Antimicrobial resistance is an emerging condition that increases the risk of spreading and prolonging infectious diseases globally. Therefore, a new alternative strategy for antibiotics is required urgently to control pathogens spreading. Probiotics are considered as an alternative for antibiotics that inhibit pathogens. In the present study, potent lactic acid bacteria (LAB) were isolated and screened for their probiotic characteristics and antagonistic activity against intestinal pathogens by agar well diffusion, Time and Dose-dependent killing assay, minimum inhibitor, and minimum bactericidal concentration (MIC/MBC), and co-culture methods. The Lactococcus lactis RWP-3 and RWP-7 fermented the different carbohydrate substrates and produced different extracellular enzymes. Both isolates showed significant tolerant capability in the gastric, duodenal, and intestinal juices. In addition, RWP-3 and RWP-7 had hydrophobicity and aggregation properties in a time-dependent manner. Furthermore, the cell-free secondary metabolites (CFS) of RWP-3 and RWP-7 showed strong antibacterial activity against Escherichia coli,Staphylococcus aureus, Pseudomonas aeruginosa and Enterococcus faecalis. A co-culture study revealed that the RWP-3 and RWP-7 strongly compete with pathogen growths. RWP-3 and RWP-7 showed strong antagonistic activities against tested pathogens with significant probiotic characteristics, suggesting that these strains obtained could be used as an alternative strategy for the antibiotic to control infectious pathogens.
Keywords: CFS; Lactococcus lactis; antagonistic activities; infectious diseases; probiotics.