does significantly increase the rate of renal failure (222). Tables 18 and 19 summarize the
antibiotic treatment approaches toS. aureusIE.
A triple antibiotic approach is required for treatment of staphylococcal PVE produced
either by MSSA, MRSA, or CoNS. Rifampin is the essential component because of its ability to
kill both CoNS and coagulase-positive staphylococci that adhere to prosthetic material as well
as being able to kill the intracellular phase of these pathogens. The main purpose of the other
two agents is to prevent the development of rifampin-resistant organisms (238). For those
staphylococci resistant to gentamicin, a fluoroquinolone may be an effective substitute (239).
The role of vancomycin in the treatment of deep-seatedS. aureusinfections needs to be
reexamined. The evidence of its inferiority in the treatment of MSSA infections as compared
with b-lactam, is approaching the overwhelming point. In patients on hemodialysis,
vancomycin was found to be inferior to cefazolin for the treatment of MSSA BSI (240). Of all
patients on vancomycin, 36.7 % were considered to be treatment failures (death or recurrence
of infection) versus 13% of patients on cefazolin. Cases of IVDA IE that were treated with
vancomycin had higher infection-related rates of death than those treated withb-lactam agents
even if the patient was switched to the latter compounds when the sensitivity patterns became
known (241). The decreasing effectiveness of vancomycin is most likely related to the
Table 19 Antibiotic Therapy ofStaphylococcus aureusInfective Endocarditisa,f
Valve type (IE type) Antibiotic Dosage
Native (MSSA) Oxacillindgentamicin Oxacillin 2g IV q4h for 4–6 wkgentamicin
3 mg/kg q 24 h as a single dose or in
divided doses q8h for 5 days
or
Vancomycinb,cgentamicin Vancomycin 15 mg/kg IV q12h for 4–6 wk
gentamicin 3 mg/kg q24h as a single
dose or in divided doses q8h for 5 days
or
CefazolinGentamicin Cefazolin 1.5 g IV q8h for 4–6 weeks (in
patients with mild allergies to penicillin)
Gentamicin 3 mg/kg q24h as a single
dose or in divided doses q8h for 5 days
Prosthetic (MSSA) Oxacillind Oxacillin 2 g IV q4h for 4–6 wk or
or Vancomycin 15 mg/kg IV q12h for 4–6 wk or
Cefazolin 1.5 g IV q8h for 4–6 wk in
patients with mild allergies to penicillin
Vancomycin
or
Cefazolin
and
Rifampin Rifampin 300 mg PO q8h for 6 wk
and
Gentamicin Gentamicin 3 mg/kg q24h as a single dose
or in divided doses q8h for 2 wk
Native (MRSA) Vancomycinc Vancomycin 15 mg/kg IV q12h for 4–6 wk
Prosthetic (MRSA)e Vancomycinc Vancomycin 15 mg/kg IV q12h for 4–6 wk
and
Rifampin Rifampin 300 mg PO q8h for 6 wk
and
Gentamicin Gentamicin 3 mg/kg q24h as a single dose
or in divided doses q8h for 2 wk
aFor patients with normal renal function.
bFor patients with severe penicillin allergy.
cSubstitute linezolid in critically ill patients or those with significant renal failure (refer to discussion in text and
Table 7).
dMay substitute nafcillin at equal doses for patients in significant renal failure.
eIf the isolate is resistant to the aminoglycosides, a quinolone to which it is proven sensitive may be substituted.
fUse of gentamicin is associated with increased risk of renal failure (222a).
Source: From Ref. 222.
244 Brusch