What is the recommended treatment for group A streptococcal (strep) infection?

Treatment for Group A Streptococcal Infection

Penicillin V (250 mg four times daily or 500 mg twice daily) or amoxicillin (50 mg/kg once daily, maximum 1000 mg) for a full 10 days is the first-line treatment for Group A streptococcal pharyngitis, with penicillin preferred due to its narrow spectrum, proven efficacy, safety profile, and low cost. 1, 2

First-Line Antibiotic Regimens

For pharyngeal infections (strep throat):

• Penicillin V is the drug of choice with dosing options of 250 mg four times daily OR 500 mg twice daily for 10 days in adolescents and adults 1, 2
• Amoxicillin 50 mg/kg once daily (maximum 1000 mg) for 10 days is equally effective and often preferred in children due to better palatability and once-daily dosing 1, 2
• Intramuscular benzathine penicillin G as a single dose (600,000 units if <27 kg; 1,200,000 units if ≥27 kg) ensures compliance when adherence to oral therapy is uncertain 1

The twice-daily penicillin V regimen (500 mg) is as effective as more frequent dosing and improves compliance 3, 4. Avoid once-daily penicillin V dosing, as it results in significantly higher bacteriologic failure rates (22% vs 8%) 5, 4.

Treatment Duration: Non-Negotiable 10 Days

The full 10-day course is essential for all antibiotics except azithromycin to achieve maximal pharyngeal eradication and prevent acute rheumatic fever 1, 2, 6. Shorter courses have not been adequately validated and increase the risk of treatment failure and rheumatic fever 1. The FDA label explicitly states that therapy must be sufficient to eliminate the organism (10-day minimum) to prevent sequelae of streptococcal disease 6.

Penicillin-Allergic Patients: Algorithmic Approach

For non-immediate (non-anaphylactic) penicillin allergy:

• First-generation cephalosporins are preferred alternatives 1, 2
• Cephalexin 20 mg/kg per dose twice daily (maximum 500 mg per dose) for 10 days 1, 2
• Cefadroxil 30 mg/kg once daily (maximum 1 g) for 10 days 2

For immediate-type hypersensitivity (anaphylaxis, urticaria, angioedema):

• Clindamycin 7 mg/kg per dose three times daily (maximum 300 mg per dose) for 10 days is the preferred alternative 1, 2
• Azithromycin 12 mg/kg once daily (maximum 500 mg) for 5 days is an option, but macrolide resistance ranges from 5-8% in the United States 1, 7

Critical Caveat: Macrolide Resistance

Azithromycin and other macrolides should be reserved for true penicillin allergy due to increasing resistance. 1, 7 The FDA label states that susceptibility tests should be performed when treating with azithromycin, and data establishing efficacy in preventing rheumatic fever are not available 7. Research demonstrates that clarithromycin fails to eradicate resistant strains (14-19% eradication vs 83% for susceptible strains), making it unreliable in areas with common resistance 8.

Severe Invasive Group A Streptococcal Infections

For necrotizing fasciitis or toxic shock syndrome:

• Penicillin G 12-24 million units/day IV PLUS clindamycin 600-900 mg IV every 8 hours is essential 9
• Clindamycin suppresses toxin production and maintains efficacy during high bacterial inocula 9
• Urgent surgical debridement is mandatory and should not be delayed 9

For severe skin and soft tissue infections with systemic toxicity:

• Start empiric broad-spectrum coverage with vancomycin or linezolid PLUS piperacillin-tazobactam or a carbapenem until Group A Streptococcus is confirmed 9
• Once confirmed, narrow to penicillin G 12-24 million units/day IV plus clindamycin 9

Treatment Failures and Chronic Carriers

If treatment fails despite adequate compliance:

• Retreatment with the same regimen is acceptable if compliance was good 2
• Clindamycin 20-30 mg/kg per day in three doses (maximum 300 mg per dose) for 10 days is effective for chronic carriers or multiple failures 2
• Consider intramuscular benzathine penicillin G if compliance is questionable 2

Chronic carriers (asymptomatic with persistently positive cultures) generally do not require treatment, as they are unlikely to spread infection or develop complications 1. However, if treatment is indicated, clindamycin is particularly effective 1.

Healthcare Worker Carriage Eradication

For pharyngeal carriage in healthcare workers:

• Oral penicillin V 500 mg four times daily for 10 days, amoxicillin 500 mg three times daily for 10 days, clindamycin 300 mg four times daily for 10 days, or azithromycin (maximum 500 mg once daily) for 3 days 10
• Clindamycin 300 mg four times daily for 10 days should be used when first-line penicillin therapy fails 10

For non-pharyngeal carriage:

• Penicillin alone may be insufficient 10
• Clindamycin 300 mg four times daily for 10 days or azithromycin 12 mg/kg per day (maximum 500 mg once daily) for 5 days, with limited reports of combining with rifampicin or vancomycin 10

Common Pitfalls to Avoid

• Never prescribe shorter courses than 10 days (except azithromycin's 5-day regimen), as this leads to treatment failure and increased risk of acute rheumatic fever 1, 6
• Do not delay surgical consultation when necrotizing infection is suspected, as antibiotics alone are insufficient 9
• Avoid aspirin in children due to risk of Reye syndrome 1
• Do not rely on oral penicillin V in severely ill patients with nausea, vomiting, or intestinal hypermotility, as absorption may be inadequate 6
• Obtain follow-up cultures after treatment completion to confirm eradication, especially in streptococcal infections where sequelae may occur if the organism is not eliminated 6