What is the recommended first-line antibiotic therapy for community-acquired pneumonia (CAP) in Australia?

First-Line Antibiotic Therapy for Community-Acquired Pneumonia in Australia

The recommended first-line antibiotic therapy for community-acquired pneumonia (CAP) in Australia is a combination of a β-lactam (such as amoxicillin) plus a macrolide (such as azithromycin or clarithromycin) for hospitalized patients, while amoxicillin monotherapy is appropriate for non-severe CAP managed in the community. 1

Severity-Based Treatment Approach

Non-Severe CAP (Outpatient Management)

• First choice: Amoxicillin monotherapy for previously untreated patients 2, 1
• Alternative options:
  • Macrolide monotherapy (clarithromycin or azithromycin) for patients with penicillin allergy 2, 1
  • Doxycycline as an alternative when macrolides or penicillins cannot be used 1

Non-Severe CAP (Requiring Hospitalization)

• First choice: Combination therapy with amoxicillin plus a macrolide (clarithromycin or azithromycin) 2, 1
• Parenteral option: When oral therapy is contraindicated, intravenous ampicillin or benzylpenicillin plus erythromycin or clarithromycin 2
• Alternative: Respiratory fluoroquinolone (levofloxacin) for patients intolerant to penicillins or macrolides, but should be used judiciously to prevent resistance 2, 1

Severe CAP (Requiring Hospitalization)

• First choice: Intravenous broad-spectrum β-lactam (co-amoxiclav, cefuroxime, cefotaxime, or ceftriaxone) plus a macrolide (clarithromycin or azithromycin) 2, 1
• Alternative: For β-lactam/macrolide intolerant patients, a respiratory fluoroquinolone with enhanced pneumococcal activity (levofloxacin) plus intravenous benzylpenicillin 2

Duration of Therapy

• Standard duration: 5-7 days for uncomplicated CAP 1
• Extended duration (10-14 days) for:
  • Severe infections
  • Legionella pneumonia
  • Staphylococcal pneumonia
  • Gram-negative enteric bacilli infections 2, 1
• Patient should be afebrile for 48-72 hours and have no more than one sign of clinical instability before discontinuing therapy 1

Special Considerations

Pathogen-Specific Considerations

• Streptococcus pneumoniae: Primary target for empiric therapy; amoxicillin is effective against >93% of strains 1
• Atypical pathogens (Mycoplasma, Chlamydophila): Covered by macrolides or doxycycline 1
• Legionella: Requires macrolide (preferably azithromycin) or fluoroquinolone; consider adding rifampicin in severe cases 1
• Pseudomonas aeruginosa: For patients with risk factors, use antipseudomonal β-lactam plus either fluoroquinolone or aminoglycoside 2, 1

Treatment Failure

• If patient fails to improve on initial therapy:
  1. Review clinical history, examination, and investigation results
  2. Consider additional investigations (repeat chest radiograph, CRP, WCC)
  3. For non-severe CAP on amoxicillin monotherapy: add or substitute a macrolide
  4. For non-severe CAP on combination therapy: consider changing to a respiratory fluoroquinolone 2

Common Pitfalls to Avoid

1. Overtreatment of mild CAP: Evidence from Australia shows that mild CAP is frequently overtreated with broad-spectrum antibiotics like ceftriaxone plus azithromycin 3

2. Delayed antibiotic administration: Antibiotics should be administered promptly after diagnosis, especially in severe cases 2

3. Inadequate coverage for resistant pathogens: Consider local resistance patterns when selecting empiric therapy 1

4. Prolonged intravenous therapy: Switch to oral therapy once patient shows clinical improvement 1

5. Insufficient follow-up: Arrange clinical review for all patients at around 6 weeks, with follow-up chest radiograph for those with persistent symptoms or at higher risk of malignancy 2

Antibiotic Stewardship Considerations

• Use narrowest spectrum antibiotics appropriate for the clinical situation
• Limit treatment duration to 5-7 days for most cases
• Consider local resistance patterns when selecting empiric therapy
• Implement systematic approaches to guide appropriate prescribing practices 1