Assessing Protection Mechanisms against Escherichia coli by Analyzing Auto-and Co-Aggregation, Adhesion Ability, Antagonistic Activity and Safety Characteristics of Potentially Probiotic Lactobacillus acidophilus B103

Background and Objectives: The aim of this study was to assess protection mechanisms against Escherichia coli by analyzing aggregation, adherence, antagonistic activity and safety characteristics of potentially probiotic Lactobacillus acidophilus B103. Materials and Methods: Potentially probiotic L. acidophilus B103 has been investigated in various aspects. Studied key characteristics included its pH and bile resistance, cell surface hydrophobicity and aggregation, cholesterol removal ability, hydroxyl radical scavenging activity and adhesion ability to Caco-2 cell monolayers. Antagonistic activity of the strain was assessed by adhesion competition on E. coli via competition, inhibition and replacement assays. Moreover, safety characteristics were investigated through DNase, hemolytic activity, biogenic amine production and antibiotic susceptibility assays. Results: L. acidophilus B103 included high stability to acidic pH (2.5 and 4.5), simulated gastric and intestinal juices and bile salt concentrations (up to 5% w/v). Moreover, L. acidophilus B103 showed relatively high hydrophobicity (51.79%), auto-aggregation (42.38%), co-aggregation (34.48%), cholesterol removal (46.27%) and hydroxyl radical scavenging activities (51.36%). Competition, replacement and inhibition anti-adhesion assays of the strain against E. coli were 52.13, 25.20 and 46.40%, respectively. Furthermore, L. acidophilus B103 adhered to simulated epithelial cells with a capacity of 11.85%. Neither DNase nor hemolytic activity was observed in the bacterial strain and the strain was highly sensitive to ciprofloxacin. Conclusions: Based on the results, safety assessments and its food origin, L. acidophilus B103 demonstrates potential for use in the food industry. It can serve as starter culture, co-culture and bio-protective agent, effectively enhancing safety and quality of the food products.