Oral bacteria affect the gut microbiome and intestinal immunity

Area of Science:

• Microbiology
• Immunology
• Gastroenterology

Background:

• Porphyromonas gingivalis, a periodontal pathogen, is known to cause gut dysbiosis.
• Oral streptococci are the predominant bacteria in the oral cavity.

Purpose of the Study:

• To compare the effects of oral administration of oral streptococci versus P. gingivalis on the intestinal tract.
• To investigate the impact of oral bacteria on gut microbiota composition, metabolites, and immune responses.

Main Methods:

• Oral gavage of mice with oral bacteria.
• Analysis of gut microbiota composition using sequencing.
• Measurement of short-chain fatty acids (SCFAs) and immune cell populations (Th17, Treg) in the small intestine.
• Quantification of fecal immunoglobulin A (IgA) levels and macrophage polarization (M1/M2 ratio).

Main Results:

• Oral bacterial administration induced gut dysbiosis, characterized by increased Bacteroides and Staphylococcus, and decreased Lactobacillus spp.
• Lactate levels increased, while succinate and n-butyrate levels decreased in the gut.
• A decrease in Th17 cells was observed in the small intestine, with no significant change in Treg cells.
• The M1/M2 macrophage ratio increased, and fecal IgA antibody titers decreased.

Conclusions:

• Oral bacteria can induce gut dysbiosis, alter gut metabolites, and suppress specific immune responses.
• These changes, including reduced Th17 cells and fecal IgA, alongside increased M1/M2 macrophages, may promote chronic gut inflammation.