Enterococcus faecalis

1. GC 105 slide explicitly lists Enterococcus diseases as: catheter-associated UTI, endocarditis, component of polymicrobial intra-abdominal/biliary infections, line sepsis — this is the exact HKUMed-examinable disease list ^[1].

2. "Resistant to many antibiotics, e.g. cephalosporins" — GC 105 flags this as the key pharmacological point. Cephalosporin resistance is intrinsic and absolute; this is the single most tested treatment trap for Enterococcus ^[1].

3. VRE = usually E. faecium, not E. faecalis; treatment options are daptomycin / linezolid / tigecycline — directly from GC 105 ^[1].

4. GC 102 (immunocompromised host): Enterococcus listed alongside aerobic G−ve bacilli as a Foley's catheter-associated UTI pathogen — reinforces the catheter-associated UTI angle ^[4].

5. Felix Lai notes (Medicine/Paeds/Surgery) all independently emphasise: "Enterococcus is intrinsically resistant to cephalosporins and aminoglycoside monotherapy — use Augmentin or nitrofurantoin" — this exact phrasing appears three times across senior notes and is clearly a favourite teaching point ^[10].

6. AOS Microbio Q3 (neonatal meningitis stem): E. faecalis is a distractor; correct answer is GBS — know the neonatal sepsis organisms (GBS, E. coli) and do not confuse with Enterococcus ^[12].

• Enterococcus vs S. bovis in IE vignette: Both are "Group D." If the stem mentions colonic pathology (CA colon, ulcerative colitis) → S. bovis. If the stem mentions GU manipulation, catheterisation, or resistant organism → Enterococcus. S. bovis responds to penicillin alone; Enterococcus requires combination therapy (ampicillin + gentamicin) ^[2][3].

• Empirical subacute IE regimen: IV ampicillin + IV gentamicin covers viridans strep, HACEK, and enterococci simultaneously. If cultures grow HACEK → switch to ceftriaxone. If Enterococcus confirmed → continue ampicillin + gentamicin ^[3].

• Aminoglycoside "synergy" concept: Aminoglycosides alone do NOT kill enterococci (intrinsic low-level resistance). They are added for synergistic bactericidal activity with a cell-wall-active agent (ampicillin or vancomycin). High-level aminoglycoside resistance (HLAR) abolishes this synergy — a potential exam question angle.

• Carbapenems: Felix Lai notes list E. faecalis and Listeria as G+ve organisms covered by carbapenems (imipenem > meropenem for E. faecalis). However, E. faecium is intrinsically resistant to carbapenems ^[11].

• UTI treatment trap: If a complicated UTI question grows Enterococcus → do NOT choose ceftriaxone or gentamicin alone. Choose augmentin (oral) or ampicillin (IV). Nitrofurantoin is an alternative for lower UTI only ^[10].

2023 Fourth Summative MCQ Q83 ^[13]:

"A neonate (day 2 of life) develops high fever, lethargy and feeding difficulty. Sepsis workup is performed including lumbar puncture. [Gram stain image of CSF provided.] Which of the following microorganisms is MOST LIKELY to be grown in culture from the cerebrospinal fluid? A. Enterococcus faecalis B. Group B streptococcus C. Staphylococcus aureus D. Streptococcus pneumoniae"

• Correct answer: B. Group B streptococcus
• Rationale: Neonatal sepsis/meningitis at day 2 = early-onset neonatal sepsis. The two key organisms are GBS (S. agalactiae) and E. coli. The Gram stain showing G+ve cocci in chains/pairs points to GBS. E. faecalis (option A) is a distractor — it is G+ve cocci in chains but is NOT a classic cause of early-onset neonatal meningitis. S. pneumoniae causes meningitis in older infants/children, not neonates. This question also appears in the AOS Microbio practice set with identical stem ^[12][13].

No other past paper questions in the indexed context directly test Enterococcus faecalis as the primary organism. However, Enterococcus features as part of empirical IE therapy discussions and UTI microbiology in multiple minicase/SAQ stems across years (e.g. cholecystitis minicases where "Strep faecalis" is listed among secondary biliary infection organisms ^[7]).