What are the complications of Streptococcal (Strep) infections in adults?

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Last updated: March 25, 2025View editorial policy

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From the Guidelines

Strep throat complications in adults can be serious if left untreated, and the most common complications include peritonsillar abscess, sinusitis, ear infections, and more severe conditions like rheumatic fever and post-streptococcal glomerulonephritis. The complications of Streptococcal (Strep) infections in adults can be severe and include:

  • Peritonsillar abscess (collection of pus near the tonsils)
  • Sinusitis
  • Ear infections
  • Rheumatic fever
  • Post-streptococcal glomerulonephritis (kidney inflammation) According to the most recent and highest quality study 1, antibiotics may prevent complications from group A streptococcal infection, including acute rheumatic fever, peritonsillar abscess, and further spread of group A Streptococcus in outbreaks. However, little evidence supports the prevention of acute glomerulonephritis 1. If diagnosed with strep throat, adults should complete the full course of prescribed antibiotics, typically penicillin V (500 mg twice daily for 10 days) or amoxicillin (500 mg twice daily for 10 days), as recommended by the Infectious Diseases Society of America 1. For those with penicillin allergies, alternatives include azithromycin (500 mg on day 1, then 250 mg daily for 4 more days) or clindamycin (300 mg three times daily for 10 days) 1. It's crucial to finish the entire antibiotic course even if symptoms improve, as incomplete treatment increases the risk of complications. Rest, adequate hydration, and over-the-counter pain relievers like acetaminophen or ibuprofen can help manage symptoms. Seek immediate medical attention if you develop high fever, difficulty breathing or swallowing, severe throat pain, or rash after starting antibiotics. These complications occur because the streptococcal bacteria can spread to nearby tissues or trigger immune responses that affect distant organs like the heart valves or kidneys if the infection isn't properly eliminated.

From the Research

Complications of Streptococcal (Strep) Infections in Adults

  • Acute rheumatic fever: Streptococcal pharyngitis can lead to acute rheumatic fever, a serious complication that can cause heart damage 2.
  • Locoregional suppuration: Signs of progression to locoregional suppuration were noted in 1% of patients receiving placebo, compared to 0.09% of patients receiving antibiotics 3.
  • Acute glomerulonephritis: There is no firm evidence that antibiotics reduce the risk of acute glomerulonephritis 3.
  • Anaphylaxis: Anaphylaxis is estimated to occur in 5 per 10 000 patients treated with injectable penicillin 3.
  • Bacterial resistance: Antibiotics can affect the bacterial ecology, encouraging resistance among some bacterial species other than group A streptococci 3.

Treatment-Related Complications

  • Adverse events: The most commonly reported study drug-related adverse events include abdominal pain, diarrhea, dyspepsia, and nausea 4, 5.
  • Relapse: Clinical relapse may be lower for cephalosporins compared with penicillin, but the evidence is uncertain 6.
  • Resistance: The use of antibiotics can lead to the development of resistant strains of bacteria, making treatment more difficult 3.

Rare but Serious Complications

  • Post-streptococcal glomerulonephritis: There is insufficient evidence to draw conclusions regarding the effectiveness of antibiotics in preventing this complication 6.
  • Suppurative complications: The evidence is scarce to draw conclusions regarding the effectiveness of antibiotics in preventing suppurative complications 6.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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