From the Guidelines
The most appropriate treatment for Methicillin-Susceptible Staphylococcus aureus (MSSA) infecting native valves, including complicated right-sided and left-sided endocarditis, is a semisynthetic, β-lactamase–resistant penicillin, such as nafcillin or oxacillin, given intravenously for a minimum of 4 to 6 weeks, as recommended by the American Heart Association 1. This recommendation is based on the high efficacy of β-lactam antibiotics in treating MSSA infections, as well as their ability to penetrate tissues and eradicate the infection. The use of gentamicin in combination with a β-lactam antibiotic is not recommended due to the increased risk of renal and otic toxicity, as noted in the guidelines 1. Some key points to consider in the treatment of MSSA endocarditis include:
- The use of β-lactam antibiotics, such as nafcillin or oxacillin, as the first-line treatment for MSSA endocarditis 1
- The recommendation for a minimum treatment duration of 4 to 6 weeks to ensure complete eradication of the infection 1
- The potential use of alternative antibiotics, such as vancomycin or daptomycin, in patients with severe β-lactam allergies or in cases where the organism is resistant to β-lactam antibiotics 1
- The importance of careful monitoring and management of potential complications, such as embolic events or heart failure, in patients with MSSA endocarditis 1 It is essential to note that the treatment of MSSA endocarditis should be individualized based on the patient's specific clinical presentation, microbiological results, and other factors, such as the presence of complications or comorbidities. Therefore, the treatment should be guided by the most recent and highest-quality evidence, as well as expert recommendations from reputable organizations, such as the American Heart Association 1.
From the Research
Treatment Options for MSSA Infecting Native Valves
The treatment options for Methicillin-Susceptible Staphylococcus aureus (MSSA) infecting native valves, including complicated right-sided and left-sided endocarditis, are as follows:
- For right-sided MSSA infective endocarditis, a minimum of 2 weeks of antimicrobial therapy is recommended 2
- For uncomplicated left-sided MSSA infective endocarditis, a minimum of 4 weeks of antimicrobial therapy is recommended 2
- For complicated left-sided MSSA infective endocarditis, a minimum of 6 weeks of antimicrobial therapy is recommended 2
- Combination therapy with a cell-wall active agent (e.g. flucloxacillin) and an aminoglycoside may be considered during the initial 3-5 days of therapy to shorten the duration of bacteraemia 2
- Ceftriaxone may be an alternative for the treatment of MSSA bloodstream infections, but its effectiveness for infective endocarditis is not well established 3
- Surgical treatment may be necessary for complicated cases, with a strategy based on debridement of the infected area, valve repair whenever possible, and use of a biological substitute if valve replacement is unavoidable 4
- Daptomycin may be an efficacious and well-tolerated alternative to standard therapy in the treatment of right-sided endocarditis, but its effectiveness for left-sided endocarditis is limited 5
Key Considerations
- The choice of antimicrobial therapy should be based on the susceptibility of the infecting organism 2
- Early and close liaison with cardiology and cardiothoracic surgery services is essential for complicated cases 2
- Patients with left-sided endocarditis tend to have a poorer clinical outcome than those with isolated right-sided endocarditis 4
- The treatment of MSSA infective endocarditis requires a comprehensive approach, including antimicrobial therapy, surgical intervention, and close monitoring of the patient's condition 2, 4, 5