Biocontrol of Listeria on cantaloupes in the field with lactic acid bacteria

Authors: YIN, HSIN-BAI - University Of Maryland; CHEN, CHI-HUNG - University Of Maryland; Boomer, Ashley; BYUN, SUYEUN - Gachon University; KUMAR, VENKITANARAYANA - University Of Connecticut; MACARISIN, DUMITRU - Food And Drug Administration(FDA); Patel, Jitu

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2020
Publication Date: 4/3/2020
Citation: Yin, H., Kumar, V.N., Macarisin, D., Patel, J.R. 2020. Biocontrol of Listeria on cantaloupes in the field with lactic acid bacteria. Journal of Food Protection. https://doi.org/10.1111/jfpp.14465.
DOI: https://doi.org/10.1111/jfpp.14465

Interpretive Summary: Listeria outbreaks associated with consumption of cantaloupe have stakeholders and consumers worried about the microbiological safety of cantaloupes. Washing of fruit with chlorine after harvest is a common practice to control contamination of bacterial pathogens. Currently, no treatment is employed at the farm level to minimize bacterial contamination on cantaloupe. We employed a novel approach of using lactic acid bacteria (LAB) spray on growing cantaloupes to kill Listeria at the farm. Cantaloupes on vines were sprayed with a cocktail of Listeria, allowed to air dry, and then sprayed with a cocktail of LAB. On 0, 5, and 7 days-post-inoculation, three cantaloupes from each group were harvested and analyzed for surviving populations of Listeria. The treatment with LAB significantly reduced Listeria populations by 2.0 and 1.5 log CFU/cm2 on day 5 and 7 as compared to the control, respectively. Results suggest that LAB could be potentially used as a biocontrol agent to reduce Listeria contamination on cantaloupes at the farm level. These findings could benefit produce growers seeking to reduce the risk of foodborne illness from consumption of fresh cantaloupes.

Technical Abstract: The efficacy of lactic acid bacteria (LAB) Lactobacillus plantarum and Pediococcus pentosaceus for reducing Listeria innocua on cantaloupes at the pre-harvest level was investigated. Cantaloupes were grown in a high-tunnel at the USDA farm, Beltsville, MD. Mature cantaloupes (N=18) on vine were spray-inoculated by a 2-strains cocktail of L. innocua on marked areas (5 cm x 10 cm square) to obtain Listeria populations at ~ 3 log CFU/cm2, allowed to air-dry for 1 h, and then 9 of these cantaloupes were sprayed with a cocktail of L. plantarum and P. pentosaceus to obtain ~ 5 log CFU/cm2 on marked area previously inoculated with Listeria. Cantaloupes sprayed with Listeria but not treated with LAB served as positive controls. On 0, 5, and 7 days-post-inoculation, three cantaloupes from each group were harvested and the inoculated areas on each cantaloupe were swabbed using sponge swabs. The swabs were transferred to 50 ml full strength buffered peptone water, pummeled for 2 min in a stomacher, and surviving populations of Listeria and LAB were enumerated by spiral plating on Rapid Lmono and MRS agars, respectively. The experiment was repeated on cantaloupes grown at the Fulton farm, Chambersburg, PA. Listeria populations on the control cantaloupes were ~ 2.8 log CFU/cm2 following inoculation and increased to ~3.8 log CFU/cm2 after 7 days. The treatment with lactic acid bacteria significantly reduced Listeria populations by 2.0 and 1.5 log CFU/cm2 on day 5 and 7 as compared to the control, respectively. Results suggest that LAB could be potentially used as biocontrol agents to reduce Listeria contamination on cantaloupes at the farm level.