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Deng K, Wang SS, Kiener S, Smith E, Chen KS, Pamboukian R, Laasri A, Pelaez C, Ulaszek J, Kmet M, De Jesus A, Hammack T, Reddy R, Wang H. Multi-laboratory validation study of a real-time PCR method for detection of Salmonella in baby spinach. Food Microbiol 2023; 114:104299. [PMID: 37290875 DOI: 10.1016/j.fm.2023.104299] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 04/18/2023] [Accepted: 04/25/2023] [Indexed: 06/10/2023]
Abstract
The FDA Bacteriological Analytical Manual (BAM) Salmonella culture method takes at least 3 days for a presumptive positive result. The FDA developed a quantitative PCR (qPCR) method to detect Salmonella from 24-h preenriched cultures, using ABI 7500 PCR system. The qPCR method has been evaluated as a rapid screening method for a broad range of foods by single laboratory validation (SLV) studies. The present multi-laboratory validation (MLV) study was aimed to measure the reproducibility of this qPCR method and compare its performance with the culture method. Sixteen laboratories participated in two rounds of MLV study to analyze twenty-four blind-coded baby spinach test portions each. The first round yielded ∼84% and ∼82% positive rates across laboratories for the qPCR and culture methods, respectively, which were both outside the fractional range (25%-75%) required for fractionally inoculated test portions by the FDA's Microbiological Method Validation Guidelines. The second round yielded ∼68% and ∼67% positive rates. The relative level of detection (RLOD) for the second-round study was 0.969, suggesting that qPCR and culture methods had similar sensitivity (p > 0.05). The study demonstrated that the qPCR yields reproducible results and is sufficiently sensitive and specific for the detection of Salmonella in food.
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Affiliation(s)
- Kaiping Deng
- FDA-Center for Food Safety and Applied Nutrition (CFSAN), 6502 S. Archer Rd, Bedford Park, IL, 60501, USA
| | - Shizhen Steven Wang
- FDA-Center for Food Safety and Applied Nutrition (CFSAN), 5001 Campus Dr, College Park, MD 20740, USA
| | - Shannon Kiener
- FDA-Center for Food Safety and Applied Nutrition (CFSAN), 6502 S. Archer Rd, Bedford Park, IL, 60501, USA
| | - Emily Smith
- FDA-Center for Food Safety and Applied Nutrition (CFSAN), 6502 S. Archer Rd, Bedford Park, IL, 60501, USA
| | - Kai-Shun Chen
- FDA-Office of Regulatory Affairs (ORA), 109 Holton Street, Winchester, MA, 01890, USA
| | - Ruiqing Pamboukian
- FDA-Office of Regulatory Affairs (ORA), 12420 Parklawn Dr, Rockville, MD, 20857, USA
| | - Anna Laasri
- FDA-Center for Food Safety and Applied Nutrition (CFSAN), 5001 Campus Dr, College Park, MD 20740, USA
| | - Catalina Pelaez
- FDA-Center for Food Safety and Applied Nutrition (CFSAN), 6502 S. Archer Rd, Bedford Park, IL, 60501, USA
| | - Jodie Ulaszek
- FDA-Center for Food Safety and Applied Nutrition (CFSAN), 6502 S. Archer Rd, Bedford Park, IL, 60501, USA
| | - Matthew Kmet
- FDA-Center for Food Safety and Applied Nutrition (CFSAN), 6502 S. Archer Rd, Bedford Park, IL, 60501, USA
| | - Antonio De Jesus
- FDA-Center for Food Safety and Applied Nutrition (CFSAN), 5001 Campus Dr, College Park, MD 20740, USA
| | - Thomas Hammack
- FDA-Center for Food Safety and Applied Nutrition (CFSAN), 5001 Campus Dr, College Park, MD 20740, USA
| | - Ravinder Reddy
- FDA-Center for Food Safety and Applied Nutrition (CFSAN), 6502 S. Archer Rd, Bedford Park, IL, 60501, USA
| | - Hua Wang
- FDA-Center for Food Safety and Applied Nutrition (CFSAN), 5001 Campus Dr, College Park, MD 20740, USA.
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Chahar M, Kroupitski Y, Gollop R, Belausov E, Melotto M, Sela-Saldinger S. Determination of Salmonella enterica Leaf Internalization Varies Substantially According to the Method and Conditions Used to Assess Bacterial Localization. Front Microbiol 2021; 12:622068. [PMID: 34803936 PMCID: PMC8603913 DOI: 10.3389/fmicb.2021.622068] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 08/27/2021] [Indexed: 11/13/2022] Open
Abstract
In a previous study, comparing the internalization of S. enterica serovar Typhimurium in various leaves by confocal microscopy, we have demonstrated that the pathogen failed to internalize tomato leaves. Numerous reasons may account for these findings, yet one such factor might be the methodology employed to quantify leaf internalization. To this end, we have systematically studied leaf localization of a Green-fluorescent protein-labeled Salmonella strain in tomato, lettuce, and Arabidopsis leaves by surface sterilization and enumeration of the surviving bacteria, side by side, with confocal microscopy observations. Leaf sterilization was performed using either sodium hypochlorite, silver nitrate, or ethanol for 1 to 7min. The level of internalization varied according to the type of disinfectant used for surface sterilization and the treatment time. Treatment of tomato leaves with 70% ethanol for up to 7min suggested possible internalization of Salmonella, while confocal microscopy showed no internalization. In the case of in lettuce and Arabidopsis leaves, both the plate-count technique and confocal microscopy demonstrated considerable Salmonella internalization thought different sterilization conditions resulted in variations in the internalization levels. Our findings highlighted the dependency of the internalization results on the specific disinfection protocol used to determine bacterial localization. The results underscore the importance of confocal microscopy in validating a particular surface sterilization protocol whenever a new pair of bacterial strain and plant cultivar is studied.
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Affiliation(s)
- Madhvi Chahar
- Department of Food Sciences, The Volcani Center, Institute for Postharvest and Food Sciences, Agriculture Research Organization, Rishon-LeZion, Israel
| | - Yulia Kroupitski
- Department of Food Sciences, The Volcani Center, Institute for Postharvest and Food Sciences, Agriculture Research Organization, Rishon-LeZion, Israel
| | - Rachel Gollop
- Department of Food Sciences, The Volcani Center, Institute for Postharvest and Food Sciences, Agriculture Research Organization, Rishon-LeZion, Israel
| | - Eduard Belausov
- Microscopy Unit, Plant Sciences, Ornamental Plants and Agricultural Biotechnology, The Volcani Center, Agriculture Research Organization, Rishon-LeZion, Israel
| | - Maeli Melotto
- Department of Plant Sciences, University of California, Davis, Davis, CA, United States
| | - Shlomo Sela-Saldinger
- Department of Food Sciences, The Volcani Center, Institute for Postharvest and Food Sciences, Agriculture Research Organization, Rishon-LeZion, Israel
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Reid AN, Conklin C, Beaton K, Donahue N, Jackson E, LoCASCIO B, Marsocci C, Szemreylo E, Szemreylo K. Inoculum Preparation Conditions Influence Adherence of Salmonella enterica Serovars to Red Leaf Lettuce (Lactuca sativa). J Food Prot 2021; 84:857-868. [PMID: 33411904 DOI: 10.4315/jfp-20-301] [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: 07/29/2020] [Accepted: 12/21/2020] [Indexed: 11/11/2022]
Abstract
ABSTRACT Salmonella enterica has been increasingly linked to outbreaks involving consumption of fresh produce. Although researchers have identified genes whose products are involved in mediating S. enterica-plant interactions, the use of various experimental approaches, serovars, and plant types has generated variable and conflicting data. The purpose of this study was to determine whether conditions under which inocula are prepared for in vitro plant interaction studies influence the outcome of these studies. Seven S. enterica serovars were grown in media that differed in salinity and physical state with incubation at 25 or 37°C. These cultures were then used to inoculate red leaf lettuce, and adherent microbes were subsequently recovered. Although all Salmonella serovars were influenced by inoculum preparation conditions, the amount of variation differed. Analysis of pooled serovar data revealed that inocula prepared from either agar plates or biphasic cultures had higher levels of interaction with red leaf lettuce than those prepared from broth cultures. Incubation at 37°C enhanced adherence after 30 s or 5 days of contact time, and adherence after 1 h of contact time was increased in low-salt medium. Broth inoculum cultures were highly influenced by medium salinity and incubation temperature, whereas plate and biphasic inoculum cultures were only minimally affected. Therefore, inocula prepared from bacteria grown on plates or in biphasic culture would be most suitable for evaluation of strategies used to interfere with plant-Salmonella interactions. However, pooled data mask serovar-specific responses, and care should be taken when extrapolating these findings to individual serovars. The previous association of a serovar with outbreaks involving leafy greens was not correlated with levels of interaction with red leaf lettuce, suggesting that the occurrence of these serovars in or on these commodities does not reflect their fitness in the plant environment. HIGHLIGHTS
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Affiliation(s)
- Anne N Reid
- Department of Biology and Biomedical Sciences, Salve Regina University, 100 Ochre Point Avenue, Newport, Rhode Island 02840, USA
| | - Courtney Conklin
- Department of Biology and Biomedical Sciences, Salve Regina University, 100 Ochre Point Avenue, Newport, Rhode Island 02840, USA
| | - Kimberly Beaton
- Department of Biology and Biomedical Sciences, Salve Regina University, 100 Ochre Point Avenue, Newport, Rhode Island 02840, USA
| | - Nora Donahue
- Department of Biology and Biomedical Sciences, Salve Regina University, 100 Ochre Point Avenue, Newport, Rhode Island 02840, USA
| | - Emily Jackson
- Department of Biology and Biomedical Sciences, Salve Regina University, 100 Ochre Point Avenue, Newport, Rhode Island 02840, USA
| | - Brianna LoCASCIO
- Department of Biology and Biomedical Sciences, Salve Regina University, 100 Ochre Point Avenue, Newport, Rhode Island 02840, USA
| | - Cristina Marsocci
- Department of Biology and Biomedical Sciences, Salve Regina University, 100 Ochre Point Avenue, Newport, Rhode Island 02840, USA
| | - Emily Szemreylo
- Department of Biology and Biomedical Sciences, Salve Regina University, 100 Ochre Point Avenue, Newport, Rhode Island 02840, USA
| | - Katlin Szemreylo
- Department of Biology and Biomedical Sciences, Salve Regina University, 100 Ochre Point Avenue, Newport, Rhode Island 02840, USA
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Karaca H, Velioglu YS. Effects of ozone and chlorine washes and subsequent cold storage on microbiological quality and shelf life of fresh parsley leaves. Lebensm Wiss Technol 2020. [DOI: 10.1016/j.lwt.2020.109421] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Trmcic A, Chen H, Trząskowska M, Tamber S, Wang S. Biofilm-Forming Capacity of Five Salmonella Strains and Their Fate on Postharvest Mini Cucumbers. J Food Prot 2018; 81:1871-1879. [PMID: 30325222 DOI: 10.4315/0362-028x.jfp-18-180] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Salmonella enterica is one of the pathogens that is frequently identified as the cause of fresh produce-related outbreaks. Biofilm formation is a factor that can contribute to pathogen survival on produce surface. The goal of our current research was to investigate the survival of five S. enterica strains representing different serotypes (i.e., Typhimurium, Enteritidis, Daytona, Poona, and Newport) on whole mini cucumbers stored at refrigeration (4°C) and room temperature (22°C). We also determined the strains survival on glass slides and in phosphate-buffered saline at 4 and 22°C, as well as the ability to form biofilms on a solid-liquid interphase. A rapid decrease in cell density (>4-log reduction over 8 days) of all five tested strains was observed on glass slides, while a slower die-off (<1-log reduction in 8 days) was observed in PBS. No significant difference in the die-off rate was observed among the five strains at 4 or 22°C. The die-off rate on the surface of mini cucumbers at 4°C was significantly slower ( P < 0.02) for Salmonella Enteritidis LMFS-S-JF-005 compared with the remaining four strains. At 22°C, Salmonella Poona S306 was able to grow by more than 1.5 log units on whole mini cucumbers over a period of 8 days, while the cell density of the other four strains remained at the same level compared with day 0. At this temperature, Salmonella Poona S306 was also able to form significantly stronger biofilms on a solid-liquid interphase ( P < 0.01) and was the only strain that presented a red, dry, and rough morphotype on Congo red agar plates, indicating the formation of both curli fimbriae and cellulose. These results revealed that the fate of Salmonella on mini cucumbers is strain specific, which highlighted the need for tailored mitigation strategies, such as the effective control of temperature and moisture for limiting the survival or growth of high-risk Salmonella strains between harvest and consumption of fresh produce.
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Affiliation(s)
- Aljosa Trmcic
- 1 Food, Nutrition and Health, Faculty of Land and Food Systems, The University of British Columbia, 2205 East Mall, Vancouver, British Columbia, Canada V6T 1Z4 (ORCID: http://orcid.org/0000-0003-2468-2483 [S.W.])
| | - Huihui Chen
- 1 Food, Nutrition and Health, Faculty of Land and Food Systems, The University of British Columbia, 2205 East Mall, Vancouver, British Columbia, Canada V6T 1Z4 (ORCID: http://orcid.org/0000-0003-2468-2483 [S.W.])
| | - Monika Trząskowska
- 2 Faculty of Human Nutrition and Consumer Sciences, Warsaw University of Life Sciences, Nowoursynowska 159 C, 02-776 Warsaw, Poland
| | - Sandeep Tamber
- 3 Bureau of Microbial Hazards, Health Canada, 251 Sir Frederick Banting Driveway, PL 2204E Ottawa, Ontario, Canada K1A 0K9
| | - Siyun Wang
- 1 Food, Nutrition and Health, Faculty of Land and Food Systems, The University of British Columbia, 2205 East Mall, Vancouver, British Columbia, Canada V6T 1Z4 (ORCID: http://orcid.org/0000-0003-2468-2483 [S.W.])
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Patel J, Keelara S, Green J. Inactivation of Escherichia coli O157:H7 and Salmonella on Fresh Herbs by Plant Essential Oils. Foodborne Pathog Dis 2018; 15:332-338. [PMID: 29638167 DOI: 10.1089/fpd.2017.2377] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Consumer awareness of fresh herbs and its demand has increased in recent years due to health benefits and distinct aroma in prepared food. There are specific markets for local growers, especially for organically grown herbs. Shiga-toxigenic Escherichia coli and Salmonella spp. have been detected and associated with foodborne outbreaks from fresh herbs. Limited treatment options are available in the processing of fresh herbs to prevent the spread of foodborne pathogens. In this study, plant-based essential oils were evaluated on fresh herbs for their antimicrobial activities against Salmonella and E. coli O157:H7. Fresh herbs (basil, cilantro, dill, parsley, and tarragon) were inoculated with cocktails of either Salmonella or E. coli O157:H7 and then dip treated with chlorine (50 ppm), cinnamaldehyde (0.3 and 0.5%), and carvacrol (0.1 and 0.3%). Control herb samples were dipped in sterile water. Samples were collected on days 0, 2, 7, and 14 for enumeration of pathogens during 4°C storage. The bactericidal efficacy differed with herbs and antimicrobial concentrations. Treatments with 0.3% carvacrol or 0.5% cinnamaldehyde reduced E. coli O157:H7 and Salmonella by 5 log CFU/g (p > 0.05%) on cilantro and dill leaves from their initial inoculum level. Bactericidal efficacy of 0.1% carvacrol and 0.3% cinnamaldehyde was significant against Salmonella compared with chlorine on all herb leaves. E. coli O157:H7 and Salmonella populations were reduced further during storage of treated herbs. There was no visual difference in herbs treated with 0.3% cinnamaldehyde or 0.1% carvacrol from control samples. Results indicate that 0.3% cinnamaldehyde and 0.1% carvacrol are effective against E. coli O157:H7 and Salmonella, retain color attributes of fresh herbs, and, therefore, may be an alternative wash treatment for fresh herbs.
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Affiliation(s)
- Jitendra Patel
- 1 U.S. Department of Agriculture, Agricultural Research Service , Beltsville, Maryland
| | - Shivramu Keelara
- 2 Department of Population Health and Pathology, College of Veterinary Medicine, North Carolina State University , Raleigh, North Carolina
| | - Jennifer Green
- 1 U.S. Department of Agriculture, Agricultural Research Service , Beltsville, Maryland
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7
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Jacobson AP, Wang H, Gill VS, Duvall R, Arce G, Chirtel S, Hammack TS. Relative effectiveness of selected preenrichment media for the detection of Salmonella from leafy green produce and herbs. Food Microbiol 2017; 63:123-128. [PMID: 28040159 DOI: 10.1016/j.fm.2016.11.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 10/17/2016] [Accepted: 11/11/2016] [Indexed: 11/16/2022]
Abstract
Four buffered preenrichment media (BAX® System MP Media (BAX)), Universal Preenrichment Broth (UPB), modified Buffered Peptone Water (mBPW), and Buffered Peptone Water (BPW)) were compared with lactose broth (LB) in the Bacteriological Analytical Manual's (BAM) Salmonella culture method for the analysis of 9 leafy green produce and herb types. Artificially contaminated test portions were pre-enriched in each medium and the results were analyzed statistically using Fisher's Exact 2-tailed F test (p < 0.05) with pairwise comparisons. There was no difference in recovery of Salmonella from curly parsley and basil among the five media (p > 0.05). UPB was consistently among the most effective media for recovery of Salmonella from the nine produce types; however, S. Typhimurium and S. Newport were isolated from cabbage more frequently with mBPW than with UPB (p < 0.05). Comparisons of the results among the preenrichment media from all experimental trials, with leafy green produce and herbs, demonstrate that Salmonella is more effectively detected and isolated using buffered enrichments than with the currently recommended LB (p < 0.05). There were no significant differences among the buffered preenrichments for the detection of Salmonella-positive test portions of the produce tested (BAX (160 Salmonella-positive test portions/480 test portions), UPB (176/480), mBPW (184/480), BPW (169/480), LB (128/480))(p > 0.05).
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Affiliation(s)
- Andrew P Jacobson
- U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 5001 Campus Dr., College Park, MD 20740, USA.
| | - Hua Wang
- U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 5001 Campus Dr., College Park, MD 20740, USA
| | - Vikas S Gill
- U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 5001 Campus Dr., College Park, MD 20740, USA.
| | - Robert Duvall
- U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 5001 Campus Dr., College Park, MD 20740, USA
| | - Gabriela Arce
- U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 5001 Campus Dr., College Park, MD 20740, USA.
| | - Stuart Chirtel
- U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 5001 Campus Dr., College Park, MD 20740, USA
| | - Thomas S Hammack
- U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 5001 Campus Dr., College Park, MD 20740, USA
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8
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Islam MT, Ogura A, Machida C, Morinaga N, Honjoh KI, Miyamoto T. Effects of ε-polylysine and Milk Serum Protein on the Attachment and Decontamination of Salmonella Enteritidis on Lettuce and Radish Sprouts. FOOD SCIENCE AND TECHNOLOGY RESEARCH 2016. [DOI: 10.3136/fstr.22.703] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Md Tariqul Islam
- Laboratory of Food Hygienic Chemistry, Division of Food Science and Biotechnology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University
- Faculty of Agriculture, Rajshahi University
| | - Aya Ogura
- Laboratory of Food Hygienic Chemistry, Division of Food Science and Biotechnology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University
| | - Chikako Machida
- Laboratory of Food Hygienic Chemistry, Division of Food Science and Biotechnology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University
| | - Noriko Morinaga
- Laboratory of Food Hygienic Chemistry, Division of Food Science and Biotechnology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University
| | - Ken-ichi Honjoh
- Laboratory of Food Hygienic Chemistry, Division of Food Science and Biotechnology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University
| | - Takahisa Miyamoto
- Laboratory of Food Hygienic Chemistry, Division of Food Science and Biotechnology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University
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Bridier A, Hammes F, Canette A, Bouchez T, Briandet R. Fluorescence-based tools for single-cell approaches in food microbiology. Int J Food Microbiol 2015; 213:2-16. [PMID: 26163933 DOI: 10.1016/j.ijfoodmicro.2015.07.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 06/26/2015] [Accepted: 07/03/2015] [Indexed: 12/31/2022]
Abstract
The better understanding of the functioning of microbial communities is a challenging and crucial issue in the field of food microbiology, as it constitutes a prerequisite to the optimization of positive and technological microbial population functioning, as well as for the better control of pathogen contamination of food. Heterogeneity appears now as an intrinsic and multi-origin feature of microbial populations and is a major determinant of their beneficial or detrimental functional properties. The understanding of the molecular and cellular mechanisms behind the behavior of bacteria in microbial communities requires therefore observations at the single-cell level in order to overcome "averaging" effects inherent to traditional global approaches. Recent advances in the development of fluorescence-based approaches dedicated to single-cell analysis provide the opportunity to study microbial communities with an unprecedented level of resolution and to obtain detailed insights on the cell structure, metabolism activity, multicellular behavior and bacterial interactions in complex communities. These methods are now increasingly applied in the field of food microbiology in different areas ranging from research laboratories to industry. In this perspective, we reviewed the main fluorescence-based tools used for single-cell approaches and their concrete applications with specific focus on food microbiology.
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Affiliation(s)
| | - F Hammes
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland
| | - A Canette
- INRA, UMR1319 Micalis, Jouy-en-Josas, France; AgroParisTech, UMR Micalis, Jouy-en-Josas, France
| | | | - R Briandet
- INRA, UMR1319 Micalis, Jouy-en-Josas, France; AgroParisTech, UMR Micalis, Jouy-en-Josas, France.
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10
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Gómez-López VM, Marín A, Allende A, Beuchat LR, Gil MI. Postharvest handling conditions affect internalization of Salmonella in baby spinach during washing. J Food Prot 2013; 76:1145-51. [PMID: 23834788 DOI: 10.4315/0362-028x.jfp-12-539] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Internalization of foodborne pathogens in fruits and vegetables is an increasing safety concern. The aim of this research was to assess the potential for internalization of an enteric pathogen (Salmonella enterica serotype Typhimurium) in a leafy vegetable (baby spinach) during washing as influenced by three postharvest handling conditions: (i) illumination, (ii) negative temperature differential, and (iii) relative humidity (RH). To compare these potential postharvest handling conditions, leaves were exposed to different levels of illumination (0, 1,000, and 2,000 lx), temperature differential (5, 11, 14, 20, and 26°C), and RH (99, 85, and 74%) for a short time before or during washing. Washing of baby spinach was carried out in water containing green fluorescent protein-tagged Salmonella Typhimurium (6.5 log CFU/ml) at 5°C for 2 min, followed by surface disinfection with chlorine (10,000 μg/ml) for 1 min, two rinses in water for 10 s, and spin drying for 15 s. Internalization was assessed by enumerating the pathogen on Salmonella-Shigella agar and by confocal laser scanning microscopy. Illumination of spinach leaves before and during washing and a negative temperature differential during washing did not significantly (P > 0.05) increase the number of internalized bacteria. However, exposure of leaves to low-RH conditions before washing, which reduced the tissue water content, decreased internalization of Salmonella compared with internalization in baby spinach exposed to high RH (P ≤ 0.05). Green fluorescent protein-tagged Salmonella Typhimurium was visualized by confocal laser scanning microscopy at a depth of up to 30 m m beneath the surface of spinach leaves after exposure to a high inoculum level (8 log CFU/ml) for an extended time (2 h). Results show that internalization of Salmonella into baby spinach leaves can occur but can be minimized under specific postharvest handling conditions such as low RH.
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Affiliation(s)
- Vicente M Gómez-López
- Research Group on Quality, Safety and Bioactivity of Plant Foods, Department of Food Science and Technology, CEBAS-CSIC, P.O. Box 164, Espinardo, Murcia, E-30100, Spain
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11
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Fate of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella on fresh-cut celery. Food Microbiol 2013; 34:151-7. [DOI: 10.1016/j.fm.2012.11.016] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 11/25/2012] [Accepted: 11/27/2012] [Indexed: 11/23/2022]
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12
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Roy D, Panchal S, Rosa BA, Melotto M. Escherichia coli O157:H7 induces stronger plant immunity than Salmonella enterica Typhimurium SL1344. PHYTOPATHOLOGY 2013; 103:326-32. [PMID: 23301812 PMCID: PMC3982233 DOI: 10.1094/phyto-09-12-0230-fi] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Consumption of fresh produce contaminated with bacterial human pathogens has resulted in various, sometimes deadly, disease outbreaks. In this study, we assessed plant defense responses induced by the fully pathogenic bacteria Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium SL1344 in both Arabidopsis thaliana and lettuce (Lactuca sativa). Unlike SL1344, O157:H7 induced strong plant immunity at both pre-invasion and post-invasion steps of infection. For instance, O157:H7 triggered stomatal closure even under high relative humidity, an environmental condition that generally weakens plant defenses against bacteria in the field and laboratory conditions. SL1344 instead induced a transient stomatal immunity. We also observed that PR1 gene expression was significantly higher in Arabidopsis leaves infected with O157:H7 compared with SL1344. These results suggest that plants may recognize and respond to some human pathogens more effectively than others. Furthermore, stomatal immunity can diminish the penetration of human pathogens through the leaf epidermis, resulting in low bacterial titers in the plant apoplast and suggesting that additional control measures can be employed to prevent food contamination. The understanding of how plant responses can diminish bacterial contamination is paramount in preventing outbreaks and improving the safety of food supplies.
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Affiliation(s)
- Debanjana Roy
- Department of Biology, University of Texas, Arlington, Texas, 76019, USA
| | - Shweta Panchal
- Department of Biology, University of Texas, Arlington, Texas, 76019, USA
| | - Bruce A Rosa
- The Genome Institute, Washington University School of Medicine, St. Louis, Missouri, 63102, USA
| | - Maeli Melotto
- Department of Biology, University of Texas, Arlington, Texas, 76019, USA
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15
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Recent advances in the microbial safety of fresh fruits and vegetables. ADVANCES IN FOOD AND NUTRITION RESEARCH 2009; 57:155-208. [PMID: 19595387 DOI: 10.1016/s1043-4526(09)57004-0] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Foodborne illness outbreaks linked to fresh produce are becoming more frequent and widespread. High impact outbreaks, such as that associated with spinach contaminated with Escherichia coli O157:H7, resulted in almost 200 cases of foodborne illness across North America and >$300 m market losses. Over the last decade there has been intensive research into gaining an understanding on the interactions of human pathogens with plants and how microbiological safety of fresh produce can be improved. The following review will provide an update on the food safety issues linked to fresh produce. An overview of recent foodborne illness outbreaks linked to fresh produce. The types of human pathogens encountered will be described and how they can be transferred from their normal animal or human host to fresh produce. The interaction of human pathogens with growing plants will be discussed, in addition to novel intervention methods to enhance the microbiological safety of fresh produce.
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Lapidot A, Romling U, Yaron S. Biofilm formation and the survival of Salmonella Typhimurium on parsley. Int J Food Microbiol 2006; 109:229-33. [PMID: 16616389 DOI: 10.1016/j.ijfoodmicro.2006.01.012] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2005] [Revised: 11/03/2005] [Accepted: 01/05/2006] [Indexed: 11/20/2022]
Abstract
Although several studies provide evidence that the formation of biofilms by human pathogens on plant tissue is possible, to date there is no direct evidence that biofilms enhance the resistance of plant-associated pathogens to disinfectants or biocides. We hypothesized that biofilm formation would enhance the adhesion and survival of Salmonella on leafy vegetables. To test our hypothesis, we compared the adhesion and persistence of Salmonella Typhimurium and its biofilm-deficient isogenic mutant. Following inoculation of parsley and rinsing with water or chlorine solution, both strains had similar survival properties, and up to 3-log reduction were observed, depending on chlorine concentration. This indicates that the biofilm matrix of Salmonella likely does not play a significant role in initial adhesion and survival after disinfection. After a week of storage the biofilm producing strain survived chlorination significantly better than the biofilm-deficient mutant. However, the recovery of the mutant was still elevated, indicating that although the biofilm matrix has a role in persistence of Salmonella after chlorination treatment of parsley, this is not the most important mechanism, and other mechanisms, probably the ability to penetrate the plant tissue or the pre-existing biofilms, or production of different polysaccharides other than cellulose, provide the protection.
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Affiliation(s)
- Anat Lapidot
- Department of Biotechnology and Food Engineering, Technion, Haifa, Israel
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