Bifidobacterium bifidum
Bacteria › Actinomycetota › Actinomycetes › Bifidobacteriales › Bifidobacteriaceae › Bifidobacterium › Bifidobacterium bifidum
Synonyms: Actinobacterium bifidum; Actinomyces bifidus; Bacillus bifidus; Bacterium bifidum; Bacteroides bifidus; Lactobacillus bifidus type II; Nocardia bifida; Tissieria bifida
Biology & Ecology
Biology
Gram Statusgram-positive
Oxygen Toleranceobligate anaerobe
Morphologybacillus (rod)
Key Traits
- acid-producing
- short-chain fatty acid (SCFA) producer
Ecology
Primary Nichesgut
Reservoirhuman
Clinical Profile
Pathobiont
yes
no
context dependent
unknown
Clinical Rolesbiomarker organism; commensal; immunomodulator; probiotic organism
Typical Specimenstool
Risk Contextscancer patients
Clinical Associations:
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
B. bifidum was significantly enriched in stool samples of patients with non-small-cell lung cancer (NSCLC) who responded to cancer therapeutics (partial response) compared to non-responders, as determined by 16S rRNA LEfSe analysis and confirmed by quantitative PCR (P=0.0022).
PMID:
33432149
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
B. bifidum abundance remained significantly higher in NSCLC responders compared to non-responders even after excluding EGFR TKI-treated patients (P=0.0128), supporting a treatment-agnostic association between B. bifidum enrichment and therapeutic response.
PMID:
33432149
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
Oral administration of B. bifidum strains K57 and K18 in combination with anti-PD-1 antibody significantly reduced tumour burden in syngeneic MC38 colon cancer mouse models compared to anti-PD-1 alone (P<0.0001 for both strains).
PMID:
33432149
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
B. bifidum K57 combined with anti-PD-1 reduced tumour burden in orthotopic and subcutaneous Lewis lung carcinoma (LLC1) syngeneic mouse models, including in anti-PD-1-resistant settings (P=0.038 for orthotopic model).
PMID:
33432149
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
B. bifidum K57 combined with anti-PD-1 significantly reduced tumour growth in anti-PD-1-resistant 4T1 breast cancer syngeneic mouse models, whereas anti-PD-1 or B. bifidum K57 alone showed little antitumour effect (P<0.0001).
PMID:
33432149
D000082082
Immune Checkpoint Inhibitors
D047368
Tumor Burden
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
Synergistic B. bifidum strains K57 and K18 induced significantly more IFN-γ secretion from human CD8+ T cells in autologous monocyte co-culture assays compared to non-synergistic strains; IFN-γ induction was abrogated by TLR2-blocking antibody, implicating peptidoglycan-TLR2 signalling as the mechanism.
PMID:
33432149
D007371
Interferon-gamma
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
In syngeneic mouse tumour models, B. bifidum K57 combined with anti-PD-1 significantly increased intratumoral CD8+ T cell and effector CD8+ T cell populations and CD8+/Treg ratios in tumour and spleen, and elevated IFN-γ and IL-2 while reducing TNF-α and IL-10 expression in tumours.
PMID:
33432149
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
Functional metagenome profiling (HUMAnN2) of stool WGS from NSCLC patients showed that the peptidoglycan biosynthesis pathway was significantly enriched in responders with B. bifidum compared to non-responders (P=0.012), linking B. bifidum peptidoglycan capacity to therapeutic response.
PMID:
33432149
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
Serum metabolomics in B. bifidum K57-treated mice showed elevated L-tryptophan levels; in vitro L-tryptophan treatment increased IFN-γ production from activated human CD8+ T cells (P=0.0082), suggesting a tryptophan-mediated immunostimulatory mechanism.
PMID:
33432149
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
Overall serum lipid levels were lower in B. bifidum-treated syngeneic tumour mice than in anti-PD-1-alone controls, with the greatest reduction in the anti-PD-1 plus B. bifidum K57 group, consistent with a lipid-lowering effect accompanying antitumour T cell activity.
PMID:
33432149
D055442
Metabolome
E2
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
In a phase 1 FMT trial (n=10 anti-PD-1-refractory metastatic melanoma patients), B. bifidum relative abundance was lower in recipient stool post-FMT plus nivolumab versus pretreatment (ANCOM); the paper contextualizes this decrease as potentially favorable for anti-tumor immune activation, citing B. bifidum's reported role in promoting immune tolerance via induction of regulatory T cells.
PMID:
33303685
D000069467
Fecal Microbiota Transplantation
D000069196
Gastrointestinal Microbiome
D008545
Melanoma
D050378
T-Lymphocytes, Regulatory
H00038
Melanoma
E1
E3 — Strong human clinical evidence
E2 — Moderate human evidence
E1 — Limited / preliminary
In a phase 1 FMT trial (n=10 anti-PD-1-refractory metastatic melanoma patients), Bifidobacterium bifidum relative abundance was lower in recipient stool post-FMT plus nivolumab versus pretreatment (ANCOM); the paper notes that B. bifidum has been reported to promote immune tolerance via induction of regulatory T cells, framing its post-FMT decrease as potentially favorable for anti-tumor immune activation.
PMID:
33303685
D000069467
Fecal Microbiota Transplantation
D000069196
Gastrointestinal Microbiome
D008545
Melanoma
D050378
T-Lymphocytes, Regulatory
H00038
Melanoma
Last reviewed: 2026-04-02
Evidence Timeline
Related Taxa
Shared Niche = same body site
Shared Risk = same vulnerable population
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