What are the recommended antibiotics for Group A Streptococcus (GAS) infections?

From the Guidelines

Penicillin V 250 mg orally four times daily for 10 days is the recommended first-line antibiotic treatment for Group A Streptococcus (GAS) pharyngitis in individuals without penicillin allergy, as it has been shown to be effective in preventing complications and improving symptoms.

Key Considerations

• The Infectious Diseases Society of America (IDSA) recommends penicillin V as the first-line treatment for GAS pharyngitis, with a strong, high-quality evidence recommendation 1.
• For individuals with penicillin allergy, alternative antibiotics such as cephalexin, cefadroxil, or clindamycin can be used, with a strong, high-quality evidence recommendation for cephalexin and cefadroxil, and a strong, moderate-quality evidence recommendation for clindamycin 1.
• Macrolides such as azithromycin can also be used as an alternative, but with a strong, moderate-quality evidence recommendation and consideration of potential resistance 1.

Treatment Options

• Penicillin V: 250 mg orally four times daily for 10 days
• Amoxicillin: 50 mg/kg once daily (max = 1000 mg) for 10 days
• Benzathine penicillin G: 1.2 million units intramuscularly as a single dose
• Cephalexin: 20 mg/kg/dose twice daily (max = 500 mg/dose) for 10 days
• Cefadroxil: 30 mg/kg once daily (max = 1 g) for 10 days
• Clindamycin: 7 mg/kg/dose three times daily (max = 300 mg/dose) for 10 days
• Azithromycin: 12 mg/kg once daily (max = 500 mg) for 5 days

Important Notes

• Complete the full course of antibiotics even if symptoms improve quickly to prevent complications like rheumatic fever and post-streptococcal glomerulonephritis.
• Patients should be advised they are no longer contagious after 24 hours of antibiotic therapy, at which point they can return to normal activities.
• The IDSA guideline emphasizes the importance of accurate diagnosis and appropriate antimicrobial therapy to prevent unnecessary exposure to antibiotics and reduce the risk of antimicrobial resistance 1.

From the FDA Drug Label

Antibiotic therapy for Group A β-hemolytic streptococcal infections should be maintained for at least 10 days to reduce the risk of rheumatic fever. The recommended dosage for Group A β-hemolytic streptococcal infections is not explicitly stated, but it is mentioned that antibiotic therapy should be maintained for at least 10 days to reduce the risk of rheumatic fever 2.

• The dosage for serious infections due to susceptible strains of streptococci is 150,000 - 300,000 units/kg/day divided in equal doses every 4 to 6 hours 2.
• It is essential to note that the specific dosage for Group A streptococcal infections is not provided, and the treatment should be individualized based on the patient's condition and the severity of the infection.

From the Research

Antibiotics for Group A Streptococcal (GAS) Infections

• The use of antibiotics in treating GAS infections, such as pharyngitis, has been studied extensively 3.
• According to a 2021 review, antibiotics provide only modest benefits in treating sore throat, but their effectiveness increases in people with positive throat swabs for GAS 3.
• The review compared different antibiotics, including penicillin, cephalosporins, macrolides, and carbacephem, and found that the certainty of the evidence was generally low due to poor reporting of randomization, allocation concealment, and blinding 3.

Comparison of Antibiotics

• Cephalosporins versus penicillin: low-certainty evidence suggests that cephalosporins may be more effective in resolving symptoms and preventing clinical relapse, but the difference is uncertain 3.
• Macrolides versus penicillin: low-certainty evidence suggests that there is no significant difference in symptom resolution or clinical relapse between macrolides and penicillin 3.
• Carbacephem versus penicillin: low-certainty evidence suggests that carbacephem may be more effective than penicillin in resolving symptoms, especially in children 3.

Resistance and Vaccine Development

• GAS is still sensitive to penicillin, but there are cases of treatment failure, and antibiotic therapy does not universally prevent subsequent disease 4.
• The development of a safe and effective vaccine against GAS is considered a high priority, especially in low- and middle-income countries where the disease burden is high 4.
• Molecular epidemiology studies have identified antimicrobial resistance mechanisms in GAS isolates, including macrolide and tetracycline resistance 5.

Alternative Prophylaxis

• A 1992 randomized clinical trial found that low-dose oral erythromycin was effective in preventing GAS infection in penicillin-allergic military recruits 6.
• The study suggested that erythromycin could be a viable alternative to benzathine penicillin G for prophylaxis against GAS infection in penicillin-allergic individuals 6.