Enterococcus faecalis
Gram-positive cocci in pairs and short chains
Identification & Growth
Identification
- Catalase-negative, PYR-positive, bile-esculin-positive, grows in 6.5% NaCl
- Arabinose-negative (differentiates from E. faecium)
Growth Conditions
- Blood agar: grey colonies, gamma- or alpha-hemolytic
- Bile-esculin: blackening of the medium; 35 °C, 24–48 h
Clinical Significance
- Urinary tract, intra-abdominal and endocarditis infections, hospital-acquired bacteremia
Intrinsic Resistance
- Cephalosporins (all generations) (EUCAST Expected Resistant Phenotypes v1.2)
- Low-level aminoglycosides — only high-level synergy testing is clinically useful
- Trimethoprim-sulfamethoxazole (may appear susceptible in vitro but is not clinically effective), clindamycin, aztreonam, polymyxins
Bench Alerts
- Never report a cephalosporin or SXT as susceptible
- In endocarditis, test high-level gentamicin/streptomycin for synergy
Clinical Notes
Clinical presentations
- Causes urinary tract infections, especially associated with indwelling urinary catheters and urologic manipulation.
- A common cause of infective endocarditis in the elderly, often following gastrointestinal or genitourinary procedures.
- Participates in polymicrobial intra-abdominal infections and device-associated bacteremia.
Specimens and collection
- Midstream or straight catheter urine (never from the collection bag) is required for reliable UTI diagnosis.
- Serial blood cultures are indicated in suspected endocarditis, given the characteristic subacute course.
- Rectal swabs are used for active screening of vancomycin-resistant Enterococcus (VRE) colonization in the hospital setting.
Epidemiology and at-risk populations
- Part of the normal intestinal microbiota, released via translocation in the setting of gastrointestinal disease or surgery.
- Hospitalized patients with prolonged cephalosporin use have increased risk of selecting resistant Enterococcus.
- It is the Enterococcus species most frequently isolated in clinical infections, exceeding E. faecium in overall prevalence.
Resistance and therapeutic implications
- Exhibits intrinsic resistance to cephalosporins, which should be reflected in the report regardless of in vitro results.
- Most isolates remain ampicillin-susceptible, unlike E. faecium, which is predominantly resistant.
- In endocarditis, high-level aminoglycoside resistance testing is required to predict therapeutic synergy with a beta-lactam.
- Vancomycin resistance (VRE) is less common in this species than in E. faecium, but should always be tested and reported.
Bench and reporting notes
- Gram-positive cocci in short chains, catalase-negative, growing on bile-esculin and in 6.5% NaCl support genus-level identification.
- The report should state intrinsic resistance to cephalosporins and clindamycin as standard, without individual testing.
- Blood and sterile-site isolates being evaluated for possible endocarditis should include high-level aminoglycoside resistance screening.
Sources
Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.
FAQ: Frequently Asked Questions
How to identify Enterococcus faecalis in the lab?
Enterococcus faecalis is identified through catalase-negative, pyr-positive, bile-esculin-positive, grows in 6.5% nacl, arabinose-negative (differentiates from e. faecium).
What are the intrinsic resistances of Enterococcus faecalis?
This organism is naturally resistant to cephalosporins (all generations) (eucast expected resistant phenotypes v1.2), low-level aminoglycosides — only high-level synergy testing is clinically useful, trimethoprim-sulfamethoxazole (may appear susceptible in vitro but is not clinically effective), clindamycin, aztreonam, polymyxins. These drugs should not be reported as susceptible.
Where is Enterococcus faecalis commonly found?
It is typically associated with urinary tract, intra-abdominal and endocarditis infections, hospital-acquired bacteremia.
Want the free Bench Kit?
Sign up to receive the PDF kit: agars, Gram, Rugai, dilutions and the antibiogram checklist.