Inhibitory action of three lactic acid bacteria cultures on some food-borne pathogens during pickling of green olive fruits

The healthy olive pickles are those ones which are made by using lactic acid bacteria (LAB) as starter and protective cultures. Three lactic acid bacteria (LAB) strains namely: Lactobacillus plantarum LPS10 (L. plantarum), Lactobacillus fermentum PP17 (L. fermentum) and Pediococcus acidilactici MH512904 (P. acidilactici) were used for inhibition of some food-borne bacterial pathogens such as Listeria monocytogenes LMG10470 (L. monocytogenes), Staphylococcus aureus ATCC25923 (S. aureus), Bacillus cereus ATCC14579 (B. cereus) and Escherichia coli ATCC25922 (E. coli) in Brain Heart Infusion Broth (BHIB) and during pickling of green olive fruits. Cell free supernatants (CFS) from LAB showed distinctive inhibition of the indicator bacterial pathogens used and the inhibitory activity was more pronounced against Gram positive bacteria than that found against Gram negative E. coli strain used; the inhibitory activity of CFS was more pronounced than that obtained by neutralized cell free supernatants (NCFS). Cultures of LAB were used for inhibition of the food-borne pathogens during pickling of green olive fruits. The food-borne bacterial cells grew in olive pickles brine (control) and their growth (CFU/mL) decreased in treated pickles samples and distinctive differences in growth values (CFU/mL) were observed between control and treated samples. CFS from L. plantarum affected target cells of both L. monocytogenes and E. coli and caused cell deformations, cell shrinkage and cell lysis as showed by Transmission Electron Microscopic (TEM) examinations.