Transcript Ecoccus synergy

Specimen: Blood
Diagnosis: Endocarditis
Enterococcus faecalis
ampicillin
vancomycin
gentamicin synergy
streptomycin synergy
S
S
S
S
Should we add any comment to the report?
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.
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)
Enterococcus spp.
Aminoglycoside-Modifying Enzymes
strep gent tob amk/kan
6-AAD
+
-
-
-
3’APH
-
-
-
+ (test kan)
2”APH/6’AAC
-
+
+
+
6’AAC*
-
-
+
+
* found in all E. faecium
+ = enzyme modifies drug; drug NOT synergistic
- = enzyme does not modify drug; drug synergistic
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
Enterococcus spp.
Predicting Synergy
Aminoglycoside or HLAR screen
Susc
Cell wall
active agent*
Res
Susc
“synergy“
Res
no synergy no synergy
*ampicillin, penicillin, or vancomycin
no synergy
Specimen: Blood
Diagnosis: Endocarditis
Final Report
Enterococcus faecalis
ampicillin
vancomycin
gentamicin synergy
streptomycin synergy
S
S
S
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””