Use of phyllosphere associated lactic acid bacteria as biocontrol agents to reduce salmonella enterica serovar poona growth on cantaloupe melons

Authors: McGarvey, Jeffery - Jeff; TRAN, THAO - University Of California; Hnasko, Robert; Gorski, Lisa

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2019
Publication Date: 11/18/2019
Citation: McGarvey, J.A., Tran, T.D., Hnasko, R.M., Gorski, L.A. 2019. Use of phyllosphere associated lactic acid bacteria as biocontrol agents to reduce salmonella enterica serovar poona growth on cantaloupe melons. Journal of Food Protection. 82(12):2148-2153. https://doi.org/10.4315/0362-028X.JFP-19-246.
DOI: https://doi.org/10.4315/0362-028X.JFP-19-246

Interpretive Summary: Every year over a million Americans become sickened from foodborne pathogens. We isolated bacteria that normally live on the surfaces of fresh produce and evaluated them for the ability to inhibit the growth of the pathogenic bacterium Salmonella enterica. We identified one bacterium that was able to reduce the growth of Salmonella enterica on cantaloupe melons by over 99.9%. We determined that this bacterium was called Lactococcus lactis, a bacterium that is often used as a food ingredient and is generally regarded as safe by the FDA. We determined that this bacterium produces large amounts of lactic acid which is known to inhibit Salmonella enterica growth. We propose that this bacterium is an effective and safe biological control agent to reduce the growth of Salmonella enterica on fresh, ready to eat produce.

Technical Abstract: Foodborne illness associated with fresh, ready to eat produce continues to be a significant challenge to public health. In this study, we created a phyllosphere associated lactic acid bacteria (PLAB) library and screened it via a high throughput in vitro fluorescent assay to identify bacteria capable of inhibiting the growth of the pathogenic bacterium Salmonella enterica. One isolate, 14B4 inhibited the growth of S. enterica by > 45-fold in vitro; and was able to grow and persist on the surfaces of cantaloupe melons at both ambient (25oC) and refrigerator (5oC) temperatures. Isolated 14B4 inhibited the growth of S. enterica on the surfaces of cantaloupes by > 3 logs when incubated at 25oC for 24 h; and by > 4 logs when the cantaloupes were stored at 5oC for 3 days and the temperature shifted to 25oC for 2 days. Genomic DNA sequence analysis of isolate 14B4 revealed that it was Lactococcus lactis and that it did not contain any known antibiotic biosynthesis gene clusters, antibiotic resistance genes, or genes encoding any known virulence factors. Volatile fatty acid analysis revealed that L. lactis produces substantial amounts of lactic acid, that is likely the inhibitory substance that reduced the growth Salmonella on the cantaloupes.