Black cherry fruit as a source of probiotic candidates with antimicrobial and antibiofilm activities against Salmonella

Salmonella spp is one of the leading causes of bacterial foodborne illnesses worldwide resulting in acute gastroenteritis. The current study aimed to explore the inhibitory activity of two newly isolated probiotic candidates Lactiplantibacillus plantarum MYSAS1 and Enterococcus faecium MYSAS4 from fermented black cherry fruit, against Salmonella enterica subsp. enterica serovar Paratyphi A. Results demonstrated effective inhibitory activity of selected Lactic acid bacteria (LAB) strains against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and Salmonella Paratyphi A. In addition, the cell-free supernatant (CFS) of both strains showed potent antimicrobial activity on growth of S. Paratyphi A were demonstrated by agar well diffusion, broth microdilution assay, in vitro time-kill assay, and co-culture experiments. Besides, Salmonella sessile cells were effectively reduced by 70% after treatment with the CFS of L. plantarum MYSAS1 and E. faecium MYSAS4, as determined by crystal violet and 3-(4, 5-dimethylthiazol-2-y1)-2, 5-diphenyltetra bromide (MTT) biofilm assays. The antimicrobial substances of CFS were thermostable but sensitive to pH neutralization, suggesting that the observed antisalmonella activity is likely due to organic acids. Liquid Chromatography- Tandem Mass Spectrometry (LC-MS/MS) analysis of CFS revealed that the antimicrobial activity is likely due to the presence of 11 different organic acids. The isolated strains exhibited important probiotic characteristics, such as sensitivity to most of the antibiotics tested (except vancomycin and kanamycin), anti-hemolytic activity, tolerance to acidic pH and 0.3% bile, and survival ability at different temperatures. L. plantarum MYSAS1 and E. faecium MYSAS4 also exhibited auto-aggregation and cell surface hydrophobicity of 45 and 80%, respectively. Our findings demonstrated important probiotic features isolated from black cherry fruits while inhibiting multiple pathogens, suggesting possible applications of these potential probiotic strains as alternatives for antibiotics and chemical preservatives in the veterinary and food sectors.