From the Guidelines
The treatment of viridans streptococcus bacteremia typically involves penicillin G as the first-line therapy, administered at 24 million U/24 h IV either continuously or in 4–6 equally divided doses for 4 weeks, as recommended by the American Heart Association 1. The choice of penicillin G is based on its ability to inhibit cell wall synthesis in these gram-positive bacteria, which typically have minimal resistance mechanisms.
- For patients with penicillin allergy, alternative treatments such as ceftriaxone 2g IV daily or vancomycin 30 mg/kg per 24 h IV in 2 equally divided doses can be used, as suggested by the American Heart Association 1.
- In cases of endocarditis or other complicated infections, treatment should be extended to 4-6 weeks, often with the addition of gentamicin 3 mg/kg per 24 h IV or IM in 1 dose for the first 2 weeks for synergistic effect, as recommended by the American Heart Association 1.
- Blood cultures should be repeated to confirm clearance of the bacteremia.
- For patients with prosthetic valves or immunosuppression, more aggressive therapy may be needed, and treatment should be adjusted based on antimicrobial susceptibility testing, as some strains may show reduced susceptibility to penicillin, as noted by the American College of Cardiology/American Heart Association 1.
- Supportive care including fever management and addressing the source of infection (such as dental procedures or mucosal damage) is also essential for complete resolution.
From the FDA Drug Label
Vancomycin Hydrochloride for Injection, USP has been reported to be effective alone or in combination with an aminoglycoside for endocarditis caused by S. viridans or S. bovis. The treatment for Viridans streptococcus bacteremia is vancomycin alone or in combination with an aminoglycoside 2.
- Vancomycin is effective against Viridans streptococcus.
- The combination of vancomycin and an aminoglycoside acts synergistically against many strains of Viridans streptococcus 2.
From the Research
Treatment Options for Viridans Streptococcus Bacteremia
- Ceftriaxone and penicillin G are considered reasonable treatment options for viridans group streptococci bloodstream infections 3
- The introduction of penicillin in prophylactic antibiotic treatments has reduced the incidence of viridans streptococcus bacteremia, but the long-term use of penicillin could be compromised by the emergence of resistant strains 4
- All viridans group streptococci isolates were susceptible to ertapenem, meropenem, linezolid, and vancomycin, while 25.8% were resistant to penicillin 5
- Ceftriaxone and cefepime were active against 96.9% of the isolates, and vancomycin, ertapenem, meropenem, and linezolid were the most active antibiotics 5
Antibiotic Susceptibility
- Viridans group streptococci blood culture isolates demonstrated resistance to penicillin, amoxicillin, ceftriaxone, erythromycin, clindamycin, rifampicin, vancomycin, and teicoplanin 6
- S. oralis and S. mitis demonstrated the highest levels of resistance to the agents tested, with 27% of S. oralis isolates resistant to penicillin and 51% resistant to erythromycin 6
- High-level resistance to ceftriaxone was found in 12 isolates, comprising S. oralis, S. mitis, and S. parasanguis 6
Risk Factors and Clinical Considerations
- Lower absolute neutrophil count (ANC) predicted viridans group streptococcal bacteremia in neutropenic patients, while recent use of vancomycin was protective 7
- No clinical factors were associated with viridans group streptococcal bacteremia in non-neutropenic cases 7
- Profound neutropenia increases the risk for viridans group streptococcal bacteremia, and antimicrobial choices should be made with this in mind 7