Transfer of Escherichia coli and attenuated Salmonella enterica Typhimurium on the surface of in-shell pecans during harvest

Authors: Bardsley, Cameron; Chasteen, Kaicie; Shapiro Ilan, David; Bock, Clive; DEV KUMAR, GOVINDARAJ - University Of Georgia

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: 8/30/2023
Publication Date: 8/30/2023
Citation: Bardsley, C.A., Chasteen, K.S., Shapiro Ilan, D.I., Bock, C.H., Dev Kumar, G. 2023. Transfer of Escherichia coli and attenuated Salmonella enterica Typhimurium on the surface of in-shell pecans during harvest. International Association for Food Protection. Volume 9, Issue 9, 2023, e19676. https://doi.org/10.1016/j.heliyon.2023.e19676.
DOI: https://doi.org/10.1016/j.heliyon.2023.e19676

Interpretive Summary:

Technical Abstract: Introduction: Harvest practices for pecans results in the nuts coming in contact with the ground, potentially for extended periods of time. This presents a contamination risk with foodborne pathogens if present on the ground. Purpose: The objective of this study was to determine the potential transfer of E. coli and Salmonella from the ground to in-shell pecans during the harvesting process. Methods: Plots (1×2 m) were laid out under pecan trees in an orchard at the USDA-ARS Fruit and Tree Nut Research Unit. Each plot was sprayed with 1 liter of either an E. coli TVS 353 or an attenuated Salmonella Typhimurium inoculum at different concentrations (low: ˜4 log CFU/ml, mid ˜6 log CFU/ml, high ˜8 log CFU/ml). The next day, pecan trees were mechanically harvested. Nut samples from each plot were collected at 1 min, 4 hrs., and 24 hrs. following harvest. Samples were washed and diluted with 0.1% peptone and plated on to tryptic soy agar with 80 µg/ml rifampicin (LOD=0.3 log CFU/g). Samples were collected in triplicate with three independent replications (n=9). Results: Inoculation concentration and replication were significant (P<0.05) factors that influenced the transfer of E. coli and Salmonella on pecans. Replicate 3 had significantly less transfer likely attributed to heavy rain or other weather variables. For the high treatments bacterial transfer to pecans ranged from 0.7±0.3 to 4.1±0.2 and 1.3±0.7 to 4.3±0.4 log CFU/g for E. coli and Salmonella respectively. For the medium treatments transfer, ranged from <0.3 to 1.5±0.1 and <0.3 to 1.9±0.2 log CFU/g for E. coli and Salmonella respectively. For the low treatments, transfer ranged from <0.3 to 0.4±0.2 and <0.3 to 0.5±0.1 log CFU/g for E. coli and Salmonella, respectively. Significance: The bacterial transfer shows the need for implementing agricultural practices that prevent potential transfer of foodborne pathogens onto the surface of inshell pecans during harvest.