Modulation of Anti-Microbial Resistant Salmonella heidelberg Using Synbiotics (Probiotics and Prebiotics) in Two In-Vitro Assays (Cross-Streaking and Agar Wells Diffusion)

Salmonellosis is the most prevalent bacterial foodborne disease in many countries worldwide. Utilization of probiotics is one of the most accepted ways to reduce Salmonella, especially lactic acid bacteria, as it has proven to reduce the enteric pathogens in monogastric and ruminant livestock animals through different mechanisms such as antimicrobials production, competitive adhesion to the gastrointestinal tract, and immune stimulation. Prebiotics could be utilized solely for health benefits as an alternative to probiotics or in addition to probiotics for a synergistic effect known as synbiotics. The aim of this study was to compare effects of different probiotic strains (Lactobacillus acidophilus (La-14), Lactobacillus paracasei (Lpc-37), Streptococcus thermophiles (St-21), Bifidobacterium bifidum (Bb-06), and Aspergillus niger (ATCC&#17416888TM) and without prebiotics (Mannose; Xylose; Galactooligosaccharides GOS; Inulin; and Dandelion extract) on lowering Salmonella heidelberg CFU in vitro. Different inhibition levels probiotic strains were assessed and compared in the presence and absence of 2.5% prebiotic compounds using cross-streaking and agar well diffusion assays. Recommendations for the growth of selected microorganisms such as temperature and oxygen conditions were taken into consideration. All the analysis was conducted in triplicates. The results showed that all the probiotics strains except S. thermophiles were able to significantly (P < 0.05) inhibit the growth of S. heidelberg in at least one of the assays. The difference in inhibition percentage confirms that probiotic strains have multiple inhibition mechanisms, such as production of antimicrobials, lower pH by producing organic acids (acetic acid, lactic acid, etc.), and inhibition of pathogen’s virulence factor expression, and production of lipopolysaccharide solubilizing compounds.