No, Enterococcus faecalis and Escherichia coli (E. coli) are completely different bacterial species.
Key Differences
These are two distinct organisms from different bacterial families:
- Enterococcus faecalis is a Gram-positive coccus (spherical-shaped bacterium) that belongs to the Enterococcaceae family
- Escherichia coli is a Gram-negative bacillus (rod-shaped bacterium) that belongs to the Enterobacteriaceae family
Why the Confusion May Arise
Both organisms share some similarities that might cause confusion:
- Both are part of normal intestinal flora in humans and animals
- Both can cause urinary tract infections 1
- Both can be isolated together in polymicrobial infections 2, 3
- Both names contain references to fecal/intestinal origin (faecalis means "of feces")
Clinical Significance of Their Differences
The distinction matters critically for treatment because these organisms have fundamentally different antibiotic susceptibilities:
- E. coli is typically susceptible to beta-lactams, fluoroquinolones, and aminoglycosides
- E. faecalis requires different antibiotics, particularly when vancomycin-resistant (VRE), including linezolid, daptomycin, or tigecycline 4
Fosfomycin is FDA-approved specifically for UTIs caused by E. faecalis 4, demonstrating the need for species-specific treatment approaches.
Co-infection Patterns
These organisms can coexist in infections 2, 3, and interestingly, E. coli can actually inhibit E. faecalis growth through production of antimicrobial substances (microcins) when present at ratios of 10-100:1 5. However, in certain conditions like iron-rich environments, E. faecalis can thrive alongside E. coli in dual-species biofilms 6.