse, but also a more stringent wash protocol involving a detergent. Such failure was more pronounced when E. coli was surface-incubated at 24°C compared to 4°C, and in the presence, rather than absence, of nutrients. Leaf venation also contributed to the ability of E. coli to survive a 50 ppm available chlorine wash and to laterally disperse by splash impact. Our findings suggest that the topographical properties of the leafy green surface, which vary by leaf age and axis, may need to be taken into consideration when developing prevention or intervention strategies to enhance the microbial safety of leafy greens.
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Affiliation(s)
- Hung K. Doan
- Department of Plant Pathology, University of California, Davis, Davis, CA, United States
| | - María L. Antequera-Gómez
- Departamento de Microbiología, Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora”, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Universidad de Málaga, Málaga, Spain
| | - Atul N. Parikh
- Department of Biomedical Engineering, University of California, Davis, Davis, CA, United States
- Department of Materials Science and Engineering, University of California, Davis, Davis, CA, United States
| | - Johan H. J. Leveau
- Department of Plant Pathology, University of California, Davis, Davis, CA, United States
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Eissenberger K, Drissner D, Walsh F, Weiss A, Schmidt H. Plant variety and soil type influence Escherichia coli O104:H4 strain C227/11ϕcu adherence to and internalization into the roots of lettuce plants. Food Microbiol 2020; 86:103316. [PMID: 31703882 DOI: 10.1016/j.fm.2019.103316] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 07/19/2019] [Accepted: 08/31/2019] [Indexed: 12/17/2022]
Abstract
Human disease outbreaks caused by pathogenic Escherichia coli are increasingly associated with the consumption of contaminated fresh produce. Internalization of enteroaggregative/enterohemorrhagic E. coli (EAEC/EHEC) strains into plant tissues may present a serious threat to public health. In the current study, the ability of the fluorescing Shiga toxin-negative E. coli O104:H4 strain C227/11ϕcu/pKEC2 to adhere to and to internalize into the roots of Lactuca sativa and Valerianella locusta grown in diluvial sand (DS) and alluvial loam (AL) was investigated. In parallel, the soil microbiota was analyzed by partial 16S rRNA gene sequencing. The experiments were performed in a safety level 3 greenhouse to simulate agricultural practice. The adherence of C227/11ϕcu/pKEC2 to the roots of both plant varieties was increased by at least a factor three after incubation in DS compared to AL. Compared to V. locusta, internalization into the roots of L. sativa was increased 12-fold in DS and 108-fold in AL. This demonstrates that the plant variety had an impact on the internalization ability, whereas for a given plant variety the soil type also affected bacterial internalization. In addition, microbiota analysis detected the inoculated strain and showed large differences in the bacterial composition between the soil types.
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Affiliation(s)
- Kristina Eissenberger
- Institute of Food Science and Biotechnology, Department of Food Microbiology and Hygiene, University of Hohenheim, Stuttgart, Germany
| | - David Drissner
- Microbiology of Plant Foods, Agroscope, Waedenswil, Switzerland; Swiss Federal Institute for Forest, Snow, and Landscape Research WSL, Birmensdorf, Switzerland; Department of Life Sciences, Albstadt-Sigmaringen University, Sigmaringen, Germany
| | - Fiona Walsh
- Department of Biology, Maynooth University, Maynooth, Ireland
| | - Agnes Weiss
- Institute of Food Science and Biotechnology, Department of Food Microbiology and Hygiene, University of Hohenheim, Stuttgart, Germany
| | - Herbert Schmidt
- Institute of Food Science and Biotechnology, Department of Food Microbiology and Hygiene, University of Hohenheim, Stuttgart, Germany.
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15
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Melotto M, Brandl MT, Jacob C, Jay-Russell MT, Micallef SA, Warburton ML, Van Deynze A. Breeding Crops for Enhanced Food Safety. FRONTIERS IN PLANT SCIENCE 2020; 11:428. [PMID: 32351531 PMCID: PMC7176021 DOI: 10.3389/fpls.2020.00428] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 03/24/2020] [Indexed: 05/12/2023]
Abstract
An increasing global population demands a continuous supply of nutritious and safe food. Edible products can be contaminated with biological (e.g., bacteria, virus, protozoa), chemical (e.g., heavy metals, mycotoxins), and physical hazards during production, storage, transport, processing, and/or meal preparation. The substantial impact of foodborne disease outbreaks on public health and the economy has led to multidisciplinary research aimed to understand the biology underlying the different contamination processes and how to mitigate food hazards. Here we review the knowledge, opportunities, and challenges of plant breeding as a tool to enhance the food safety of plant-based food products. First, we discuss the significant effect of plant genotypic and phenotypic variation in the contamination of plants by heavy metals, mycotoxin-producing fungi, and human pathogenic bacteria. In addition, we discuss the various factors (i.e., temperature, relative humidity, soil, microbiota, cultural practices, and plant developmental stage) that can influence the interaction between plant genetic diversity and contaminant. This exposes the necessity of a multidisciplinary approach to understand plant genotype × environment × microbe × management interactions. Moreover, we show that the numerous possibilities of crop/hazard combinations make the definition and identification of high-risk pairs, such as Salmonella-tomato and Escherichia coli-lettuce, imperative for breeding programs geared toward improving microbial safety of produce. Finally, we discuss research on developing effective assays and approaches for selecting desirable breeding germplasm. Overall, it is recognized that although breeding programs for some human pathogen/toxin systems are ongoing (e.g., Fusarium in wheat), it would be premature to start breeding when targets and testing systems are not well defined. Nevertheless, current research is paving the way toward this goal and this review highlights advances in the field and critical points for the success of this initiative that were discussed during the Breeding Crops for Enhanced Food Safety workshop held 5-6 June 2019 at University of California, Davis.
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Affiliation(s)
- Maeli Melotto
- Department of Plant Sciences, University of California, Davis, Davis, CA, United States
- *Correspondence: Maeli Melotto,
| | - Maria T. Brandl
- United States Department of Agriculture-Agricultural Research Service, Produce Safety and Microbiology Research, Albany, CA, United States
| | - Cristián Jacob
- Department of Plant Sciences, University of California, Davis, Davis, CA, United States
| | - Michele T. Jay-Russell
- Western Center for Food Safety, University of California, Davis, Davis, CA, United States
| | - Shirley A. Micallef
- Department of Plant Science and Landscape Architecture, Center for Food Safety and Security Systems, University of Maryland, College Park, MD, United States
| | - Marilyn L. Warburton
- United States Department of Agriculture-Agricultural Research Service, Corn Host Plant Research Resistance Unit Mississippi State, Starkville, MS, United States
| | - Allen Van Deynze
- Plant Breeding Center, Department of Plant Sciences, University of California, Davis, Davis, CA, United States
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16
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Wassermann B, Müller H, Berg G. An Apple a Day: Which Bacteria Do We Eat With Organic and Conventional Apples? Front Microbiol 2019; 10:1629. [PMID: 31396172 PMCID: PMC6667679 DOI: 10.3389/fmicb.2019.01629] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 07/02/2019] [Indexed: 12/12/2022] Open
Abstract
Apples are among the most consumed fruits world-wide. They represent a source of direct human exposure to bacterial communities, which is less studied. We analyzed the apple microbiome to detect differences between tissues and the impact of organic and conventional management by a combined approach of 16S rRNA gene amplicon analysis and qPCR, and visualization using fluorescence in situ hybridization and confocal laser scanning microscopy (FISH-CLSM). Each apple fruit harbors different tissues (stem, peel, fruit pulp, seeds, and calyx), which were colonized by distinct bacterial communities. Interestingly, fruit pulp and seeds were bacterial hot spots, while the peel was less colonized. In all, approximately 108 16S rRNA bacterial gene copy numbers were determined in each g apple. Abundances were not influenced by the management practice but we found a strong reduction in bacterial diversity and evenness in conventionally managed apples. In addition, despite the similar structure in general dominated by Proteobacteria (80%), Bacteroidetes (9%), Actinobacteria (5%), and Firmicutes (3%), significant shifts of almost 40% of bacterial genera and orders were monitored. Among them, especially bacterial signatures known for health-affecting potential were found to be enhanced in conventionally managed apples. Our results suggest that we consume about 100 million bacterial cells with one apple. Although this amount was the same, the bacterial composition was significantly different in conventionally and organically produced apples.
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Affiliation(s)
- Birgit Wassermann
- Institute of Environmental Biotechnology, Graz University of Technology, Graz, Austria
| | - Henry Müller
- Institute of Environmental Biotechnology, Graz University of Technology, Graz, Austria
| | - Gabriele Berg
- Institute of Environmental Biotechnology, Graz University of Technology, Graz, Austria
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17
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Darlison J, Mieli M, Bengtsson T, Hartmann R, Mogren L, Vågsholm I, Karlsson M, Alsanius BW. Plant species affects establishment of Escherichia coli O157:H7 gfp+ on leafy vegetables. J Appl Microbiol 2019; 127:292-305. [PMID: 31054164 DOI: 10.1111/jam.14299] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 04/18/2019] [Accepted: 04/29/2019] [Indexed: 01/25/2023]
Abstract
AIMS Greenhouse trials were conducted with different cultivars of baby leaf spinach, rocket and Swiss chard and inoculation of Escherichia coli O157:H7 gfp+, to determine whether plant species and cultivar have an impact on the establishment of this strain. METHODS AND RESULTS Three cultivars each of spinach, rocket and Swiss chard were spray inoculated with E. coli O157:H7 gfp+ at doses of log 7 CFU per ml. Due to the different lengths of growing period spinach and Swiss chard were spray inoculated three times and rocket five times, with final inoculation performed 3 days prior to harvest. After a growing period of 26-33 days, E. coli O157:H7 gfp+ was recovered from the leaf surface in mean populations between log 1 and 6 CFU per gram. The lowest occurrence of E. coli O157:H7 gfp+ was found on rocket leaves and the highest on spinach. There was no significant difference in the establishment of E. coli O157:H7 gfp+ between cultivars, but there were differences between plant species. Indigenous phyllosphere bacteria were pure cultured and identified with 16S rRNA gene sequencing. CONCLUSIONS Despite the same high inoculation dose of E. coli O157:H7 gfp+ on leaves, the establishment rate differed between plant species. However, plant cultivar did not affect establishment. Pantoea agglomerans dominated the identified bacterial isolates. SIGNIFICANCE AND IMPACT OF THE STUDY As previous studies are inconclusive on choice of model plant species and cultivar, we studied whether plant species or cultivar determines the fate of E. coli O157:H7 gfp+ on leafy vegetables. The findings indicate that plant species is a key determinant in the establishment of E. coli O157:H7 gfp+.
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Affiliation(s)
- J Darlison
- Department of Biosystems and Technology, Microbial Horticulture Laboratory, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - M Mieli
- Department of Biosystems and Technology, Microbial Horticulture Laboratory, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - T Bengtsson
- Department of Biosystems and Technology, Microbial Horticulture Laboratory, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - R Hartmann
- Department of Biosystems and Technology, Microbial Horticulture Laboratory, Swedish University of Agricultural Sciences, Alnarp, Sweden.,Department of Horticultural Production Systems, Wilhelm Leibniz University, Hannover, Germany
| | - L Mogren
- Department of Biosystems and Technology, Microbial Horticulture Laboratory, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - I Vågsholm
- Department of Biomedical Sciences and Veterinary Health, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - M Karlsson
- Department of Biosystems and Technology, Microbial Horticulture Laboratory, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - B W Alsanius
- Department of Biosystems and Technology, Microbial Horticulture Laboratory, Swedish University of Agricultural Sciences, Alnarp, Sweden
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18
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Safety risks associated with dispersal of E. coli O157:H7 in home sprouting modules. Lebensm Wiss Technol 2019. [DOI: 10.1016/j.lwt.2018.11.086] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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Luziatelli F, Ficca AG, Colla G, Baldassarre Švecová E, Ruzzi M. Foliar Application of Vegetal-Derived Bioactive Compounds Stimulates the Growth of Beneficial Bacteria and Enhances Microbiome Biodiversity in Lettuce. FRONTIERS IN PLANT SCIENCE 2019; 10:60. [PMID: 30804958 PMCID: PMC6370708 DOI: 10.3389/fpls.2019.00060] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Accepted: 01/16/2019] [Indexed: 05/02/2023]
Abstract
Many studies on plant biostimulants and organic fertilizers have been focused on the ability of these products to increase crop productivity and ameliorate crop tolerance to abiotic stresses. However, little information is available on their effect on plant microbiota, whereas it is well known that microorganisms associated with plant play crucial roles on the health and productivity of their host. The aim of this study was to evaluate the effect of a vegetal-derived protein hydrolysate (PH), a vegetal-derived PH enriched with copper (Cu-PH), and a tropical plant extract enriched with micronutrients (PE) on shoot growth and the epiphytic bacterial population of lettuce plants and the ability of these products to enhance the growth of beneficial or harmful bacteria. The three plant-derived products enhanced shoot biomass of lettuce plants indicating a biostimulant effect of the products. Data obtained using culture-independent (Terminal Restriction Fragment Length Polymorphism and Next Generation Sequencing) and culture-dependent approaches indicated that foliar application of commercial products altered the composition of the microbial population and stimulated the growth of specific bacteria belonging to Pantoea, Pseudomonas, Acinetobacter, and Bacillus genus. Data presented in this work demonstrated that some of these strains exhibited potential plant growth-promoting properties and/or biocontrol activity against fungi and bacteria phytopathogens including Fusarium, Trichoderma, and Erwinia species. No indication of potential health risks associated to the enrichment of human or plant bacterial pathogens emerged by the analysis of the microbiota of treated and no-treated plants. Overall, the findings presented in this study indicate that the commercial organic-based products can enhance the growth of beneficial bacteria occurring in the plant microbiota and signals produced by these bacteria can act synergistically with the organic compounds to enhance plant growth and productivity.
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Affiliation(s)
- Francesca Luziatelli
- Department for Innovation in Biological, Agrofood and Forest Systems, University of Tuscia, Viterbo, Italy
| | - Anna Grazia Ficca
- Department for Innovation in Biological, Agrofood and Forest Systems, University of Tuscia, Viterbo, Italy
| | - Giuseppe Colla
- Department of Agriculture and Forest Sciences, University of Tuscia, Viterbo, Italy
| | | | - Maurizio Ruzzi
- Department for Innovation in Biological, Agrofood and Forest Systems, University of Tuscia, Viterbo, Italy
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20
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Wassermann B, Müller H, Berg G. An Apple a Day: Which Bacteria Do We Eat With Organic and Conventional Apples? Front Microbiol 2019. [PMID: 31396172 DOI: 10.3389/fmicb.2019.01629/full] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023] Open
Abstract
Apples are among the most consumed fruits world-wide. They represent a source of direct human exposure to bacterial communities, which is less studied. We analyzed the apple microbiome to detect differences between tissues and the impact of organic and conventional management by a combined approach of 16S rRNA gene amplicon analysis and qPCR, and visualization using fluorescence in situ hybridization and confocal laser scanning microscopy (FISH-CLSM). Each apple fruit harbors different tissues (stem, peel, fruit pulp, seeds, and calyx), which were colonized by distinct bacterial communities. Interestingly, fruit pulp and seeds were bacterial hot spots, while the peel was less colonized. In all, approximately 108 16S rRNA bacterial gene copy numbers were determined in each g apple. Abundances were not influenced by the management practice but we found a strong reduction in bacterial diversity and evenness in conventionally managed apples. In addition, despite the similar structure in general dominated by Proteobacteria (80%), Bacteroidetes (9%), Actinobacteria (5%), and Firmicutes (3%), significant shifts of almost 40% of bacterial genera and orders were monitored. Among them, especially bacterial signatures known for health-affecting potential were found to be enhanced in conventionally managed apples. Our results suggest that we consume about 100 million bacterial cells with one apple. Although this amount was the same, the bacterial composition was significantly different in conventionally and organically produced apples.
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Affiliation(s)
- Birgit Wassermann
- Institute of Environmental Biotechnology, Graz University of Technology, Graz, Austria
| | - Henry Müller
- Institute of Environmental Biotechnology, Graz University of Technology, Graz, Austria
| | - Gabriele Berg
- Institute of Environmental Biotechnology, Graz University of Technology, Graz, Austria
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21
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Gilfillan D, Hall K, Joyner TA, Scheuerman P. Canonical Variable Selection for Ecological Modeling of Fecal Indicators. JOURNAL OF ENVIRONMENTAL QUALITY 2018; 47:974-984. [PMID: 30272784 DOI: 10.2134/jeq2017.12.0474] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
More than 270,000 km of rivers and streams are impaired due to fecal pathogens, creating an economic and public health burden. Fecal indicator organisms such as are used to determine if surface waters are pathogen impaired, but they fail to identify human health risks, provide source information, or have unique fate and transport processes. Statistical and machine learning models can be used to overcome some of these weaknesses, including identifying ecological mechanisms influencing fecal pollution. In this study, canonical correlation analysis (CCorA) was performed to select parameters for the machine learning model, Maxent, to identify how chemical and microbial parameters can predict impairment and F-somatic bacteriophage detections. Models were validated using a bootstrapping cross-validation. Three suites of models were developed; initial models using all parameters, models using parameters identified in CCorA, and optimized models after further sensitivity analysis. Canonical correlation analysis reduced the number of parameters needed to achieve the same degree of accuracy in the initial model (84.7%), and sensitivity analysis improved accuracy to 86.1%. Bacteriophage model accuracies were 79.2, 70.8, and 69.4% for the initial, CCorA, and optimized models, respectively; this suggests complex ecological interactions of bacteriophages are not captured by CCorA. Results indicate distinct ecological drivers of impairment depending on the fecal indicator organism used. impairment is driven by increased hardness and microbial activity, whereas bacteriophage detection is inhibited by high levels of coliforms in sediment. Both indicators were influenced by organic pollution and phosphorus limitation.
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22
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Impact of the source of organic manure on persistence of E. coli O157:H7 gfp + in rocket ( Diplotaxis tenuifolia ) and Swiss chard ( Beta vulgaris cicla). Food Control 2017. [DOI: 10.1016/j.foodcont.2017.06.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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23
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High relative humidity pre-harvest reduces post-harvest proliferation of Salmonella in tomatoes. Food Microbiol 2017; 66:55-63. [DOI: 10.1016/j.fm.2017.04.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 04/04/2017] [Indexed: 11/21/2022]
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24
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Koukkidis G, Haigh R, Allcock N, Jordan S, Freestone P. Salad Leaf Juices Enhance Salmonella Growth, Colonization of Fresh Produce, and Virulence. Appl Environ Microbiol 2017; 83:e02416-16. [PMID: 27864173 PMCID: PMC5165107 DOI: 10.1128/aem.02416-16] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 10/24/2016] [Indexed: 11/20/2022] Open
Abstract
We show in this report that traces of juices released from salad leaves as they become damaged can significantly enhance colonization of salad leaves by Salmonella enterica Salad juices in water increased Salmonella growth by 110% over the level seen with the unsupplemented control and in host-like serum-based media by more than 2,400-fold over control levels. In serum-based media, salad juices induced growth of Salmonella via provision of Fe from transferrin, and siderophore production was found to be integral to the growth induction process. Other aspects relevant to salad leaf colonization and retention were enhanced, such as motility and biofilm formation, which were increased over control levels by >220% and 250%, respectively; direct attachment to salad leaves increased by >350% when a salad leaf juice was present. In terms of growth and biofilm formation, the endogenous salad leaf microbiota was largely unresponsive to leaf juice, suggesting that Salmonella gains a marked growth advantage from fluids released by salad leaf damage. Salad leaf juices also enhanced pathogen attachment to the salad bag plastic. Over 5 days of refrigeration (a typical storage time for bagged salad leaves), even traces of juice within the salad bag fluids increased Salmonella growth in water by up to 280-fold over control cultures, as well as enhancing salad bag colonization, which could be an unappreciated factor in retention of pathogens in fresh produce. Collectively, the study data show that exposure to salad leaf juice may contribute to the persistence of Salmonella on salad leaves and strongly emphasize the importance of ensuring the microbiological safety of fresh produce. IMPORTANCE Salad leaves are an important part of a healthy diet but have been associated in recent years with a growing risk of food poisoning from bacterial pathogens such as Salmonella enterica Although this is considered a significant public health problem, very little is known about the behavior of Salmonella in the actual salad bag. We show that juices released from the cut ends of the salad leaves enabled the Salmonella cells to grow in water, even when it was refrigerated. Salad juice exposure also helped the Salmonella cells to attach to the salad leaves so strongly that washing could not remove them. Collectively, the results presented in this report show that exposure to even traces of salad leaf juice may contribute to the persistence of Salmonella on salad leaves as well as priming it for establishing an infection in the consumer.
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Affiliation(s)
- Giannis Koukkidis
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
| | - Richard Haigh
- Department of Genetics, University of Leicester, Leicester, United Kingdom
| | - Natalie Allcock
- Core Biotechnology Services, University of Leicester, Leicester, United Kingdom
| | - Suzanne Jordan
- Campden BRI, Chipping Campden, Gloucestershire, United Kingdom
| | - Primrose Freestone
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
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25
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Martemyanov VV, Belousova IA, Pavlushin SV, Dubovskiy IM, Ershov NI, Alikina TY, Kabilov MR, Glupov VV. Phenological asynchrony between host plant and gypsy moth reduces insect gut microbiota and susceptibility to Bacillus thuringiensis. Ecol Evol 2016; 6:7298-7310. [PMID: 28725398 PMCID: PMC5513265 DOI: 10.1002/ece3.2460] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 07/26/2016] [Accepted: 08/12/2016] [Indexed: 01/15/2023] Open
Abstract
The phenological synchrony between the emergence of overwintering herbivorous insects and the budding of host plants is considered a crucial factor in the population dynamics of herbivores. However, the mechanisms driving the interactions between the host plant, herbivores, and their pathogens are often obscure. In the current study, an artificially induced phenological asynchrony was used to investigate how the asynchrony between silver birch Betula pendula and gypsy moth Lymantria dispar affects the immunity of the insect to bacteria, its susceptibility to the entomopathogenic bacteria Bacillus thuringiensis, and the diversity in its midgut microbiota. The lysozyme-like activity in both the midgut and hemolymph plasma and the nonspecific esterase activity and antimicrobial peptide gene expression in the midgut were studied in both noninfected and B. thuringiensis-infected larvae. Our results provide the first evidence that phenologically asynchronous larvae are less susceptible to B. thuringiensis infection than phenologically synchronous larvae, and our results show that these effects are related to the high basic levels and B. thuringiensis-induced levels of lysozyme-like activities. Moreover, a 16S rRNA analysis revealed that dramatic decreases in the diversity of the larval gut bacterial consortia occurred under the effect of asynchrony. Larvae infected with B. thuringiensis presented decreased microbiota diversity if the larvae were reared synchronously with the host plant but not if they were reared asynchronously. Our study demonstrates the significant effect of phenological asynchrony on innate immunity-mediated interactions between herbivores and entomopathogenic bacteria and highlights the role of nonpathogenic gut bacteria in these interactions.
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Affiliation(s)
- Vyacheslav V. Martemyanov
- Laboratory of Ecological ParasitologyInstitute of Systematics and Ecology of Animals Siberian BranchRussian Academy of SciencesNovosibirskRussia
- Biological InstituteNational Research Tomsk State UniversityTomskRussia
| | - Irina A. Belousova
- Laboratory of Ecological ParasitologyInstitute of Systematics and Ecology of Animals Siberian BranchRussian Academy of SciencesNovosibirskRussia
- Institute of BiologyIrkutsk State UniversityIrkutskRussia
| | - Sergey V. Pavlushin
- Laboratory of Ecological ParasitologyInstitute of Systematics and Ecology of Animals Siberian BranchRussian Academy of SciencesNovosibirskRussia
| | - Ivan M. Dubovskiy
- Laboratory of Insect PathologyInstitute of Systematics and Ecology of Animals Siberian BranchRussian Academy of SciencesNovosibirskRussia
| | - Nikita I. Ershov
- Institute of Cytology and GeneticsSiberian BranchRussian Academy of SciencesNovosibirskRussia
| | - Tatyana Y. Alikina
- Genomics Core FacilityInstitute of Chemical Biology and Fundamental MedicineSiberian BranchRussian Academy of SciencesNovosibirskRussia
| | - Marsel R. Kabilov
- Genomics Core FacilityInstitute of Chemical Biology and Fundamental MedicineSiberian BranchRussian Academy of SciencesNovosibirskRussia
| | - Victor V. Glupov
- Laboratory of Insect PathologyInstitute of Systematics and Ecology of Animals Siberian BranchRussian Academy of SciencesNovosibirskRussia
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26
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Chopyk J, Moore RM, DiSpirito Z, Stromberg ZR, Lewis GL, Renter DG, Cernicchiaro N, Moxley RA, Wommack KE. Presence of pathogenic Escherichia coli is correlated with bacterial community diversity and composition on pre-harvest cattle hides. MICROBIOME 2016; 4:9. [PMID: 27000779 PMCID: PMC4802634 DOI: 10.1186/s40168-016-0155-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2015] [Accepted: 02/10/2016] [Indexed: 05/10/2023]
Abstract
BACKGROUND Since 1982, specific serotypes of Shiga toxin-producing Escherichia coli (STEC) have been recognized as significant foodborne pathogens acquired from contaminated beef and, more recently, other food products. Cattle are the major reservoir hosts of these organisms, and while there have been advancements in food safety practices and industry standards, STEC still remains prevalent within beef cattle operations with cattle hides implicated as major sources of carcass contamination. To investigate whether the composition of hide-specific microbial communities are associated with STEC prevalence, 16S ribosomal RNA (rRNA) bacterial community profiles were obtained from hide and fecal samples collected from a large commercial feedlot over a 3-month period. These community data were examined amidst an extensive collection of prevalence data on a subgroup of STEC that cause illness in humans, referred to as enterohemorrhagic E. coli (EHEC). Fecal 16S rRNA gene OTUs (operational taxonomic units) were subtracted from the OTUs found within each hide 16S rRNA amplicon library to identify hide-specific bacterial populations. RESULTS Comparative analysis of alpha diversity revealed a significant correlation between low bacterial diversity and samples positive for the presence of E. coli O157:H7 and/or the non-O157 groups: O26, O111, O103, O121, O45, and O145. This trend occurred regardless of diversity metric or fecal OTU presence. The number of EHEC serogroups present in the samples had a compounding effect on the inverse relationship between pathogen presence and bacterial diversity. Beta diversity data showed differences in bacterial community composition between samples containing O157 and non-O157 populations, with certain OTUs demonstrating significant changes in relative abundance. CONCLUSIONS The cumulative prevalence of the targeted EHEC serogroups was correlated with low bacterial community diversity on pre-harvest cattle hides. Understanding the relationship between indigenous hide bacterial communities and populations may provide strategies to limit EHEC in cattle and provide biomarkers for EHEC risk assessment.
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Affiliation(s)
- Jessica Chopyk
- Delaware Biotechnology Institute, University of Delaware, Delaware Biotechnology Inst., 15 Innovation Way, Newark, DE, 19711, USA
| | - Ryan M Moore
- Delaware Biotechnology Institute, University of Delaware, Delaware Biotechnology Inst., 15 Innovation Way, Newark, DE, 19711, USA
| | - Zachary DiSpirito
- Delaware Biotechnology Institute, University of Delaware, Delaware Biotechnology Inst., 15 Innovation Way, Newark, DE, 19711, USA
| | - Zachary R Stromberg
- Delaware Biotechnology Institute, University of Delaware, Delaware Biotechnology Inst., 15 Innovation Way, Newark, DE, 19711, USA
| | - Gentry L Lewis
- Delaware Biotechnology Institute, University of Delaware, Delaware Biotechnology Inst., 15 Innovation Way, Newark, DE, 19711, USA
| | - David G Renter
- College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
| | | | - Rodney A Moxley
- School of Veterinary Medicine & Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - K Eric Wommack
- Delaware Biotechnology Institute, University of Delaware, Delaware Biotechnology Inst., 15 Innovation Way, Newark, DE, 19711, USA.
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27
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Esseili MA, Gao X, Tegtmeier S, Saif LJ, Wang Q. Abiotic Stress and Phyllosphere Bacteria Influence the Survival of Human Norovirus and Its Surrogates on Preharvest Leafy Greens. Appl Environ Microbiol 2016; 82:352-63. [PMID: 26497461 PMCID: PMC4702653 DOI: 10.1128/aem.02763-15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 10/21/2015] [Indexed: 12/27/2022] Open
Abstract
Foodborne outbreaks of human noroviruses (HuNoVs) are frequently associated with leafy greens. Because there is no effective method to eliminate HuNoV from postharvest leafy greens, understanding virus survival under preharvest conditions is crucial. The objective of this study was to evaluate the survival of HuNoV and its surrogate viruses, murine norovirus (MNV), porcine sapovirus (SaV), and Tulane virus (TV), on preharvest lettuce and spinach that were subjected to abiotic stress (physical damage, heat, or flood). We also examined the bacteria culturable from the phyllosphere in response to abiotic stress and in relation to viral persistence. Mature plants were subjected to stressors 2 days prior to inoculation of the viruses on leaves. We quantified the viral RNA, determined the infectivity of the surrogates, and performed bacterial counts on postinoculation days (PIDs) 0, 1, 7, and 14. For both plant types, time exerted significant effects on HuNoV, MNV, SaV, and TV RNA titers, with greater effects being seen for the surrogates. Infectious surrogate viruses were undetectable on PID 14. Only physical damage on PID 14 significantly enhanced HuNoV RNA persistence on lettuce, while the three stressors differentially enhanced the persistence of MNV and TV RNA. Bacterial counts were significantly affected by time and plant type but not by the stressors. However, bacterial counts correlated significantly with HuNoV RNA titers on spinach and with the presence of surrogate viruses on both plant types under various conditions. In conclusion, abiotic stressors and phyllosphere bacterial density may differentially influence the survival of HuNoV and its surrogates on lettuce and spinach, emphasizing the need for the use of preventive measures at the preharvest stage.
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Affiliation(s)
- Malak A Esseili
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, Ohio, USA
| | - Xiang Gao
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, Ohio, USA
| | - Sarah Tegtmeier
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, Ohio, USA
| | - Linda J Saif
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, Ohio, USA
| | - Qiuhong Wang
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, Ohio, USA
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Oliveira M, Abadias M, Colás-Medà P, Usall J, Viñas I. Biopreservative methods to control the growth of foodborne pathogens on fresh-cut lettuce. Int J Food Microbiol 2015; 214:4-11. [PMID: 26210531 DOI: 10.1016/j.ijfoodmicro.2015.07.015] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 07/08/2015] [Accepted: 07/09/2015] [Indexed: 11/18/2022]
Abstract
Fruits and vegetables can become contaminated by foodborne pathogens such as Escherichia coli O157:H7, Salmonella and Listeria monocytogenes, and it has been demonstrated that current industrial sanitizing treatments do not eliminate the pathogens when present. Chemical control is widely used, but biological control appears to be a better solution, mainly using the native microbiota present on fresh produce. The first objective of this study was to isolate native microbiota from whole and fresh-cut produce and to determine whether these bacteria were antagonistic toward foodborne pathogens. A total of 112 putative antagonist isolates were screened for their ability to inhibit the growth of Salmonella enterica on lettuce disks. Five different genera reduced S. enterica growth more than 1-log unit at 20°C at the end of 3 days. When tested against L. monocytogenes 230/3, only Pseudomonas sp. strain M309 (M309) was able to reduce pathogen counts by more than 1-log unit. Therefore, M309 strain was selected to be tested on lettuce disks at 10°C against S. enterica, E. coli O157:H7 and L. monocytogenes. M309 strain was only able to reduce S. enterica and E. coli O157:H7 populations. The second objective was to test different biopreservative methods including M309 strain, Pseudomonas graminis CPA-7 (CPA-7), bacteriophages (Listex P100 and Salmonelex) and nisin at conditions simulating commercial applications against Salmonella and L. monocytogenes on fresh-cut lettuce. The addition of the biopreservative agents did not result in a significant reduction of Salmonella population. However, CPA-7 strain together with nisin reduced L. monocytogenes numbers after 6 days of storage at 10°C. The cocktail of Salmonella and L. monocytogenes was not markedly inactivated by their respective bacteriophage solutions. This study highlighted the potential of biocontrol, but the combination with other technologies may be required to improve their application on fresh-cut lettuce.
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Affiliation(s)
- M Oliveira
- Food Technology Department, University of Lleida, XaRTA-Postharvest, Agrotecnio Center, Rovira Roure 191, 25198 Lleida, Catalonia, Spain
| | - M Abadias
- IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, 25003 Lleida, Catalonia, Spain.
| | - P Colás-Medà
- Food Technology Department, University of Lleida, XaRTA-Postharvest, Agrotecnio Center, Rovira Roure 191, 25198 Lleida, Catalonia, Spain
| | - J Usall
- IRTA, XaRTA-Postharvest, Edifici Fruitcentre, Parc Científic i Tecnològic Agroalimentari de Lleida, Parc de Gardeny, 25003 Lleida, Catalonia, Spain
| | - I Viñas
- Food Technology Department, University of Lleida, XaRTA-Postharvest, Agrotecnio Center, Rovira Roure 191, 25198 Lleida, Catalonia, Spain
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Zilelidou EA, Rychli K, Manthou E, Ciolacu L, Wagner M, Skandamis PN. Highly Invasive Listeria monocytogenes Strains Have Growth and Invasion Advantages in Strain Competition. PLoS One 2015; 10:e0141617. [PMID: 26529510 PMCID: PMC4631365 DOI: 10.1371/journal.pone.0141617] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 10/09/2015] [Indexed: 12/22/2022] Open
Abstract
Multiple Listeria monocytogenes strains can be present in the same food sample; moreover, infection with more than one L. monocytogenes strain can also occur. In this study we investigated the impact of strain competition on the growth and in vitro virulence potential of L. monocytogenes. We identified two strong competitor strains, whose growth was not (or only slightly) influenced by the presence of other strains and two weak competitor strains, which were outcompeted by other strains. Cell contact was essential for growth inhibition. In vitro virulence assays using human intestinal epithelial Caco2 cells showed a correlation between the invasion efficiency and growth inhibition: the strong growth competitor strains showed high invasiveness. Moreover, invasion efficiency of the highly invasive strain was further increased in certain combinations by the presence of a low invasive strain. In all tested combinations, the less invasive strain was outcompeted by the higher invasive strain. Studying the effect of cell contact on in vitro virulence competition revealed a complex pattern in which the observed effects depended only partially on cell-contact suggesting that competition occurs at two different levels: i) during co-cultivation prior to infection, which might influence the expression of virulence factors, and ii) during infection, when bacterial cells compete for the host cell. In conclusion, we show that growth of L. monocytogenes can be inhibited by strains of the same species leading potentially to biased recovery during enrichment procedures. Furthermore, the presence of more than one L. monocytogenes strain in food can lead to increased infection rates due to synergistic effects on the virulence potential.
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Affiliation(s)
- Evangelia A. Zilelidou
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
| | - Kathrin Rychli
- Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Vienna, Austria
- * E-mail:
| | - Evanthia Manthou
- Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
| | - Luminita Ciolacu
- Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Vienna, Austria
- “Dunarea de Jos” University of Galaţi, Galaţi, Romania
| | - Martin Wagner
- Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Panagiotis 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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Oni RA, Sharma M, Buchanan RL. Survival of Salmonella enterica in Dried Turkey Manure and Persistence on Spinach Leaves. J Food Prot 2015; 78:1791-9. [PMID: 26408127 DOI: 10.4315/0362-028x.jfp-15-047] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Concerns about the microbiological safety of fresh produce have attracted attention in the past three decades due to multiple foodborne outbreaks. Animal manure contaminated with enteric pathogens has been identified as an important preharvest pathogen source. This study investigated the survival of Salmonella enterica in dust particles of dehydrated turkey manure and how association with manure dust may enhance the survival of salmonellae on leafy greens in the field. The survival of a cocktail of multiple Salmonella serotypes in the dried fecal material of various particle sizes (125 to 500 μm) was examined at varying moisture contents (5, 10, and 15%). Survival times of the pathogen were inversely related to moisture content and particle size of manure dust, with viable Salmonella still detectable for up to 291 days in the smallest particle size (125 μm) with 5% moisture. Association with manure dust particles increased the survival of Salmonella when subjected to UV light both under laboratory conditions and on the surface of spinach leaves in a greenhouse setting. The results of this study suggest that aerosolized manure particles could be a potential vehicle for Salmonella dispersal to leafy greens if the microorganism is present in the dry manure.
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Affiliation(s)
- Ruth A Oni
- Department of Nutrition and Food Science, College of Agriculture and Natural Resources, University of Maryland, College Park, Maryland 20742, USA
| | - Manan Sharma
- Environmental Microbial and Food Safety Laboratory, U.S. Department of Agriculture-Agricultural Research Service, Beltsville Area Research Center, 10300 Baltimore Avenue, Beltsville, Maryland 20705, USA
| | - Robert L Buchanan
- Department of Nutrition and Food Science, Center for Food Safety and Security Systems, College of Agriculture and Natural Resources, University of Maryland, College Park, Maryland 20742, USA.
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Factors affecting cell population density during enrichment and subsequent molecular detection of Salmonella enterica and Escherichia coli O157:H7 on lettuce contaminated during field production. Food Control 2015. [DOI: 10.1016/j.foodcont.2015.01.041] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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32
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Uyttendaele M, Jaykus LA, Amoah P, Chiodini A, Cunliffe D, Jacxsens L, Holvoet K, Korsten L, Lau M, McClure P, Medema G, Sampers I, Rao Jasti P. Microbial Hazards in Irrigation Water: Standards, Norms, and Testing to Manage Use of Water in Fresh Produce Primary Production. Compr Rev Food Sci Food Saf 2015. [DOI: 10.1111/1541-4337.12133] [Citation(s) in RCA: 173] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
| | - Lee-Ann Jaykus
- Dept. of Food, Bioprocessing and Nutrition Sciences; North Carolina State Univ; U.S.A
| | | | - Alessandro Chiodini
- ILSI Europe, Intl. Life Sciences Inst; European Branch; 83 Ave. E. Mounier, B6, B-1200 Brussels Belgium
| | - David Cunliffe
- Dept. of Health; Public Health; P.O. Box 6, Rundle Mall 5000 South Australia
| | | | - Kevin Holvoet
- Dept. Food Safety & Food Quality; Ghent Univ; Ghent Belgium
| | - Lise Korsten
- Dept. of Plant and Crop Sciences; Univ. of Pretoria; 0002 Pretoria South Africa
| | - Mathew Lau
- School of Chemical & Life Sciences; Nanyang Polytechnic; Singapore
| | - Peter McClure
- Mondelez Intl., Bayerwaldstrasse 8; 81737 München; Germany
| | - Gertjan Medema
- KWR, Watercycle Research Inst; Delft Univ. of Technology; Postbus 1072 3430 BB Nieuwegein The Netherlands
| | - Imca Sampers
- Dept. of Industrial Biological Sciences; Ghent Univ. Campus Kortrijk; Kortrijk Belgium
| | - Pratima Rao Jasti
- ILSI Europe, Intl. Life Sciences Inst; European Branch; 83 Ave. E. Mounier, B6, B-1200 Brussels Belgium
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33
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Pagadala S, Marine SC, Micallef SA, Wang F, Pahl DM, Melendez MV, Kline WL, Oni RA, Walsh CS, Everts KL, Buchanan RL. Assessment of region, farming system, irrigation source and sampling time as food safety risk factors for tomatoes. Int J Food Microbiol 2014; 196:98-108. [PMID: 25540859 DOI: 10.1016/j.ijfoodmicro.2014.12.005] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2014] [Revised: 10/07/2014] [Accepted: 12/07/2014] [Indexed: 11/29/2022]
Abstract
In the mid-Atlantic region of the United States, small- and medium-sized farmers use varied farm management methods and water sources to produce tomatoes. It is unclear whether these practices affect the food safety risk for tomatoes. This study was conducted to determine the prevalence, and assess risk factors for Salmonella enterica, Shiga toxin-producing Escherichia coli (STEC) and bacterial indicators in pre-harvest tomatoes and their production areas. A total of 24 organic and conventional, small- to medium-sized farms were sampled for six weeks in Maryland (MD), Delaware (DE) and New Jersey (NJ) between July and September 2012, and analyzed for indicator bacteria, Salmonella and STEC. A total of 422 samples--tomato fruit, irrigation water, compost, field soil and pond sediment samples--were collected, 259 of which were tomato samples. A low level of Salmonella-specific invA and Shiga toxin genes (stx1 or stx2) were detected, but no Salmonella or STEC isolates were recovered. Of the 422 samples analyzed, 9.5% were positive for generic E. coli, found in 5.4% (n=259) of tomato fruits, 22.5% (n=102) of irrigation water, 8.9% (n=45) of soil, 3/9 of pond sediment and 0/7 of compost samples. For tomato fruit, farming system (organic versus conventional) was not a significant factor for levels of indicator bacteria. However, the total number of organic tomato samples positive for generic E. coli (1.6%; 2/129) was significantly lower than for conventional tomatoes (6.9% (9/130); (χ(2) (1)=4.60, p=0.032)). Region was a significant factor for levels of Total Coliforms (TC) (p=0.046), although differences were marginal, with western MD having the highest TC counts (2.6 log CFU/g) and NJ having the lowest (2.0 log CFU/g). Tomatoes touching the ground or plastic mulch harbored significantly higher levels of TC compared to vine tomatoes, signaling a potential risk factor. Source of irrigation water was a significant factor for all indicator bacteria (p<0.0001), and groundwater had lower bacterial levels than surface water. End of line surface water samples were not significantly different from source water samples, but end of line groundwater samples had significantly higher bacterial counts than source (p<0.0001), suggesting that Good Agricultural Practices that focus on irrigation line maintenance might be beneficial. In general, local effects other than cropping practices, including topography, land use and adjacent industries, might be important factors contributing to microbiological inputs on small- and medium-sized farms in the mid-Atlantic region.
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Affiliation(s)
- Sivaranjani Pagadala
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA
| | - Sasha C Marine
- Department of Plant Science and Landscape Architecture, University of Maryland, located at Lower Eastern Shore Research and Education Center, Salisbury, MD, USA
| | - Shirley A Micallef
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA; Center for Food Safety and Security Systems, University of Maryland, College Park, MD, USA.
| | - Fei Wang
- Department of Nutrition and Food Science, University of Maryland, College Park, MD, USA
| | - Donna M Pahl
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA
| | - Meredith V Melendez
- Rutgers Cooperative Extension of Mercer County, Rutgers University, Trenton, NJ, USA
| | - Wesley L Kline
- Rutgers Cooperative Extension of Cumberland County, Rutgers University, Millville, NJ, USA
| | - Ruth A Oni
- Department of Nutrition and Food Science, University of Maryland, College Park, MD, USA
| | - Christopher S Walsh
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA
| | - Kathryne L Everts
- Department of Plant Science and Landscape Architecture, University of Maryland, located at Lower Eastern Shore Research and Education Center, Salisbury, MD, USA; Joint Appointment with University of Delaware, Georgetown, DE, USA
| | - Robert L Buchanan
- Center for Food Safety and Security Systems, University of Maryland, College Park, MD, USA; Department of Nutrition and Food Science, University of Maryland, College Park, MD, USA
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Yaron S, Römling U. Biofilm formation by enteric pathogens and its role in plant colonization and persistence. Microb Biotechnol 2014; 7:496-516. [PMID: 25351039 PMCID: PMC4265070 DOI: 10.1111/1751-7915.12186] [Citation(s) in RCA: 156] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 09/16/2014] [Indexed: 12/28/2022] Open
Abstract
The significant increase in foodborne outbreaks caused by contaminated fresh produce, such as alfalfa sprouts, lettuce, melons, tomatoes and spinach, during the last 30 years stimulated investigation of the mechanisms of persistence of human pathogens on plants. Emerging evidence suggests that Salmonella enterica and Escherichia coli, which cause the vast majority of fresh produce outbreaks, are able to adhere to and to form biofilms on plants leading to persistence and resistance to disinfection treatments, which subsequently can cause human infections and major outbreaks. In this review, we present the current knowledge about host, bacterial and environmental factors that affect the attachment to plant tissue and the process of biofilm formation by S. enterica and E. coli, and discuss how biofilm formation assists in persistence of pathogens on the plants. Mechanisms used by S. enterica and E. coli to adhere and persist on abiotic surfaces and mammalian cells are partially similar and also used by plant pathogens and symbionts. For example, amyloid curli fimbriae, part of the extracellular matrix of biofilms, frequently contribute to adherence and are upregulated upon adherence and colonization of plant material. Also the major exopolysaccharide of the biofilm matrix, cellulose, is an adherence factor not only of S. enterica and E. coli, but also of plant symbionts and pathogens. Plants, on the other hand, respond to colonization by enteric pathogens with a variety of defence mechanisms, some of which can effectively inhibit biofilm formation. Consequently, plant compounds might be investigated for promising novel antibiofilm strategies.
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Affiliation(s)
- Sima Yaron
- Faculty of Biotechnology and Food Engineering, Technion – Israel Institute of TechnologyHaifa, 32000, Israel
| | - Ute Römling
- Department of Microbiology, Tumor and Cell Biology, Karolinska InstitutetStockholm, Sweden
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35
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Ziuzina D, Patil S, Cullen P, Keener K, Bourke P. Atmospheric cold plasma inactivation of Escherichia coli, Salmonella enterica serovar Typhimurium and Listeria monocytogenes inoculated on fresh produce. Food Microbiol 2014; 42:109-16. [DOI: 10.1016/j.fm.2014.02.007] [Citation(s) in RCA: 226] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Revised: 01/13/2014] [Accepted: 02/11/2014] [Indexed: 10/25/2022]
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36
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Lau YY, Yin WF, Chan KG. Enterobacter asburiae strain L1: complete genome and whole genome optical mapping analysis of a quorum sensing bacterium. SENSORS 2014; 14:13913-24. [PMID: 25196111 PMCID: PMC4178997 DOI: 10.3390/s140813913] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 07/07/2014] [Accepted: 07/23/2014] [Indexed: 01/01/2023]
Abstract
Enterobacter asburiae L1 is a quorum sensing bacterium isolated from lettuce leaves. In this study, for the first time, the complete genome of E. asburiae L1 was sequenced using the single molecule real time sequencer (PacBio RSII) and the whole genome sequence was verified by using optical genome mapping (OpGen) technology. In our previous study, E. asburiae L1 has been reported to produce AHLs, suggesting the possibility of virulence factor regulation which is quorum sensing dependent. This evoked our interest to study the genome of this bacterium and here we present the complete genome of E. asburiae L1, which carries the virulence factor gene virK, the N-acyl homoserine lactone-based QS transcriptional regulator gene luxR and the N-acyl homoserine lactone synthase gene which we firstly named easI. The availability of the whole genome sequence of E. asburiae L1 will pave the way for the study of the QS-mediated gene expression in this bacterium. Hence, the importance and functions of these signaling molecules can be further studied in the hope of elucidating the mechanisms of QS-regulation in E. asburiae. To the best of our knowledge, this is the first documentation of both a complete genome sequence and the establishment of the molecular basis of QS properties of E. asburiae.
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Affiliation(s)
- Yin Yin Lau
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia.
| | - Wai-Fong Yin
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia.
| | - Kok-Gan Chan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia.
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37
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Hernlem BJ, Ravva SV, Sarreal CZ. Rapid detection of predation of Escherichia coli O157:H7 and sorting of bacterivorous Tetrahymena by flow cytometry. Front Cell Infect Microbiol 2014; 4:57. [PMID: 24847471 PMCID: PMC4017142 DOI: 10.3389/fcimb.2014.00057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 04/15/2014] [Indexed: 11/23/2022] Open
Abstract
Protozoa are known to harbor bacterial pathogens, alter their survival in the environment and make them hypervirulent. Rapid non-culture based detection methods are required to determine the environmental survival and transport of enteric pathogens from point sources such as dairies and feedlots to food crops grown in proximity. Grazing studies were performed on a soil isolate of Tetrahymena fed green fluorescent protein (GFP) expressing Escherichia coli O157:H7 to determine the suitability of the use of such fluorescent prey bacteria to locate and sort bacterivorous protozoa by flow cytometry. In order to overcome autofluorescence of the target organism and to clearly discern Tetrahymena with ingested prey vs. those without, a ratio of prey to host of at least 100:1 was determined to be preferable. Under these conditions, we successfully sorted the two populations using short 5–45 min exposures of the prey and verified the internalization of E. coli O157:H7 cells in protozoa by confocal microscopy. This technique can be easily adopted for environmental monitoring of rates of enteric pathogen destruction vs. protection in protozoa.
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Affiliation(s)
- Bradley J Hernlem
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, US Department of Agriculture, Agricultural Research Service Albany, CA, USA
| | - Subbarao V Ravva
- Produce Safety and Microbiology Research Unit, Western Regional Research Center, US Department of Agriculture, Agricultural Research Service Albany, CA, USA
| | - Chester Z Sarreal
- Produce Safety and Microbiology Research Unit, Western Regional Research Center, US Department of Agriculture, Agricultural Research Service Albany, CA, USA
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38
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Martínez-Vaz BM, Fink RC, Diez-Gonzalez F, Sadowsky MJ. Enteric pathogen-plant interactions: molecular connections leading to colonization and growth and implications for food safety. Microbes Environ 2014; 29:123-35. [PMID: 24859308 PMCID: PMC4103518 DOI: 10.1264/jsme2.me13139] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 01/19/2014] [Indexed: 11/12/2022] Open
Abstract
Leafy green vegetables have been identified as a source of foodborne illnesses worldwide over the past decade. Human enteric pathogens, such as Escherichia coli O157:H7 and Salmonella, have been implicated in numerous food poisoning outbreaks associated with the consumption of fresh produce. An understanding of the mechanisms responsible for the establishment of pathogenic bacteria in or on vegetable plants is critical for understanding and ameliorating this problem as well as ensuring the safety of our food supply. While previous studies have described the growth and survival of enteric pathogens in the environment and also the risk factors associated with the contamination of vegetables, the molecular events involved in the colonization of fresh produce by enteric pathogens are just beginning to be elucidated. This review summarizes recent findings on the interactions of several bacterial pathogens with leafy green vegetables. Changes in gene expression linked to the bacterial attachment and colonization of plant structures are discussed in light of their relevance to plant-microbe interactions. We propose a mechanism for the establishment and association of enteric pathogens with plants and discuss potential strategies to address the problem of foodborne illness linked to the consumption of leafy green vegetables.
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Affiliation(s)
| | - Ryan C. Fink
- Department of Food Science and Nutrition, University of Minnesota, St Paul, MN 55108, USA
| | | | - Michael J. Sadowsky
- Biotechnology Institute, University of Minnesota, St Paul, MN 55108, USA
- Department of Soil, Water and Climate, University of Minnesota, St Paul, MN 55108, USA
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39
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Vidovic S, Korber DR. Escherichia coli O157: Insights into the adaptive stress physiology and the influence of stressors on epidemiology and ecology of this human pathogen. Crit Rev Microbiol 2014; 42:83-93. [PMID: 24601836 DOI: 10.3109/1040841x.2014.889654] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Escherichia coli O157, a foodborne pathogen of major concern for public health, has been associated with numerous outbreaks of haemorrhagic colitis and hemolytic uremic syndrome worldwide. Human infection with E. coli O157 has been primarily associated with the food-chain transmission route. This transmission route commonly elicits a multi-faceted adaptive stress response of E. coli O157 for an extended period of time prior to human infection. Several recent research articles have indicated that E. coli O157:H7 has evolved unique survival characteristics which can affect the epidemiology and ecology of this zoonotic pathogen. This review article summarizes the recent knowledge of the molecular responses of E. coli O157 to the most common stressors found within the human food chain, and further emphasizes the influence of these stressors on the epidemiology and ecology of E. coli O157.
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Affiliation(s)
- Sinisa Vidovic
- a Department of Food and Bioproducts Sciences , University of Saskatchewan , Saskatchewan , Canada
| | - Darren R Korber
- a Department of Food and Bioproducts Sciences , University of Saskatchewan , Saskatchewan , Canada
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40
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Jayaraman D, Valdés-López O, Kaspar CW, Ané JM. Response of Medicago truncatula seedlings to colonization by Salmonella enterica and Escherichia coli O157:H7. PLoS One 2014; 9:e87970. [PMID: 24551073 PMCID: PMC3925098 DOI: 10.1371/journal.pone.0087970] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 01/02/2014] [Indexed: 11/18/2022] Open
Abstract
Disease outbreaks due to the consumption of legume seedlings contaminated with human enteric bacterial pathogens like Escherichia coli O157:H7 and Salmonella enterica are reported every year. Besides contaminations occurring during food processing, pathogens present on the surface or interior of plant tissues are also responsible for such outbreaks. In the present study, surface and internal colonization of Medicago truncatula, a close relative of alfalfa, by Salmonella enterica and Escherichia coli O157:H7 were observed even with inoculum levels as low as two bacteria per plant. Furthermore, expression analyses revealed that approximately 30% of Medicago truncatula genes were commonly regulated in response to both of these enteric pathogens. This study highlights that very low inoculum doses trigger responses from the host plant and that both of these human enteric pathogens may in part use similar mechanisms to colonize legume seedlings.
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Affiliation(s)
- Dhileepkumar Jayaraman
- Department of Agronomy, University of Wisconsin–Madison, Madison Madison, Wisconsin, United States of America
| | - Oswaldo Valdés-López
- Department of Agronomy, University of Wisconsin–Madison, Madison Madison, Wisconsin, United States of America
| | - Charles W. Kaspar
- Department of Bacteriology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Jean-Michel Ané
- Department of Agronomy, University of Wisconsin–Madison, Madison Madison, Wisconsin, United States of America
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41
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Jackson CR, Randolph KC, Osborn SL, Tyler HL. Culture dependent and independent analysis of bacterial communities associated with commercial salad leaf vegetables. BMC Microbiol 2013; 13:274. [PMID: 24289725 PMCID: PMC4219373 DOI: 10.1186/1471-2180-13-274] [Citation(s) in RCA: 131] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 11/26/2013] [Indexed: 02/01/2023] Open
Abstract
Background Plants harbor a diverse bacterial community, both as epiphytes on the plant surface and as endophytes within plant tissue. While some plant-associated bacteria act as plant pathogens or promote plant growth, others may be human pathogens. The aim of the current study was to determine the bacterial community composition of organic and conventionally grown leafy salad vegetables at the point of consumption using both culture-dependent and culture-independent methods. Results Total culturable bacteria on salad vegetables ranged from 8.0 × 103 to 5.5 × 108 CFU g-1. The number of culturable endophytic bacteria from surface sterilized plants was significantly lower, ranging from 2.2 × 103 to 5.8 × 105 CFU g-1. Cultured isolates belonged to six major bacterial phyla, and included representatives of Pseudomonas, Pantoea, Chryseobacterium, and Flavobacterium. Eleven different phyla and subphyla were identified by culture-independent pyrosequencing, with Gammaproteobacteria, Betaproteobacteria, and Bacteroidetes being the most dominant lineages. Other bacterial lineages identified (e.g. Firmicutes, Alphaproteobacteria, Acidobacteria, and Actinobacteria) typically represented less than 1% of sequences obtained. At the genus level, sequences classified as Pseudomonas were identified in all samples and this was often the most prevalent genus. Ralstonia sequences made up a greater portion of the community in surface sterilized than non-surface sterilized samples, indicating that it was largely endophytic, while Acinetobacter sequences appeared to be primarily associated with the leaf surface. Analysis of molecular variance indicated there were no significant differences in bacterial community composition between organic versus conventionally grown, or surface-sterilized versus non-sterilized leaf vegetables. While culture-independent pyrosequencing identified significantly more bacterial taxa, the dominant taxa from pyrosequence data were also detected by traditional culture-dependent methods. Conclusions The use of pyrosequencing allowed for the identification of low abundance bacteria in leaf salad vegetables not detected by culture-dependent methods. The presence of a range of bacterial populations as endophytes presents an interesting phenomenon as these microorganisms cannot be removed by washing and are thus ingested during salad consumption.
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Affiliation(s)
- Colin R Jackson
- Department of Biology, The University of Mississippi, University 38677, USA.
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42
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Markland SM, Shortlidge KL, Hoover DG, Yaron S, Patel J, Singh A, Sharma M, Kniel KE. Survival of pathogenic Escherichia coli on basil, lettuce, and spinach. Zoonoses Public Health 2013; 60:563-71. [PMID: 23280331 DOI: 10.1111/zph.12033] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Indexed: 11/28/2022]
Abstract
The contamination of lettuce, spinach and basil with pathogenic E. coli has caused numerous illnesses over the past decade. E. coli O157:H7, E. coli O104:H4 and avian pathogenic E. coli (APECstx- and APECstx+) were inoculated on basil plants and in promix substrate using drip and overhead irrigation. When overhead inoculated with 7 log CFU/ml of each strain, E. coli populations were significantly (P = 0.03) higher on overhead-irrigated plants than on drip-irrigated plants. APECstx-, E. coli O104:H4 and APECstx+ populations were recovered on plants at 3.6, 2.3 and 3.1 log CFU/g at 10 dpi (days post-inoculation), respectively. E. coli O157:H7 was not detected on basil after 4 dpi. The persistence of E. coli O157:H7 and APECstx- were similar when co-inoculated on lettuce and spinach plants. On spinach and lettuce, E. coli O157:H7 and APEC populations declined from 5.7 to 6.1 log CFU/g and 4.5 log CFU/g, to undetectable at 3 dpi and 0.6-1.6 log CFU/g at 7 dpi, respectively. The detection of low populations of APEC and E. coli O104:H4 strains 10 dpi indicates these strains may be more adapted to environmental conditions than E. coli O157:H7. This is the first reported study of E. coli O104:H4 on a produce commodity.
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Affiliation(s)
- S M Markland
- Department of Animal and Food Sciences, University of Delaware, Newark, DE, USA
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43
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Liu NT, Nou X, Lefcourt AM, Shelton DR, Lo YM. Dual-species biofilm formation by Escherichia coli O157:H7 and environmental bacteria isolated from fresh-cut processing facilities. Int J Food Microbiol 2013; 171:15-20. [PMID: 24296258 DOI: 10.1016/j.ijfoodmicro.2013.11.007] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Revised: 11/06/2013] [Accepted: 11/08/2013] [Indexed: 11/28/2022]
Abstract
Biofilm formation is a mechanism adapted by many microorganisms that enhances the survival in stressful environments. In food processing facilities, foodborne bacterial pathogens, which many are poor biofilm formers, could potentially take advantage of this protective mechanism by interacting with other strong biofilm producers. The objective of this study was to determine the influence of bacteria native to fresh produce processing environments on the incorporation of Escherichia coli O157:H7 in biofilms. Bacteria strains representing 13 Gram-negative species isolated from two fresh produce processing facilities in a previous study were tested for forming dual-species biofilms with E. coli O157:H7. Strong biofilm producing strains of Burkholderia caryophylli and Ralstonia insidiosa exhibited 180% and 63% increase in biofilm biomass, and significant thickening of the biofilms (B. caryophylli not tested), when co-cultured with E. coli O157:H7. E. coli O157:H7 populations increased by approximately 1 log in dual-species biofilms formed with B. caryophylli or R. insidiosa. While only a subset of environmental isolates with strong biofilm formation abilities increased the presence of E. coli O157:H7 in biofilms, all tested E. coli O157:H7 exhibited higher incorporation in dual-species biofilms with R. insidiosa. These observations support the notion that E. coli O157:H7 and specific strong biofilm producing bacteria interact synergistically in biofilm formation, and suggest a route for increased survival potential of E. coli O157:H7 in fresh produce processing environments.
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Affiliation(s)
- Nancy T Liu
- Environmental Microbial and Food Safety Laboratory, USDA Agricultural Research Service, Beltsville, MD 20705, United States; Department of Nutrition and Food Science, University of Maryland, College Park, MD 20740, United States
| | - Xiangwu Nou
- Environmental Microbial and Food Safety Laboratory, USDA Agricultural Research Service, Beltsville, MD 20705, United States.
| | - Alan M Lefcourt
- Environmental Microbial and Food Safety Laboratory, USDA Agricultural Research Service, Beltsville, MD 20705, United States
| | - Daniel R Shelton
- Environmental Microbial and Food Safety Laboratory, USDA Agricultural Research Service, Beltsville, MD 20705, United States
| | - Y Martin Lo
- Department of Nutrition and Food Science, University of Maryland, College Park, MD 20740, United States
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44
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Goñi M, Tomadoni B, Moreira M, Roura S. Application of tea tree and clove essential oil on late development stages of Butterhead lettuce: Impact on microbiological quality. Lebensm Wiss Technol 2013. [DOI: 10.1016/j.lwt.2013.04.021] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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45
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Lau YY, Sulaiman J, Chen JW, Yin WF, Chan KG. Quorum sensing activity of Enterobacter asburiae isolated from lettuce leaves. SENSORS (BASEL, SWITZERLAND) 2013; 13:14189-99. [PMID: 24152877 PMCID: PMC3859116 DOI: 10.3390/s131014189] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 09/26/2013] [Accepted: 09/30/2013] [Indexed: 02/02/2023]
Abstract
Bacterial communication or quorum sensing (QS) is achieved via sensing of QS signaling molecules consisting of oligopeptides in Gram-positive bacteria and N-acyl homoserine lactones (AHL) in most Gram-negative bacteria. In this study, Enterobacteriaceae isolates from Batavia lettuce were screened for AHL production. Enterobacter asburiae, identified by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) was found to produce short chain AHLs. High resolution triple quadrupole liquid chromatography mass spectrometry (LC/MS) analysis of the E. asburiae spent supernatant confirmed the production of N-butanoyl homoserine lactone (C4-HSL) and N-hexanoyl homoserine lactone (C6-HSL). To the best of our knowledge, this is the first report of AHL production by E. asburiae.
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Affiliation(s)
- Yin Yin Lau
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (Y.Y.L.); (J.S.); (J.W.C.); (W.-F.Y.)
| | - Joanita Sulaiman
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (Y.Y.L.); (J.S.); (J.W.C.); (W.-F.Y.)
| | - Jian Woon Chen
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (Y.Y.L.); (J.S.); (J.W.C.); (W.-F.Y.)
| | - Wai-Fong Yin
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (Y.Y.L.); (J.S.); (J.W.C.); (W.-F.Y.)
| | - Kok-Gan Chan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (Y.Y.L.); (J.S.); (J.W.C.); (W.-F.Y.)
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46
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Rastogi G, Coaker GL, Leveau JH. New insights into the structure and function of phyllosphere microbiota through high-throughput molecular approaches. FEMS Microbiol Lett 2013; 348:1-10. [DOI: 10.1111/1574-6968.12225] [Citation(s) in RCA: 140] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 07/21/2013] [Accepted: 07/24/2013] [Indexed: 10/26/2022] Open
Affiliation(s)
- Gurdeep Rastogi
- Department of Plant Pathology; University of California; Davis; CA; USA
| | - Gitta L. Coaker
- Department of Plant Pathology; University of California; Davis; CA; USA
| | - Johan H.J. Leveau
- Department of Plant Pathology; University of California; Davis; CA; USA
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47
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Moyne AL, Harris LJ, Marco ML. Assessments of total and viable Escherichia coli O157:H7 on field and laboratory grown lettuce. PLoS One 2013; 8:e70643. [PMID: 23936235 PMCID: PMC3728298 DOI: 10.1371/journal.pone.0070643] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 06/19/2013] [Indexed: 02/07/2023] Open
Abstract
Leafy green produce has been associated with numerous outbreaks of foodborne illness caused by strains of Escherichia coli O157:H7. While the amounts of culturable E. coli O157:H7 rapidly decline after introduction onto lettuce in the field, it remains to be determined whether the reduction in cell numbers is due to losses in cell viability, cell injury and a subsequent inability to be detected by standard laboratory culturing methods, or a lack of adherence and hence rapid removal of the organism from the plants during application. To assess which of these options is most relevant for E. coli O157:H7 on leafy green produce, we developed and applied a propidium monoazide (PMA) real-time PCR assay to quantify viable (with PMA) and total (without PMA) E. coli O157:H7 cells on growth chamber and field-grown lettuce. E. coli O157:H7, suspended in 0.1% peptone, was inoculated onto 4-week-old lettuce plants at a level of approximately 10(6) CFU/plant. In the growth chamber at low relative humidity (30%), culturable amounts of the nontoxigenic E. coli O157:H7 strain ATCC 700728 and the virulent strain EC4045 declined 100 to 1000-fold in 24 h. Fewer E. coli O157:H7 cells survived when applied onto plants in droplets with a pipette compared with a fine spray inoculation. Total cells for both strains were equivalent to inoculum levels for 7 days after application, and viable cell quantities determined by PMA real-time PCR were approximately 10(4) greater than found by colony enumeration. Within 2 h after application onto plants in the field, the number of culturable E. coli ATCC 700728 was reduced by up to 1000-fold, whereas PCR-based assessments showed that total cell amounts were equivalent to inoculum levels. These findings show that shortly after inoculation onto plants, the majority of E. coli O157:H7 cells either die or are no longer culturable.
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Affiliation(s)
- Anne-Laure Moyne
- Department of Food Science and Technology, University of California Davis, Davis, California, United States of America
- Western Center for Food Safety, University of California Davis, Davis, California, United States of America
| | - Linda J. Harris
- Department of Food Science and Technology, University of California Davis, Davis, California, United States of America
- Western Center for Food Safety, University of California Davis, Davis, California, United States of America
| | - Maria L. Marco
- Department of Food Science and Technology, University of California Davis, Davis, California, United States of America
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48
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Patel J, Singh M, Macarisin D, Sharma M, Shelton D. Differences in biofilm formation of produce and poultry Salmonella enterica isolates and their persistence on spinach plants. Food Microbiol 2013; 36:388-94. [PMID: 24010621 DOI: 10.1016/j.fm.2013.06.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 01/03/2013] [Accepted: 06/28/2013] [Indexed: 11/28/2022]
Abstract
Spinach plants were irrigated biweekly with water containing 2.1 log CFU Salmonella/100 ml water (the maximum Escherichia coli MPN recommended by the Leafy Greens Marketing Agreement; LGMA), or 4.1 CFU Salmonella/100 ml water to determine Salmonella persistence on spinach leaves. Green Fluorescent protein expressing Salmonella were undetectable by most-probable number (MPN) at 24 h and 7 days following each irrigation event. This study indicates that Salmonella are unlikely to persist on spinach leaves when irrigation water is contaminated at a level below the LGMA standards. In a parallel study, persistence of Salmonella isolated from poultry or produce was compared following biweekly irrigation of spinach plants with water containing 6 log CFU Salmonella/100 ml. Produce Salmonella isolates formed greater biofilms on polystyrene, polycarbonate and stainless steel surfaces and persisted at significantly higher numbers on spinach leaves than those Salmonella from poultry origin during 35 days study. Poultry Salmonella isolates were undetectable (<1 log CFU/g) on spinach plants 7 days following each irrigation event when assayed by direct plating. This study indicates that Salmonella persistence on spinach leaves is affected by the source of contamination and the biofilm forming ability of the strain.
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Affiliation(s)
- Jitendra Patel
- US Department of Agriculture, Agricultural Research Service, Beltsville, MD 20707, USA.
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49
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Williams TR, Moyne AL, Harris LJ, Marco ML. Season, irrigation, leaf age, and Escherichia coli inoculation influence the bacterial diversity in the lettuce phyllosphere. PLoS One 2013; 8:e68642. [PMID: 23844230 PMCID: PMC3699665 DOI: 10.1371/journal.pone.0068642] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 05/30/2013] [Indexed: 01/28/2023] Open
Abstract
The developmental and temporal succession patterns and disturbance responses of phyllosphere bacterial communities are largely unknown. These factors might influence the capacity of human pathogens to persist in association with those communities on agriculturally-relevant plants. In this study, the phyllosphere microbiota was identified for Romaine lettuce plants grown in the Salinas Valley, CA, USA from four plantings performed over 2 years and including two irrigation methods and inoculations with an attenuated strain of Escherichia coli O157:H7. High-throughput DNA pyrosequencing of the V5 to V9 variable regions of bacterial 16S rRNA genes recovered in lettuce leaf washes revealed that the bacterial diversity in the phyllosphere was distinct for each field trial but was also strongly correlated with the season of planting. Firmicutes were generally most abundant in early season (June) plantings and Proteobacteria comprised the majority of bacteria recovered later in the year (August and October). Comparisons within individual field trials showed that bacterial diversity differed between sprinkler (overhead) and drip (surface) irrigated lettuce and increased over time as the plants grew. The microbiota were also distinct between control and E. coli O157:H7-inoculated plants and between E. coli O157:H7-inoculated plants with and without surviving pathogen cells. The bacterial inhabitants of the phyllosphere therefore appear to be affected by seasonal, irrigation, and biological factors in ways that are relevant for assessments of fresh produce food safety.
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Affiliation(s)
- Thomas R. Williams
- Department of Food Science & Technology, University of California, Davis, California, United States of America
| | - Anne-Laure Moyne
- Department of Food Science & Technology, University of California, Davis, California, United States of America
- Western Center for Food Safety, University of California, Davis, California, United States of America
| | - Linda J. Harris
- Department of Food Science & Technology, University of California, Davis, California, United States of America
- Western Center for Food Safety, University of California, Davis, California, United States of America
| | - Maria L. Marco
- Department of Food Science & Technology, University of California, Davis, California, United States of America
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50
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Fernández-Suárez R, Ramírez-Villatoro G, Díaz-Ruiz G, Eslava C, Calderón M, Navarro-Ocaña A, Trejo-Márquez A, Wacher C. Effect of postharvest UV-C treatment on the bacterial diversity of Ataulfo mangoes by PCR-DGGE, survival of E. coli and antimicrobial activity. Front Microbiol 2013; 4:134. [PMID: 23761788 PMCID: PMC3673002 DOI: 10.3389/fmicb.2013.00134] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2012] [Accepted: 05/07/2013] [Indexed: 12/05/2022] Open
Abstract
Since Mexico is the second largest exporter of mangoes, its safety assurance is essential. Research in microbial ecology and knowledge of complex interactions among microbes must be better understood to achieve maximal control of pathogens. Therefore, we investigated the effect of UV-C treatments on bacterial diversity of the Ataulfo mangoes surface using PCR-DGGE analysis of variable region V3 of 16S rRNA genes, and the survival of E. coli, by plate counting. The UV-C irradiation reduced the microbial load on the surface of mangoes immediately after treatment and the structure of bacterial communities was modified during storage. We identified the key members of the bacterial communities on the surface of fruits, predominating Enterobacter genus. Genera as Lactococcus and Pantoea were only detected on the surface of non-treated (control) mangoes. This could indicate that these genera were affected by the UV-C treatment. On the other hand, the treatment did not have a significant effect on survival of E. coli. However, genera that have been recognized as antagonists against foodborne pathogens were identified in the bands patterns. Also, phenolic compounds were determined by HPLC and antimicrobial activity was assayed according to the agar diffusion method. The main phenolic compounds were chlorogenic, gallic, and caffeic acids. Mango peel methanol extracts (UV-C treated and control mangoes) showed antimicrobial activity against strains previously isolated from mango, detecting significant differences (P < 0.05) among treated and control mangoes after 4 and 12 days of storage. Ps. fluorescens and Ps. stutszeri were the most sensitive.
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Affiliation(s)
- Rocío Fernández-Suárez
- Lab 324, Conjunto E, Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Guadalupe Ramírez-Villatoro
- Lab 324, Conjunto E, Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Gloria Díaz-Ruiz
- Lab 324, Conjunto E, Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Carlos Eslava
- Departamento de Salud Pública, Facultad de Medicina, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Montserrat Calderón
- Ingeniería Química, Biotecnología de Alimentos, Instituto Tecnológico de TepicTepic, Mexico
| | - Arturo Navarro-Ocaña
- Lab 324, Conjunto E, Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Andrea Trejo-Márquez
- Laboratorio de Postcosecha de Productos Vegetales, Facultad de Estudios Superiores Cuautitlán, Centro de Asimilación Tecnológica, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
| | - Carmen Wacher
- Lab 324, Conjunto E, Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de MéxicoMexico City, Mexico
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