Bifidobacterium longum
1. Identity, Taxonomy, and Classification
Bifidobacterium longum is a Gram-positive, obligately anaerobic, non-motile bacterium belonging to the phylum Actinomycetota (formerly Actinobacteria), class Actinomycetes, order Bifidobacteriales, and family Bifidobacteriaceae. Its full taxonomic lineage is: cellular organisms → Bacteria → Bacillati → Actinomycetota → Actinomycetes → Bifidobacteriales → Bifidobacteriaceae → Bifidobacterium → Bifidobacterium longum. The type strain of B. longum subsp. longum is held under culture-collection designations including ATCC 15707, DSM 20219, and JCM 1217, among others.
In 2002, three previously distinct species of Bifidobacterium — B. infantis, B. longum, and B. suis — were unified into a single species named B. longum with the biotypes infantis, longum, and suis, respectively. This unification occurred because the three species had extensive DNA similarity, including a 16S rRNA gene sequence similarity greater than 97%. Additionally, the three original species were phenotypically difficult to distinguish due to different carbohydrate fermentation patterns among strains of the same species.
B. longum strains are currently assigned to three subspecies — longum sensu stricto, infantis, and suis — and colonize adults, infants, and animals respectively. Notably, subspecies longum strains are isolated from infants as well. Strain identification is currently performed through polymerase chain reaction (PCR) on the subtly different 16S rRNA gene sequences.
The organism typically exists in a characteristic Y-shaped or "bifid" branching morphology, which gave the genus its name. When grown on general anaerobic medium, B. longum forms white, glossy colonies with a convex shape. The genus Bifidobacterium contains over 50 species of Gram-positive anaerobes isolated from host-associated environments, including the lower gastrointestinal tract of primates, other animals, and social insects.
The pangenome of B. longum is notably large and open: the B. longum pangenome contains almost 17,000 genes, with over 85% of genes found in ≤28 of 191 strains; B. longum genomes share a small core gene set of only approximately 500 genes, representing roughly 3% of the total pangenome. This genetic diversity underlies the considerable variation in functional properties observed across strains.
2. Natural Sources and Habitat
B. longum is one of the most common bifidobacteria present in the gastrointestinal tracts of both children and adults. It is non-pathogenic, is often added to food products, and its production of lactic acid is believed to prevent the growth of pathogenic organisms.
B. longum colonizes the human gastrointestinal tract, where it, along with other Bifidobacterium species, represents up to 90% of the bacteria of an infant's gastrointestinal tract. As we age, the amount of bifidobacterium, including B. longum, decreases. However, all humans are believed to have some amount of bifidobacteria in their gut, regardless of age.
Bifidobacterium longum subsp. longum represents one of the most prevalent bifidobacterial species in the infant, adult, and elderly (human) gut. A substantial number of strains have been found to be transmitted across family members, a phenomenon that was shown not to be confined to mother–infant pairs. This suggests that the ubiquitous distribution of B. longum subsp. longum across the human lifespan is at least partly due to extensive transmission between relatives.
In terms of dietary occurrence, B. longum can be obtained from dietary supplements and some fermented foods, such as kefir, sauerkraut, kimchi, buttermilk, and certain types of yogurt. Five species of Bifidobacterium have attracted attention in the dairy industry for manufacturing probiotic milk products: Bifidobacterium adolescentis, Bifidobacterium bifidum, Bifidobacterium breve, Bifidobacterium infantis, and Bifidobacterium longum. In the manufacture of fermented milks, Bif. bifidum is the species most commonly used, followed by Bif. longum and Bif. breve.
3. Common Forms and Preparations
B. longum is commercially available in several delivery formats, most commonly as a live freeze-dried preparation. Forms encountered in commerce and clinical research include:
- Freeze-dried capsules and tablets — the predominant supplement format, in which cells are lyophilized to preserve viability.
- Powder sachets — designed to be mixed into food or beverage and widely used in pediatric formulations.
- Fermented dairy products — yogurts, yogurt drinks, and non-fermented milks supplemented with specific strains; mounting clinical evidence has shown that consumption of dairy products containing BB536, including yogurts, yogurt drinks, and non-fermented milks, can improve the frequency of defecation and fecal characteristics in healthy adults with constipation.
- Microencapsulated or enteric-coated preparations — engineered to protect cells during gastric transit.
Well-characterized commercial strains include BB536 (Morinaga Milk Industry, Japan), 1714 (APC Microbiome Ireland/Alimentary Health), NCC3001 (Nestlé Research, Switzerland), 35624 (Alimentary Health/Pfizer Consumer Healthcare), R0175 (Lallemand Health Solutions), and W11, among others. Each strain is distinguished by unique genetic features and strain-specific evidence bases.
BB536 has been awarded FOSHU (Food for Specified Health Uses) status by Japan's Ministry of Health, Labour and Welfare — a status granted to food products shown in human clinical studies to demonstrate specific health benefits. Additionally, BB536 obtained GRAS (Generally Recognised As Safe) certification in the USA from the FDA.
4. Historical and Traditional Use
Bifidobacterium was first isolated in 1899 from the feces of breast-fed infants by Tissier of the Pasteur Institute. When first isolated, the organism was named Bacillus bifidus, based on its morphology, as the organism typically exists in a Y-shaped or "bifid" form. An Italian scientist also discovered a bacterium in similar conditions as described by Tissier and classified the organism as belonging to the genus Lactobacillus. Although differences existed between these two bacteria, a common name, Lactobacillus bifidus, was proposed.
The broader genus-level understanding of Bifidobacterium developed through the early twentieth century. In 1924, Orla-Jensen was responsible for a decisive shift in the direction of the history of taxonomy of lactic acid bacteria. By the mid-twentieth century, molecular methods began clarifying species boundaries. In 2002, three previously distinct species were unified into a single species named B. longum based on extensive DNA similarity.
While B. longum as a formally named species is a product of modern microbiology, the organisms it encompasses have a far longer history of indirect human use. The history of probiotics provides an explanation for why dairy products — specifically yogurt-like products — form the largest segment of the market for probiotic products. Probiotic bacteria are sold mainly in fermented foods, and dairy products play a predominant role as carriers of probiotics. Fermented milk products including yogurt and kefir have been consumed across cultures for centuries, with the empirical observation that such foods supported digestive health and general wellbeing preceding scientific characterization of the bacterial species responsible.
Bifidobacterium longum BB536 was discovered in the intestines of healthy breastfed infants in 1969. Clinical and commercial application of specific B. longum strains as intentionally added probiotics in food products and dietary supplements developed primarily in Japan and Europe from the 1970s onward, accelerating substantially with the advent of molecular strain identification techniques in the 1980s–1990s.
5. Key Constituents and Active Compounds
B. longum does not supply the body with discrete phytochemical constituents in the way botanical supplements do. Its bioactivity arises from the live bacterium itself and the metabolites it produces during colonization. The principal biologically active components and structural features are:
5.1 Short-Chain Fatty Acids (SCFAs)
In the gut, B. longum metabolizes carbohydrates to short-chain fatty acids (SCFAs), acetate and lactate. In co-culture systems, Bifidobacterium is necessary for either the establishment of a butyrate producer or for enhancing butyrate production through the metabolism of human milk oligosaccharides (HMOs) into monosaccharides and the production of acetate. This butyrogenic effect also results from cross-feeding interactions between Bifidobacteria and Clostridiales, which negatively correlate with inflammatory bowel disorders.
5.2 Carbohydrate Utilization Machinery
Up to 19 types of permease exist to transport various carbohydrates, with 13 being ATP-binding cassette transporters. B. longum has several glycosyl hydrolases to metabolize complex oligosaccharides for carbon and energy. This is necessary as mono- and disaccharides have usually been consumed by the time they reach the lower gastrointestinal tract where B. longum resides. Additionally, B. longum can uniquely ferment galactomannan-rich natural gum using glucosaminidases and alpha-mannosidases that participate in the fermentation of glucosamine and mannose, respectively.
The high number of genes associated with oligosaccharide metabolism is a result of gene duplication and horizontal gene transfer, indicating that B. longum is under selective pressure to increase its capability to compete for various substrates in the gastrointestinal tract. Many B. longum strains are enriched by host-indigestible dietary carbohydrates, also referred to as prebiotics, which include substrates such as inulin and arabinoxylan.
5.3 Cell Surface and Adhesion Structures
B. longum's colonization of the gut is attributed to glycoprotein-binding fimbriae structures and bacterial polysaccharides, the latter of which possess strong electrostatic charges that aid in the adhesion of B. longum to intestinal endothelial cells. This adhesion is also enhanced by the fatty acids in the lipoteichoic acid of the bacterium.
5.4 Exopolysaccharides, Serine Protease Inhibitors, and Other Bioactive Molecules
Research into the beneficial properties of B. longum has unveiled a range of mechanisms, including the production of bioactive molecules such as short-chain fatty acids, polysaccharides, and serine protease inhibitors.
5.5 Tryptophan Metabolites
Tryptophan metabolism is an important mediator of bifidobacterial immune modulation. Specific B. longum strains produce tryptophan-derived indole metabolites, including indole-3-lactic acid, indole-3-acetic acid, and related compounds, which interact with the aryl hydrocarbon receptor (AhR) to modulate inflammatory signaling.
6. Mechanisms of Action
6.1 Gut Barrier Reinforcement
Supplementation with B. longum resulted in a significant increase in the expression of occludin (a tight junction protein) in the intestine, indicating a modulating effect on gut barrier function. This evidence was strengthened by an increased Trans-epithelial electrical resistance (TEER) measurement during incubation of the probiotic strains on a Caco-2 cell monolayer.
6.2 SCFA-Mediated Cross-Feeding and Colonocyte Nutrition
Microbial short-chain fatty acids, including butyrate and propionate, strengthen epithelial junctions and support metabolic control. BB536 ferments complex carbohydrates into acetate and lactate, feeding other microbes like Eubacterium rectale, a key butyrate producer. This cross-feeding promotes a gut ecosystem that generates SCFAs, strengthens epithelial integrity, and nourishes colonocytes.
6.3 Immune Modulation
From its intestinal niche, B. longum can have far-reaching effects in the body, influencing immune responses in the lungs and even skin, as well as influencing brain activity. The mechanisms involve interaction with gut-associated lymphoid tissue, induction of regulatory T cells, and modulation of dendritic cell function. Certain microbes also promote regulatory T-cell activity, reinforcing immune tolerance and restraining excessive inflammation.
6.4 Gut–Brain Axis
Disruptions in gut microbiota may trigger or exacerbate symptoms of anxiety and depression by interfering with communication pathways between the gut and brain. These pathways include neural signaling through the vagus nerve, hormone regulation via the hypothalamic–pituitary–adrenal (HPA) axis, immune responses involving pro-inflammatory cytokines, and metabolic processes related to short-chain fatty acids.
6.5 Competitive Exclusion and Luminal Acidification
B. longum's production of lactic acid and acetate lowers luminal pH, creating an environment that is inhospitable to many pathogenic bacteria. Its production of lactic acid is believed to prevent the growth of pathogenic organisms.
7. Scientific Evidence by Area of Use
7.1 Gastrointestinal Function: Constipation and Bowel Regularity
Bifidobacterium is a representative microbial probiotic genus frequently used to regulate bowel movements. Multiple randomized controlled trials have shown that bifidobacteria intake increases bowel movement frequency or shortens gut transit time. However, the response to bifidobacteria supplementation varies from subject to subject, and some trials have reported that bifidobacteria supplementation alleviates IBS symptoms while others have not observed an effect.
Probiotics have historically been used in the treatment and prevention of many forms of gastrointestinal disorders, for which BB536 has long been recognized as one of the most effective probiotic strains for improvement of gastrointestinal conditions. Mounting clinical evidence has shown that consumption of dairy products containing BB536, including yogurts, yogurt drinks, and non-fermented milks, can improve the frequency of defecation and fecal characteristics in healthy adults with constipation.
A randomized double-blind placebo-controlled crossover trial was conducted in adults with constipation to determine the effect of B. longum BB536 supplementation on bowel movement frequency. Fecal microbiome and metabolome analyses were conducted during the trial to evaluate the effect of BB536 supplementation on the intestinal environment, and individual differences in response were estimated using a Bayesian statistical model.
Evidence strength: Moderate. Multiple RCTs support benefits in constipation, but responses are heterogeneous and strain-specific. Many studies are conducted with BB536 and involve small sample sizes or short durations.
7.2 Irritable Bowel Syndrome (IBS)
In patients with IBS, intestinal populations of B. longum are typically highly reduced in size, and accumulating evidence indicates that the administration of B. longum is beneficial for the treatment of IBS.
The strain B. longum 35624 has been studied in multiple clinical contexts. One study evaluated the effectiveness and tolerability of B. longum 35624 in adults (aged 18 or over) with IBS as defined by the Rome IV criteria. In an open-label, observational, post-market study conducted in Germany, adults with IBS filled out a weekly questionnaire enabling calculation of a total IBS symptom score (TISS) and the IBS severity scoring system (IBS-SSS) score. Thirty-seven patients were included. The course of B. longum 35624 was associated with a significant reduction (43.4%) in the TISS versus baseline.
A systematic review covering studies from 2000 to 2023 specifically examined B. longum 35624 in IBS patients. The final analysis included 5 studies in 796 patients with IBS carried out in France (n=2), Ireland (n=1), Great Britain (n=1), and Russia (n=1). Two studies used Rome II Diagnostic Criteria for IBS, and three studies used Rome IV.
For IBS with constipation (IBS-C), the strain B. longum W11 has been evaluated. A study evaluated the clinical efficacy of B. longum W11 in IBS-C patients, with 51 IBS patients recruited and symptom severity assessed using the IBS-SSS before and after a 3-month intervention. Both probiotic formulations significantly reduced IBS-SSS scores, particularly improving bloating, abdominal pain, and overall quality of life. The impact of treatment was independent of age, though greater improvements in bloating and life interference were observed in older IBS-C patients.
Formulations containing B. longum have also generated promising results in improving symptoms of IBS in children. A multicentre, crossover RCT reported that administration of a mixture of B. infantis M-63, B. breve M-16V, and B. longum BB536 for 6 weeks to children with IBS resulted in a complete resolution of abdominal pain in a significantly higher number of children compared with placebo (p = 0.006), and significantly improved abdominal pain frequency (p = 0.02). However, it is not known if the washout period of 2 weeks was sufficient to prevent a "carryover" effect between treatments, which can be a limitation of crossover trials.
A study of strain NCC3001 in IBS patients also demonstrated depression-related outcomes: a 6-week intervention with the B. longum strain NCC3001 significantly improved depression scores, in association with a decreased emotional reaction to fearful stimuli in non-constipated patients with IBS.
An evidence-based review covering Bifidobacterium supplementation and IBS noted, using the Strength of Recommendation Taxonomy, that a randomized, placebo-controlled study of B. longum R0175 administered orally daily for eight weeks in Canada showed improvement in the severity of symptoms in all groups, but no significant improvement in the IBS-constipation subgroup; in the IBS-diarrhea group, there was significant improvement in stool frequency.
Evidence strength: Moderate to good for certain strains (particularly 35624, NCC3001, W11). Most positive RCTs involve specific strains that cannot be generalized to all B. longum preparations. Placebo effects in IBS trials are acknowledged to be substantial.
7.3 Mental Health, Stress, and the Gut–Brain Axis (Psychobiotic Effects)
Bifidobacterium longum is among the most frequently studied probiotic strains in the context of anxiety and depression clinical trials, appearing in twelve of the studies surveyed in a comprehensive review of 2014–2023 clinical trials.
A key early clinical study involved B. longum 1714: healthy volunteers received B. longum 1714 or placebo for 4 weeks at a dose of 1 × 10⁹ CFU/day. Brain activity was measured using magnetoencephalography and health status using the 36-item short-form health survey. A total of 40 healthy volunteers completed the study. Forty-three subjects were randomized to either B. longum 1714 or placebo, with n = 20 per intervention group.
A follow-up exploratory clinical trial tested another B. longum strain for perceived psychological stress. A 6-week intervention with the B. longum strain NCC3001 significantly improved depression scores in association with a decreased emotional reaction to fearful stimuli in non-constipated patients with IBS.
However, the evidence is not uniformly positive. One week of B. longum did not significantly reduce stress, depression, or anxiety in young adults. Only one study to date had used B. longum alone with mixed results; the majority of studies utilized two or more strains of probiotic, and the singular strain examined could be considered a methodological weakness. Based on these findings, it is plausible that a synergistic effect between B. longum and other strains of mutualistic bacteria could be responsible for observed changes in overall mental and physiological health.
Animal model work has provided mechanistic insight: in a mouse model of chronic stress, the combination of B. longum R0175 and Lactobacillus R0052 significantly improved depressive behavior, reduced the level of corticosterone, and restored the intestinal barrier. The decrease in cortisol level was related to the reduction of HPA axis hyperactivity.
Evidence strength: Preliminary to moderate in humans. Mechanistic plausibility is well established through preclinical and gut–brain axis research. Human RCTs, while promising for specific strains (particularly 1714 and NCC3001), are generally small, short in duration, and heterogeneous in design. Findings should not be generalized across all B. longum strains.
7.4 Immune Health and Allergy
Superior protective effects of BB536 against allergic rhinitis have been demonstrated in an in vivo study using a mouse model of poly-sensitization to major birch and grass pollen allergens. The immunosuppressive properties of BB536 at a dose of 5 × 10⁸ CFU were compared with another probiotic strain. Treatment with both strains significantly suppressed allergen-specific immune responses. However, when applied prior to sensitization and challenge, only BB536 had a long-lasting protective effect, indicating BB536 can be applied for both prevention and treatment of allergic rhinitis. Collectively, clinical and animal study findings support prominent beneficial effects of BB536 in improving allergic conditions and immune responses.
Research suggests that taking B. longum BB536 during pollen season might reduce nasal and eye symptoms of Japanese cedar pollen allergy. However, some conflicting evidence exists, and this strain does not appear to reduce sneezing or throat symptoms associated with Japanese cedar pollen allergy.
A randomized, double-blind, placebo-controlled study investigated a Bifidobacterium mixture containing BB536 in children with seasonal allergic rhinitis and intermittent asthma. A mixture containing B. longum BB536 (3 × 10⁹ CFU), B. infantis M-63 (1 × 10⁹ CFU), and B. breve M-16V (1 × 10⁹ CFU) was evaluated in a prospective, double-blind, placebo-controlled, randomized study. Globally, 40 children were enrolled, attending the Department of Woman, Child and General and Specialized Surgery of the Second University of Naples, suffering from seasonal allergic rhinitis and well-controlled asthma.
A 2024 randomized controlled trial evaluated B. longum subsp. infantis YLGB-1496 in children over 3 months. Eligible healthy children were randomly assigned to an intervention group (n = 50) receiving the probiotic or a control group (n = 50) receiving a placebo for 3 months, with the primary outcome being morbidity of upper respiratory tract infections (URTIs). The morbidity of URTIs was significantly lower in the intervention group. Daily administration of YLGB-1496 at a dosage of 1.5 × 10¹⁰ CFU for 3 months significantly reduced episodes of cough, fever, dry stool, and eczematous changes of the skin, while beneficially modulating gut microbiome composition and immune function without any adverse effects.
Evidence strength: Moderate, particularly for BB536 in allergic rhinitis. Several RCTs show reductions in allergic symptom scores. The evidence base for respiratory infection prevention is growing but remains preliminary, with most positive findings from single strains or multi-strain combinations.
7.5 Infant and Neonatal Health
The significance of Bifidobacterium to human health can be appreciated from its early colonization of the neonatal gut, where Bifidobacterium longum represents the most abundant species. While its relative abundance declines with age, it is further reduced in several diseases.
A growing body of evidence suggests that B. longum may play a pivotal role in promoting optimal infant health. While probiotic effects are believed to be strain-specific, different strains share common mechanisms to some extent. Noteworthy correlations have been established, linking B. longum to favorable outcomes such as enhanced weight gain in infants and a decreased incidence of the serious condition necrotizing enterocolitis (NEC). The metabolites produced by B. longum have been identified as crucial mediators in the maturation of the infant immune system and as agents that impede the invasion and proliferation of potentially harmful pathogens.
B. infantis strains have specific and generalizable traits, such as HMO utilization. B. longum biotype infantis demonstrated significant growth on human milk oligosaccharides as the sole carbon source.
Evidence strength: Moderate to preliminary depending on outcome. The strongest evidence concerns gut colonization support and microbiome maturation in breast-fed infants. Evidence for NEC prevention is more robust for multi-strain combinations than for B. longum alone.
7.6 Non-alcoholic Fatty Liver Disease (NAFLD)
Animal (preclinical) research has investigated B. longum's effects on the gut–liver axis. A study evaluated the effect of B. longum on NAFLD pathology using multi-omics approaches, including human stool analysis from healthy subjects (n = 25) and NAFLD patients (n = 32). Mice were fed a normal chow diet, Western diet, or Western diet with B. longum (10⁹ CFU/g) for 8 weeks. The B. longum group showed improved liver histology and function, with improved NAFLD activity scores compared to the Western diet group. Strain treatment showed ameliorative effects on gut barrier function.
Evidence strength: Preliminary; primarily from animal and in vitro models. Human RCT data specifically for B. longum in NAFLD remain limited.
8. Body Systems and Health Areas of Association
- Gastrointestinal system: Bowel regularity, IBS symptom management, gut microbiota composition, gut barrier integrity, enterocolitis prevention in preterm neonates.
- Immune system: Modulation of innate and adaptive immunity, regulatory T-cell induction, plasmacytoid dendritic cell activation, mucosal IgA stimulation.
- Respiratory/Allergic system: Allergic rhinitis symptom reduction (particularly Japanese cedar pollen allergy with BB536), potential reduction in upper respiratory tract infection incidence.
- Central nervous system / Mental health: Gut–brain axis signaling, potential reduction in perceived psychological stress and depression scores (strain-specific; particularly 1714 and NCC3001).
- Metabolic/Hepatic system: Preliminary evidence of modulation in NAFLD pathology through gut–liver axis interactions (primarily preclinical).
- Neonatal/Pediatric health: Gut microbiome colonization and maturation in infants, HMO metabolism, support for immune development.
9. Dosage Forms and Dosages Reported in Studies
Well-characterized strains are dosed in the range of 1 × 10⁸ to 1 × 10¹¹ CFU/day, with strain-specific evidence for improving bowel function, reducing antibiotic-associated diarrhea, modulating immune responses, and exerting emerging psychobiotic effects. The following dosages were specifically reported in published research:
- B. longum 1714 (gut–brain axis study): 1 × 10⁹ CFU/day for 4 weeks in healthy volunteers.
- B. longum BB536 (immunosuppressive comparison study): 5 × 10⁸ CFU in the allergic rhinitis comparison study.
- Bifidobacteria mixture including BB536 (seasonal allergic rhinitis in children): B. longum BB536 (3 × 10⁹ CFU), B. infantis M-63 (1 × 10⁹ CFU), and B. breve M-16V (1 × 10⁹ CFU).
- B. longum subsp. infantis YLGB-1496 (pediatric RCT): 1.5 × 10¹⁰ CFU/day for 3 months.
- B. longum NAFLD mouse study: 10⁹ CFU/g for 8 weeks.
- B. longum 35624 (IBS observational study): Adults with IBS received B. longum 35624 over an 8-week course as recommended by family physicians.
- B. longum W11 (IBS-C study): IBS-C patients received B. longum W11 with symptom severity assessed before and after a 3-month intervention.
10. Safety Considerations and Interactions
10.1 General Safety Profile
Bifidobacterium species, including B. longum, have been occasionally isolated from human clinical specimens. However, such occurrences have been rare and were mainly encountered in immunocompromised patients or in those with severe underlying illnesses. The Scientific Committee concluded that most Bifidobacterium species can be considered nonpathogenic to humans and therefore pose no specific safety concerns.
Common side effects include gas and an upset stomach. Serious side effects are rare, but they may include infections in some people who are at high risk of infections.
10.2 Bacteremia and Translocation Risk
Multiple groups have reported that bacterial translocation can occur in infants and immunocompromised hosts. This bacterial translocation has the potential to cause sepsis and is one of the most serious probiotic safety concerns. Some scientists have also reported the possibility of bacteremia and endocarditis due to the administration of probiotic strains.
However, the majority of Bifidobacterium species, such as B. longum and B. pseudocatenulatum, did not display mucolytic activity, which is relevant because mucolytic capacity is associated with translocation potential.
A number of cases of B. longum infection have been reported in the scientific literature. These are primarily cases in preterm infants undergoing probiotic treatment, although there are also reports of infection in adults.
10.3 High-Risk Populations
Based on the available literature, specific clinical populations warrant particular caution:
- Severe immunocompromise (e.g., uncontrolled HIV with severe CD4 depletion, chemotherapy-induced severe neutropenia) — live probiotics should be avoided without infectious disease consultation.
- Patients with central venous catheters in critical care settings face a risk of catheter-related bacteremia.
- Short bowel syndrome or severe mucosal barrier disruption, and severe acute pancreatitis in ICU contexts, are also considered high-risk situations for live probiotic use.
10.4 Antibiotic Resistance Profile and Drug Interactions
All Bifidobacterium species in one assessed sample were susceptible to ampicillin, chloramphenicol, clindamycin, erythromycin, penicillin G, rifampicin, and vancomycin (MIC ranging from 0.01 to 4 µg/ml) and generally resistant to aminoglycoside antibiotics such as gentamicin, kanamycin, neomycin, and streptomycin (MIC >32 µg/ml).
Antibiotics may reduce probiotic viability. When B. longum is taken alongside antibiotics, timing of administration should be considered to reduce the extent of antibiotic-mediated killing of the probiotic organism, though the evidence base for specific timing recommendations remains limited.
10.5 Infant Safety Data
Regarding the safety of B. longum in infants, several studies have reported adverse effects in clinical trials, including gastrointestinal disorders, feeding intolerance, diarrhea, fever, and respiratory symptoms. However, due to the relatively limited sample size, it remains unclear whether these adverse effects can be conclusively attributed to B. longum supplementation.
10.6 Regulatory Status
The Food and Drug Administration (FDA) has not reviewed B. longum for safety and effectiveness, and it is not approved by the FDA as a drug. Several strains, including BB536, have received FDA GRAS (Generally Recognized As Safe) determinations for use in food. The FDA evaluates probiotics case-by-case. Many probiotic products are marketed as dietary supplements under DSHEA. Some strains or uses that would involve therapeutic claims for disease treatment would require drug approval. Some strains have GRAS determinations for use in foods.
References
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