What is the recommended antibiotic treatment for an acute bacterial infection?

Antibiotic Treatment for Acute Bacterial Infections

For acute bacterial infections, initiate short-course antibiotic therapy (3-5 days) with pathogen-specific agents, prioritizing amoxicillin for respiratory infections, nitrofurantoin or TMP-SMZ for uncomplicated UTIs, and amoxicillin-clavulanate for skin infections, with treatment duration guided by clinical response rather than arbitrary extended courses. 1

Treatment Duration: The Shift to Shorter Courses

The most critical evidence-based change in antibiotic management is the move away from prolonged courses:

• For community-acquired pneumonia (CAP): A 5-day course is sufficient when patients achieve clinical stability (no fever for 48 hours), with 70% of patients successfully completing treatment at this duration without increased failure rates 1

• For uncomplicated cystitis in women: Use nitrofurantoin for 5 days, TMP-SMZ for 3 days, or fosfomycin as a single dose 1

• For uncomplicated pyelonephritis: Fluoroquinolones for 5-7 days (not 10 days) or TMP-SMZ for 14 days based on susceptibility 1

• For cellulitis (including COPD patients): A 5-day course is recommended, with extension only if infection has not improved 2

• For complicated intra-abdominal infections: After adequate source control, 3-5 days of antibiotics produces similar outcomes to longer courses 1

First-Line Antibiotic Selection by Infection Type

Respiratory Tract Infections

Acute Bacterial Sinusitis:

• Delay antibiotics until symptoms persist ≥10 days or worsen after 5-7 days to distinguish bacterial from viral etiology 1
• First-line: Amoxicillin 3g/day for adults 1 or amoxicillin-clavulanate for children 1
• Duration: 10-14 days for sinusitis 1, though shorter courses of newer agents show similar efficacy 1

Community-Acquired Pneumonia:

• Adults without risk factors: Amoxicillin 3g/day orally for suspected pneumococcal infection (especially >40 years) 1
• Adults <40 years without underlying disease: Macrolides for atypical bacterial pneumonia 1
• Children: Amoxicillin 80-100 mg/kg/day in three divided doses for <30 kg 1
• Duration: 10 days for pneumococcal pneumonia, 14 days for atypical pneumonia 1

Acute Bronchitis:

• Do not prescribe antibiotics for acute bronchitis in healthy adults—it is predominantly viral and antibiotics provide no benefit over placebo 1

Pediatric Infections

Acute Bacterial Sinusitis in Children:

• Severe presentation (fever ≥39°C + purulent discharge ≥3 days) or worsening symptoms: Immediate antibiotic therapy 1
• Persistent symptoms (≥10 days): Either antibiotic therapy OR additional 3-day observation period 1
• First-line: Amoxicillin with or without clavulanate 1

Acute Otitis Media:

• Azithromycin: 30 mg/kg as single dose, OR 10 mg/kg daily for 3 days, OR 10 mg/kg day 1 then 5 mg/kg days 2-5 3
• Number needed to treat is 3-5 for persistent symptoms 1

Urinary Tract Infections

Uncomplicated Cystitis (Women):

• Nitrofurantoin 5 days, TMP-SMZ 3 days, or fosfomycin single dose 1
• Avoid fluoroquinolones empirically due to adverse effect profile; reserve for resistant organisms 1

Uncomplicated Pyelonephritis:

• Fluoroquinolones 5-7 days (not 10 days) OR TMP-SMZ 14 days based on susceptibility 1
• Clinical cure rates exceed 93% with 5-day fluoroquinolone courses 1

Skin and Soft Tissue Infections

Cellulitis:

• 5-day course with extension only if no improvement 2
• Mild-moderate: Clindamycin 300-450 mg orally four times daily for 5 days (especially for penicillin allergies) 2
• Alternative: Amoxicillin-clavulanate for dual coverage of respiratory and skin pathogens 2
• Add MRSA coverage (TMP-SMZ or clindamycin) only with specific risk factors 2
• Adjunctive measure: Elevate affected area to promote drainage 2

Critical Assessment Points

Evaluate treatment response at 48-72 hours:

• For sinusitis: Symptoms should decrease within this timeframe; do not change antibiotics before 72 hours unless clinical worsening 1
• For cellulitis: Assess within 3-4 days; if no improvement by 5 days, extend therapy and reassess for alternative causes rather than defaulting to longer treatment 2
• For pneumonia: Clinical stability criteria include no fever for 48 hours 1

When to extend beyond short-course therapy:

• Patients with ongoing signs of infection beyond 5-7 days warrant diagnostic investigation for uncontrolled source or treatment failure 1
• Each additional day of antibiotics carries 5% increased risk of adverse events without added benefit 1

Common Pitfalls to Avoid

Do not treat viral infections with antibiotics:

• Acute bronchitis in healthy adults is viral; antibiotics provide no benefit 1
• Purulent sputum during acute bronchitis does not indicate bacterial superinfection 1

Do not use antibiotics for dental infections without surgical intervention:

• For acute dental abscesses, treatment is surgical only (root canal or extraction) 1
• For acute dentoalveolar abscesses, perform incision and drainage first, then amoxicillin for 5 days 1

Avoid unnecessary broad-spectrum coverage:

• Start with narrow-spectrum agents and de-escalate once organism identified 4
• Combination therapy is not more effective than monotherapy in most ICU trials 4

Do not prescribe antibiotics for uncomplicated acute bacterial sinusitis before 10 days:

• Bacterial sinusitis is uncommon with symptoms <10 days duration 1
• This approach reduces unnecessary antibiotic use in viral infections 1