For both MSSA and MRSA infections, use of adjunctive gentamicin for the treatment of S aureus bacteremia or right-sided NVE is discouraged Recommendation 1. Gentamicin is not recommended for treatment of right-sided staphylococcal NVE (Class III; Level of Evidence B). In patients for whom parenteral antibiotic therapy is problem- atic, oral treatment may be a reasonable option. Two studies have evaluated the use of predominantly oral 4-week antibiotic regimens (featuring ciprofloxacin plus rifampin) for the ther- apy of uncomplicated right-sided MSSA IE in IDUs.150,151 In each study, including one in which >70% of patients were HIV cure rates were >90%. However, the relatively high rate of quinolone resistance among contemporary S aureus strains has made this alternative treatment strategy problematic. IE in Non-IDUs Older anecdotal case reports in non-IDUs with S aureus IE suggested that the use of combined gentamicin-methicillin therapy may be of benefit in patients who fail to respond to monotherapy with methicillin.152 This issue was addressed in a multicenter, prospective trial comparing nafcillin alone for 6 weeks with nafcillin plus gentamicin (for the initial 2 weeks) in the treatment of predominantly left-sided IE caused by S Nafcillin-gentamicin therapy reduced the duration of bacteremia by 1 day compared with nafcillin monotherapy. However, combination therapy did not reduce mortality or the frequency of cardiac complications. Furthermore, combina- tion therapy increased the frequency of gentamicin-associated nephrotoxicity. As noted above,149 the risk of clinically sig- nificant nephrotoxicity with even short courses of adjunctive low-dose gentamicin for S aureus bacteremia and right-sided IE can be substantial. In addition, gentamicin should not be used with vancomycin in patients with MRSA NVE because of the nephrotoxicity risk.13,149 In cases of brain abscess com- plicating MSSA IE, nafcillin is the preferred agent rather than cefazolin, which has inadequate blood-brain barrier penetra- bility. 