What is the recommended antibiotic treatment for a patient with bacterial tonsillitis, possibly caused by group A streptococcus?

Antibiotic Treatment for Bacterial Tonsillitis

Penicillin V (250 mg four times daily or 500 mg twice daily) or amoxicillin (50 mg/kg once daily, maximum 1000 mg) for 10 days is the first-line treatment for Group A streptococcal tonsillitis in non-allergic patients, with no documented resistance anywhere in the world. 1

First-Line Treatment for Non-Allergic Patients

Penicillin remains the gold standard due to its proven efficacy, narrow spectrum, safety profile, and low cost 1. The recommended regimens are:

• Penicillin V (oral): 250 mg twice or three times daily in children; 250 mg four times daily or 500 mg twice daily in adolescents and adults for 10 days 1
• Amoxicillin (oral): 50 mg/kg once daily (maximum 1000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days—often preferred in children due to better taste acceptance 1
• Benzathine penicillin G (intramuscular): Single dose of 600,000 units for patients under 27 kg; 1,200,000 units for patients 27 kg or greater—particularly useful when compliance is questionable 1

The 10-day course is essential to achieve maximal pharyngeal eradication and prevent acute rheumatic fever 2, 1. Antibiotics shorten symptom duration by only 1-2 days, but critically prevent complications including acute rheumatic fever, peritonsillar abscess, and further spread 2.

Treatment for Penicillin-Allergic Patients

Non-Immediate (Non-Anaphylactic) Penicillin Allergy

First-generation cephalosporins are the preferred first-line alternatives with strong, high-quality evidence 1, 3:

• Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg/dose) for 10 days in children; 500 mg twice daily for 10 days in adults 1, 3
• Cefadroxil: 30 mg/kg once daily (maximum 1 gram) for 10 days 3

The cross-reactivity risk with first-generation cephalosporins is only 0.1% in patients with non-severe, delayed penicillin reactions 3.

Immediate/Anaphylactic Penicillin Allergy

All beta-lactam antibiotics must be avoided due to up to 10% cross-reactivity risk with cephalosporins 1, 3. Clindamycin is the preferred alternative:

• Clindamycin: 7 mg/kg per dose three times daily (maximum 300 mg/dose) for 10 days in children; 300 mg three times daily for 10 days in adults 1, 3
• Clindamycin has strong, moderate-quality evidence and only ~1% resistance among Group A Streptococcus in the United States 1, 3
• Particularly effective in chronic carriers and treatment failures due to superior intracellular penetration 1, 4

Macrolides are acceptable alternatives but less preferred:

• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days—the only antibiotic requiring just 5 days due to prolonged tissue half-life 1, 3
• Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg/dose) for 10 days 3
• Erythromycin: 20-40 mg/kg/day divided 2-3 times daily (maximum 1 gram per day) for 10 days—less preferred due to gastrointestinal side effects 3, 5

Critical Resistance Considerations

Macrolide resistance among Group A Streptococcus is approximately 5-8% in the United States but varies geographically and temporally 1, 3. In areas with high macrolide resistance, clindamycin or first-generation cephalosporins are strongly preferred 1. Local resistance patterns should always be considered before prescribing macrolides 1, 3.

Clindamycin resistance remains very low at approximately 1%, making it more reliable than macrolides when beta-lactams cannot be used 3.

Management of Treatment Failures

For patients who fail initial penicillin therapy, several factors may be responsible including noncompliance, beta-lactamase-producing bacteria (BLPB) that "shield" Group A Streptococcus, or chronic carrier state 4, 6. Beta-lactamase-producing bacteria were recovered from over 75% of tonsils in patients with recurrent infection 4.

Retreatment options for failures 2, 1:

• Clindamycin: 20-30 mg/kg/day in children or 600 mg/day in 2-4 divided doses in adults for 10 days—particularly effective following penicillin failures due to ability to eradicate BLPB and superior intracellular penetration 2, 1
• Amoxicillin-clavulanate: 40 mg/kg/day in 3 equally divided doses for 10 days (maximum 750 mg amoxicillin per day) 2
• Benzathine penicillin G: Useful if compliance with previous oral antimicrobials is questionable; limited data suggest adding rifampin (10 mg/kg twice daily for 4 days, maximum 300 mg twice daily) may be beneficial 2

Common Pitfalls to Avoid

• Do not use cephalosporins in patients with immediate/anaphylactic penicillin reactions due to 10% cross-reactivity risk 1, 3
• Do not prescribe shorter courses than recommended (except azithromycin's 5-day regimen)—this leads to treatment failure and increased risk of acute rheumatic fever 1, 3
• Do not assume all penicillin-allergic patients cannot receive cephalosporins—only those with immediate/anaphylactic reactions should avoid them 3
• Do not prescribe broad-spectrum cephalosporins (cefaclor, cefuroxime, cefixime, cefdinir, cefpodoxime) when narrow-spectrum first-generation agents are appropriate—they are more expensive and more likely to select for antibiotic-resistant flora 3
• Do not perform routine follow-up throat cultures for asymptomatic patients who have completed therapy 2, 3

Adjunctive Symptomatic Treatment

Acetaminophen or NSAIDs (such as ibuprofen) should be considered for moderate to severe symptoms or high fever 1, 3. Aspirin must be avoided in children due to risk of Reye syndrome 3. Corticosteroids are not recommended as adjunctive therapy 1, 3.

Special Considerations for Recurrent Tonsillitis

For patients with multiple repeated culture-positive episodes over months to years, it may be difficult to differentiate viral infections from true Group A streptococcal infections in a streptococcal carrier 2. Chronic carriers generally do not require antimicrobial therapy as they are unlikely to spread infection and are at little risk for complications 3.

Continuous antimicrobial prophylaxis is not recommended except for preventing recurrences of acute rheumatic fever 2. Tonsillectomy may be considered for rare patients whose symptomatic episodes do not diminish in frequency over time, but it decreases recurrences only for a limited period 2.