From the Guidelines
Streptococcus mitis bacteremia should be treated with intravenous penicillin G at 3-4 million units every 4 hours for 2 weeks, or ceftriaxone 2g IV daily for 2 weeks in penicillin-allergic patients. For severe infections or endocarditis, treatment should be extended to 4-6 weeks, often with the addition of gentamicin 3mg/kg/day for the first 2 weeks 1. Blood cultures should be obtained before starting antibiotics to confirm the diagnosis and test for antibiotic susceptibility, as some strains may have reduced penicillin susceptibility. Echocardiography is recommended to rule out endocarditis, particularly in patients with heart valve abnormalities, prosthetic valves, or persistent fever.
Key Considerations
- S. mitis is part of the viridans group streptococci and normally inhabits the oral cavity but can enter the bloodstream during dental procedures or with poor oral hygiene 2.
- While generally less virulent than other streptococci, it can cause serious infections in immunocompromised patients or those with cardiac abnormalities.
- Follow-up blood cultures should be obtained to ensure clearance of the infection.
Treatment Approach
- The choice of antibiotic therapy should be guided by the results of blood cultures and antibiotic susceptibility testing.
- In cases of penicillin-resistant S. mitis, alternative therapies such as vancomycin or daptomycin may be considered 1.
- The use of rifampin should be avoided in the initial treatment of S. mitis bacteremia, as it may promote the development of resistant strains 1.
From the Research
Strep Mitis Bacteremia Overview
- Strep mitis bacteremia is a type of bloodstream infection caused by the Streptococcus mitis bacteria, which is a member of the viridans group streptococci (VGS) 3, 4.
- The bacteria can cause a range of infections, including endocarditis, which is an infection of the heart valves 4, 5.
Treatment Options
- Ceftriaxone and penicillin G are considered reasonable treatment options for VGS bloodstream infections, including Strep mitis bacteremia 3.
- Vancomycin-based regimens may be effective for treating highly penicillin-resistant VGS infections, including those caused by Strep mitis 5.
- Oral antibiotic step-down therapy may be appropriate for the treatment of uncomplicated Strep mitis bacteremia, depending on factors such as patient comorbidities and clinical progress 6.
Clinical Outcomes
- The clinical outcomes of patients with Strep mitis bacteremia can vary depending on the treatment used and the presence of underlying health conditions 3, 7.
- Hospital readmission due to VGS bacteremia or therapy complications is a common outcome in patients with complicated VGS bacteremia 3.
- The use of vancomycin-based regimens has been shown to be effective in treating highly penicillin-resistant VGS infections, including those caused by Strep mitis 5.
Antibiotic Resistance
- Antibiotic resistance is a concern in the treatment of Strep mitis bacteremia, with some strains showing high levels of resistance to penicillin and other antibiotics 4, 5.
- The emergence of high-level daptomycin resistance among VGS strains warrants caution in the use of daptomycin therapy for VGS infections 5.