Specimen: Blood Diagnosis: Endocarditis Enterococcus faecalis

1
Specimen BloodDiagnosis EndocarditisEnteroc
occus faecalis
Case 11

• ampicillin S
• vancomycin S
• gentamicin synergy S
• streptomycin synergy S

Should we add any comment to the report?
2
Enterococcus spp. CLSI Rx Comment

• Rx Combination therapy of ampicillin,
  penicillin, or vancomycin (for susceptible
  strains), plus an aminoglycoside, is usually
  indicated for serious enterococcal infections,
  such as endocarditis, unless high-level
  resistance to both gentamicin and streptomycin is
  documented such combinations are predicted to
  result in synergistic killing of the
  enterococcus.

CLSI M100-S21. Table 2D.
3
(No Transcript)
4
Enterococcus spp. HLAR (Synergy) Screening

• Disk diffusion
• 120 µg gentamicin 300 µg streptomycin
• ? 10 mm NO HLAR
• 6 mm HLAR
• 7-9 mm inconclusive perform MIC
• MIC screen
• gentamicin 500 µg/ml
• streptomycin 1000 µg/ml (broth) 2000 µg/ml
  (agar)
• no growth NO HLAR
• Perform testing when combination therapy is
  desired (e.g., endocarditis)

5
Enterococcus spp. Aminoglycoside-Modifying
Enzymes

• strep gent tob amk/kan
• 6-AAD - - -
• 3APH - - - (test
  kan)
• 2APH/6AAC -
• 6AAC - -
• found in all E. faecium

enzyme modifies drug drug NOT synergistic -
enzyme does not modify drug drug synergistic
6
Enterococcus spp.
HLAR Test

• Gent Strep Choice of aminoglycoside
• S S either
• S R gentamicin
• R S streptomycin
• R R none
• HLAR to gentamicin confers HLAR to amikacin and
  tobramycin

7
Enterococcus spp. Predicting Synergy
Aminoglycoside or HLAR screen

• Susc Res
• Susc synergy no synergy
• Res no synergy no synergy

Cell wall active agent
ampicillin, penicillin, or vancomycin
8
Specimen BloodDiagnosis EndocarditisEnteroc
occus faecalis
Final Report
Case 11

• ampicillin S
• vancomycin S
• gentamicin synergy S
• streptomycin synergy S

Serious enterococcal infections need combination
therapy with ampicillin or vancomycin plus an
aminoglycoside. Synergy occurs only when both
drugs in the combination are S