This systematic review evaluated whether Eubacterium saphenum is associated with periodontitis and whether its detection or relative abundance increases with disease severity. The review followed PRISMA 2020 and was registered in PROSPERO (CRD420251273182). Eight observational studies (304 healthy controls versus 510 periodontitis cases) from Asia, Europe, and the Americas met inclusion criteria. Across multiple detection platforms, E. saphenum was more frequently detected and/or had higher relative abundance in periodontitis than in periodontal health, with enrichment often observed in advanced disease (stages III–IV). Certainty of evidence was rated low due to observational, predominantly cross-sectional designs, methodological heterogeneity, and lack of temporality. The review concludes a low-certainty directional association and calls for longitudinal, interventional, and mechanistic studies to determine temporality and functional contribution.
Periodontitis is initiated by a polymicrobial biofilm but disease progression reflects a dysregulated host response influenced by genetic and environmental factors. Classical periodontal pathobionts (for example, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Filifactor alocis) do not fully explain inter-individual differences in severity or progression. Contemporary models emphasize polymicrobial synergy and dysbiosis, motivating evaluation of non-classical taxa that may mark severity or contribute to dysbiotic communities.
Eubacterium saphenum is a Gram-positive obligate anaerobe originally isolated from human periodontal pockets. Its ecology—preference for low-redox, anaerobic environments and association with asaccharolytic and proteolytic communities—makes its enrichment in advanced pockets biologically plausible. Molecular diagnostics have increasingly detected E. saphenum, and recent reports suggested enrichment in periodontitis, particularly in advanced stages. The available evidence is fragmented across populations, sample types, periodontal diagnostic criteria, and detection platforms, prompting this systematic appraisal.
Is Eubacterium saphenum associated with periodontitis compared with periodontal health, and does its abundance increase with disease severity?
The review was conducted per PRISMA 2020 and prospectively registered in PROSPERO (CRD420251273182). The PECO framework specified systemically healthy adults (population), periodontitis (exposure) versus periodontal health (comparator), and detection, prevalence or relative abundance of E. saphenum in subgingival biofilm and/or saliva (outcome). Eligible designs were observational clinical studies (cross-sectional and case–control) reporting original in vivo data with laboratory confirmation of E. saphenum. Exclusions included non-human studies, lack of a healthy comparator, unclear periodontitis definitions, case reports/series, reviews, in vitro work, or outcomes unrelated to E. saphenum and periodontitis.
A comprehensive search of PubMed/MEDLINE, Scopus, Web of Science Core Collection, the Cochrane Library, and Google Scholar was undertaken between June and September 2025 with no publication date limits. For Google Scholar, the first 200 references were screened. Search terms combined Eubacterium saphenum synonyms with periodontitis/periodontal disease. Records were exported and de-duplicated using Zotero and Rayyan following a hierarchical protocol (DOI/PMID match, normalized title/author/year, then title/abstract screening). After screening and eligibility assessment, eight articles were included; the selection process is summarised in a PRISMA flow diagram.
Data extraction was performed independently and in duplicate, capturing authorship, year, location, study design, periodontal diagnostic criteria, sample size, sample type (subgingival biofilm and/or saliva), detection methods, association with severity, quantitative/statistical findings, and main findings. Study quality and reporting transparency were appraised using the AXIS tool. Certainty of the cumulative evidence was assessed using the GRADE framework.
Eight observational studies from Asia, Europe, and the Americas met inclusion criteria, totalling 304 periodontal health controls and 510 periodontitis cases. Detection approaches included PCR-based assays and high-throughput sequencing platforms. Across these varied platforms and study populations, E. saphenum demonstrated a qualitatively consistent direction of association: it was more frequently detected and/or present at higher relative abundance in periodontitis than in periodontal health controls.
Among the subset of studies that applied the 2018 EFP/AAP periodontal classification and reported stage-specific analyses, higher detection or enrichment of E. saphenum was generally reported in advanced disease (stages III–IV). The pattern suggests that E. saphenum is more associated with established, deeper-pocket disease rather than with periodontal health. The review interpreted these findings as associations, not causal evidence.
Overall certainty of evidence was rated as low using GRADE. Contributing factors included the observational and predominantly cross-sectional design of the available studies, heterogeneity in methods (sampling, diagnostic criteria, detection platforms), and lack of temporality to support causation. AXIS-based quality assessments were applied to individual studies; details on specific study-level bias assessments are reported in the original paper.
The recurring detection and enrichment of E. saphenum in periodontitis—especially advanced Stage III–IV disease—is consistent with an ecological dysbiosis model in which non-classical taxa may mark or participate in dysbiotic communities. Given the taxon’s anaerobic niche suitability and association with proteolytic communities, its enrichment in deeper pockets is biologically plausible. However, observational associations cannot distinguish whether E. saphenum contributes functionally to disease progression or primarily represents a marker of established dysbiosis.
Key limitations include the predominance of cross-sectional designs, methodological heterogeneity across studies, absence of longitudinal or interventional data to establish temporality, and limited geographic and sampling diversity across included studies. The review explicitly treats findings as associative and acknowledges that mechanistic or causal roles remain unproven.
The review reports low-certainty evidence that Eubacterium saphenum is more frequently detected and/or enriched in periodontitis compared with periodontal health, with a tendency to be associated with advanced Stage III–IV disease. The authors recommend longitudinal, interventional, and mechanistic studies to clarify temporality and determine whether E. saphenum has a functional role in periodontal dysbiosis or primarily serves as a marker of established disease.