The likelihood of cross‐contamination of head lettuce by E. coli O157:H7, Salmonella and norovirus during hand harvest and recommendations for glove sanitizing and use.

The likelihood of cross‐contamination of head lettuce by E. coli O157:H7, Salmonella and norovirus during hand harvest and recommendations for glove sanitizing and use.

Jan. 1, 2011 - Dec. 31, 2012

2011-143

$330,541.00

Jennifer L. Cannon, Ph.D.
University of Georgia

Marilyn Erickson, Ph.D., Mussie Habteselassie, Ph.D.

Final Report

Mandatory glove use when handling raw produce and the practice of sanitizing gloves with bleach is common despite uncertainty that these practices improve the safety of foods. Here, the impacts of glove use (frequency of changing and glove composition) and sanitation (using bleach and a novel sanitizer developed at UGA) on cross-contamination of raw head lettuce by bacterial (E. coli O157:H7, Salmonella) and viral (norovirus) pathogens during harvest will be investigated. Since build-up (soil and lettuce residue) on gloves likely impacts transfer of pathogens to and from gloves, accumulation ofthese materials on glovesover time (0.5, 1,2 and 4 hr) will be quantified for volunteer harvesters wearing either rubber or nitrile gloves. In the lab, natural accumulation will be mimicked on gloves and the likelihood of pathogen transfer to gloves and head lettuce will be investigated. Finally, a novel sanitizer
will be evaluated for its efficacy in removing organic material accumulation and inactivating pathogens on gloves as compared to bleach. This study will provide a scientific basis for making recommendations on glove use and sanitation during harvesting head lettuce and will contribute to improving the safety of fresh produce.

Technical Abstract

In response to growing concerns regarding the safety of raw produce, the mandatory use of gloves when handling raw produce and the practice of sanitizing gloves with bleach (in rinse buckets) has become common in the leafy green industry. However, it is uncertain that these practices actually improve the safety of leafy greens. In this study, the impacts of glove use (frequency of changing and glove composition) and sanitation (using bleach and a novel sanitizer developed at UGA) on cross‐contamination of raw head lettuce by bacterial (E. coli O157:H7, Salmonella) and viral (norovirus) pathogens during harvest will be investigated. Since build‐up (soil and lettuce material) on gloves likely impacts transfer of pathogens to and from gloves, accumulation of this material on gloves over time (0.5, 1, 2, and 4 hr) will be quantified for volunteer harvesters wearing either rubber or nitrile gloves. To do this, we will first optimize methods for characterizing and quantifying levels of soil and lettuce latex residues accumulating on gloves by carbon and nitrogen isotopic ratio analyses. Next, natural accumulation of organic material on gloves will be quantified by conducting a field study in which the gloves of harvesters/corers will be collected and analyzed using the optimized methods. Once natural accumulation of organic material on gloves is characterized and soil to latex ratios are quantified for each harvest time increment and for each glove type, a subset of these levels (high, medium, low and none) will be mimicked on gloves in the lab using a mock organic material carefully formulated with varying ratios of soil and lettuce latex. Next, the likelihood and degree of pathogen transfer to gloves from mock contaminated soil and lettuce, and to lettuce from mock contaminated gloves will be investigated. Mock contaminated [bacterial (E. coli O157:H7, Salmonella) or viral (murine norovirus, a surrogate for human norovirus) pathogens] soil or lettuce will be touched by a pathogen‐free, gloved hand to determine cross‐contamination of gloves by soil or lettuce. Similarly, for investigating how many lettuce heads can become contaminated following a single glove contamination event, pathogens will be inoculated on gloves and multiple lettuce heads will be touched. Pathogens eluted from the gloves or lettuce will be quantified by standard culture or plaque assays. Finally, a novel sanitizer will be evaluated for its efficacy in removing organic material and inactivating pathogens on gloves as compared to bleach. To do this, gloves mock coated in 4 concentrations of organic material (high, medium, low and none) and inoculated with bacterial or viral pathogens will be exposed to varying concentrations of a novel levulinic acid plus SDS sanitizer or bleach, with or without 1 M NaCl (which enhances dissociation of viruses from hard surfaces). After neutralization, reductions in viable bacteria or virus will be assayed from gloves. The results of this study will provide a scientific basis for making recommendations on glove use (frequency of changing and type) and sanitation during harvesting head lettuce and will contribute to improving the safety of fresh produce.