Food Safety Research Information Office
Title:Microbial Ecology and Safety of Fresh Produce
Objective:

Objective 1. Investigate the mechanism(s) of introduction and transference of Shiga toxigenic E. coli (STEC) and Salmonella to fresh produce during growing, harvest, and postharvest handlings: (1a) Evaluate the growth and survival potential of Enterohemorrhagic E. coli (EHEC) and Salmonella in compost manure applied to leafy green fields and validate cross-contamination and temperature control steps in a Hazard Analysis Critical Control Point (HACCP) system for compost, (1b) Develop a science-based proximity assessment index for airborne bioaerosol emissions for tomato and fresh produce (leafy greens -LG) fields, (1c) Determine the influence of biocontrols and insect amplification and transmission of EHEC and Salmonella in tomato and leafy green crops, and (1d) Evaluate the role of cultivars and fertilization on leafy-green damage during processing and its potential for pathogen contamination.

Objective 2. Determine the persistence and survival of pathogens on fresh and fresh-cut leafy green produce: (2a) Determine the persistence of pathogens introduced at different levels on spinach and lettuce plants to verify the adequacy of the California Leafy Greens Marketing Agreement (LGMA), (2b) Identify and evaluate suitable surrogate microorganism for generic E. coli in irrigation water, and (2c) Develop a field-scale-zero valent or slow sand filtration column to inactivate E. coli O157:H12 (surrogate strain) in a field study.

Objective 3. Determine the effects of pathogen attachment, biofilm formation, and internalization on the extent of contamination of fresh produce: (3a) Determine the role of various virulence and stress factors on the ability of EHEC to persist on leafy green surfaces, and (3b) Determine the effect of biofilm formation on survival of STEC and Salmonella on fresh produce.

Objective 4: Develop effective intervention technologies during processing to inactivate pathogens, and/or to reduce their survival and growth while maintaining produce quality and shelf-life: (4a) Minimizing pathogen transference and infiltration during produce harvesting and post-harvest handling, (4b) Optimizing fresh-cut produce wash system configurations and operations to improve pathogen inactivation and minimize cross-contamination, and (4c) Effect of temperature and packaging atmospheric conditions on survival, growth, and virulence of EHEC.

More Info:
APPROACH: Mechanisms of introduction and transfer of pathogens on fresh produce (lettuce, spinach, tomatoes, leafy greens) at the farm level will be investigated. Growth and survival patterns of avirulent strains of Enterohemorrhagic E. coli (EHEC) and Salmonella will be evaluated in composted manure with different pile size and configuration. Deposition of airborne-microbes onto fresh produce will be evaluated during different times of the year to determine proximity distance between fields and suspected nearby source of contamination. The role of insect vectors in transmission of pathogens to fresh produce will be studied and biocontrols will be used as a potential deterrent to insects. Bacterial analysis will include the use of microbial culture and molecular methods to detect target pathogens in samples. Persistence of EHEC and Salmonella on fresh produce will be determined when these pathogens are introduced at different levels via irrigation water. Clostridium perfringens and coliphages will be evaluated as suitable indicators for fecal contamination of irrigation water. Zero-valent iron (ZVI) columns will be evaluated as an intervention for removing pathogens from irrigation water. The role of specific virulence and stress factors on the ability of EHEC to attach and persist on fresh produce will be determined. Wild-type and curli- and cellulose-deficient strains of EHEC and Salmonella will be evaluated for their attachment and biofilm formation on fresh produce; biofilm formation on foliar surfaces will be determined by confocal laser scanning microscopy (CLSM). Existing and novel new antimicrobial wash treatments which remove biofilm from foliar surfaces will be evaluated. The effect of tomato dump tank management parameters on the probability and extent of Salmonella infiltration will be determined; the infiltration pattern will be determined by CLSM. The effect of the wash-cut sequence on pathogen cross-contamination during cutting and washing of fresh produce will be investigated. To minimize the chlorine degradation of wash water used for fresh produce wash, chlorine stabilizer will be used in wash water to evaluate its effect on chlorine stability of wash water and additional pathogen reduction on fresh produce. Pathogen growth and virulence as impacted by temperature abuse at a retail level and modified atmosphere packaging (MAP) of fresh produce will be evaluated.
Funding Source:United States Department of Agriculture (USDA), Agricultural Research Service (ARS)
Type:Appropriated
Start Date:2011
End Date:2016
Project Number:1245-32420-005-00
Accession Number:420692
Institutions:USDA/ARS - Beltsville Area Research Center
Investigators:Luo, Yaguang
Millner, Patricia
Nou , Xiangwu
Patel, Jitu
Schmidt, Walter
Sharma, Manan
Project Reports:2013 Annual Report
2012 Annual Report
2011 Annual Report
Pending USDA ARS Publications (NP 108):
Published Journal
Articles USDA
ARS (NP 108):
Comparison of U.S. Environmental Protection Agency and U.S. Composting Council microbial detection methods in finished compost and regrowth potential of Salmonella spp. and Escherichia coli O157:H7 in finished compost
Reynnells R, Ingram DT, Roberts C, Stonebraker R, Handy ET, Felton G, Vinyard BT, Millner PD, Sharma M.
Foodborne Pathog Dis. 2014 Jul;11(7):555-67.
Role of curli and plant cultivation conditions on Escherichia coli O157:H7 internalization into spinach grown on hydroponics and in soil
Macarisin D, Patel J, Sharma VK.
Int J Food Microbiol. 2014 Mar 3;173:48-53.
Differences in biofilm formation of produce and poultry Salmonella enterica isolates and their persistence on spinach plants
Patel J, Singh M, Macarisin D, Sharma M, Shelton D.
Food Microbiol. 2013 Dec;36(2):388-94.
Survival of pathogenic Escherichia coli on basil, lettuce, and spinach
Markland SM, Shortlidge KL, Hoover DG, Yaron S, Patel J, Singh A, Sharma M, Kniel KE.
Zoonoses Public Health. 2013 Dec;60(8):563-71.
The antimicrobial effects of cinnamon leaf oil against multi-drug resistant Salmonella Newport on organic leafy greens
Todd J, Friedman M, Patel J, Jaroni D, Ravishankar S.
Int J Food Microbiol. 2013 Aug 16;166(1):193-9.
Persistence of salmonella Typhimurium in Nopal
Landa-Salgado P, Hernandez Anguiano AM, Vargas Hernandez M, Eslava Campos C, Chaidez Quiroz C, Patel JR .
Revista Fitotecnia Mexicana. 2013 Jun 18;36(2):147-53.
Antimicrobial activity of oregano oil against antibiotic-resistant Salmonella enterica on organic leafy greens at varying exposure times and storage temperatures
Moore-Neibel K, Gerber C, Patel J, Friedman M, Jaroni D, Ravishankar S.
Food Microbiol. 2013 May;34(1):123-9.
Dynamic effects of free chlorine concentration, organic load, and exposure time on the inactivation of Salmonella, Escherichia coli O157:H7, and non-O157 Shiga toxin-producing E. coli
Shen C, Luo Y, Nou X, Wang Q, Millner P.
J Food Prot. 2013 Mar;76(3):386-93.
Lytic bacteriophages reduce Escherichia coli O157:H7 on fresh cut lettuce introduced through cross-contamination
Ferguson SE, Handy ET, Roberts CL, Sharma M .
Bacteriophage. 2013 Jan 1;3(1):e24323.
Biocontrol of Escherichia coli O157:H7 on fresh-cut leafy greens: using a bacteriophage cocktail
Boyacioglu O, Sharma M, Sulakvelidze A, Goktepe I .
Bacteriophage. 2013 Jan 1;3(1):e24620.
Biocontrol of Escherichia coli O157: H7 on fresh-cut leafy greens
Boyacioglu O, Sharma M, Sulakvelidze A, Goktepe I.
Bacteriophage. 2013 Jan 1;3(1):e24620.
Lytic bacteriophages reduce Escherichia coli O157: H7 on fresh cut lettuce introduced through cross-contamination
Ferguson S, Roberts C, Handy E, Sharma M.
Bacteriophage. 2013 Jan 1;3(1):e24323.
Antimicrobial activity of plant essential oils against Escherichia coli O157:H7 and Salmonella on lettuce
Yossa N, Patel J, Millner P, Ravishankar S, Lo YM.
Foodborne Pathog Dis. 2013 Jan;10(1):87-96.
Enhanced inactivation of Salmonella and Pseudomonas biofilms on stainless steel by use of T-128, a fresh-produce washing aid, in chlorinated wash solutions
Shen C, Luo Y, Nou X, Bauchan G, Zhou B, Wang Q, Millner P.
Appl Environ Microbiol. 2012 Oct;78(19):6789-98.
Human enteric pathogen internalization by root uptake into food crops
Hirneisen KA, Sharma M, Kniel KE.
Foodborne Pathog Dis. 2012 May;9(5):396-405.
Antimicrobial activity of lemongrass oil against Salmonella enterica on organic leafy greens
Moore-Neibel K, Gerber C, Patel J, Friedman M, Ravishankar S.
J Appl Microbiol. 2012 Mar;112(3):485-92.
Use of zero-valent iron biosand filters to reduce Escherichia coli O157:H12 in irrigation water applied to spinach plants in a field setting
Ingram DT, Callahan MT, Ferguson S, Hoover DG, Chiu PC, Shelton DR, Millner PD, Camp MJ, Patel JR, Kniel KE, Sharma M.
J Appl Microbiol. 2012 Mar;112(3):551-60.
Essential oils reduce Escherichia coli O157:H7 and Salmonella on spinach leaves
Yossa N, Jitendra P, Patricia M.
J Food Prot. 2012 Mar;75(3):488-96.
Role of curli and cellulose expression in adherence of Escherichia coli O157:H7 to spinach leaves
Macarisin D, Patel J, Bauchan G, Giron JA, Sharma VK.
Foodborne Pathog Dis. 2012 Feb;9(2):160-7.
Non-Journal Publications:
Glucosinolate-derived compounds as a green manure for controlling Escherichia coli O157:H7 and Salmonella in soil - (Abstract Only)
(31-May-13)
Survival of generic E. coli and surrogate E. coli O157:H7 in manure-amended soils - (Abstract Only)
(22-Mar-13)
Persistence of Escherichia coli in manure-amended soil in Pennsylvania - (Abstract Only)
(22-Mar-13)
Persistence of Escherichia coli and Attenuated E. coli O157:H7 in manure-enriched soils in the Eastern Shore of Maryland - (Abstract Only)
(22-Mar-13)
Comparison of microbial methods to detect fecal coliforms, E. coli and Salmonella spp. in finished compost - (Abstract Only)
(22-Mar-13)
Recovery of Escherichia coli O157:H7 by immunomagnetic separation techniques and potential for regrowth in finished composts- (Abstract Only)
(22-Mar-13)
The effect of UV radiation on survival of Salmonella enterica in dried manure dust - (Abstract Only)
(22-Mar-13)
Survival of Salmonella in manure dust on spinach leaves - (Abstract Only)
(22-Mar-13)
Comparative survival of Escherichia coli O157:H7, Salmonella Typhimurium, and Murine Norovirus on spinach plants - (Abstract Only)
(22-Mar-13)
Role of curli and contamination level on Escherichia coli O157:H7 internalization into organic spinach plants grown on hydroponics and in soil - (Abstract Only)
(18-Mar-13)
The Antimicrobial effects of Glucosinolates Hydrolysis compounds on E. Coli O157:H12 into field soil - (Abstract Only)
(18-Mar-13)
Use of Bacteriophages to control bacterial pathogens - (Abstract Only)
Sharma, M. 2013. Use of Bacteriophages to control bacterial pathogens. [abstract]. 11th Annual Mid-Atlantic Nutrition Conference abstract book p.137-144.
Haccp Implementation in the Production of Fresh-Cut Produce - (Proceedings)
Patel, J.R. 2013. HACCP implementation in the production of fresh-cut produce. Proceedings of the International Congress on Food Technology, Quality, and Safety. Pub #11CPT/INCOFTECH 2013/LP-026.
Haccp Implementation in the Production of Fresh-Cut Produce - (Abstract Only)
Patel, J.R. 2013. HACCP implementation in the production of fresh-cut produce. [abstract].
Fresh produce washing aid, T-128, enhances inactivation of Salmonella and Pseudomonas Biofilms on stainless steel and cantaloupe rinds in chlorinated wash solutions - (Abstract Only)
Shen, C., Luo, Y., Nou, X., Bauchan, G.R., Wang, Q., Millner, P.D. 2012. Fresh produce washing aid, T-128, enhances inactivation of Salmonella and Pseudomonas Biofilms on stainless steel and cantaloupe rinds in chlorinated wash solutions. BARC Poster Day.
Effects of simulated packing house operating conditions on pathogen internalization in tomatoes - (Abstract Only)
Zhou, B., Luo, Y., Yang, Y., Wu, Y., Paul, Y., Nou, X., Wang, Q. 2012. Effects of simulated packing house operating conditions on pathogen internalization in tomatoes. [abstract] BARC Poster Day.
Effects of temperature differential and immersion time on internalization of Salmonella Newport in tomatoes - (Abstract Only)
Zhou, B., Luo, Y., Yang, Y., Wu, Y., Paul, Y., Nou, X., Wang, Q. 2012. Effects of temperature differential and immersion time on internalization of Salmonella Newport in tomatoes. [abstract].
Effects of temperature differential and immersion time on internalization of salmonella newport in tomatoes - (Abstract Only)
Zhou, B., Luo, Y., Yang, Y., Wu, Y., Paul, Y., Nou, X., Wang, Q. 2012. Effects of temperature differential and immersion time on internalization of salmonella newport in tomatoes. [abstract].
Inactivation of Salmonella, Escherichia coli O157:H7 and non-O157 STEC by hypochlorite solutions with high organic loads - (Abstract Only)
Shen, C., Luo, Y., Nou, X., Wang, Q., Millner, P.D. 2012. Inactivation of Salmonella, Escherichia coli O157:H7 and non-O157 STEC by hypochlorite solutions with high organic loads. [abstract]
Fresh produce washing aid, T-128, enhances inactivation of Salmonella and pseudomonas biofilms on stainless steel coupons in chlorinated wash solutions - (Abstract Only)
Shen, C., Luo, Y., Nou, X., Zhou, B., Bauchan, G.R., Wang, Q., Millner, P.D. 2012. Fresh produce washing aid, T-128, enhances inactivation of Salmonella and pseudomonas biofilms on stainless steel coupons in chlorinated wash solutions. [abstract].
The mechanism of bactericidal action of cinnamaldehyde and Sporan on Escherichia coli and Salmonella - (Abstract Only)
Yossa, N., Patel, J.R., Macarisin, D., Millner, P.D., Murphy, C.A., Bauchan, G.R., Lo, M. 2012. The mechanism of bactericidal action of cinnamaldehyde and Sporan on Escherichia coli and Salmonella. BARC Poster Day. #57.
Survival of non-pathogenic E. coli and E. coli O157:H7 in Delmarva field plots amended with animal manure - (Abstract Only)
Cotton, C., Hashem, F., Jones, K., Sharma, M., Millner, P.D. 2012. Survival of non-pathogenic E. coli and E. coli O157:H7 in Delmarva field plots amended with animal manure. International Association for Food Protection. [abstract].
Effect of spinach cultivar and strain variation on survival of Escherichia coli O157:H7 on spinach leaves - (Abstract Only)
Patel, J.R., Macarisin, D., Bauchan, G.R. 2012. Effect of spinach cultivar and strain variation on survival of Escherichia coli O157:H7 on spinach leaves. International Association for Food Protection. Paper No. T4-09.
The use of zero-valent iron filtration to reduce Escherichia coli and Listeria innocua in irrigation water - (Abstract Only)
Banerjee, R., Singh, A., Callahan, M.L., Roberts, C.L., Ingram, D.T., Patel, J.R., Hoover, D., Kniel, K., Sharma, M. 2012. The use of zero-valent iron filtration to reduce Escherichia coli and Listeria innocua in irrigation water. [abstract] International Association for Food Protection. P3-32. p.182.
Survival of Salmonella enterica in dried turkey manure - (Abstract Only)
Oni, R., Buchanan, R., Sharma, M. 2012. Survival of Salmonella enterica in dried turkey manure. International Association for Food Protection. [abstract].
A comparison of E. coli persistence on basil plants and soil using drip and overhead irrigation - (Abstract Only)
Markland, S., Shortlidge, K., Cook, L., Lestrange, K., Sharma, M., Kniel, K. 2012. A comparison of E. coli persistence on basil plants and soil using drip and overhead irrigation. International Association for Food Protection. [abstract].
Influence of poultry litter and dairy manure on persistence of non-pathogenic E. coli and E. coli O157:H7 applied to fields - (Abstract Only)
Jones, K., Hashem, F., Cotton, C., Roberts, C.L., Sharma, M., Millner, P.D. 2012. Influence of poultry litter and dairy manure on persistence of non-pathogenic E. coli and E. coli O157:H7 applied to fields. International Association for Food Protection. [abstract].
Influence of poultry litter and dairy manure on persistence of non-pathogenic E. coli and E. coli O157:H7 in two geographically distinct mid-Atlantic fields - (Abstract Only)
Millner, P.D., Sharma, M., Hashem, F., Cotton, C., Jones, K. 2012. Influence of poultry litter and dairy manure on persistence of non-pathogenic E. coli and E. coli O157:H7 in two geographically distinct mid-Atlantic fields. [abstract].
Effectiveness of lytic bacteriophages in reducing E. coli O157:H7 populations introduced through cross-contamination on fresh cut lettuce - (Abstract Only)
Ferguson, S.E., Roberts, C.L., Sharma, M. 2012. Effectiveness of lytic bacteriophages in reducing E. coli O157:H7 populations introduced through cross-contamination on fresh cut lettuce. Annual Meeting of the Institute of Food Technologists.
Effectiveness of lytic bacteriophages in reducing E. coli O157:H7 populations introduced through cross-contamination on fresh cut lettuce - (Abstract Only)
(09-Feb-12)
Gram-negative phytopathogenic and soil bacteria enhance the presence of Escherichia coli O157:H7 in dual-species biofilms - (Abstract Only)
Liu, N., Nou, X., Lo, Y. 2012. Gram-negative phytopathogenic and soil bacteria enhance the presence of Escherichia coli O157:H7 in dual-species biofilms. [abstract].
Strategies for the reduction of human pathogens in tomatoes and leafy greens: A farm to fork systems approach - (Abstract Only)
Ingram, D.T., Zhou, B., Shen, C., Yang, Y., Sharma, M., Nou, X., Millner, P.D., Luo, Y. 2012. Strategies for the reduction of human pathogens in tomatoes and leafy greens: A farm to fork systems approach. [abstract].
Effectiveness of lytic bacteriophages in reducing E. coli O157:H7 populations introduced through cross-contamination on fresh cut lettuce - (Abstract Only)
Ferguson, S.E., Roberts, C.L., Sharma, M. 2012. Effectiveness of lytic bacteriophages in reducing E. coli O157:H7 populations introduced through cross-contamination on fresh cut lettuce. [abstract].
Use of zero-valent iron biosand filters to reduce E. coli O157:H12 in irrigation water applied to spinach plants in a field setting - (Abstract Only)
Ingram, D.T., Hoover, D., Shelton, D.R., Millner, P.D., Patel, J.R., Kniel, K., Sharma, M. 2012. Use of zero-valent iron biosand filters to reduce E. coli O157:H12 in irrigation water applied to spinach plants in a field setting. International Association for Food Protection. 112:551-560.
Pathogen risk associated with farming practices - (Abstract Only)
Sharma, M. 2011. Pathogen risk associated with farming practices. [abstract].
Survival and stress responses of E. coli exposed to alkaline cleaners - (Abstract Only)
Sharma, M. 2011. Survival and stress responses of E. coli exposed to alkaline cleaners. [abstract].
Improving the safety and post-harvest quality of field grown organic leafy greens: assessment of good agricultural/production practices along the farm to fork continuum - (Abstract Only)
Ravishankar, S., Bright, K., Fonseca, J., Gerba, C., Nolte, K., Jaroni, D., Patel, J.R., Friedman, M. 2011. Improving the safety and post-harvest quality of field grown organic leafy greens: assessment of good agricultural/production practices along the farm to fork continuum. [abstract] 46(9):5290.
Defense response in Nopal Cladodes infiltrated with Salmonella Typhimurium - (Proceedings)
Landa, S., Hernandez, A., Vargas, H., Eslava, C., Chaidez, Q., Patel, J.R. 2011. Defense response in Nopal Cladodes infiltrated with Salmonella Typhimurium. Meeting Proceedings. p. 126-129.
Persistence of salmonella typhimurium in nopal cladodes - (Abstract Only)
Landa, S., Hernandez, A., Vargas, H., Eslava, C., Lopez, J., Chaidez, Q., Patel, J.R. 2011. Persistence of salmonella typhimurium in nopal cladodes. [abstract]. 13th International COntress on Food Safety and 28th National meeting of Microbiology Hygiene and Toxicology. 100-103.
Viruses - (Book / Chapter)
Sharma, M., Sharma, G. 2012. Viruses. In: Decontamination of Fresh and Minimally Processed Produe. ed. V.M. Gomez-Lopez. Wiley Blackwell. Hoboken, NJ. p. 285-295.
Improving produce safety by stabilizing chlorine in washing solutions with high organic loads - (Abstract Only)
Luo, Y., Nou, X., Millner, P.D., Shelton, D.R. 2011. Improving produce safety by stabilizing chlorine in washing solutions with high organic loads. Meeting Abstract.
Food Safety Categories:Food Quality Characteristics
Food and Feed Handling and Processing
On-Farm Food Safety
Sanitation and Pathogen Control
Contaminants and Contamination
Pathogen Biology
Farm-to-Table Categories:On-farm food production
Food processing
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