What is the antibiotic of choice for Upper Respiratory Tract Infections (URTI) of bacterial origin?

Antibiotic of Choice for Bacterial Upper Respiratory Tract Infections

Amoxicillin is the first-line antibiotic of choice for bacterial upper respiratory tract infections (URTIs), including streptococcal pharyngitis, acute otitis media, and bacterial sinusitis. 1, 2

Diagnosis and Treatment Algorithm

Step 1: Determine if antibiotics are needed

• Antibiotics should NOT be prescribed for:

  • Common cold
  • Viral rhinosinusitis
  • Acute bronchitis (in most cases)
  • Laryngitis
  • COVID-19
  • Influenza 1, 3

• Antibiotics SHOULD be considered for:

  • Confirmed Group A β-hemolytic streptococcal pharyngitis
  • Acute otitis media (especially in children <2 years)
  • Acute bacterial sinusitis with specific criteria 1

Step 2: Confirm bacterial etiology when possible

• For streptococcal pharyngitis: Use rapid antigen tests or throat cultures 1, 4
• For sinusitis: Consider Anthonisen criteria (increased dyspnea, increased sputum purulence, increased sputum volume) 1
• For acute otitis media: Base on history, physical examination and otoscopic exam 4

Step 3: Select appropriate antibiotic

• First-line: Amoxicillin

  • For streptococcal pharyngitis: 500 mg every 12 hours for adults; 25-45 mg/kg/day divided every 12 hours for children 1, 2
  • For acute otitis media: Standard dose 35-45 mg/kg/day; high-dose 80-90 mg/kg/day in areas with high rates of non-susceptible S. pneumoniae 1
  • For bacterial sinusitis: Same dosing as above 1, 4

• Alternative options (if penicillin allergy or treatment failure):

  • Macrolides for suspected atypical bacteria in children over 3 years 1
  • Amoxicillin/clavulanate for treatment failures (provides better coverage against beta-lactamase producing H. influenzae and M. catarrhalis) 4

Duration of Treatment

• Most infections: 7-10 days
• Streptococcal infections: At least 10 days
• Continue treatment for 48-72 hours beyond symptom resolution 1, 2

Monitoring Response

• Clinical improvement expected within 48-72 hours
• Reassess if symptoms worsen or fail to improve after 72 hours
• Consider atypical bacteria and macrolide therapy if no improvement after 48 hours 1

Important Considerations and Pitfalls

Pitfall #1: Overuse of antibiotics

Many URTIs are viral in origin but are unnecessarily treated with antibiotics. This contributes to antibiotic resistance, adverse events, and unnecessary costs 3, 5. Studies show that up to 26.8% of patients with URTIs and negative throat cultures still receive antibiotics 5.

Pitfall #2: Using broad-spectrum antibiotics when not needed

Narrow-spectrum antibiotics (like amoxicillin) should be used when appropriate to reduce antibiotic resistance 1.

Pitfall #3: Inadequate dosing

For areas with high rates of non-susceptible S. pneumoniae, higher doses of amoxicillin (80-90 mg/kg/day) may be needed for acute otitis media 1.

Pitfall #4: Incorrect diagnosis

Clinical findings like tonsillar enlargement, tonsillar exudates, and cervical lymphadenopathy may lead to overdiagnosis of bacterial infections. Confirmation with throat cultures or rapid antigen tests is recommended when possible 5.

Pitfall #5: Inadequate treatment duration

Stopping antibiotics too early can lead to treatment failure. Complete the full course as prescribed 1.

Remember that amoxicillin should be taken at the start of a meal to minimize gastrointestinal intolerance 2, and should only be used for infections proven or strongly suspected to be caused by susceptible bacteria 2.