What antibiotics are used to treat streptococcal (Streptococcus) infections?

From the Guidelines

Penicillin V is the first-line antibiotic treatment for strep throat (streptococcal pharyngitis), with a recommended dose of 250 mg orally 4 times daily or 500 mg twice daily for 10 days for adolescents and adults, as stated in the 2012 update by the Infectious Diseases Society of America 1.

Key Considerations

• The diagnosis of strep throat should be established through accurate testing, as the signs and symptoms of GAS and nonstreptococcal pharyngitis overlap broadly, making clinical diagnosis alone usually impossible 1.
• Antibiotic treatment is crucial for preventing acute rheumatic fever, suppurative complications, and reducing contagiousness, with penicillin V being the preferred choice due to its high efficacy and the bacteria's susceptibility to it 1.
• For patients with penicillin allergy, alternative antibiotics such as cephalexin, cefadroxil, clindamycin, azithromycin, or clarithromycin can be used, with specific dosages and durations outlined in the guidelines 1.

Treatment Options

• Penicillin V: 250 mg orally 4 times daily or 500 mg twice daily for 10 days for adolescents and adults 1.
• Amoxicillin: 50 mg/kg once daily (max = 1000 mg) or 25 mg/kg twice daily (max = 500 mg) for 10 days 1.
• Benzathine penicillin G: a single intramuscular dose of 600,000 U for children under 27 kg or 1,200,000 U for those 27 kg or heavier 1.
• For penicillin-allergic patients:
  • Cephalexin: 20 mg/kg/dose twice daily (max = 500 mg/dose) for 10 days 1.
  • Clindamycin: 7 mg/kg/dose three times daily (max = 300 mg/dose) for 10 days 1.
  • Azithromycin: 12 mg/kg once daily (max = 500 mg) for 5 days 1.

Importance of Adherence

• Completing the full course of antibiotics is essential for preventing complications and ensuring the infection is fully cleared, even if symptoms improve before finishing the treatment 1.

From the FDA Drug Label

Penicillin G is highly active in vitro against streptococci (groups A, B, C, G, H, L, and M) 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. The recommended antibiotic for streptococcal infections is penicillin G 2.

• Penicillin G is highly active against streptococci, including groups A, B, C, G, H, L, and M.
• Penicillin is the usual drug of choice for Streptococcus pyogenes infection and rheumatic fever prophylaxis 3.

From the Research

Antibiotics for Streptococcal Pharyngitis

• The use of antibiotics for streptococcal pharyngitis is recommended only for patients with a confirmed diagnosis of group A beta-hemolytic streptococcal (GABHS) infection 4, 5, 6.
• Penicillin and amoxicillin are considered first-line antibiotics for the treatment of GABHS pharyngitis, with a recommended course of 10 days 4, 6.
• First-generation cephalosporins are recommended for patients with nonanaphylactic allergies to penicillin 4, 6.
• Macrolides, such as azithromycin and clarithromycin, may be used as alternative antibiotics, but there is significant resistance to these antibiotics in some parts of the United States 4, 5.
• The use of antibiotics for streptococcal pharyngitis has been shown to provide only modest benefits in terms of symptom resolution and duration of illness 5, 7.

Diagnostic Methods

• The diagnosis of GABHS pharyngitis can be made using a combination of clinical scoring systems, rapid antigen detection tests, throat culture, and nucleic acid amplification tests 5, 6, 7.
• The modified Centor score can be used to help physicians decide which patients need no testing, throat culture/rapid antigen detection testing, or empiric antibiotic therapy 6.
• Clinical guidelines developed by professional associations can help medical professionals choose among available techniques to diagnose strep throat, but there is substantial evidence that most physicians do not follow any published guidelines 7.

Treatment Outcomes

• The treatment of GABHS pharyngitis with antibiotics has been shown to reduce the risk of nonsuppurative and suppurative complications, such as acute rheumatic fever and post-streptococcal glomerulonephritis 4, 5, 6.
• However, the use of antibiotics for streptococcal pharyngitis also carries the risk of adverse events, such as allergic reactions and antibiotic resistance 4, 5, 7.
• The optimal management strategy for strep throat remains a topic of controversy, with significant debate regarding the best methods to diagnose GABHS and under what conditions antibiotics should be prescribed 5, 7.