What is a good antibiotic for Streptococcus (Strep) pyogenes infection?

From the Guidelines

Penicillin V is the recommended first-line antibiotic treatment for Streptococcus pyogenes infections, with a typical adult dosage of 250 mg 4 times daily or 500 mg twice daily for 10 days, as it has maintained nearly complete susceptibility to penicillin over decades 1. The dosage for children is 250 mg twice daily or 3 times daily, and for adolescents and adults, it is 250 mg 4 times daily or 500 mg twice daily, with a duration of 10 days 1. For patients with penicillin allergy, alternatives include:

• Cephalexin, with a dosage of 20 mg/kg/dose twice daily (max = 500 mg/dose) for 10 days 1
• Cefadroxil, with a dosage of 30 mg/kg once daily (max = 1 g) for 10 days 1
• Clindamycin, with a dosage of 7 mg/kg/dose 3 times daily (max = 300 mg/dose) for 10 days 1
• Azithromycin, with a dosage of 12 mg/kg once daily (max = 500 mg) for 5 days 1 It's crucial to complete the full 10-day course even if symptoms improve earlier to prevent complications like rheumatic fever or glomerulonephritis. Penicillin remains the preferred treatment because S. pyogenes has maintained nearly complete susceptibility to it over decades, unlike many other antibiotics that have developed resistance, as seen in the 2012 update by the Infectious Diseases Society of America 1. Additionally, penicillin has a narrow spectrum of activity which helps reduce disruption to the normal gut microbiome and limits the development of antimicrobial resistance. The 2014 practice guidelines for the diagnosis and management of skin and soft tissue infections also support the use of penicillin for streptococcal infections, although it focuses on skin and soft tissue infections rather than pharyngitis 1. However, the most recent and relevant guideline for streptococcal pharyngitis is the 2012 update, which provides clear recommendations for antibiotic treatment 1.

From the FDA Drug Label

Azithromycin, at the recommended dose, is effective in the eradication of susceptible strains of Streptococcus pyogenes from the nasopharynx. Pharyngitis/tonsillitis caused by Streptococcus pyogenes as an alternative to first-line therapy in individuals who cannot use first-line therapy. NOTE: Penicillin by the intramuscular route is the usual drug of choice in the treatment of Streptococcus pyogenes infection and the prophylaxis of rheumatic fever. Erythromycin tablets are indicated in the treatment of infections caused by susceptible strains of the designated microorganisms in the diseases listed below: Upper respiratory tract infections of mild to moderate degree caused by Streptococcus pyogenes;

Good antibiotics for Streptococcus pyogenes are:

• Penicillin (first-line therapy)
• Azithromycin (alternative therapy) 2
• Erythromycin (alternative therapy) 3

From the Research

Antibiotic Options for Strep Pyogenes

• Penicillin remains the first-choice treatment for Streptococcus pyogenes infection 4
• Macrolides are important alternatives for allergic patients, and lincosamides are recommended together with β-lactams in invasive infections 4
• Clindamycin has been found to be the most efficacious regimen for eradicating pharyngeal S. pyogenes carriage in asymptomatic individuals 5
• Azithromycin, clarithromycin, erythromycin, and roxithromycin have been shown to be effective against S. pyogenes in vitro, with erythromycin having the lowest MIC90 6

Treatment Considerations

• The failure of treatment for invasive infections with penicillin has been consistently reported, and strains with reduced susceptibility to β-lactams have emerged 7
• Isolates responsible for outbreaks of severe infections are increasingly resistant to other antibiotics of choice, such as clindamycin and macrolides 7
• The optimal dosing interval for penicillin treatment of streptococcal pharyngitis is twice daily, with 500 mg of penicillin V being the recommended dose 8

Resistance and Susceptibility

• S. pyogenes may exhibit macrolide resistance due to active efflux or target modification, with the latter conferring cross-resistance to lincosamides and streptogramin B 4
• Resistance to erythromycin and other macrolides is relatively low, with only 0.5% of strains being resistant in one study 6
• Continued surveillance is needed to obtain further insights into the forces governing macrolide resistance in S. pyogenes 4