Lactobacillus salivarius is a species of beneficial bacteria classified within the lactic acid bacteria group, widely recognized for its probiotic properties. This natural inhabitant of the human body contributes to maintaining a balanced microbial environment in the areas it colonizes. Though historically known as Lactobacillus salivarius, in 2020 it was reclassified into the new genus Ligilactobacillus, though many commercial products and scientific literature still use the original name.
Biological Identity and Primary Habitats
This Gram-positive bacterium exhibits robust tolerance to the harsh conditions of the upper gastrointestinal tract, including resistance to stomach acid and bile salts, which is necessary for transit to the lower gut. It achieves its beneficial effects primarily through the production of antimicrobial compounds, such as organic acids like lactic and acetic acids, which lower the local pH. L. salivarius also secretes bacteriocins, which are potent, narrow-spectrum antibiotics that selectively inhibit the growth of competing bacteria.
Its ability to adhere to mucosal surfaces, such as the lining of the digestive tract, allows it to establish stable colonies and compete effectively with less beneficial microbes. The primary habitats for this bacterium are the oral cavity, where its species name originates from saliva, and the entire gastrointestinal tract, from the small intestine to the colon.
Specific Contribution to Oral Health
The high concentration of L. salivarius in saliva and on the tongue makes it an important regulator of the oral microbiome. It helps maintain a balanced environment by actively inhibiting pathogenic species linked to common dental issues. Strains of L. salivarius have been shown to antagonize Streptococcus mutans, the primary bacterium responsible for dental caries, by competing for adhesion sites and utilizing its antimicrobial arsenal.
Beyond cavity prevention, L. salivarius plays a role in managing periodontal health by targeting bacteria implicated in gingivitis and periodontitis. It suppresses the growth of specific pathogens, including Porphyromonas gingivalis and Prevotella intermedia, which are major contributors to gum disease. This action results in measurable improvements, such as reduced plaque accumulation and decreased bleeding on probing in clinical studies. The strain also aids in neutralizing volatile sulfur compounds (VSCs), which are gases produced by certain oral bacteria and are the cause of chronic halitosis.
Supporting Digestive and Immune Function
Once L. salivarius successfully navigates the upper digestive tract, it contributes significantly to intestinal homeostasis. In the gut, the bacterium supports the structural integrity of the intestinal lining by promoting the expression of tight junction proteins, such as occludin and claudin-1. These proteins form the physical barrier that separates the gut contents from the rest of the body. This barrier function is necessary for optimal nutrient absorption and prevents the translocation of unwanted substances.
The organism also interacts directly with the gut-associated lymphoid tissue, which houses a large portion of the body’s immune cells. Certain strains modulate immune responses by influencing the production of signaling molecules called cytokines. For example, L. salivarius can help reduce levels of pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and tumor necrosis factor-alpha (TNF-α), while promoting anti-inflammatory activity. This immunomodulatory function contributes to easing symptoms associated with certain gastrointestinal disorders, including abdominal pain and bloating experienced by individuals with irritable bowel syndrome.
Sources and Supplementation Considerations
While L. salivarius is a natural part of the human microbiota, consuming specific strains through diet or supplements is the most reliable way to ensure consistent intake. Some fermented foods, such as yogurt or kefir, may contain the species, but commercial supplements are formulated to deliver specific, high-colony counts of designated strains. The effectiveness of a probiotic is highly dependent on the particular strain used, meaning not all L. salivarius products will yield the same results.
When selecting a supplement, look for products that clearly list the strain designation, such as L. salivarius UCC118, which has been extensively characterized in scientific literature. The supplement should also specify the dosage in Colony Forming Units (CFUs) to ensure a sufficient number of live organisms are delivered. Due to the organism’s sensitivity to antibiotics, individuals taking these medications should take their L. salivarius supplement at least two hours before or after the antibiotic to maximize viability.