Treatment of Streptococcus Group C Pharyngitis
Important Clarification
Group C streptococcal pharyngitis should be treated with the same antibiotic regimens as Group A streptococcal (GAS) pharyngitis, as the clinical approach and antimicrobial susceptibility patterns are similar. 1
First-Line Treatment for Non-Allergic Patients
Penicillin or amoxicillin remains the treatment of choice based on proven efficacy, narrow spectrum, safety profile, and low cost. 1
Oral Penicillin Options:
- Penicillin V: 250 mg four times daily OR 500 mg twice daily for 10 days in adults 1, 2
- Penicillin V (pediatric): 250 mg two to three times daily for 10 days 2
- Amoxicillin: 50 mg/kg once daily (maximum 1000 mg) OR 25 mg/kg twice daily (maximum 500 mg/dose) for 10 days 1, 2
Intramuscular Option:
- Benzathine penicillin G: Single injection of 600,000 units for patients <60 lbs or 1,200,000 units for patients >60 lbs 2
- Reserved for patients unlikely to complete oral therapy 1
Treatment for Penicillin-Allergic Patients
For Non-Immediate (Non-Anaphylactic) Hypersensitivity:
First-generation cephalosporins are preferred alternatives, with cross-reactivity risk <3-10%. 1, 3, 2
- Cephalexin: 20 mg/kg/dose twice daily (maximum 500 mg/dose) for 10 days 1, 2
- Cefadroxil: 30 mg/kg once daily (maximum 1 g) for 10 days 1, 2
For Immediate/Anaphylactic Hypersensitivity:
Clindamycin is the preferred alternative, with macrolides as acceptable options. 1, 3, 2
Clindamycin: 7 mg/kg/dose three times daily (maximum 300 mg/dose) for 10 days 1, 2
- Resistance in the United States is approximately 1% 1
Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 1, 2, 4
Clarithromycin: 7.5 mg/kg/dose twice daily (maximum 250 mg/dose) for 10 days 1, 2
- Resistance to macrolides is well-known and varies geographically 1
Duration of Therapy
All antibiotics except azithromycin require a full 10-day course to achieve maximal pharyngeal eradication and prevent complications. 1, 2
- Azithromycin is the only agent approved for 5-day therapy 1, 2
- Short-course cephalosporin regimens (5 days) cannot be endorsed due to lack of strict study criteria and broader spectrum 1
Adjunctive Symptomatic Treatment
Analgesics/antipyretics should be considered for moderate to severe symptoms or high fever. 1
- Acetaminophen or NSAIDs are recommended 1, 2
- Avoid aspirin in children due to risk of Reye syndrome 1, 2
- Corticosteroids are not recommended 1
Critical Pitfalls to Avoid
Antibiotics That Should NOT Be Used:
- Tetracyclines: High prevalence of resistant strains 1, 2
- Sulfonamides and trimethoprim-sulfamethoxazole: Do not eradicate streptococci from the pharynx 1, 2
- Older fluoroquinolones (ciprofloxacin): Limited activity against streptococci 1, 2
- Newer fluoroquinolones (levofloxacin, moxifloxacin): Unnecessarily broad spectrum and expensive 1
Cephalosporin Use in Penicillin Allergy:
- Never use cephalosporins in patients with immediate/anaphylactic penicillin reactions due to 10% cross-reactivity risk 1, 2
Macrolide Resistance:
- There is significant resistance to azithromycin and clarithromycin in some parts of the United States, making susceptibility testing important when using these agents 4, 5
Follow-Up and Special Circumstances
Routine Follow-Up:
- Posttreatment throat cultures or rapid antigen tests are not recommended routinely 1
- Patients with worsening symptoms after 48-72 hours or symptoms lasting >5 days after treatment initiation should be reevaluated 5
Asymptomatic Household Contacts:
- Diagnostic testing or empiric treatment of asymptomatic household contacts is not routinely recommended 1, 6
- Penicillin prophylaxis has not been shown to reduce subsequent infection rates 1, 6