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.

This paper introduces the concept of Auto–Engel polygroups via the heart of hypergroups and investigates the relation between of Auto–Engel polygroups and Auto–nilpotent polygroups. Indeed, we show that the concept of heart of hypergroups plays an important role on construction of Auto–Engel polygroups. This study considers the notation of characteristic set in hypergroups with respect to Automorphism of hypergroups and shows that the heart of hypergroups is a characteristic set in hypergroups.

Probiotics have been used for over a century to prevent and treat diseases. They can reduce the effects of gastroenteritis and are now used to treat acute diarrhea. This study aimed to evaluate the co-aggregative effects of probiotics bacteria against diarrheal causative bacteria. For this purpose, 11 isolates of probiotic bacteria were used in the current study, including three Lactobacillus plantarum, one Lactobacillus gasseri, two Lactobacillus fermentum, three Lactobacillus acidophilus, and two Lactococcus garvieae isolates. All isolates were tested for antibiotic susceptibility, Autoaggregation ability, adhesion ability, antibacterial activity, acid tolerance, and bile salts tolerance. The results showed that most of them had the ability to Autoaggregate after 4 h, with the highest percentage of 57.14% for L. fermentum. For the antibiotic susceptibility test, all the isolates showed resistance against trimethoprim/sulfamethoxazole, except one isolate. Moreover, all the isolates, except one, were susceptible to both vancomycin and tetracycline. All tested isolates had adhesion ability with different survival rates, which reached 34.57% for L. plantarum in acidic conditions. Besides, the highest survival rate was 85.17%, which belonged to L. garvieae, for bile salt tolerance. Probiotic isolates had an antibacterial effect against diarrhea-causative bacteria with an inhibition diameter of 17-49 mm for different Lactobacillus spp. and Lactococcus spp. isolates. Furthermore, the co-aggregation ability of probiotic isolates against diarrhea-causative bacteria was studied, and results showed that probiotic isolates had a co-aggregative effect against diarrhea-causative bacteria, Escherichia coli, Shigella sonnei, and Providencia alcalifaciens, after 24 h of incubation. The highest co-aggregative effect of probiotics isolates belonged to L. fermentum and L. acidophilus against P. alcalifaciens with a co-aggregation percentage of 100%, while the lowest co-aggregation rate was 14.29% against E. coli.  The findings revealed the probiotic properties and co-aggregative effects of probiotic bacteria against diarrhea-causative bacteria.