Is Augmentin (amoxicillin-clavulanate) effective for treating Streptococcus anginosus infections?

Effectiveness of Augmentin (Amoxicillin-Clavulanate) for Streptococcus anginosus Infections

Augmentin (amoxicillin-clavulanate) is effective for treating Streptococcus anginosus infections, particularly when there is concern for mixed infections or beta-lactamase-producing organisms. 1

Streptococcus anginosus Group Characteristics

• S. anginosus belongs to the S. anginosus group (also known as S. milleri group), which includes S. intermedius, S. anginosus, and S. constellatus 1
• This group has a tendency to form abscesses and cause hematogenously disseminated infections (e.g., myocardial and visceral abscesses, septic arthritis, and vertebral osteomyelitis) 1
• While most S. anginosus strains are penicillin-susceptible, some may exhibit variable penicillin resistance 1
• S. anginosus group infections often present as invasive pyogenic infections that can be highly disseminated 2

Treatment Recommendations

First-line Options

• For penicillin-susceptible S. anginosus (MIC ≤0.125 μg/mL):

  • Penicillin G 12-18 million U/day IV in 4-6 doses for 4 weeks 1
  • Amoxicillin 100-200 mg/kg/day IV in 4-6 doses for 4 weeks 1
  • Ceftriaxone 2 g/day IV or IM in 1 dose for 4 weeks 1

• For mixed infections or when beta-lactamase-producing organisms are suspected:

  • Augmentin (amoxicillin-clavulanate) is recommended at a dose of 40 mg amoxicillin/kg/day in three doses (maximum = 2,000 mg amoxicillin per day) for 10 days 1

Special Considerations

• Augmentin is particularly valuable when mixed infections involving beta-lactamase-producing staphylococci and streptococci are present 3
• The addition of clavulanic acid to amoxicillin protects against beta-lactamase-mediated resistance, making it effective against mixed infections where beta-lactamase-producing organisms might inactivate amoxicillin 4
• For S. anginosus infections, short-term therapy (2 weeks) is not recommended; full course treatment is necessary 1
• When S. anginosus causes abscess formation, surgical drainage is often required in addition to antimicrobial therapy 2

Evidence Supporting Augmentin Use

• Augmentin has demonstrated effectiveness against a wide range of respiratory tract infections caused by beta-lactamase-producing pathogens 5
• In studies of mixed infections, amoxicillin-clavulanate successfully eliminated streptococci even in the presence of beta-lactamase-producing S. aureus, while amoxicillin alone failed 4
• Clinical studies have shown high cure rates with Augmentin in various infections, including respiratory tract infections 5, 6
• Augmentin has been specifically recommended for chronic streptococcal carriers with a strong, moderate level of evidence 1

Treatment Considerations and Pitfalls

• Abscess formation is common with S. anginosus infections, so surgical drainage should be considered alongside antibiotic therapy 1, 2
• Blood cultures should be obtained every 24-48 hours until bloodstream infection has cleared in cases of infective endocarditis 1
• If S. anginosus is isolated from blood cultures, evaluation for metastatic abscesses should be considered due to the organism's propensity for abscess formation 1, 2
• For disseminated S. anginosus infections, combination of surgical procedures with antimicrobial therapy is crucial for achieving full clinical recovery 2
• In cases of penicillin allergy, vancomycin can be used as an alternative 1

Duration of Therapy

• For most S. anginosus infections, a 4-week course of antibiotics is recommended 1
• For S. anginosus endocarditis, a full 4-week course is necessary 1
• For less severe infections such as skin/soft tissue infections without abscess formation, a 10-day course of Augmentin may be sufficient 1

Augmentin remains an important antimicrobial agent for treating S. anginosus infections, particularly when there is concern for mixed infections or beta-lactamase-producing organisms that might compromise the effectiveness of penicillin or amoxicillin alone.