| APPROACH:
GFP-labeled strains of E. coli O157:H7 will be used throughout the project. Bacteriophages and competitive exclusion microorganisms will be applied to compost piles to serve as biological control agents for E. coli O157:H7. To assist in thermal inactivation of E. coli O157:H7 contaminating the surface of fresh compost, piles will be covered with mature compost, straw, or pine shavings and turf reinforcement mesh. In growth chamber studies, leafy green plants will be subjected to varying levels of soil fertility, heat stress, water stress, and biological control agents to determine the impact on internalization of E. coli O157:H7 into the plant through the roots. In separate studies, plant leaves will also be exposed to E. coli O157:H7 dispersed either in water or a manure exudate to determine effect on the pathogen's survival. In field studies, the ability of lettuce, spinach, and parsley to internalize avirulent strains of E. coli O157:H7 as contamination level and
plant maturity varies will be assessed. Using a combination of internally contaminated, surface-inoculated, and uninoculated leafy greens, the degree of cross-contamination will be monitored for E. coli O157:H7 at three key processing points: 1) conveyance on a conveyor belt; 2) dewatering step; and 3) mechanical shredding. A protocol for detecting low numbers of E. coli O157:H7 in lettuce process waters using a tangential flow filtration system, immunomagnetic separation system, and real-time PCR will be developed and evaluated in fresh-cut processing facilities and growing fields. To determine the potential for low-energy X-ray treatments to inactivate E. coli O157:H7 in leafy greens, a quantitative relationship between radiation dose and inactivation will be developed. In addition, the dose distribution within a commercial package of leafy greens will be mapped and validations of overall lethality in packages of leafy greens subjected to low-energy X-ray treatments will be
conducted. The behavior of E. coli O157:H7 inoculated onto the spinach leaf surface or internalized will be compared under different packaging conditions and storage. Data collected in this project as well as other studies focusing on contamination at farm, factory, and retail/home will be used to used to develop exposure assessment estimations. Using surrogate and E. coli O157 outbreak data, hazard characterizations will also be assessed and combined with the exposure assessment models for risk characterization of E. coli O157:H7 in leafy greens. From these models and data, critical control points and possible mitigation strategies will be identified using a Food Safety Objective (FSO) approach. Dissemination of the project's research outcomes and proposed management strategies will be through scientific symposia, extension agent workshops, and a grower meeting.
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CRIS NUMBER: 0210519
SUBFILE: CRIS
PROJECT NUMBER: GEO-2007-01899
SPONSOR AGENCY: NIFA
PROJECT TYPE: OTHER GRANTS
PROJECT STATUS: EXTENDED
MULTI-STATE PROJECT NUMBER: (N/A)
START DATE: Sep 1, 2007
TERMINATION DATE: Aug 31, 2012
GRANT PROGRAM: IP-FOOD SAFETY & QUALITY
GRANT PROGRAM AREA: Integrated Programs
CLASSIFICATION
|
| 712 | 1430 | 1100 | 4.1 | 70% |
| 712 | 1430 | 2080 | 4.1 | 10% |
| 722 | 5370 | 1100 | 4.2 | 10% |
| 903 | 4010 | 1100 | 3.1 | 10% |
|
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CLASSIFICATION HEADINGS
KA722 - Zoonotic Diseases and Parasites Affecting Humans
KA712 - Protect Food from Contamination by Pathogenic Microorganisms, Parasites, and Naturally Occurring Toxins
KA903 - Communication, Education, and Information Delivery
S5370 - Sewage and waste disposal facilities and systems
S4010 - Bacteria
S1430 - Greens and leafy vegetables
F1100 - Bacteriology
F2080 - Mathematics and computer sciences
G4.2 - Reduce Number and Severity of Pest and Disease Outbreaks
G3.1 - Economic Opportunities for Growth
G4.1 - Reduce Incidence of Foodborne Illnesses and Contaminants
RESEARCH EFFORT CATEGORIES
| BASIC |
60% |
| APPLIED |
20% |
| DEVELOPMENTAL |
20% |
KEYWORDS: escherichia coli o157:h7; fresh-cut; lettuce; leafy greens; spinach; parsley; internalization; x-rays; cross-contamination; risk assessment; compost; water; bacteriophage; competitive exclusion; plant stress; shredding; modified atmosphere; sanitizing rinses; storage
PROGRESS: Sep 1, 2010 TO Aug 31, 2011
OUTPUTS: The research findings for 2011 were disseminated through a symposium on Systems Approach to Minimize E coli O157 Food Safety Hazards Associated with Fresh Leafy Greens held at the International Association for Food Protection (IAFP) Annual Meeting in Milwaukee, WI on August 3 (approx. 150 attendees and evaluations were very favorable). Additional presentations included the IIT Institute for Food Safety and Health 2011 Annual Meeting Working Group on Produce Safety Issues in Bedford Park, IL on April 26; F. Perez-Rodriquez et al, Growth of E coli O157 on packed fresh cut lettuce, IAFP Ann. Meeting, Milwaukee, and Bio World 2011, Torremolinos, Spain, and Modeling growth of E coli O157 in extract of leafy vegetables, Int. Conf. Predict Model of Foods, Dublin, Ireland; Ryser et al. Potential impact of pathogens cross-contamination and growth on risks associated with leafy greens, Impact of organic load in sanitizer efficacy, Persistence of E coli O157 during processing of iceberg lettuce, Quantitative transfer of E coli O157 to leafy greens during shaker dewatering, Impact of hold time on E coli O157 transfer during production of fresh-cut greens, Enhanced resistance of sanitizer-injured E coli O157 on spinach during X-ray irradiation, IAFP Ann. Mtg., Milwuakee; M. Erickson et al Preharvest field exposure of seeds or cut leafy greens to E coli O157 internalization, IAFP Ann. Mtg., Milwaukee, Leafy green internalization of E coli O157 after repeated exposure to low-dose contaminated irrigation water, UGA Center for Food Safety Ann. Mtg., Atlanta, GA; T.J. Fu et al Factors affecting sanitizer efficacy in preventing cross-contamination of E coli O157 during postharvest lettuce washing, and Evaluation of commercial rapid tests and immunomagnetic separation to detect E coli O157 in lettuce wash water, Inst. Food Technol. Ann. Mtg., New Orleans, LA; A. Lee et al Use of high power ultrasound to improve efficacy of fresh-cut produce washing, Inst Food Technol Ann. Mtg., New Orleans; Jiang et al indigenous microorganisms impacts E coli O157 growth in cured compost, Am. Soc. Microbiol. Ann. Mtg., San Diego, CA. Results of studies conducted as part of this project were presented on a website http://www.ugacfs.org/producesafety/index.html. The site also serves as a resource of information on the safety of leafy greens by listing and summarizing other pre- and post-harvest research studies that have been conducted. PARTICIPANTS: Co-investigators on the project include Michael Doyle and Marilyn Erickson at the University of Georgia Center for Food Safety; George Boyhan, Juan Carlos Diaz-Perez, and Sharad Phatak at University of Georgia, Department of Horticulture, Tifton; Xiuping Jiang at Clemson University Department of Food Science and Human Nutrition; Elliot Ryser, Toby TenEyck, and Ewen Todd at Michigan State University Department of Food Science and Human Nutrition; Peter Slade, Martin Cole, Tong-Jen Fu, Alvin Lee, and Mary Lou Tortorello at the Illinois Institute of Technology, National Center for Food Safety and Technology; and John Luchansky, U.S. Department of Agriculture - ARS, Wyndmoor, PA. A Steering Committee comprised of Bob Buchanan (chair) at the University of Maryland; Kathleen O'Donnell, Wegmans; Will Daniels and Charles Sweat, Earthbound Farms; Carolyn Smith deWaal, Center for Science in the Public Interest; Alex Rilco, Whole Foods; Jill Hollingsworth, Food Marketing Institute; Joan Rosen, Fresh Express; John Luchansky, USDA ARS; Linda Harris, University of California at Davis; Bob Mills, Tanimura and Antle; and Larry Cohen, Kraft Foods, meets once or twice annually to review results and provide guidance for future research directions. TARGET AUDIENCES: Two primary audiences to date, i.e. (1) research scientists addressing produce safety and (2) leafy green fresh-cut processors. One meeting was held in 2011 addressing interests of both groups. An additional meeting was held addressing the processors only. Titles and location of these meetings are listed in the Outputs section of this report. A web site also noted in the Output section was put online for all parties interested in leafy greens food safety research findings. PROJECT MODIFICATIONS: Not relevant to this project.
IMPACT: 2010-09-01 TO 2011-08-31
Key findings for this reporting period include: (1) compost heaps covered with finished compost maintained 7 to 15 degrees C higher temperatures and caused rapid E coli O157 reduction compared to compost heaps covered with fresh straw or uncovered; (2) bacteriophages specific to E coli O157 and Salmonella spp. isolated from sewage reduced ca. 3 to 5 log of E coli O157 in dairy manure slurry and ca. 3 log on fresh compost, and ca. 2 log of Salmonella in finished compost; (3) E coli O157 growth in compost was negatively correlated with the cell numbers of indigenous microorganisms, especially actinomycetes and fungi; (4) a web-based probabilistic risk model for leafy greens was developed and predicted the burden-of-illness caused by E coli O157 associated with fresh and fresh-cut leafy greens; (5) the point at which leafy greens become contaminated will impact the extent of cross-contamination during processing, with significantly less E coli O157 transfer occurring from field-contaminated lettuce as opposed to product contaminated closer to the time of processing; (6) cross-contamination of leafy greens can readily occur via leaf-to-leaf contact with E coli O157-contaminated product during shaker table dewatering; (7) chemical oxygen demand, total solids, maximum filterable volume and turbidity are useful in assessing the antimicrobial efficacy of a chlorine-based sanitizer which was ineffective in the presence of 5% (w/v) lettuce solids; (8) high temperature and low oxygen levels are contributing risk factors for E Coli O157 growth in packaged baby spinach; (9) survival of E coli O157 in spinach leaves that were damaged by compression or cutting was no different than its survival in undamaged product; (10) whether exposed to sublethal concentrations of hypochlorite in solution or on spinach surfaces, there was no difference in the behavior of E coli O157 compared to untreated controls; (11) leafy green plants misted with E coli O157-contaminated water (103 CFU/ml) once every minute for 30 min. resulted in internalization of E coli O157 in leaves of 56 of 180 parsley and 82 of 240 spinach samples 1 hour after exposure, and when spinach plants were exposed on 5 consecutive days to a similar spray protocol, E coli O157 internalization occurred in 25 of 40 samples 1 hour after misting but there were no internalized cells 2 days after misting; (2) no E coli O157 was detected in 5-ppm chlorinated wash water although contamination was detected in 4 out of 6 uninoculated lettuce samples after washing at 3oC, hence sufficiently chlorinated wash water may not be a good marker for the contamination status of a production batch.
PUBLICATION INFORMATION: 2010-09-01 TO 2011-08-31
Li, Y.; Fu, T.-J. 2011. Factors affecting sanitizer efficacy in preventing cross-contamination of E. coli O157:H7 during postharvest washing of lettuce. IFT Annual Meeting, June 11-15, New Orleans, LA.
PROJECT CONTACT INFORMATION
| NAME: |
Doyle, M. P. |
| PHONE: |
770-228-7284 |
| FAX: |
770-229-3216 |
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