Bioprotection of Golden Delicious apples and Iceberg lettuce against foodborne bacterial pathogens by lactic acid bacteria

Lactic acid bacteria were isolated from fresh vegetables and fruit and its ability to inhibit the growth of foodborne human pathogens (Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella typhimurium, and Staphylococcus aureus) was tested using the agar spot assay. Eighteen isolates showed a strong antagonistic capacity and were further characterised and identified using 16S rDNA sequencing and API 50CH. Most of them pertained to Leuconostoc spp. and Lactobacillus plantarum, and a few corresponded to Weissella spp. and Lactococcus lactis. Growth and efficacy of control of foodborne pathogen test bacteria by selected strains were tested in wounded Golden Delicious apples and Iceberg lettuce leaf cuts. The strains grew on the substrates and did not cause negative effects on the general aspect of tissues of apple or lettuce. Treatment of apple wounds and lettuce cuts with the antagonistic strains reduced the cell count of S. typhimurium and E .coli by 1 to 2 log cfu/wound or g, whereas the growth of L. monocytogenes was completely inhibited. Results support the potential use of lactic acid bacteria as bioprotective agents against foodborne human pathogens in ready-to-eat fresh fruit and vegetable products.