Screening of Lactic Acid Bacteria with Anti-Helicobacter pylori Activity and Evaluation of Their Probiotic Characteristics

Objective: To screen lactic acid bacteria (LAB) with anti-Helicobacter pylori activity and great probiotic properties from fermented food, dairy products and infant feces. Method: A total of 39 LAB-like strains with stable curd state were screened from 175 samples. 9 Strains with anti-H. pylori activity were initially isolated by agar diffusion assay and H. pylori urease activity test and identified by 16S rDNA sequence analysis. Subsequently, the acid and bile tolerance, antibiotic resistance, antibacterial activity, cell surface hydrophobicity, and cell auto-aggregation of the selected LAB strains were determined. Results: Two probiotic strains with anti-Helicobacter pylori activity were screened: Lactobacillus helveticus GQ1702 and Lactobacillus plantarum D1, and their cell culture supernatants exhibited anti-H. pylori activity equivalent to the anti-H. pylori activity of 0.038 and 0.034 mg/mL metronidazole, respectively. The survival rates of GQ1702 and D1 were above 70% after incubation at pH3 for 3 h, the survival rates of GQ1702 and D1 after incubation at 0.3% bile salt were 0.47% and 1.08%, respectively. Cell surface hydrophobicities of GQ1702 and D1 were 25.10% and 11.79%, respectively. The self-agglutination rate reached 75.53% and 68.61% respectively after 24 hours. The auto-aggregation percentages of GQ1702 and D1 were 61.18% and 57.25%, respectively, after 24 hours. The two LAB strains were not resistant to chloramphenicol, penicillin, erythromycin, ampicillin, or cefazolin, and exhibited antimicrobial activity against Staphylococcus aureus, Listeria monocytogenes, E. coli O157:H7, and Salmonella typhimurium. Conclusion: Lactobacillus helveticus GQ1702 and Lactobacillus plantarum D1 with anti-Helicobacter pylori activity were obtained in this experiment, which could provide a source of strains for development and research of functional dairy products.