Structure, Function, and Biology of the Enterococcus faecalis Cytolysin Original paper
Researched by:
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Divine Aleru
ID
Divine Aleru
Read MoreI am a biochemist with a deep curiosity for the human microbiome and how it shapes human health, and I enjoy making microbiome science more accessible through research and writing. With 2 years experience in microbiome research, I have curated microbiome studies, analyzed microbial signatures, and now focus on interventions as a Microbiome Signatures and Interventions Research Coordinator.
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Microbes
Microbes
Microbes are microscopic organisms living in and on the human body, shaping health through digestion, vitamin production, and immune protection. When microbial balance is disrupted, disease can occur. This guide explains key microbe types—bacteria, viruses, fungi, protozoa, and archaea—plus major pathogenic and beneficial examples.
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Divine Aleru
Read More
Researched by:
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Divine Aleru
ID
Divine Aleru
Read More
Microbiome Signatures identifies and validates condition-specific microbiome shifts and interventions to accelerate clinical translation. Our multidisciplinary team supports clinicians, researchers, and innovators in turning microbiome science into actionable medicine.
Divine Aleru
What was reviewed?
This review examined the structure, biosynthesis, regulation, and biological function of the cytolysin toxin produced by Enterococcus faecalis, a normal gut microbiome organism that can become a multidrug-resistant pathogen. The authors reviewed experimental, microbiological, and clinical evidence showing that cytolysin functions as a quorum-regulated, pore-forming lantibiotic toxin that lyses bacterial competitors and host cells, allowing E. faecalis to alter microbiome composition, enhance colonization, and increase virulence.
Who was reviewed?
The review evaluated microbiome isolates, clinical infection strains, and experimental models involving humans, hospitalized patients, infants, mice, rabbits, and C. elegans. These included commensal gut microbiome populations and pathogenic strains associated with bacteremia, endocarditis, and hospital-acquired infections, comparing cytolysin-producing and non-producing strains to assess toxin-associated microbiome and disease effects.
What were the most important findings?
Cytolysin production strongly enhances Enterococcus faecalis survival, microbiome dominance, and pathogenicity by directly lysing competing Gram-positive bacteria and host immune and epithelial cells. This toxin allows cytolysin-positive strains to outcompete other microbiome organisms, especially after antibiotics reduce microbial diversity, leading to microbial imbalance and pathogen expansion. Cytolysin-positive strains were found in up to 45–60% of clinical isolates and increased mortality risk five-fold in bacteremia patients. Major microbial associations include increased abundance and virulence of cytolysin-producing Enterococcus faecalis, reduced microbiome competition, immune cell destruction, enhanced colonization efficiency, and increased systemic infection risk. Cytolysin also functions as a quorum sensing-regulated molecule, allowing E. faecalis to detect target cells and increase toxin production dynamically, further strengthening microbiome dominance and pathogenic potential.
What are the greatest implications of this review?
This review identifies cytolysin-producing Enterococcus faecalis as a microbiome-derived pathobiont that disrupts microbial balance and drives infection severity through microbial competition, immune evasion, and enhanced colonization. Cytolysin enables microbiome dominance and systemic invasion, linking microbiome dysbiosis to pathogen emergence and worse clinical outcomes. These findings establish cytolysin as an important microbiome virulence biomarker and therapeutic target for preventing microbiome-driven infections.
Enterococcus faecalis
Enterococcus faecalis is a gut‑adapted, Gram‑positive, non‑spore‑forming facultative anaerobe that becomes an important opportunistic pathogen in healthcare when host barriers are breached or antibiotics select for enterococcal overgrowth. Its clinical impact is driven more by persistence, adhesion, and biofilm biology, quorum‑regulated secreted effectors (fsr‑controlled gelatinase GelE), and high genome plasticity than by a broad repertoire of classical tissue‑destroying toxins. Antimicrobial decision‑making must account for the intrinsic poor activity of cephalosporins, the potential for transferable glycopeptide resistance mediated by van gene clusters, and the need for regimen selection in endocarditis that respects synergy/tolerance and local high‑level aminoglycoside resistance patterns.