What is the treatment for Streptococcus anginosus (S. anginosus) endocarditis?

From the Guidelines

The treatment for Streptococcus anginosus (S. anginosus) endocarditis typically involves a 4-week course of intravenous antibiotics, with penicillin G (12-18 million U/day i.v. either in 4-6 doses or continuously) or amoxicillin (100-200 mg/kg/day i.v. in 4-6 doses) being the preferred options, as recommended by the 2015 ESC guidelines 1. The choice of antibiotic regimen depends on the susceptibility of the S. anginosus strain to penicillin, with strains susceptible to penicillin (MIC ≤ 0.125 mg/L) being treated with penicillin G or amoxicillin for 4 weeks 1. For patients with beta-lactam allergy, vancomycin (30 mg/kg/day i.v. in 2 doses) is recommended for 4 weeks 1. Some key points to consider in the treatment of S. anginosus endocarditis include:

• The use of gentamicin (3 mg/kg/day i.v. or i.m. in 1 dose) in combination with penicillin G or amoxicillin for the first 2 weeks, especially in patients with complicated endocarditis 1
• The importance of monitoring renal function and serum gentamicin concentrations once a week, with pre-dose (trough) concentrations < 1 mg/L and post-dose (peak) serum concentrations of 10-12 mg/L 1
• The need for regular cardiac monitoring and follow-up echocardiography to assess valve function after completing therapy 1
• The potential for surgical intervention in cases of complications such as heart failure, persistent bacteremia despite appropriate antibiotics, large vegetations (>10 mm), or embolic events 1

From the Research

Treatment for Streptococcus anginosus (S. anginosus) Endocarditis

• The treatment for S. anginosus endocarditis is not directly addressed in the provided studies, but the treatment for endocarditis caused by other streptococci can be applied.
• For penicillin-susceptible streptococci, treatment options include:
  • Aqueous penicillin G administered intravenously for four weeks 2
  • Intravenous aqueous penicillin G for four weeks combined with streptomycin for the first two weeks of therapy 2
  • Parenterally administered penicillin plus streptomycin for two weeks 2
  • Ceftriaxone once daily for four weeks 3
• For streptococcal endocarditis, a combination of a beta-lactam with an aminoglycoside can shorten the treatment duration 4
• The American Heart Association guidelines recommend 4 weeks of benzylpenicillin (or ceftriaxone) for uncomplicated cases of endocarditis due to penicillin-susceptible viridans streptococci or Streptococcus bovis 5
• A 2-week course of treatment can be used when gentamicin is added, in patients at low risk for adverse events caused by gentamicin therapy 5

Considerations for Treatment

• The choice of treatment should be guided by the identification of the causative micro-organism and its susceptibility to antibiotics 5
• Patients with endocarditis caused by strains of viridans streptococci or S. bovis relatively resistant to penicillin, or by enterococci, may require combination therapy with benzylpenicillin and gentamicin 5
• The treatment regimen should be individualized based on the patient's risk factors, such as the presence of prosthetic valves or the duration of symptoms 2, 4