From the FDA Drug Label
Serious infections, such as pneumonia and endocarditis, due to susceptible strains of streptococci (including S pneumoniae) and meningococcus 150,000 - 300,000 units/kg/day divided in equal doses every 4 to 6 hours; duration depends on infecting organism and type of infection
- Streptococcus mitis is a type of streptococci, and the recommended dosage for serious infections due to susceptible strains of streptococci is 150,000 - 300,000 units/kg/day.
- The dosage should be divided into equal doses every 4 to 6 hours.
- The duration of treatment depends on the infecting organism and type of infection 1.
Note: There is no specific mention of Streptococcus mitis bacteremia in the provided drug label, but it can be inferred that the treatment for serious infections due to susceptible strains of streptococci can be applied to Streptococcus mitis bacteremia. However, the treatment should be guided by the severity of the infection, the patient's condition, and the susceptibility of the organism to penicillin G.
Alternatively, Ceftriaxone can be used to treat streptococcal infections, including Streptococcus mitis.
The usual adult daily dose is 1 to 2 grams given once a day (or in equally divided doses twice a day) depending on the type and severity of infection.
- The recommended dosage for adults with serious infections is 1 to 2 grams per day, which can be administered once a day or divided into two doses 2.
From the Research
Streptococcus mitis bacteremia should be treated with ceftriaxone 2g IV daily for 2 weeks, as it has been shown to be a reasonable treatment option with no significant increase in risk of adverse events or treatment failure compared to penicillin G 3.
Treatment Considerations
- For severe infections or endocarditis, treatment should be extended to 4-6 weeks, often with the addition of gentamicin 1mg/kg IV every 8 hours for the first 2 weeks for synergistic effect.
- Blood cultures should be repeated to confirm clearance of the bacteremia.
- Susceptibility testing is essential as some S. mitis strains have reduced penicillin susceptibility.
- If the minimum inhibitory concentration (MIC) for penicillin is >0.5 μg/mL, higher doses of penicillin or alternative agents like vancomycin 15-20mg/kg IV every 12 hours may be necessary.
Source Control and Prevention
- Source control is critical, so any potential sources such as intravascular catheters, dental infections, or endocarditis should be addressed.
- S. mitis is part of the viridans group streptococci and normally inhabits the oral cavity but can cause bacteremia following dental procedures or in immunocompromised patients, with potential complications including endocarditis if left untreated.
Key Points
- Ceftriaxone is a suitable alternative to penicillin G for the treatment of S. mitis bacteremia, especially in penicillin-allergic patients.
- Vancomycin-based regimens may be considered for highly penicillin-resistant VGS IE, but further clinical studies are needed to confirm its role 4.
- The emergence of high-level daptomycin resistance among VGS strains warrants caution in the use of daptomycin therapy for VGS IE 4.