In vitro evaluation of the synbiotic effect of probiotic Lactobacillus strains and garlic extract against Salmonella species

Abstract The study was carried out to screen potential probiotic strains of Lactobacillus spp. For its synbiotic antibacterial action with garlic extract against Salmonella strains in vitro. Initially, five Lactobacillus isolates viz. L. plantarum NG6, AM3, DS11, NG13 and L. paracasei DB3 isolated from faecal sources were selected based on its antimicrobial activity against Salmonella strains. The five Lactobacillus strains demonstrated good level of in vitro probiotic attributes in terms of acid and bile tolerance, auto- and co-aggregation, BSH activity and cell surface hydrophobicity. Multivariate PCA analysis and heatmap visualization of the probiotic atrributes of the five strains confirmed L. plantarum NG6 as the best probiotic lactobacilli. Based on the results of the antimicrobial testing of various concentration of garlic extract (GE) it was observed that 12.5% GE showed bactericidal effect against both Salmonella Typhi and Typhimurium, but not against Lactobacillus spp., rather the combination demonstrated synergistic antimicrobial action against the test strains which was also validated by Scanning electron microscopy. Overall, the study is a first attempt to demonstrate that probiotics can be combined with herbal preparations such as garlic to fight against Salmonella, which can further pave way for development of more natural formulations for combating gastrointestinal infections.