Enterococcus faecium

1. GC 102 ^[3]: Enterococcus listed as a key pathogen in Foley catheter–related UTI in immunocompromised hosts; device-related infections are difficult to eradicate without catheter removal due to biofilm.

2. Multiple senior notes ^[4][5] emphasize the critical teaching point: "Enterococcus is intrinsically resistant to cephalosporins and aminoglycosides — therefore should use Augmentin or nitrofurantoin." This is the single most testable pharmacology fact for Enterococcus on HKUMed papers.

3. IE lectures ^[1][2]: Enterococcus is classified under "Group D streptococci" for IE teaching; source is GI/GU tract; empirical subacute IE regimen = IV ampicillin + IV gentamicin. The aminoglycoside here is used for synergistic bactericidal activity, not as monotherapy.

4. UTI teaching ^[6][7]: Enterococcus spp accounts for ~5% of uncomplicated UTI but ~11% of complicated UTI — frequency rises with catheterisation and hospitalisation.

5. AOS Microbio ^[9]: Neonatal sepsis question explicitly uses E. faecalis as a distractor vs GBS — the teaching point is that day-2 neonatal meningitis with G+ve cocci in chains = GBS, not Enterococcus.

6. PD peritonitis ^[8]: Enterococcus is among G+ve organisms causing CAPD peritonitis; empirical Rx = cefazolin + amikacin; adjust after culture.

• E. faecium vs E. faecalis: faecium is the "more resistant" species — more likely ampicillin-R and VRE. If a vignette says "ampicillin-resistant Enterococcus," think E. faecium first.
• Enterococcus vs Streptococcus on Gram stain: both are G+ve cocci in chains. Bile-esculin +ve and growth in 6.5% NaCl clinch Enterococcus.
• Cephalosporin trap: A patient on empirical ceftriaxone grows Enterococcus → treatment is failing because cephalosporins have no activity against Enterococcus. Must switch to ampicillin or vancomycin.
• S. bovis vs Enterococcus in IE: Both are "Group D." S. bovis IE → colonoscopy (association with colon cancer). Enterococcal IE → look for GU/GI source of entry (instrumentation, catheterisation).
• VRE significance: E. faecium with VanA phenotype = resistant to both vancomycin AND teicoplanin. Treatment options: linezolid, daptomycin. This is a notifiable multidrug-resistant organism in HK hospitals requiring contact isolation.

2023 Fourth Summative MCQ Q83 ^[10]:

"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 shown.] 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: Day 2 neonate = early-onset neonatal sepsis. G+ve cocci in chains on CSF Gram stain in this age group → GBS (S. agalactiae). E. faecalis (option A) is a deliberate distractor — also G+ve cocci in chains, but GBS is overwhelmingly the most common cause of early-onset neonatal meningitis. Key discriminator: clinical context (age < 7 days) overrides morphological similarity.

No other past paper questions in the indexed context directly test E. faecium specifically. However, IE and UTI questions frequently include Enterococcus as part of differential or treatment selection stems (e.g., "which antibiotic does NOT cover Enterococcus?" → answer: cephalosporin).