Characterization, mechanism and in vivo validation of Helicobacter pylori antagonism by probiotics screened from infants' feces and oral cavity.

Abstract

Helicobacter pylori (H. pylori) infection is a major cause of chronic gastritis, intestinal metaplasia, and gastric carcinoma. Antibiotics, the conventional regimen for eliminating H. pylori, cause severe bacterial resistance, gut dysbiosis and hepatic insufficiency. Here, fifty lactic acid bacteria (LAB) were initially screened out of 266 strains obtained from infants' feces and oral cavity. The antagonistic properties of these 50 strains against H. pylori were investigated. Based on eight metrics combined with principal component analysis, three LAB with probiotic function and excellent anti-H. pylori capacity were affirmed. Combining dynamics test, metabolite assays, adhesion assays, co-cultivation experiments, and SEM and TEM observations, LAB were found to antagonize H. pylori by causing coccoid conversion and intercellular adhesion. Furthermore, it was found that LAB antagonized H. pylori by four pathways, i.e., production of anti-H. pylori substances, inhibition of H. pylori colonization, enhancement of the gastric mucosal barrier, and anti-inflammatory effect. In addition, animal model experiments verified that the final screened superior strain L. salivarius NCUH062003 had anti-H. pylori activity in vivo. LAB also reduced IL-8 secretion, ultimately alleviating the inflammatory response of gastric mucosa. Whole genome sequencing (WGS) data showed that the NCUH062003 genome contained the secondary metabolite biosynthesis gene cluster T3PKS. Furthermore, NCUH062003 had a strong energy metabolism and substance transport capacity, and produced a small molecule heat stable peptide (SHSP, 4.1-6.5 kDa). Meanwhile, LAB proved to be safe through antibiotic susceptibility testing and CARD database comparisons.