Treatment of MSSA Bacteremia

First-Line Treatment Options

• The American Heart Association recommends nafcillin or oxacillin as the preferred first-line agent for MSSA bacteremia, with a recommended duration of 6 weeks for uncomplicated left-sided infective endocarditis (IE) and at least 6 weeks for complicated IE 2
• Cefazolin is an acceptable alternative to nafcillin/oxacillin in patients with non-severe penicillin allergies 1

Clinical Scenarios and Treatment Algorithms

• Piperacillin/tazobactam may be appropriate for initial empiric coverage when polymicrobial infection is suspected, including both gram-negative and anaerobic organisms 1
• Piperacillin/tazobactam may be appropriate for initial empiric coverage when the patient has risk factors for healthcare-associated infections 1

Special Considerations

• In cases of MSSA bacteremia with brain abscess, nafcillin is preferred over cefazolin due to better blood-brain barrier penetration 2
• For patients with right-sided IE, gentamicin should not be added to beta-lactam therapy (Class III; Level of Evidence B) 2

Duration of Therapy

• For complicated infections, such as endocarditis, osteomyelitis, etc., 4-6 weeks of therapy is recommended 2
• For left-sided IE, 6 weeks of therapy is recommended 2