Obtaining blood concentrations of vancomycin and gentamicin, as well as renal function tests, weekly because of the possibility of nephrotoxicity with multiple nephrotoxic antibiotic drugs may be con- sidered (Class IIb; Level of Evidence C). Prosthetic Cardiac Valves or Other Prosthetic Material In cases in which endocarditis occurs in the setting of prosthetic material and is caused by a penicillin-susceptible streptococcal strain, therapy is continued for 6 weeks with penicillin, ampi- cillin, or ceftriaxone combined with gentamicin for the first 2 weeksoftherapy.Inthecaseofinfectionscausedbyastrainwith an MIC >0.1 g of penicillin per milliliter or by Abiotrophia or Granulicatella species, a combination of penicillin, ampicillin, or ceftriaxone combined with gentamicin for 6 weeks is rec- ommended. For patients unable to tolerate -lactam therapy, vancomycin for 6 weeks is combined with gentamicin for the first 2 weeks of therapy. In -lactam intolerant patients with Abiotrophia infections, therapy consists of a combination of vancomycin and gentamicin for 6 weeks. Recommendation 1. In cases in which endocarditis occurs in the setting of prosthetic material and is caused by a penicil- lin-susceptible streptococcal strain, therapy is con- tinued for 6 weeks with penicillin, ampicillin, or ceftriaxone combined with gentamicin for the first 2 weeks of therapy. In the case of infections caused by a strain with an MIC >0.1 g of penicillin per milliliter or by Abiotrophia or Granulicatella species, a combination of penicillin, ampicillin, or ceftriaxone combined with gentamicin for 6 weeks is recom- mended (Class I; Level of Evidence C). Enterococcal IE on Native Cardiac Valves or Prosthetic Material Enterococcal endocarditis is relatively rare in children. 