If CoNS are resistant to gentamicin, then an amino- glycoside to which they are susceptible may be con- sidered (Class IIb; Level of Evidence C). 3. If CoNS are resistant to all aminoglycosides, then substitution with a fluoroquinolone may be consid- ered if the isolate is susceptible to a fluoroquinolone (Class IIb; Level of Evidence C). from patients who have had a bacteriological relapse should be carefully retested for complete antibiotic susceptibility profiles (Class I; Level of Evidence C). S aureus Because of the high mortality rate associated with S aureus combination antimicrobial therapy is recommended (Table 11). The use of combination therapy is based not on studies of in vitro synergy but rather on the efficacy of this therapy for treatment of CoNS PVE, as well as the results of treatment of experimental IE and infected devices. In animal studies, rifampin appears to be key in the complete steriliza- tion of foreign bodies infected by MRSA.184,185 For infection caused by MSSA, nafcillin or oxacillin together with rifampin is suggested; with MRSA, vancomycin and rifampin should be used. Gentamicin should be adminis- tered for the initial 2 weeks of therapy with either -lactam or vancomycin-containing regimens. If a strain is resistant to gentamicin, then a fluoroquinolone may be used if the strain is susceptible. Early cardiac surgical interventions play an important role in maximizing outcomes in S aureus PVE,186 especially in the presence of heart failure.11 Recommendations 1. Combination antimicrobial therapy is recom- mended (Class I; Level of Evidence C). Baddour et al Infective Endocarditis in Adults 1455 2. Gentamicin should be administered for the initial 2 weeks of therapy with either -lactam or vancomycin- containing regimens (Class I; Level of Evidence C). 