Biofilm Formation Capacity in E. faecalis
The majority (approximately 75%) of E. faecalis strains possess biofilm-forming ability, not just 25%. Research demonstrates that biofilm formation is a widespread characteristic among clinical E. faecalis isolates, though the strength of biofilm production varies considerably between strains.
Evidence from Clinical Isolate Studies
The available research directly contradicts the 25% figure:
- A study of 53 clinical E. faecalis isolates found that 40 strains (75.47%) demonstrated biofilm-forming ability, indicating this is a common rather than rare trait 1
- All 18 clinical isolates examined in another transcriptomic study retained biofilm formation capacity, though they were classified into strong, weak, or laboratory strain-like biofilm formers based on intensity 2
- The variation lies not in whether strains can form biofilms, but in the strength and robustness of biofilm production 2, 1
Molecular Basis of Widespread Biofilm Formation
The genetic foundation explains why biofilm formation is so prevalent:
- Comprehensive functional genomics identified 68 genetic loci in the core genome of E. faecalis involved in biofilm formation, indicating this capability is fundamentally encoded in the species' genetic architecture 3
- Most of these biofilm-associated genes are highly conserved across gram-positive bacterial pathogens 3
- Biofilm formation occurs independently of specific virulence factors like the Esp surface protein, demonstrating multiple redundant pathways for biofilm development 4
Clinical Implications
The high prevalence of biofilm-forming E. faecalis has significant clinical consequences:
- E. faecalis biofilms demonstrate uniform resistance to high concentrations of antibiotics (ampicillin and vancomycin at 256-4096 μg/mL) regardless of whether they are strong or weak biofilm formers 2
- E. faecalis is commonly isolated from biofilms on indwelling medical devices including urinary catheters, where it contributes to device-related infections 5
- Subinhibitory antibiotic concentrations can enhance biofilm formation by more than 50% in clinical isolates, potentially worsening treatment outcomes 6
Important Caveats
While most E. faecalis strains form biofilms, clinicians should recognize:
- The clinical manifestation may correlate with biofilm strength rather than presence/absence—isolates from teeth without fistulas showed better biofilm formation than those from teeth with fistulas 1
- Environmental conditions significantly modulate biofilm formation and maintenance, meaning in vitro testing may not fully predict in vivo behavior 4
- The biofilm develops through multiple stages including attachment, microcolony formation, and maturation into complex multilayered structures with water channels 4