What is the recommended antibiotic for a suspected bacterial upper respiratory infection?

Antibiotic Treatment for Suspected Bacterial Upper Respiratory Infection

Most upper respiratory tract infections are viral and do not require antibiotics; however, when bacterial infection is suspected based on specific clinical criteria, amoxicillin is the first-line antibiotic of choice for adults and children. 1, 2

Critical First Step: Distinguish Viral from Bacterial Infection

The vast majority of URTIs are viral and antibiotics cause more harm than benefit. 1, 3 The key is identifying which infections warrant antibiotic therapy:

URTIs That Do NOT Require Antibiotics:

• Common cold/acute rhinopharyngitis - antibiotics do not enhance resolution and are not recommended 1, 4
• Acute bronchitis in healthy adults - no benefit demonstrated even with purulent sputum or fever persisting <7 days 5, 1
• Influenza, COVID-19, or laryngitis 3

URTIs That DO Require Antibiotics:

Acute Otitis Media (AOM):

• Children <2 years: antibiotics recommended 5
• Children ≥2 years: only if marked symptoms (high fever, intense earache); otherwise observe for 48-72 hours 5

Acute Bacterial Sinusitis:

• Indicated when: unilateral infraorbital pain worsening with bending forward, pulsatile pain peaking evening/night, failure of initial symptomatic treatment, or complications 1

Group A Streptococcal Pharyngitis:

• Confirmed by rapid antigen test or culture 3

Recommended Antibiotic Regimens

First-Line Treatment:

Amoxicillin is the reference antibiotic for suspected bacterial URTI 5, 1, 2:

• Adults: 750-1750 mg/day divided every 8-12 hours 2
• Children >3 months: 20-45 mg/kg/day divided every 8-12 hours 2
• For high-risk pneumococcal infection (children <2 years, daycare, recent antibiotics): 80-100 mg/kg/day up to 3 g/day 5, 6

Rationale: Amoxicillin provides optimal coverage for Streptococcus pneumoniae, the most important bacterial pathogen in URTIs, and maintains activity against most strains including those with intermediate penicillin resistance 5

Second-Line Treatment (Use When):

Amoxicillin-Clavulanate for 5, 1:

• Treatment failure after 48-72 hours on amoxicillin
• Suspected β-lactamase-producing organisms (H. influenzae, M. catarrhalis)
• Acute bacterial sinusitis requiring antibiotics
• Recurrent infections or recent antibiotic use

Alternative agents for β-lactam allergy:

• Macrolides (azithromycin, clarithromycin) - particularly for suspected atypical bacteria in adults <40 years 5
• Second-generation cephalosporins (cefuroxime-axetil) 5, 1
• Third-generation cephalosporins (cefpodoxime-proxetil, cefotiam-hexetil) - NOT cefixime due to poor pneumococcal coverage 5, 1

Treatment Duration and Monitoring

Standard duration: 7-10 days for most bacterial URTIs 5, 1

Assess response at 48-72 hours: 5

• Fever should resolve within 2-3 days of effective treatment
• Do not change antibiotics within first 72 hours unless clinical worsening
• If no improvement by 72 hours, consider clinical/radiological reassessment and possible hospitalization 1

Common Pitfalls to Avoid

Do not prescribe antibiotics based on:

• Purulent nasal discharge alone - this is common in viral infections and does not predict bacterial infection or antibiotic benefit 4
• Duration of symptoms <7 days in otherwise healthy adults with bronchitis 5
• Isolated tympanic membrane redness without other AOM criteria 5

Avoid these antibiotics for URTIs:

• Fluoroquinolones inactive against pneumococci (ciprofloxacin, ofloxacin) 5
• Cefixime (poor pneumococcal coverage) 5
• Trimethoprim-sulfamethoxazole (inconsistent pneumococcal activity, poor benefit/risk ratio) 5

Critical caveat: Even when bacteria (H. influenzae, M. catarrhalis, S. pneumoniae) are isolated from nasopharyngeal secretions, antibiotics only benefit this specific subgroup - the majority of URTI patients remain culture-negative and derive no benefit from antibiotics 7