Lactobacillus pentosus

Lactobacillus pentosus (Lactiplantibacillus pentosus)

Identity, Nomenclature, and Taxonomy

Current accepted name: Lactiplantibacillus pentosus (Zanoni et al. 1987 ex Fred et al. 1921) Zheng et al. 2020. Former name: Lactobacillus pentosus (Fred, Peterson, and Anderson) Zanoni, Farrow, Phillips and Collins 1987. The older binomial Lactobacillus pentosus remains the designation most commonly encountered in the dietary supplement and clinical research literature, and both names refer to the same organism.

The name Lactobacillus pentosus is listed as a synonym in the current nomenclature, with the accepted correct name now being Lactiplantibacillus pentosus. The formal reclassification was published by Zheng et al. in the International Journal of Systematic and Evolutionary Microbiology in 2020 (70:2782–2858), which described 23 novel genera and emended the description of the genus Lactobacillus Beijerinck 1901.

The organism is classified within the phylum Bacillota (Firmicutes), class Bacilli, order Lactobacillales, family Lactobacillaceae, genus Lactobacillus (Group B lactobacilli, facultatively heterofermentative, unique phylogenetic group). Morphologically, cells are Gram-positive, straight rods measuring 1–1.2 × 2–5 µm with rounded ends, occurring singly, in pairs, or in short chains.

Lactobacilli are Gram-positive, non-spore-forming rods or coccobacilli, catalase-negative (although some strains possess a pseudocatalase), aerotolerant or anaerobic, aciduric or acidophilic, and nutritionally fastidious.

The species name pentosus derives from the Latin pentosus, meaning "of pentose," reflecting the organism's capacity to ferment pentose sugars — a key biochemical characteristic. L. pentosus shows very high 16S rRNA sequence similarity (99.7–99.9%) with Lactobacillus plantarum and Lactobacillus paraplantarum, making differentiation difficult by standard methods. For reliable species-level identification, a multiplex PCR assay using recA gene-derived primers has been developed.

The chromosomal genome of representative strain L. pentosus LPG1 has a size of 3,619,252 bp with a GC content of 46.34%, two plasmids, and a total of 3,345 coding genes and 89 non-coding sequences. The genome of L. pentosus MP-10 is currently considered the largest genome among lactobacilli, highlighting the microorganism's ecological flexibility and adaptability.

Natural Sources and Ecological Niches

Lactobacilli have been isolated from different sources including plants, foods, and the mucosal surfaces (oral, gastrointestinal, and reproductive tracts) of mammalian hosts. Within this broad group, L. pentosus occupies several well-defined ecological niches.

Fermented vegetables and olives: The Lactobacillus pentosus species is the main inhabitant in the economically important Spanish-style green olive fermentation process. This lactic acid bacterium contributes to the preservation of olives by producing large amounts of lactic acid as well as antibacterial compounds such as bacteriocins. Spanish-style green olive fermentation usually relies on a spontaneous, traditional method in which both the olives and the environment are handled to favor the development of L. pentosus.

Other fermented foods: L. pentosus strains are lactic acid bacteria commonly found in various fermented olives from the Mediterranean region, with several strains exhibiting probiotic characteristics. Beyond olives, the species has been isolated from a variety of traditional fermented foods across cultures. Pineapple tepache, a traditional Mexican fermented beverage, was used for isolation of lactic acid bacteria with probiotic potential, with one isolate identified as L. pentosus ABHEAU-05. Lactiplantibacillus pentosus is reported to be present in fermented olives and other fermented foods and significantly influences human health; a strain has been isolated from traditional fermented rice and shown to have an assortment of beneficial attributes. Lactobacillus pentosus strain b240 (b240) is an anaerobic, non-sporulating, Gram-positive bacterium originally isolated from fermented tea leaves.

Fermented meat: L. pentosus strains have also been isolated from fermented sausages. L. pentosus L33, isolated from fermented sausages, contains an exopolysaccharide (EPS) biosynthesis cluster and does not carry transferable antibiotic resistance genes; KEGG pathway analyses showed it possesses biosynthetic pathways for seven amino acids and can degrade a wide array of carbohydrates.

Fermented dairy and sourdough: Some strains initially classified as L. plantarum may actually belong to L. pentosus or L. paraplantarum, since both phenotypic determination tools and 16S rRNA gene sequence analysis cannot reliably distinguish among members of the L. plantarum group.

Human microbiome: L. pentosus is also found as a component of normal human intestinal, vaginal, and oral microbiota, consistent with the broader ecology of lactobacilli. Lactic acid bacteria derived from plants have attracted research attention; Lactobacillus pentosus strain S-PT84, isolated from Kyoto pickles, was identified among 16 LAB of plant origin as the strongest interleukin (IL)-12-inducing strain.

Traditional and Historical Use

Lactobacillus pentosus has a long history of use in cooked and uncooked fermented foods. Unlike many botanical supplements with documented ethnomedical records, L. pentosus does not appear in classical pharmacopeias as a discrete therapeutic agent. Its traditional relevance is inseparable from the fermented foods in which it occurs naturally.

Mediterranean fermented olives: The spontaneous lactic acid fermentation of olives is an ancient practice in Mediterranean cultures, where table olives have been produced using traditional methods for millennia. Spanish-style green olive fermentation relies on a spontaneous, traditional method in which both the olives and the environment are managed to favor L. pentosus; as the use of starter cultures was not historically common, the fermentation was driven by indigenous microflora.

Japanese fermented pickles (tsukemono): The strain S-PT84 was isolated from Kyoto-style pickles — a traditional Japanese fermented vegetable preparation — illustrating the occurrence of L. pentosus in East Asian fermented vegetable traditions. Kyoto pickles have been produced in Japan for centuries as both a food preservation technique and a dietary staple.

Japanese fermented tea (batabata-cha): Strain b240 was originally isolated from fermented tea leaves, consistent with traditional post-fermented tea preparations such as batabata-cha, a centuries-old fermented tea consumed in the Toyama region of Japan.

Mesoamerican traditional beverages: L. pentosus has been isolated from pineapple tepache, a pre-Hispanic fermented beverage with roots in indigenous Mexican cultures, demonstrating the species' presence in traditional fermented beverages of the Americas.

Numerous ethnic groups around the world have a history of integrating fermented foods into their religious and cultural customs; probiotic bacteria that can generate organic acids, ethanol, and antibiotic compounds are often present in such foods.

It is important to note that the specific attribution of health effects to L. pentosus as a discrete entity within traditional fermented food practices is a modern scientific framing; traditional users consumed the whole fermented food product, not isolated bacterial strains.

Key Constituents and Active Compounds

L. pentosus is a living microorganism rather than a plant-derived extract, and its bioactive "compounds" are the metabolites it produces, structural cell components, and functional genomic elements.

Lactic Acid and Organic Acids

The antimicrobial function of lactic acid bacteria is largely attributed to the synthesis of organic acids such as lactic acid and phenyllactic acid. These lower environmental pH, creating conditions hostile to pathogens. This lactic acid bacterium contributes to the preservation of olives by means of the large amounts of lactic acid produced, as well as by producing antibacterial compounds such as bacteriocins.

Bacteriocins — Pentocins

Pentocin is a novel bacteriocin produced by L. pentosus with high antibacterial activity, but sensitive to proteolytic enzymes. Multiple structurally distinct pentocins have been characterized from different strains. Pentocin ZFM94, produced by L. pentosus ZFM94 and isolated from infant feces, was purified and characterized; the molecular mass of the purified bacteriocin was 3,547.74 Da. It exhibited broad-spectrum antimicrobial activity against tested Gram-positive and Gram-negative bacteria, with minimal inhibitory concentrations (MICs) against Micrococcus luteus, Staphylococcus aureus, and Escherichia coli of 1.75, 2.00, and 2.50 µM, respectively.

Lacidophilin

A bacteriocin-like substance designated lacidophilin has been characterized from L. pentosus; its thermal stability and sensitivity to trypsin were evaluated, and the best antibacterial ability was obtained under acidic conditions. Lacidophilin destroys the cytomembrane of bacteria and increases cytomembrane permeability, resulting in the leakage of proteins, nucleic acids, and electrolytes.

Exopolysaccharides (EPS)

Genes coding for proteins involved in cell recognition and adhesion to intestinal mucosae, including genes for exopolysaccharide biosynthesis proteins, have been identified in the L. pentosus genome. Exopolysaccharides play a key role in the dynamic interaction of bacteria with their environment; EPS can be found loosely attached to the cell surface or excreted in the growth medium, with production yields fluctuating based on growth conditions.

Immunomodulatory Cell Wall Components

Cell wall components, including lipoteichoic acid and peptidoglycan fragments, are important structural elements of L. pentosus that interact with host pattern-recognition receptors. The essential role of Toll-like receptors for dendritic cell and NK1.1⁺ cell-dependent activation of type 1 immunity by Lactobacillus pentosus strain S-PT84 has been demonstrated.

Genomic Functional Features

The probiotic potential of L. pentosus has been further demonstrated by the presence of genes coding for proteins involved in adhesion, exopolysaccharide biosynthesis, tolerance to low pH and bile salts, immunomodulation, and vitamin and enzyme production. L. pentosus possesses biosynthetic pathways for seven amino acids and is capable of degrading a wide array of carbohydrates.

Mechanisms of Action

Antimicrobial Activity

Lactic acid bacteria exhibit antimicrobial activity through various mechanisms such as competition with pathogens for food, attachment to intestinal epithelial cells, and the production of antimicrobial compounds. The mechanism of antimicrobial activity of lactic acid bacteria differs between Gram-negative and Gram-positive bacteria, involving the production of hydrogen peroxide, carbon dioxide, and organic acids for inhibiting Gram-negative bacteria, and bacteriocin for destroying Gram-positive bacteria.

The antibacterial mechanism of pentocin against Bacillus cereus focused on cytomembrane destruction, disruption of biofilm formation, and inhibition of DNA replication and protein synthesis. Earlier studies indicated that L. pentosus pentocin exhibited strong antibacterial activity against Listeria monocytogenes. Pentocin JL-1 produced by L. pentosus JL-1 had a significant antibacterial effect on drug-resistant Staphylococcus aureus, with cell membranes regarded as the targets.

Immunomodulation

L. pentosus has been shown to have a beneficial function in regulating the host's immune system and plays an indispensable role in intestinal health. Several distinct immunological mechanisms have been identified across different strains:

• IL-10 induction and regulatory T cells: An in vitro screening system identified Lactobacillus pentosus KF340 (LP340) as an immunoregulatory bacterium present in various fermented foods; LP340 induced a regulatory phenotype in mouse antigen-presenting cells which, in turn, induced IL-10 and IFN-γ-producing Type 1 regulatory T cells (Tr1 cells) from naïve CD4⁺ T cells.
• Th1/Th2 balance modulation: Strain S-PT84, isolated from Kyoto pickles, was identified among 16 LAB of plant origin as the strongest interleukin (IL)-12-inducing strain. Studies have reported that the intervention of L. pentosus S-PT84 can modulate T-helper (Th)1/Th2 balance through regulatory T cells and can effectively promote type 1 immunity by activating dendritic cells and natural killer cells.
• NK cell activation: The L. pentosus strain S-PT84 activates helper T cells and natural killer/natural killer T cells.
• Mucosal IgA enhancement: Oral administration of strain b240 to mice resulted in increased synthesis of IgA from mucosal tissue and increased serum IgG levels.

Gut Barrier and Microbiota Modulation

Probiotics mediate their effects by reshaping the structure of the intestinal flora, promoting the metabolic activities of beneficial flora, and improving intestinal immune activity. A comparative genomic investigation of L. pentosus and L. plantarum revealed that L. pentosus possesses similar probiotic traits, such as the production of antimicrobial compounds, stress response genes, and genes involved in adhesion to the intestinal mucosa, and supports the maintenance of a healthy gut.

Anti-Helicobacter pylori Activity

The probiotic Lactiplantibacillus pentosus SLC13 has been shown to inhibit H. pylori. All three tested lactobacilli strains, including SLC13, were tolerant to simulated gastrointestinal conditions; SLC13 showed the highest adhesion ability to gastric cell lines compared to reference strains L. gasseri BCRC 14619T and L. rhamnosus LGG. The inhibitory activity is thought to be mediated through lactic acid production and urease inhibition.

Scientific Evidence by Area of Use

1. Mucosal Immunity and Respiratory Infection Prevention

This is the area with the most substantial human clinical evidence for L. pentosus.

Salivary SIgA enhancement (elderly): A randomized, placebo-controlled, double-blind trial enrolled 80 healthy elderly individuals randomly allocated to an intervention group receiving a beverage containing heat-killed b240 at 4 × 10⁹ cells once daily for 12 weeks, or a placebo beverage. The mean salivary SIgA secretion rate in the b240 group steadily increased until week 4 (exhibiting a 20% elevation relative to that at week 0) and then remained stable until week 12; changes in SIgA secretion rate were significantly greater in the b240 group than in the placebo group. Oral intake of L. pentosus strain b240 for 12 weeks significantly accelerated salivary SIgA secretion, indicating its potential utility in the improvement of mucosal immunity and resistance against infection in the elderly.

Common cold incidence (elderly, RCT): A randomized, double-blind, placebo-controlled trial with parallel three-group comparison enrolled 300 eligible elderly adults, randomly allocated to a placebo group, a low-dose b240 group (tablets containing 2 × 10⁹ cells of heat-killed b240 once daily), or a high-dose b240 group (2 × 10¹⁰ cells once daily); each group consumed tablets for 20 weeks. Oral intake of heat-killed b240 significantly dose-dependently reduced the incidence of the common cold in elderly adults; the accumulated incidence rate at week 20 was 29.0% and 34.8% for the high-dose and low-dose groups, respectively, while that for the placebo group was 47.3%. There was no apparent pattern in adverse health events during the intervention period among the placebo and b240 groups, and no differing change in any blood variables from pre- to post-intervention.

SIgA with exercise (low-fitness elderly, RCT): A randomized, double-blind, placebo-controlled trial evaluated the combined effects of strain b240 intake and appropriate physical training on salivary SIgA secretion in elderly adults with low physical fitness (daily step count below 3,500 steps), who were divided into a b240-plus-exercise group and a placebo-plus-exercise group for 12 weeks. Subjects in the b240 group took 125 mL of lactobacillus beverage containing heat-killed b240 (2 × 10⁹ cells) in sterile water every morning after breakfast for 12 weeks. Secretory immunoglobulin A secretion in 57 subjects was significantly greater in the b240 group than in the placebo group.

Evidence strength: Moderate. Multiple small-to-medium sized RCTs using the heat-killed b240 strain in elderly populations consistently show enhanced salivary SIgA and reduced cold incidence. Limitations include that all pivotal trials used a single strain (b240), mostly in elderly Japanese subjects, and cannot be generalized to other strains or populations without further study.

2. Natural Killer (NK) Cell Activity Enhancement

The effect on human NK activity of supplementation with a combination of strain S-PT84 and vitamin B mixture (VBM: vitamins B1, B2, and B6) was investigated in randomized, placebo-controlled, double-blind, parallel-group studies; in the first study, healthy middle-aged (30–69 year-old) subjects with low NK activity received a combination of S-PT84 (1.5 × 10⁹ cells) and VBM or placebo for 4 weeks with a 4-week follow-up, and in the second study, healthy middle-aged (40–69 year-old) subjects received the same combination or placebo for 12 weeks. After 12 weeks of dosing, the increases in NK activity in the S-PT84-VBM-treated group were significantly larger than those in the placebo group; the supplementation with the combination of S-PT84 and VBM was confirmed to be efficacious in providing elevated levels of NK activity. These results suggest that daily supplementation with 1.5 × 10⁹ cells of S-PT84 and VBM enhances NK activity in humans, even during long-term (12-week) administration.

Evidence strength: Preliminary. These human studies used S-PT84 in combination with a vitamin B mixture, making it impossible to attribute the NK activity effect solely to L. pentosus. Sample sizes and populations are not described in detail in available source extracts. Mechanistic data exist in animal/in vitro models but direct human data are limited.

3. Atopic Dermatitis (AD)

Preclinical (mouse): Oral administration of LP340 in mice with atopic dermatitis reduced cellular infiltration in affected ear lobes and serum IgE levels, thus ameliorating disease symptoms; this suggests a systemic immunoregulatory effect mediated through LP340.

Human RCT: A clinical trial investigated the clinical and immunological effects of L. pentosus in children with mild-to-moderate AD; children aged 2–13 years with AD were randomized to receive either 1.0 × 10¹⁰ colony-forming units of L. pentosus or placebo daily for 12 weeks, with evaluation of AD severity (SCORAD), transepidermal water loss, blood eosinophil counts, serum total IgE, cytokine levels, and gut microbiota. Eighty-two children were recruited, and 41 were assigned to the probiotics intervention group; mean SCORAD indices at baseline were 30.4 and 34.3 for the probiotics and placebo groups, respectively. Overall, improved symptoms were observed in both groups, and no additional effect of L. pentosus was found in AD overall; however, the mean subjective SCORAD scores for the probiotics group were significantly improved compared with the placebo group in allergen-sensitized AD specifically.

Evidence strength: Mixed/weak. The pediatric RCT showed benefit only in the allergen-sensitized subgroup, not in the overall AD population. The overall primary outcome was negative. Animal and in vitro mechanistic studies show a plausible immune-regulatory mechanism, but human evidence remains limited and strain-specific.

4. Gut Health and Inflammatory Bowel Disease

Preclinical (murine colitis model): A study investigated the mechanism by which L. pentosus relieves dextran sulfate sodium (DSS)-induced ulcerative colitis; 24 mice were randomly divided into three groups receiving either a basic diet, drinking water with 2.5% DSS (DSS group), or drinking water with 2.5% DSS and intragastric administration of L. pentosus (DSS + L. pentosus group). The study found that L. pentosus increased the abundance of Akkermansia — a genus associated with gut mucosal health — and favorably modified the serum metabolome. This is preclinical evidence only.

Evidence strength: Preclinical only. No human RCT data for IBD are available. Murine data are hypothesis-generating.

5. Anti-Helicobacter pylori Activity

The anti-H. pylori activity of L. pentosus SLC13 was evaluated and compared to L. gasseri BCRC 14619T and L. rhamnosus LGG using phenotypic assays including growth curve, cell adhesion, and cytotoxicity; anti-H. pylori activity was determined by disk diffusion and co-culture assay. A separate strain, LPS16, produces lactic acid inhibitory to multidrug-resistant H. pylori. All three lactobacilli strains were tolerant to simulated gastrointestinal conditions; SLC13 showed the highest adhesion ability to gastric cell lines.

Evidence strength: Preclinical/in vitro only. Evidence is currently limited to in vitro and cell adhesion assays. No human clinical trials assessing L. pentosus-specific anti-H. pylori outcomes have been published to date in the sources reviewed.

6. Metabolic and Hepatic Effects

Preclinical (mouse): Intestinal mucosal barrier dysfunction is closely related to the pathogenesis of nonalcoholic steatohepatitis (NASH); in a mouse study, C57BL/6 mice were fed a normal chow or a high-cholesterol/high-fat diet with or without 1 × 10¹⁰ S-PT84 for 22 weeks. S-PT84 administration improved hepatic steatosis, decreasing triglyceride and free fatty acid levels by 34% and 37%, respectively.

Evidence strength: Preclinical only. Animal data are promising but no human clinical data on metabolic endpoints are available from the sources reviewed.

7. Allergy and Food Allergy

Preclinical (egg allergy model, mouse): Studies indicate that L. pentosus S-PT84 can modulate Th1/Th2 balance through regulatory T cells; in a murine model, mice sensitized with ovalbumin (OVA) were administered three different doses of L. pentosus S-PT84 via pelleted diet. The high-dose group (0.6% L. pentosus S-PT84 in pelleted diet) significantly reduced clinical allergenic symptoms and reduced histamine and mast cell protease levels in serum. However, L. pentosus S-PT84 did not affect OVA-specific IgE or IgG concentrations, but led to lower total IgE and total IgG titers, suggesting the therapeutic effect may be due to development of immune tolerance.

Evidence strength: Preclinical only for food allergy endpoints. Human evidence (from the AD trial above) is mixed.

8. Vaginal Health and Bacterial Vaginosis

Multiple studies have shown significant improvements in treating vaginal infections with probiotics versus traditional antibiotic treatments, but few strains have been clinically proven effective, and no study had previously determined the impact of a single Lactobacillus strain on both the vaginal and gut microbiome simultaneously. A study examined the effects of 14 days of oral feeding of L. pentosus KCA1 on vaginal and gut microbiota compositions of women diagnosed with bacterial vaginosis (BV), and measured the levels of pro-inflammatory cytokines IL-1β and IL-6 before and after consumption.

Several L. pentosus strains, including MP-10, have exhibited probiotic capacities when tested in vitro, including good growth and survival under simulated gastrointestinal conditions, ability to auto-aggregate and co-aggregate with pathogenic bacteria, and adherence to intestinal and vaginal cell lines.

Evidence strength: Preliminary/in vitro-predominant. Vaginal adhesion and antagonism against vaginal pathogens have been demonstrated in vitro. A preliminary human study (posted as a preprint on medRxiv) exists for KCA1 in BV, but robust peer-reviewed RCT data are not yet available in the reviewed sources.

Body Systems Associated with Lactobacillus pentosus

• Gastrointestinal system: Gut microbiota modulation, mucosal barrier integrity, potential inhibition of H. pylori, and lactic acid-mediated preservation of the intestinal environment.
• Immune system: Modulation of mucosal IgA, NK cell activity, Th1/Th2 balance, dendritic cell activation, regulatory T cell induction, and cytokine regulation (particularly IL-10 and IL-12).
• Skin: Clinical and preclinical investigation in atopic dermatitis, via gut-skin immune axis modulation.
• Respiratory tract: Reduction in common cold incidence in elderly, linked to enhanced mucosal SIgA secretion.
• Urogenital tract: In vitro and preliminary human data for vaginal pathogen antagonism and bacterial vaginosis.
• Metabolic/hepatic: Preclinical data in murine NASH and metabolic disorder models.

Dosage Forms and Dosages Reported in Studies

L. pentosus is administered in several formulations across research studies. Dosages are highly strain-specific. The following are reported in reviewed clinical and preclinical studies only:

• Heat-killed b240 (beverage, 4 × 10⁹ cells/day, 12 weeks): Used in a 12-week RCT in 80 healthy elderly individuals; delivered as a 125 mL sterile water beverage containing heat-killed b240 at 4 × 10⁹ cells, consumed once daily.
• Heat-killed b240 (beverage, 2 × 10⁹ cells/day, 12 weeks): Used in an exercise-plus-probiotic RCT; delivered as 125 mL of lactobacillus beverage (heat-killed b240, 2 × 10⁹ cells in sterile water) taken every morning after breakfast for 12 weeks.
• Heat-killed b240 (tablet, low dose: 2 × 10⁹ cells/day; high dose: 2 × 10¹⁰ cells/day, 20 weeks): In a 300-subject RCT, the low-dose group received tablets containing 2 × 10⁹ cells once daily and the high-dose group received 2 × 10¹⁰ cells once daily, each for 20 weeks.
• S-PT84 (1.5 × 10⁹ cells/day combined with vitamin B mixture, 4–12 weeks): Used in two randomized, placebo-controlled, double-blind studies; the first used 4 weeks of supplementation with a 4-week follow-up, and the second used 12 weeks.
• Live L. pentosus (1.0 × 10¹⁰ CFU/day, 12 weeks, children with AD): Children aged 2–13 years were randomized to receive 1.0 × 10¹⁰ colony-forming units of L. pentosus or placebo, daily, for 12 weeks.

Probiotic formulations of L. pentosus appear in the literature in both live (viable) and heat-killed (non-viable) preparations, with meaningful clinical data for both. Delivery vehicles reported in studies include beverages, tablets, and capsules.

Safety Considerations

Regulatory Status

The FDA and European Food Safety Authority certify some Lactobacillus species as Generally Recognized As Safe (GRAS) or having a Qualified Presumption of Safety (QPS), respectively. The risk classification for L. pentosus (now Lactiplantibacillus pentosus) under Canadian biosafety regulations is Risk Group 1, with no designation as a security-sensitive biological agent and no designation as a terrestrial animal pathogen under Canadian Food Inspection Agency authority.

Formal Toxicology Studies

Viable and heat-killed nonviable preparations of L. pentosus strain b240 were evaluated for short-term and subchronic toxicity and genotoxic potential; acute oral toxicity tests with viable b240 gave an LD₅₀ > 2500 mg/kg, and with nonviable b240 an LD₅₀ > 2000 mg/kg. In the short-term study, rats received 2500 mg/kg/day (approximately 1.7 × 10¹¹ CFU/kg/day) of viable b240 for 28 days; in the subchronic study, rats received 500, 1000, or 2000 mg/kg/day of nonviable b240 for 91 days followed by a 28-day recovery. No mortalities occurred, and no treatment-related effects were identified for general condition, body weight, food/water consumption, ophthalmology, urinalysis, hematology, blood chemistry, organ weights, histopathology, or gross pathology. The no-observed-adverse-effect level (NOAEL) for nonviable b240 was 2000 mg/kg/day, the highest dose tested.

Nonviable b240 (≤ 5000 µg/plate) was not mutagenic in Salmonella typhimurium or Escherichia coli tester strains, nor did nonviable b240 orally administered to rats at levels ≤ 2000 mg/kg/day for two days induce a clastogenic response.

Clinical Safety Observations

In the 20-week common cold RCT in elderly adults, there was no apparent pattern in adverse health events during the intervention period among the placebo and b240 groups, and no differing change in any blood variables from pre- to post-intervention. In the 12-week SIgA RCT in 80 elderly individuals, the treatment groups exhibited no significant differences in adverse events.

Genomic Safety Assessments

The safety of L. pentosus CF2-10N was shown by the absence of virulence determinants and the determination of acquired antibiotic resistance genes; the resistome is mostly represented by efflux-pump resistance genes responsible for intrinsic resistance. Whole-genome analysis of Lactiplantibacillus pentosus TBRC 20328 confirmed the absence of virulence and antimicrobial resistance genes, supporting its safety for food applications. Bioinformatic analyses revealed L. pentosus MP-10 to be absent of acquired antibiotic resistance genes, with most resistance genes related to efflux mechanisms and no virulence determinants found in the genome, suggesting that L. pentosus MP-10 could be considered safe and with high-adaptation potential.

Strain Specificity

Lactobacillus strains are specific in their action, and data from one strain should not be used to infer that another untested strain will provide the same benefit. This principle applies with equal force to safety and efficacy: all available clinical safety and toxicology data pertain to specific strains (primarily b240 and S-PT84) and cannot automatically be generalized to other L. pentosus strains used in commercial preparations.

Absence of Data in Specific Populations

Available clinical data are concentrated in elderly adults and children with atopic dermatitis. Formal safety evaluation in pregnant women, immunocompromised individuals, and neonates has not been described in the sources reviewed.

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