What is the recommended treatment for an adult patient with streptococcal (strep) infection?

Treatment for Adult Streptococcal Pharyngitis

For confirmed Group A streptococcal pharyngitis in adults, treat with penicillin V 250 mg four times daily or 500 mg twice daily for 10 days, or amoxicillin 500 mg twice daily for 10 days. 1

Confirm the Diagnosis Before Treating

• Only treat patients with laboratory-confirmed Group A streptococcal infection using either rapid antigen detection test (RADT) or throat culture 1
• Use the modified Centor criteria to determine who needs testing: fever by history, tonsillar exudates, tender anterior cervical adenopathy, and absence of cough 1
• Patients with fewer than 3 Centor criteria do not need testing and should not receive antibiotics 1
• For adults, a negative RADT does not require confirmation with throat culture, unlike in children 1

Common pitfall: Over 60% of adults with sore throat receive antibiotics, but only 10% actually have Group A streptococcal infection 1, 2. Testing before prescribing prevents unnecessary antibiotic use.

First-Line Antibiotic Therapy

For Patients Without Penicillin Allergy

• Penicillin V (oral): 250 mg four times daily OR 500 mg twice daily for 10 days 1
• Amoxicillin (oral): 500 mg twice daily for 10 days 1
• Benzathine penicillin G (intramuscular): 1.2 million units as a single dose 1

Penicillin remains the agent of choice due to its proven efficacy, narrow spectrum, safety profile, and low cost 1. Amoxicillin is equally effective and often preferred for better palatability 1.

For Patients With Penicillin Allergy

• First-generation cephalosporins: Cephalexin 500 mg twice daily for 10 days OR cefadroxil 1 g once daily for 10 days (avoid in immediate hypersensitivity reactions) 1
• Clindamycin: 300 mg three times daily for 10 days 1
• Azithromycin: 500 mg on day 1, then 250 mg daily for days 2-5 (total 5 days) 1
• Clarithromycin: 250 mg twice daily for 10 days 1

Important caveat: Significant resistance to azithromycin and clarithromycin exists in some U.S. regions 2. First-generation cephalosporins are preferred alternatives when there is no history of immediate-type hypersensitivity to beta-lactams 1.

Treatment Duration and Rationale

• Standard duration is 10 days for oral penicillin or amoxicillin to ensure eradication of Group A Streptococcus from the pharynx 1
• Therapy can be safely initiated up to 9 days after symptom onset and still prevent acute rheumatic fever 1
• Shorter courses (5 days) with azithromycin are acceptable alternatives but have lower strength of evidence 1

Symptomatic Management

• Offer analgesics such as acetaminophen, NSAIDs, or throat lozenges for moderate to severe symptoms 1
• Avoid aspirin in children, but it is acceptable for adults 1
• Do not use corticosteroids for routine treatment of streptococcal pharyngitis 1

Clinical Benefits and Limitations

• Antibiotics shorten symptom duration by only 1-2 days, with a number needed to treat of 6 at 3 days and 21 at 1 week 1
• The primary benefit is prevention of complications: acute rheumatic fever (rare in adults), peritonsillar abscess, and spread during outbreaks 1
• Antibiotics do not reliably prevent acute glomerulonephritis 1

When NOT to Treat

• Do not treat chronic Group A Streptococcus carriers who have repeated viral infections with positive tests, as they are at low risk for complications and transmission 1
• Do not routinely perform post-treatment testing in asymptomatic patients 1
• Do not test or treat asymptomatic household contacts 1

Reevaluation Criteria

• Patients with worsening symptoms after appropriate antibiotic initiation or symptoms lasting 5 days after treatment starts should be reevaluated 2
• Consider treatment failure if symptoms persist, and evaluate for complications such as peritonsillar abscess, parapharyngeal abscess, or Lemierre syndrome 1
• Be vigilant for Lemierre syndrome in adolescents and young adults with severe pharyngitis, as this rare condition requires urgent diagnosis and treatment 1

Special Considerations for Recurrent Infections

• Tonsillectomy is rarely indicated: consider only after 7 episodes in 1 year, 5 episodes per year for 2 years, or 3 episodes per year for 3 years 2
• For recurrent pharyngitis shortly after treatment completion, consider a second course with the same agent or switch to intramuscular benzathine penicillin G if compliance is questionable 1