Table 1.

The significant contributions of the E. faecalis quorum-sensing systems to virulence against humans and model organisms.

Associated Disease	Host	Virulence Factors	Observed Activities	References
Endocarditis	Human	Fsr system	A higher prevalence of the fsr locus in the endocarditis isolates (100%) compared with fecal isolates (53%)	[57]
1 IBD	Human	Gelatinase	The expression of gelE gene was significantly higher in the IBD patients compared with that in the controls	[58]
IBD	Mice	Gelatinase	The gelE positive E. faecalis strain induced a significantly higher colitis and ileitis in the mice compared with that of the gelE mutant strains	[51]
Peritonitis	Mice	Cytolysin and gelatinase	Adding 2 SRFE to the inoculum considerably lowered the LD50 for E. faecalis OG1RF	[59]
Systemic infection	Mice and G. mellonella	Cytolysin and gelatinase	Injections of a gelE positive strain cause death in the G. mellonella larvae within 8 h and over 2 days in mice. Meanwhile, cytolysin was highly expressed in heart and spleen of mice	[60]
Ulcerative colitis	Mice	Gelatinase	Gelatinase can regulate intestinal permeability through 3 PAR2	[50]
Endophthalmitis	Rabbit	Fsr system	An fsrB positive strain reduced the B-wave amplitude significantly compared with an fsrB negative strain	[61]
Endophthalmitis	Rabbit	Gelatinase and serine protease	100 CFU/mL of E. faecalis OG1RF caused significant loss of retinal function after 24 h compared with fsrB mutant strains	[62]
Endocarditis	Rabbit	Gelatinase	A gelE positive phenotype increased bacterial burden in the heart tissues	[48]
Persistent infection	C. elegans	Fsr system and cytolysin	Feeding on lawns containing E. faecalis (cytolysin and fsrB positive) caused a lethal infection	[39]
Persistent infection	C. elegans	Cytolysin and gelatinase	Ingestion of different strains of E. faecalis having the fsr locus and cytolysin operon significantly increased its pathogenicity	[63]
Aerial tissue damage	A. thaliana	Fsr system	Parental strain OG1RF caused mortality after 7 days post-inoculation while fsrB and sprE mutant strains significantly attenuated virulence	[64]
Systemic infection	D. melanogaster	Gelatinase, serine protease, and enterocin O16	gelE, sprE, and ef1097 mutant strains attenuated virulence significantly compared with the V583 parental strain	[30]

¹ Inflammatory Bowel Diseases (IBD); ² Sterile Rat Fecal Extracts (SRFE); ³ Protease-Activated Receptor 2 (PAR2).