Most staphylococcal strains are susceptible to rifampin, and in experimental systems, it has good tissue penetration. The overall mortality rate associated with prosthetic valve endocarditis is relatively high but is highest for infec- tions caused by S aureus.128 Although 1 study reporting cases from the 1970s showed that many cases of pediatric IE with patches or prostheses could be treated successfully with medical management alone, surgical management is gener- Moreover, prosthetic valve infection caused by S aureus has been shown to be an independent risk factor for death.130,131 Many authorities have concluded that valve replacement surgery is preferable in most if not all patients with pros- thetic valve infection caused by S aureus. Decisions regard- ing transition to outpatient care in cases of prosthetic valve endocarditis should be individualized and should be made in consultation with pediatric infectious diseases consultants, taking into consideration the elements discussed at the end of Staphylococcal Endocarditis on Native Valves or Prosthetic Material. Recommendation 1. Valve replacement surgery may be considered and is preferable in most if not all patients with prosthetic valve infection caused by S aureus (Class IIb; Level of Evidence C). Gram-Negative IE (Including HACEK Species) The Gram-negative bacteria that most often cause IE in chil- dren are the HACEK group of fastidious coccobacilli. The consensus of experts recommending therapy for IE caused by the HACEK group is a 4-week course of ceftriaxone or another third-generation cephalosporin alone, or ampicillin Other Gram-negative bacteria, such as Escherichia coli, Pseudomonas aeruginosa, or Serratia marcescens, are rare causes of IE. Few data are available to determine a single best antimicrobial agent, and thus, treatment is individualized according to the judgment of the expert consultant and guided by identification of the organism and antimicrobial suscepti- bility testing. 