Does Augmentin (amoxicillin-clavulanate) treat gamma-hemolytic strep and Viridans strep infections?

Augmentin for Gamma-Hemolytic and Viridans Streptococcal UTI

Augmentin (amoxicillin-clavulanate) is effective against viridans streptococci and can be used for urinary tract infections caused by these organisms, though plain amoxicillin alone is typically sufficient since these streptococci are generally beta-lactamase negative. 1

Spectrum of Activity

Viridans Streptococci Coverage

• Amoxicillin (the active component of Augmentin) is FDA-approved for infections caused by alpha-hemolytic streptococci, which includes viridans group streptococci 1
• Viridans streptococci are typically susceptible to penicillins, including amoxicillin, though resistance rates have increased to 13-50% in some populations 2
• Ticarcillin, piperacillin, cefepime, and carbapenems all demonstrate excellent activity against most viridans streptococcal strains 2

Gamma-Hemolytic Streptococci

• The term "gamma-hemolytic strep" refers to non-hemolytic streptococci, which includes some enterococcal species and other streptococcal variants 1
• Amoxicillin is specifically FDA-approved for Enterococcus faecalis (a common gamma-hemolytic organism) in genitourinary tract infections 1
• For enterococcal UTIs, high-dose amoxicillin (500 mg every 8 hours) achieves sufficient urinary concentrations even against resistant strains 2

Clinical Considerations for UTI Treatment

When Augmentin is Preferred Over Plain Amoxicillin

• The clavulanate component is only necessary if beta-lactamase-producing co-pathogens are suspected 3
• In mixed infections with beta-lactamase producers (like certain Staphylococcus aureus strains), plain amoxicillin may fail while amoxicillin-clavulanate succeeds 3
• For uncomplicated streptococcal UTI without mixed flora, plain amoxicillin is equally effective and has fewer gastrointestinal side effects 4

Dosing for UTI

• Standard adult dosing: 500 mg orally every 8 hours or 875 mg every 12 hours 1
• For resistant enterococcal UTI: Consider 500 mg every 8 hours to maximize urinary drug concentrations 2
• Treatment duration: Minimum 48-72 hours beyond symptom resolution 1

Important Caveats

Resistance Patterns

• Viridans streptococci show 13-15% resistance to amoxicillin in some studies, with higher rates (17-50%) in immunocompromised populations 2
• Macrolide resistance is significantly higher (22-58%), making amoxicillin a better choice than azithromycin or clarithromycin 2
• Cephalexin shows 96% resistance rates against viridans streptococci and should be avoided 2

When to Avoid or Supplement

• If penicillin-resistant viridans streptococci are documented or suspected in high-risk patients (neutropenic, cancer patients), vancomycin may be necessary 2
• Quinolones (ciprofloxacin) are not as effective as beta-lactams for gram-positive infections and may predispose to viridans streptococcal sepsis 2
• For serious systemic viridans infections (not simple UTI), mortality may be higher without vancomycin coverage 2

Practical Algorithm

1. Confirm organism identification: Distinguish true viridans/gamma-hemolytic strep from colonization 2
2. Assess for mixed infection: If purulent drainage or polymicrobial UTI suspected, use Augmentin over plain amoxicillin 3
3. Check local susceptibility data: If local viridans resistance to penicillins exceeds 20%, consider alternative agents 2
4. For uncomplicated UTI with confirmed susceptible streptococci: Plain amoxicillin 500 mg every 8 hours is sufficient 1, 5
5. For complicated UTI or uncertain susceptibility: Augmentin 500 mg every 8 hours provides broader coverage 1, 6