Ceftriaxone-ampicillin therapy is reasonable and is given for 6 weeks. The rationale for double -lactam therapy is outlined above. For gentamicin-resistant and streptomycin-susceptible E faecalis, ampicillin-ceftriaxone is reasonable. The 2005 AHA recommended streptomycin for patients with gentamicin-resistant strains of enterococci. The limitations of streptomycin use are summarized above. The total number of cases published in the European studies far exceeds the rela- tively small number of reported streptomycin-treated patients with enterococcal IE. Although there are no published data comparing ampicillin-ceftriaxone with streptomycin-con- taining regimens, we believe that ampicillin-ceftriaxone is reasonable for these patients. Disadvantages of streptomycin- containing regimens are outlined above. Recommendations 1. Ceftriaxone-ampicillin combination therapy is reasonable for IE caused by aminoglycoside- resistant enterococcal strains (Class IIa; Level of Evidence B). 2. For gentamicin-resistant and streptomycin-suscep- tible Enterococcus species, ampicillin-ceftriaxone combination therapy is reasonable (Class IIa; Level of Evidence B). Vancomycin Therapy for Enterococcal IE in Patients Unable to Tolerate -Lactams or Patients With E faecalis Resistant to Penicillin The regimens that are reasonable for these patients are shown in Table 14.Vancomycin should be administered only if a patient is unable to tolerate penicillin or ampicillin. Combinations of pen- icillin or ampicillin with gentamicin are preferable to combined vancomycin-gentamicin because of the potential increased risk of ototoxicity and nephrotoxicity with the vancomycin-genta- micin combination. Moreover, combinations of penicillin or ampicillin and gentamicin are more active than combinations of vancomycin and gentamicin in vitro and in animal models of experimental IE. It is reasonable that patients with NVE receive 6 weeks of vancomycin-gentamicin therapy and that patients with PVE receive at least 6 weeks of therapy. Baddour et al Infective Endocarditis in Adults 1459 Rarely,strainsofEfaecalisproduceaninducible -lactamase. These -lactamase producing strains are susceptible to ampicil- lin-sulbactam and to vancomycin. 