Ampicillin 2 g IV every 4 h is a reasonable alternative to penicillin if a penicillin shortage exists. Plus Gentamicin sulfate 3 mg/kg per 24 h IV or IM in 1 dose 2 Ceftriaxone may be a reasonable alternative treatment option for VGS isolates that are susceptible to ceftriaxone (Class IIb; Level of Evidence C). Vancomycin hydrochloride 30 mg/kg per 24 h IV in 2 equally divided doses 4 Class IIa; Level of Evidence C Vancomycin therapy is reasonable only for patients unable to tolerate penicillin or ceftriaxone therapy. IE indicates infective endocarditis; IM, intramuscular; IV, intravenous; MIC, minimum inhibitory concentration; NVE, native valve infective endocarditis; and VGS, viridans group streptococci. MIC is >0.12 to <0.5 g/mL for penicillin. The subdivisions differ from Clinical and Laboratory Standards Institute recommended break points that are used to define penicillin susceptibility.) *Doses recommended are for patients with normal renal function. See Table 7 for appropriate dose of gentamicin. Although it is preferred that gentamicin (3 mg/kg) be given as a single daily dose to adult patients with endocarditis caused by viridans group streptococci, as a second option, gentamicin can be administered daily in 3 equally divided doses. See Table 7 for appropriate dosage of vancomycin. Baddour et al Infective Endocarditis in Adults 1449 S pneumoniae resistant to penicillin (MIC, 0.1 4 g/mL), patients were evaluated and compared with 39 patients who were infected with penicillin-susceptible strains. Several key observations were made. Infection by penicillin-resis- tant strains did not worsen prognosis. High-dose penicillin or a third-generation cephalosporin is reasonable in patients with penicillin-resistant IE without meningitis. In patients with IE and meningitis, high doses of cefotaxime are rea- sonable. If the isolate is resistant (MIC 2 g/mL) to cefo- taxime, then the addition of vancomycin and rifampin may be considered. 