penicillin allergies. There have been failures of cefazolin in treatment of IE. These are ascribed
to the production of type Ab-lactamases by the organism (235).
Right-sided, MSSA IVDA IE has been successfully treated with two weeks of intravenous
therapy with the combination of nafcillin/oxacillin (2 gms every four hours IV for two weeks
and 1 mg/kg of gentamicin every eight hours for five days). Possible explanations for the
abbreviated antibiotic course in right-sided disease are greater penetration of antibiotics into
right-sided vegetations and the decreased concentration of bacteria compared with left-sided
disease because of the low oxygen tension of the right ventricle. Therapy cannot be shortened in
those patients with advanced AIDS, left-sided disease, or evidence of metastatic infection (236).
The addition of gentamicin to a penicillin or to vancomycin, in the treatment of MSSA
NVE, lessens the duration of bacteremia and fever. In doing so, it may minimize both the intra-
and extra-cardiac complicationsS. aureusIE (237). It does not decrease overall mortality but
Table 17 Treatment of Enterococcal Native Valve Infective Endocarditisf
Type of resistance Regimenc
- None Penicillin G (18–30 million units/24 hr IV)a
or
Ampicillin (12 gms/24 hr IV)
or
Vancomycin (30 mg/kg/24 hr IV)
plus
Gentamicin (3 mg/kg/24 hr IV/IM) - Resistant to penicillins due tob-lactamase production Ampicillin-sulbactam (12 gms/24 hr IV)a
or
Vancomycin (30 mg/kg/24 hr) - Intrinsic penicillin resistanced,e Vancomycin (30 mg/kg/24 hr)
plus
Gentamicin (3 mg/kg/24 hr) - Resistance to penicillins Aminoglycosides and vancomycind,e
A)Enterococcus faecium Linezolid (1200 mg/24 hr IV/PO)b,d
or
Quinupristin/dalfopristin (22.5 mg/kg/24 hr IV)b,d
B)Enterococcus faecalis Imipenem (2 gm/24 hr)b,d
plus
Ampicillin (12 gm/24 hr IV)
a4 wk duration in symptoms<3 mo; 6 wk if symptoms>3 mo.
bTreatment should extend for at least 8 wk.
cFor adults with normal renal function.
dFor both native and prosthetic valve endocarditis.
eMay require emergent valve surgery for cure.
fUse of gentamicin is associated with increased risk of renal failure (222a).
Source: From Ref. 222.
Table 18 Alternative Treatment Regimens for Endocarditis Caused by Highly Resistant Gram-Positive
Organismsa
Antibiotic and dosage Undesired effects
Linezolid 600 mg every 12 hr IV or POb Peripheral neuropathy
Optic neuritis
Hematological effects
Development of resistance
Quipristin/dalfopristin 7.5 mg/kg every 8 hr Thrombophlebitis
Myalgias
Daptomycin 6 or 12 mg/kg every 24 hrc Myositis
Increasing resistance
Tigecycline initial dose 100 mg IV; 50 mg IV every 12 hr Gastrointestinal intolerance
aSee text for discussion.
bExcellent PO absorption is useful for transition therapy.
cHigher dosage has been used in relatively resistant organisms.
Infective Endocarditis and Its Mimics in Critical Care 243