Eubacterium

Eubacterium is a genus of Gram-positive, obligately anaerobic, non-spore-forming bacteria characterized by straight or curved rod-shaped cells, belonging to the family Eubacteriaceae in the phylum Firmicutes.^[1][2] The genus was first proposed by Prévot in 1938 to describe beneficial intestinal bacteria, with the type species being E. limosum, and was later emended by Cato et al. in 1981 to refine its taxonomic boundaries based on phenotypic and chemotaxonomic traits.^[3][2] Species of Eubacterium exhibit phenotypic diversity, including variations in motility (some possess peritrichous flagella while others are non-motile), saccharolytic or amino acid-fermenting metabolism, and production of major end products such as butyrate, acetate, and hydrogen from carbohydrate or purine substrates.^[4] They are chemoorganotrophs commonly isolated from anaerobic environments, particularly the human gastrointestinal tract and oral cavity, where they contribute to dietary fiber breakdown, short-chain fatty acid production, bile acid transformation, and overall host metabolic homeostasis.^[5][6] Certain species, such as Anaerobutyricum hallii (formerly E. hallii) and Lachnospira eligens (formerly E. eligens), are notable for their roles in butyrate synthesis, which supports intestinal barrier function and anti-inflammatory responses.^[6][7][8][9] The genus currently encompasses 28 validly named species as of 2024, though ongoing phylogenetic analyses based on 16S rRNA gene sequencing and whole-genome data have led to reclassifications of several taxa (e.g., some former Eubacterium species now in genera like Anaerobutyricum), reflecting its polyphyletic nature and evolutionary complexity within the Clostridia class.^[2][1] While generally commensal, some Eubacterium species can be opportunistic pathogens in immunocompromised individuals, associated with conditions like bacteremia or colorectal cancer modulation.^[10][7]

Taxonomy and Phylogeny

Etymology and History

The genus name Eubacterium derives from the Greek prefix "eu-" (εὖ), meaning true or good, and "bakterion" (βακτήριον), meaning small rod or staff, reflecting its original description as a group of beneficial, rod-shaped bacteria.^[2] This etymology was established when French microbiologist André-Robert Prévot proposed the genus in 1938 within his systematic studies of anaerobic bacteria, specifically to encompass non-spore-forming, Gram-positive rods isolated primarily from human fecal samples. Prévot's work emphasized their role as "true" anaerobes in the intestinal microbiota, distinguishing them from other rod-shaped forms based on strict anaerobiosis and phenotypic traits like saccharolytic fermentation.^[11] In its early history, Eubacterium served as a broad repository for diverse anaerobic isolates from the human gut and other environments, contributing significantly to foundational research in anaerobic microbiology during the mid-20th century. Studies in the 1930s–1950s, including those by Eggerth and colleagues, highlighted species like E. limosum and E. lentum as key components of normal fecal flora, aiding early understandings of microbial fermentation and intestinal ecology.^[11] Pre-1980s classifications, such as those in the 7th (1957) and 8th (1974) editions of Bergey's Manual of Determinative Bacteriology, grouped these organisms phenotypically without phylogenetic rigor, resulting in a heterogeneous assemblage that included saccharolytic, asaccharolytic, and even motile forms.^[2] This phenotypic approach facilitated initial isolation techniques but obscured deeper evolutionary relationships, as the genus encompassed bacteria from varied ecological niches beyond the gut.^[11] The advent of 16S rRNA gene sequencing in the 1980s prompted major taxonomic revisions, revealing Eubacterium as polyphyletic and distributed across multiple Firmicutes clades, leading to the transfer of numerous species to new genera between the 1990s and 2010s. For instance, phylogenetic analyses in the 2000s reclassified E. formicigenerans and related strains into the genus Dorea based on low 16S rRNA similarity to core Eubacterium species.^[12] Further refinements included the 2010 reassignment of E. plautii to Flavonifractor plautii due to its distinct phylogenetic position and flavonoid-degrading capabilities, and the 2014 transfer of E. biforme to Holdemanella biformis within the Erysipelotrichaceae family.^[13][14] More recently, E. hallii was reclassified as Anaerobutyricum hallii in 2018 following polyphasic studies showing only 92–93% 16S rRNA gene sequence identity to remaining Eubacterium type species and unique butyrate production pathways.^[15] These changes narrowed the genus to a more coherent core while highlighting its historical over-inclusivity.^[11]

Current Classification

The genus Eubacterium belongs to the domain Bacteria, phylum Bacillota (formerly Firmicutes), class Clostridia, order Eubacteriales, family Eubacteriaceae, with Eubacterium limosum designated as the type species.^[16][2] Membership criteria for the genus combine phenotypic traits and molecular data. Phenotypically, Eubacterium species are characterized as Gram-positive, obligately anaerobic, non-spore-forming rods possessing rigid cell walls; they are typically chemoorganotrophic and saccharolytic, producing organic acids such as butyric, acetic, or formic acid from carbohydrate fermentation.^[4][17] Molecular delineation relies on 16S rRNA gene sequences, with species thresholds at >98.7% similarity and genus affiliation at >95% similarity to the type species, supplemented by whole-genome metrics like average nucleotide identity (ANI) >95-96% and digital DNA-DNA hybridization (dDDH) >70% where applicable.^[18][11] As of November 2025, the List of Prokaryotic names with Standing in Nomenclature (LPSN) recognizes 28 validly published species within the genus, while the NCBI Taxonomy database lists additional records including synonyms and proposed names, totaling over 50 taxa.^[2][16] Recent genomic analyses have driven reclassifications, such as the transfer of strain KIST612 from E. limosum to E. callanderi in 2023 and the description of new species like E. album in 2024; the Genome Taxonomy Database (GTDB) release R10-RS226 (as of April 2025) further refines placements using phylogenomic criteria, reflecting ongoing polyphasic revisions to address phylogenetic diversity.^[19][20]

Phylogenetic Position

Eubacterium is positioned within the phylum Bacillota, specifically in the class Clostridia and order Eubacteriales, with traditional classifications placing the genus in the family Eubacteriaceae, closely related to Clostridiaceae due to shared anaerobic traits and phylogenetic proximity based on early molecular analyses.^[21] However, the Genome Taxonomy Database (GTDB), which employs whole-genome phylogenomics including relative evolutionary divergence metrics, reclassifies many Eubacterium species into families like Lachnospiraceae, reflecting greater resolution than 16S rRNA-based trees and highlighting polyphyletic origins within Bacillota.^[22] The divergence of Bacillota lineages, including those ancestral to Eubacterium and Clostridiaceae, is estimated at approximately 2.5–3.2 billion years ago, coinciding with the anaerobic bacterial radiation prior to the Great Oxidation Event, as calibrated by molecular clock analyses of conserved genes. Within Bacillota, Eubacterium species form key clades such as Cluster XIVa, prominent in human gut microbiota studies, encompassing butyrate-producing taxa like Eubacterium rectale and E. hallii, which show close relationships to genera including Clostridium and Roseburia based on 16S rRNA gene sequencing and comparative phylogenomics.^[23] These clades are defined by sequence similarities exceeding 95% in 16S rRNA V1-V3 regions, with GTDB classifications further delineating subclusters through 120 conserved bacterial markers, revealing Eubacterium's evolutionary ties to other clostridial fermenters.^[24] For instance, E. rectale has been reclassified as Agathobacter rectalis in GTDB, underscoring dynamic taxonomic shifts driven by genomic data that emphasize functional and phylogenetic coherence over morphological traits.^[22] Evolutionary insights into Eubacterium highlight ancestral acetogenic capabilities, as seen in species like E. limosum, which utilize the Wood-Ljungdahl pathway for CO2 fixation—a trait likely retained from early anaerobic Bacillota ancestors adapted to low-oxygen environments.^[21] Horizontal gene transfer (HGT) events have significantly shaped fermentation pathways, with acquisitions of glycoside hydrolase and polysaccharide utilization loci from distantly related bacteria enhancing dietary fiber degradation and short-chain fatty acid production in gut-adapted lineages. Metagenomic studies, including data from the Human Microbiome Project up to integrated analyses in 2020, have illuminated these dynamics by reconstructing Eubacterium phylogenies from thousands of gut metagenome-assembled genomes, confirming Cluster XIVa's dominance in healthy microbiomes and its role in metabolic cross-feeding networks.

Biological Characteristics

Morphology and Structure

Eubacterium species exhibit a rod-shaped morphology, typically appearing as straight, curved, or slightly branched rods that occur singly, in pairs, or in short chains. Cell dimensions generally range from 0.3 to 1.5 μm in width and 1 to 10 μm in length, with variations across species; for example, Eubacterium maltosivorans forms short rods of 0.4 to 0.7 μm by 2.0 to 2.5 μm. Pleomorphic forms are observed in some species, where cells may appear irregular or coccoid under stress or specific growth conditions.^[4] As Gram-positive bacteria, Eubacterium cells possess a thick peptidoglycan layer in their cell wall, ranging from 20 to 80 nm in thickness, which provides structural rigidity and is characteristic of the genus. This layer lacks an outer membrane, distinguishing them from Gram-negative bacteria, and constitutes a significant portion of the cell wall dry weight. The rigid cell walls support the non-spore-forming nature of the genus, with no endospore production observed in any species.^[25][26][4] Motility varies among Eubacterium species; while many are non-motile, such as Eubacterium limosum, others exhibit motility through peritrichous flagella distributed across the cell surface, as in Eubacterium cellulosolvens. No pili or other appendages beyond flagella have been consistently reported for motility in the genus.^[27][28][4] Ultrastructural examinations via electron microscopy have historically identified mesosome-like invaginations of the plasma membrane in Eubacterium cells, though these features are now recognized as artifacts from chemical fixation methods in older studies. Genome sizes for sequenced Eubacterium species typically fall within 2.5 to 4.5 Mb, reflecting compact organization suited to their anaerobic lifestyle; for instance, Eubacterium callanderi has a 4.33 Mb genome, and Eubacterium limosum has approximately 4.2 Mb.^[29][30]

Physiology and Metabolism

Eubacterium species are obligate anaerobes, characterized by their extreme sensitivity to oxygen, which inhibits growth and survival due to the absence of protective mechanisms like catalase or superoxide dismutase. These Gram-positive, non-spore-forming rods inhabit oxygen-depleted niches such as the human gastrointestinal tract, where they derive ATP primarily through substrate-level phosphorylation via fermentation of carbohydrates or, in select acetogenic species, through the reduction of CO₂ using hydrogen or other electron donors.^[11][31][27] The core metabolic pathways in Eubacterium revolve around the anaerobic fermentation of complex carbohydrates, including dietary fibers and resistant starches, yielding short-chain fatty acids (SCFAs) such as acetate, butyrate, and lactate as end products. For instance, butyrate-producing species ferment glucose via glycolysis to produce butyrate through the butyryl-CoA:acetate CoA-transferase pathway, involving key enzymes that facilitate the conversion of butyryl-CoA to butyrate while recycling acetate. Certain acetogenic members, notably E. limosum, employ the Wood-Ljungdahl pathway to fix CO₂ into acetate, harnessing one-carbon metabolism with the overall reaction: $$4\mathrm{H_2} + 2\mathrm{CO_2} \rightarrow \mathrm{CH_3COOH} + 2\mathrm{H_2O}$$4H2​+2CO2​→CH3​COOH+2H2​O This pathway enables autotrophic growth on H₂/CO₂ or heterotrophic utilization of substrates like methanol and lactate, producing acetate and butyrate while conserving energy via ion-translocating complexes. Additionally, versatile species such as E. maltosivorans exhibit mixed metabolism, including propionogenesis from 1,2-propanediol within bacterial microcompartments to sequester toxic aldehydes, and demethylation of quaternary amines like choline to generate acetate and butyrate, thereby mitigating trimethylamine formation.^{[11][32][33][27]} Growth of Eubacterium species is optimized under mesophilic conditions, with human gut isolates thriving at 37°C and a pH range of 6.5–7.5, reflecting their adaptation to colonic environments; broader tolerances extend to pH 5.0–7.5 and temperatures of 30–45°C in rumen-derived strains like E. limosum. These bacteria require anaerobic media supplemented with complex nutrients, including peptides, amino acids, and microbiota-accessible carbohydrates such as fructans and inulin, while some acetogens benefit from corrinoid cofactors akin to vitamin B₁₂ for methyltransferase activities in one-carbon metabolism. Enzyme systems, such as the lctABCDEF cluster for lactate utilization in E. maltosivorans, underpin substrate specificity and energy yield.^{[11][33][27][34]} In terms of stress responses, gut-associated Eubacterium species demonstrate tolerance to bile acids through enzymatic modifications, including deconjugation via bile salt hydrolase, which aids in cholesterol homeostasis and antimicrobial defense. Regarding antibiotics, most strains are susceptible to metronidazole, a nitroimidazole effective against anaerobes due to its activation under low redox conditions, though sporadic resistance occurs in up to 16% of isolates, necessitating combination therapies in clinical contexts.^[11][35]

Ecology and Distribution

Natural Habitats

Eubacterium species are primarily found in anaerobic environments, with the human and animal gastrointestinal tracts serving as key habitats where they can constitute a significant portion of the microbiota. In the human gut, members of the genus are among the most abundant bacteria, often ranking second only to Bacteroides in prevalence within fecal samples.^[36][11] Similarly, in the rumen of herbivores such as sheep and cows, Eubacterium strains, including E. limosum, are frequently isolated and contribute to microbial communities in these oxygen-depleted zones.^[37] Abundance in gut environments typically ranges from 10^7 to 10^9 colony-forming units per gram of feces for certain species.^[38] Beyond host-associated niches, Eubacterium is prevalent in environmental anoxic settings such as soil, sediments, sewage, and anaerobic digesters. The genus was first isolated from human feces in 1938 by Prévot, who described it as a group of beneficial anaerobic rods.^[11] Strains like E. limosum have since been recovered from diverse sources including soil, sewage sludge, and compost heaps, highlighting their adaptability to oxygen-limited terrestrial and waste-processing systems.^[38][39] In anaerobic digesters treating organic waste, Eubacterium species appear in bacterial profiles, often alongside other Firmicutes in biogas-producing communities.^[40] Globally, Eubacterium exhibits a ubiquitous distribution in anoxic habitats. These patterns underscore Eubacterium's role in worldwide anaerobic ecosystems, from digestive tracts to contaminated sediments.

Ecological Roles

Eubacterium species play a key role in the decomposition of complex plant polysaccharides, such as xylan, through anaerobic fermentation that produces short-chain fatty acids (SCFAs) like butyrate, acetate, and propionate. These processes contribute to carbon cycling by breaking down undigested dietary fibers in the gut and recalcitrant organic matter in anaerobic soil environments, releasing bioavailable carbon compounds that support microbial communities and nutrient turnover. For instance, Eubacterium rectale efficiently ferments xylan and starch to generate butyrate, which serves as an energy source for surrounding microbes and helps maintain anaerobic conditions conducive to further decomposition.^[41][42][43] In microbial ecosystems, Eubacterium engages in symbiotic interactions via cross-feeding mechanisms that enhance community stability and function. Species such as Anaerobutyricum hallii (formerly Eubacterium hallii) utilize lactate produced by Bifidobacterium to synthesize butyrate, providing this SCFA to colonocytes for energy and barrier maintenance while promoting the growth of other anaerobes. These interactions occur in anaerobic consortia, where Eubacterium contributes to interspecies hydrogen transfer, indirectly inhibiting methanogenesis by competing for substrates like H2 and acetate with methanogenic archaea. Such cross-feeding exemplifies Eubacterium's role in fostering trophic networks that optimize resource use in oxygen-limited habitats.^[44][45][46] Certain Eubacterium species exhibit environmental impacts through bioremediation capabilities and modulation of soil processes. For example, Eubacterium limosum demonstrates reductive dechlorination of halogenated compounds like methoxychlor, aiding in the detoxification of contaminated anaerobic sites.^[47] Abundance of Eubacterium is influenced by dietary factors, with fiber-rich diets increasing levels in gut microbiomes and potentially analogous effects in soil via plant residue inputs.^[48] Within microbial communities, Eubacterium acts as a keystone taxon, particularly in recovery from dysbiosis following perturbations like antibiotic exposure or dietary shifts. Studies from the 2020s highlight its resilience, with Eubacterium rectale depletion linked to prolonged microbiome instability in conditions such as COVID-19 severity, underscoring its role in restoring butyrate production and overall eubiosis. As a butyrate producer, it supports community dynamics by stabilizing pH and providing metabolic intermediates, facilitating the rebound of diverse taxa after disruptions.^[11][49][50]

Species Diversity

Type Species

Eubacterium limosum (Eggerth 1935) Prévot 1938 is the type species of the genus Eubacterium, officially designated as such in a judicial opinion to replace the previous type, E. foedans, due to nomenclatural and phylogenetic considerations.^[51] Originally described as Bacteroides limosus by Eggerth in 1935 from a single strain isolated from human feces, it was reclassified into the genus Eubacterium by Prévot in 1938 based on its Gram-positive staining and anaerobic characteristics.^[52] The type strain is ATCC 8486 (also DSM 20543, JCM 6421), which serves as the reference for genus-level criteria, including obligate anaerobiosis, Gram-positive cell wall composition, and non-spore-forming nature.^[53] This species exemplifies the acetogenic lifestyle typical of many Eubacterium members, functioning as a strict anaerobe capable of chemolithoautotrophic growth on C1 substrates such as H₂/CO₂ and methanol, with acetate as the primary fermentation product via the Wood-Ljungdahl pathway.^[1] Cells are rod-shaped, measuring 0.5–1.5 μm in width and 1–5 μm in length, occurring singly or in pairs, and are generally non-motile under standard conditions.^[52] The complete genome of the type strain ATCC 8486 spans 4.42 Mb with a G+C content of 47.2 mol%, encoding key genes for the Wood-Ljungdahl pathway (e.g., formyltetrahydrofolate synthetase and carbon monoxide dehydrogenase) as well as methyl transferases for methanol utilization.^[54] Additional metabolic versatility allows growth on organic substrates like sugars, lactate, and amino acids such as valine, yielding products including butyrate and ethanol in varying proportions depending on the substrate.^[55] As a model organism for acetogenesis research, E. limosum has been extensively studied for its role in carbon fixation and syngas fermentation, with adaptive laboratory evolution enhancing its growth on CO-rich gases for improved bioproduct yields.^[34] In biotechnology, it is harnessed for sustainable acetate production from industrial waste gases and methanol, leveraging its autotrophic capabilities to convert greenhouse gases into value-added chemicals without requiring complex genetic modifications in some strains.^[56] Although occasionally isolated from clinical samples and classified as a potential opportunistic pathogen in immunocompromised individuals, it lacks inherent virulence factors and is not considered highly pathogenic in healthy hosts.^[10] Its defining traits—anaerobic acetogenesis, rod morphology, and metabolic flexibility—thus anchor the genus Eubacterium in systematic bacteriology.^[4]

Notable Species

Agathobacter rectalis (formerly Eubacterium rectale) is a prominent gut-associated species recognized for its role as a butyrate producer in the human intestinal microbiota. Most strains of A. rectalis are auxotrophic for vitamins B1 (thiamine) and B9 (folate), requiring these vitamins from dietary sources or microbial cross-feeding; thus, diets rich in B1 (e.g., whole grains) and B9 (e.g., leafy greens) may indirectly support its growth, although high-fiber intake remains the primary driver for its abundance.^[57] It constitutes a significant portion of the Firmicutes phylum, detected in over 90% of healthy adult individuals and contributing to short-chain fatty acid production that supports gut health.^[58][59] Another key gut species, Eubacterium siraeum, is associated with the degradation of dietary fibers, enhancing microbial breakdown of complex polysaccharides in the colon.^[60] In environmental contexts, Eubacterium barkeri exemplifies adaptation to soil habitats, where it was isolated from mud and exhibits specialized catabolic pathways for organic compounds like nicotinate.^[61][62] Similarly, Eubacterium callanderi, originally isolated from an anaerobic digester in sewage treatment, demonstrates hydrogen-oxidizing capabilities as an acetogen, utilizing H₂ and CO₂ for growth.^[63][64] The genus has undergone taxonomic revisions based on phylogenetic and phenotypic analyses. As of November 2025, the List of Prokaryotic names with Standing in Nomenclature (LPSN) recognizes 28 validly published species in Eubacterium.^[2] Species diversity within Eubacterium is marked by phenotypic variations, including saccharolytic types that ferment carbohydrates and asaccharolytic ones that produce acetate and butyrate from amino acids or peptides, as seen in oral and gut isolates.^[65] Genomically, several species cluster in the human gut-associated Clostridium XIVa group, reflecting shared adaptations to anaerobic, fiber-rich environments.^[66]

Human Health Implications

Beneficial Contributions

Eubacterium species play a key role in promoting gut health through the production of short-chain fatty acids (SCFAs), particularly butyrate, which serves as an energy source for colonocytes and exhibits anti-inflammatory properties by modulating immune responses in the intestinal epithelium.^[45] These bacteria ferment dietary fibers, such as resistant starches, into SCFAs that inhibit cholesterol absorption in the gut, thereby contributing to lipid homeostasis and reducing circulating cholesterol levels.^[11] For instance, Eubacterium coprostanoligenes converts cholesterol to coprostanol, a less absorbable form, further supporting cardiovascular health via microbial metabolism.^[67] In disease prevention, higher abundances of Eubacterium are associated with reduced risk of inflammatory bowel disease (IBD), as these bacteria help maintain microbial balance and suppress chronic inflammation.^[11] Enrichment of Agathobacter rectalis (formerly known as Eubacterium rectale) occurs in response to high-fiber diets, correlating with lower obesity risk through enhanced SCFA production that regulates energy harvest and adiposity.^[68] Diets rich in B1 (thiamine; e.g., whole grains) and B9 (folate; e.g., leafy greens) may indirectly support its growth by providing essential vitamins for which most strains are auxotrophic, though high-fiber intake remains the primary driver for its abundance rather than B vitamin supplementation alone.^[69][70] Similarly, Eubacterium hallii strains show probiotic potential in the infant gut, where they cross-feed with bifidobacteria to produce butyrate, fostering early microbial development and preventing dysbiosis-related disorders.^[44] These protective effects are mediated by SCFAs, which inhibit histone deacetylases (HDACs), altering gene expression to promote anti-inflammatory pathways and metabolic regulation.^[71] Recent Mendelian randomization studies as of 2024 indicate limited causal evidence linking Eubacterium abundance directly to metabolic outcomes, with nuanced associations for specific species like E. hallii.^[72] Emerging therapies, such as fecal microbiota transplantation (FMT), increase Eubacterium abundance to treat gut dysbiosis, restoring microbial diversity and alleviating symptoms in conditions like ulcerative colitis.^[73] For example, FMT from healthy donors has been shown to elevate Eubacterium hallii levels, enhancing butyrate production and intestinal barrier function in recipients.^[74]

Pathogenic and Opportunistic Aspects

Species of the genus Eubacterium are primarily commensal gut bacteria but can act as opportunistic pathogens, particularly in immunocompromised individuals, leading to rare cases of bacteremia, abscesses, and other infections. For instance, E. nodatum has been implicated in oral infections such as periodontitis, where it is part of the "orange complex" of bacteria associated with disease progression, and in intrauterine infections mimicking actinomycosis. Similarly, E. brachy has been isolated from pleuropulmonary infections and lung abscesses, often in patients with underlying respiratory compromise. According to CDC surveillance data, these anaerobes are classified as common commensals with minor clinical importance in most infections, typically requiring anaerobic conditions and host vulnerability for pathogenesis.^{[75][76][77][78]} Dysbiosis involving Eubacterium species is linked to several human diseases, with studies showing reduced abundance in conditions like Crohn's disease and colorectal cancer. In Crohn's disease patients, genera such as Eubacterium and species like E. rectale exhibit significantly lower levels compared to healthy controls, contributing to impaired gut homeostasis. Recent analyses from 2020 to 2025 confirm this depletion, associating it with decreased butyrate production and exacerbated inflammation. In colorectal cancer, reduced relative abundance of E. eligens and other Eubacterium groups correlates with tumor development, as observed in both human cohorts and animal models. Antibiotic-associated diarrhea often involves dysbiosis with overall depletion of Eubacterium species due to broad-spectrum antimicrobial disruption of the microbiota.^{[79][80][81][82]} Virulence factors in Eubacterium include cell wall components like lipoteichoic acids (LTA), which function similarly to endotoxins in gram-positive bacteria by inducing pro-inflammatory cytokine release and contributing to tissue damage in infections. LTA from these anaerobes can trigger immune responses akin to those seen in sepsis or chronic inflammation. Additionally, some species, such as E. brachy, demonstrate biofilm formation capabilities, aiding persistence in the gut or abscess environments and enhancing resistance to host defenses and antimicrobials. Case reports highlight E. brachy infections following surgical interventions or in disrupted mucosal barriers, underscoring its opportunistic nature.^[83][84] Key risk factors for Eubacterium-related infections include immunosuppression, gut barrier disruption from conditions like IBD, and prior antibiotic exposure, which alters microbiota balance and promotes translocation. Antibiotic resistance patterns, particularly to clindamycin, affect 10-20% of isolates, complicating treatment in clinical settings. These factors collectively heighten susceptibility in vulnerable populations, though infections remain infrequent overall.^[85][86]