Lactobacillus salivarius LS33

Lactobacillus salivarius LS33 is a probiotic strain that produces salivaricin, a bacteriocin-class antimicrobial peptide that inhibits gram-positive and gram-negative pathogens. It modulates gut microbiota composition by favorably shifting Bacteroides-Prevotella ratios, particularly in metabolically at-risk populations.

Origin & History

Lactobacillus salivarius LS33 is a probiotic strain originally isolated from the gastrointestinal tract of broiler chickens, belonging to the lactic acid bacteria family. This gram-positive, rod-shaped bacterium is typically propagated through fermentation and lyophilized into powder form for commercial applications. It produces antimicrobial compounds including bacteriocins like salivaricin and possesses genomic features for adhesion and stress tolerance.

Historical & Cultural Context

L. salivarius LS33 has no documented traditional or historical use in medicine systems. It is a modern probiotic strain first studied around 2013, primarily developed for clinical and poultry applications rather than derived from traditional fermented foods or folk remedies.

Health Benefits

• Gut microbiota modulation: Significantly increased beneficial Bacteroides-Prevotella ratios in obese adolescents (p≤0.05, moderate evidence)
• Antimicrobial activity: Produces salivaricin effective against pathogens including E. coli, Salmonella, and S. aureus (preliminary evidence)
• GI survival and colonization: Demonstrates 92.3% survival at pH 3 and 65% in bile salts with strong intestinal adhesion (in vitro evidence)
• Potential anti-inflammatory effects: Prevented colitis in mouse models with good bile and pancreatin tolerance (animal evidence only)
• Short-chain fatty acid production: Modifies fecal microbiota composition potentially increasing SCFA levels (preliminary evidence)

How It Works

Lactobacillus salivarius LS33 produces salivaricin, a ribosomally synthesized bacteriocin that disrupts pathogen cell membrane integrity by forming pores in lipid bilayers, inhibiting organisms including E. coli, Salmonella spp., and Staphylococcus aureus. The strain also competitively excludes pathogens via adhesion to intestinal epithelial mucins and modulates Toll-like receptor 2 and 4 signaling to dampen pro-inflammatory cytokine cascades. Its acid and bile tolerance allows it to survive gastric transit and colonize the distal small intestine and colon, where it selectively promotes growth of Bacteroides-Prevotella species through metabolic cross-feeding.

Scientific Research

Human clinical evidence for LS33 is limited to one double-blind RCT in 50 obese adolescents showing significant microbiota changes but no metabolic effects (NCT01020617; PMID: 23510724). Most supporting data comes from in vitro studies and mouse models, with related L. salivarius strains showing benefits for oral health (PMID: 25178882) and atopic dermatitis (PMID: 25291124).

Clinical Summary

The most cited clinical data comes from a controlled study in obese adolescents, where LS33 supplementation significantly increased Bacteroides-Prevotella ratios compared to baseline (p≤0.05); however, sample sizes in available trials are small, limiting generalizability. Antimicrobial properties of LS33-derived salivaricin have been characterized primarily in in vitro assays against E. coli, Salmonella, and S. aureus, representing preliminary rather than clinical evidence. GI survival has been confirmed in passage studies, but robust randomized controlled trials in adult or diverse populations are lacking. Overall, evidence strength is moderate for microbiota modulation and low-to-preliminary for antimicrobial and broader metabolic outcomes.

Nutritional Profile

Lactobacillus salivarius LS33 is a probiotic microorganism, not a conventional food ingredient, so macronutrient and micronutrient profiling differs from standard nutritional analysis. As a live bacterial strain, it contributes negligible caloric value (<1 kcal per typical dose). Bioactive compounds of primary significance include salivaricin — a bacteriocin-class antimicrobial peptide produced endogenously by the strain — along with exopolysaccharides (EPS) that facilitate mucosal adhesion and immune modulation. The strain produces short-chain fatty acids (SCFAs) including acetate and lactate as metabolic byproducts of carbohydrate fermentation, contributing indirectly to colonocyte energy supply. Typical therapeutic doses range from 1×10⁸ to 1×10¹⁰ CFU per serving. Notably, LS33 demonstrates exceptional acid tolerance (92.3% survival at pH 3) and moderate bile salt resistance (65% survival), which directly enhances gastrointestinal bioavailability and colonization efficacy compared to less robust probiotic strains. No significant vitamin or mineral contributions are attributed directly to this strain at standard doses.

Preparation & Dosage

No specific CFU dosage established for LS33 in human trials; the adolescent obesity study used the strain for 12 weeks without specifying dose. Related L. salivarius strains have been studied at 2.0×10^9 CFU/day in tablet form for 2 weeks. Consult a healthcare provider before starting any new supplement.

Synergy & Pairings

Lactobacillus salivarius LS33 pairs strongly with prebiotic fructooligosaccharides (FOS) or inulin (3–5g/day), which serve as selective fermentation substrates that amplify LS33 colonization and SCFA output via synbiotic interaction, further enhancing the Bacteroides-Prevotella ratio modulation already demonstrated in clinical data. Combining LS33 with Bifidobacterium longum creates complementary colonization across distinct intestinal niches — LS33 acting primarily in the small intestine and upper GI tract while B. longum dominates the colon — producing additive immune-modulatory effects through independent toll-like receptor (TLR-2 and TLR-4) signaling pathways. Additionally, pairing with zinc (8–11mg elemental zinc) and vitamin D3 (1000–2000 IU) supports the intestinal epithelial barrier integrity through tight-junction protein upregulation, creating a favorable mucosal environment that reinforces LS33 adhesion and potentiates its antimicrobial salivaricin activity against pathogens such as S. aureus and E. coli.

Safety & Interactions

Lactobacillus salivarius LS33 is generally regarded as safe for healthy adults and adolescents, with no serious adverse events reported in available studies. Individuals who are immunocompromised, have short bowel syndrome, or have central venous catheters should avoid live probiotic supplementation due to rare risk of bacteremia. No clinically significant drug interactions have been formally documented, though concurrent antibiotic use may reduce viable colony counts and diminish efficacy. Pregnancy and lactation safety has not been specifically evaluated for the LS33 strain, so consultation with a healthcare provider is advised before use in these populations.