Initial Treatment for Community-Acquired Pneumonia (CAP)
The initial empiric antibiotic therapy for community-acquired pneumonia should be based on the patient's risk factors, severity of illness, and treatment setting, with a combination of a β-lactam plus a macrolide being the recommended regimen for hospitalized non-ICU patients. 1
Treatment Algorithm Based on Setting and Severity
Outpatient Treatment
- For previously healthy outpatients with no risk factors for drug-resistant pathogens, a macrolide (such as azithromycin) is recommended as first-line therapy 1
- Amoxicillin 1g every 8 hours is an alternative first-line therapy for outpatients without comorbidities 1
- Doxycycline 100mg twice daily is another alternative first-line option for outpatients without comorbidities 1
- For outpatients with comorbidities or recent antibiotic use, a respiratory fluoroquinolone or a β-lactam plus a macrolide is recommended 1, 2
Hospitalized Non-ICU Patients
- Combined oral therapy with amoxicillin and a macrolide (erythromycin or clarithromycin) is preferred for patients who require hospital admission for clinical reasons 3
- When oral treatment is contraindicated, recommended parenteral choices include intravenous ampicillin or benzylpenicillin, together with erythromycin or clarithromycin 3
- A respiratory fluoroquinolone alone (levofloxacin or moxifloxacin) can be used as an alternative treatment option 1, 4
- For patients without risk factors for resistant bacteria, ceftriaxone combined with azithromycin is recommended for a minimum of 3 days 5
Severe CAP/ICU Treatment
- Patients with severe pneumonia should be treated immediately after diagnosis with parenteral antibiotics 3
- An intravenous combination of a broad-spectrum β-lactamase stable antibiotic (co-amoxiclav, cefuroxime, cefotaxime, or ceftriaxone) together with a macrolide (clarithromycin or erythromycin) is preferred 3
- For patients with risk factors for Pseudomonas, an antipseudomonal β-lactam plus either ciprofloxacin or levofloxacin, an aminoglycoside plus azithromycin, or an aminoglycoside plus an antipneumococcal fluoroquinolone is recommended 1
Antibiotic Selection Considerations
β-lactam Options
- Aminopenicillin (e.g., amoxicillin) 3
- Aminopenicillin/β-lactamase inhibitor (e.g., co-amoxiclav) 3
- Non-antipseudomonal cephalosporin (e.g., cefuroxime, cefotaxime, ceftriaxone) 3
- Penicillin G 3
Macrolide Options
- Azithromycin is indicated for treatment of CAP due to Chlamydia pneumoniae, Haemophilus influenzae, Legionella pneumophila, Moraxella catarrhalis, Mycoplasma pneumoniae, Staphylococcus aureus, or Streptococcus pneumoniae 6
- Clarithromycin or erythromycin are alternatives, with newer macrolides preferred to erythromycin 3
Fluoroquinolone Options
- Levofloxacin is indicated for the treatment of CAP due to methicillin-susceptible Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, Haemophilus parainfluenzae, Klebsiella pneumoniae, Moraxella catarrhalis, Chlamydophila pneumoniae, Legionella pneumophila, or Mycoplasma pneumoniae 4
- New fluoroquinolones are not recommended as first-line agents or for community use for pneumonia but may provide a useful alternative in selected hospitalized patients with CAP 3
Duration of Therapy
- For patients with severe microbiologically undefined pneumonia, 10 days of treatment is proposed 3
- Treatment should be extended to 14-21 days where legionella, staphylococcal, or Gram-negative enteric bacilli pneumonia are suspected or confirmed 3
- The minimum duration of therapy is 5 days for most patients, with the patient required to be afebrile for 48-72 hours and have no more than one sign of clinical instability before discontinuing therapy 1
Common Pitfalls and Caveats
- Overreliance on fluoroquinolones can lead to resistance, and they should be reserved for patients with β-lactam allergies or when specifically indicated 1
- Inadequate coverage for atypical pathogens should be avoided, ensuring coverage for Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila 1
- A distinct diagnosis of pneumonia seems mandatory before initiation of antibiotic treatment 3
- For patients who fail to improve as expected, there should be a careful review of the clinical history, examination, prescription chart, and results of all available investigation results 3
- When a change in empirical antibiotic treatment is considered necessary, a macrolide could be substituted for or added to the treatment for those with non-severe pneumonia treated with amoxicillin monotherapy 3