What pathogens should be treated empirically in Community-Acquired Pneumonia (CAP)?

From the Guidelines

Empiric treatment for community-acquired pneumonia (CAP) should target Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila, with the choice of antibiotic regimen depending on patient variables such as comorbidities, recent antibiotic use, and severity of illness. When considering the treatment of CAP, it is essential to take into account the patient's specific characteristics, such as the presence of comorbidities, recent antibiotic use, and the severity of the illness.

• For outpatient treatment of previously healthy adults without recent antibiotic therapy, a macrolide (e.g., azithromycin) or doxycycline is recommended 1.
• For patients with comorbidities or recent antibiotic use, a respiratory fluoroquinolone (e.g., levofloxacin) or combination therapy with amoxicillin-clavulanate plus a macrolide is appropriate 1.
• Hospitalized non-ICU patients should receive a respiratory fluoroquinolone or combination therapy with a beta-lactam (e.g., ceftriaxone) plus a macrolide 1.
• For ICU patients, broader coverage with a beta-lactam (e.g., ceftriaxone) plus either a macrolide or a respiratory fluoroquinolone is recommended 1. It is crucial to note that these regimens target the most common bacterial causes of CAP while accounting for regional resistance patterns, and treatment should be adjusted based on culture results, clinical response, and local antibiotic resistance patterns, with de-escalation when possible to reduce antimicrobial resistance development 1.

From the FDA Drug Label

1. 2 Community-Acquired Pneumonia: 7 to 14 Day Treatment Regimen Levofloxacin tablets are indicated for the treatment of community-acquired pneumonia due to methicillin-susceptible Staphylococcus aureus, Streptococcus pneumoniae (including multi-drug-resistant Streptococcus pneumoniae [MDRSP]), Haemophilus influenzae, Haemophilus parainfluenzae, Klebsiella pneumoniae, Moraxella catarrhalis, Chlamydophila pneumoniae, Legionella pneumophila, or Mycoplasma pneumoniae

Treatment of pneumonia In the treatment of pneumonia, azithromycin has only been shown to be safe and effective in the treatment of community-acquired pneumonia due to Chlamydia pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae or Streptococcus pneumoniae in patients appropriate for oral therapy

The pathogens that should be treated empirically in community-acquired pneumonia are:

• Streptococcus pneumoniae
• Haemophilus influenzae
• Mycoplasma pneumoniae
• Chlamydophila pneumoniae
• Legionella pneumophila
• Moraxella catarrhalis
• Klebsiella pneumoniae
• Methicillin-susceptible Staphylococcus aureus 2 3

From the Research

Pathogens to be Treated Empirically in Community-Acquired Pneumonia

The following pathogens should be considered for empirical treatment in community-acquired pneumonia:

• Streptococcus pneumoniae
• Legionella pneumophila
• Mycoplasma pneumoniae
• Chlamydia pneumoniae
• Haemophilus influenzae
• Moraxella catarrhalis

Recommended Empirical Treatment Regimens

The recommended empirical treatment regimens for community-acquired pneumonia include:

• Beta-lactam monotherapy (e.g., penicillin, amoxicillin, or second-generation cephalosporin) 4
• Beta-lactam and macrolide combination therapy (e.g., ceftriaxone plus azithromycin) 5, 6
• Fluoroquinolone monotherapy (e.g., levofloxacin) 7, 8, 5

Rationale for Empirical Treatment

The choice of empirical treatment regimen is based on the potential causes of community-acquired pneumonia, including typical and atypical pathogens 4, 7, 8. The use of beta-lactam and macrolide combination therapy or fluoroquinolone monotherapy may be preferred in certain cases, such as:

• Severe community-acquired pneumonia requiring intensive care unit admission 4
• Suspected infection with atypical pathogens (e.g., Legionella pneumophila, Mycoplasma pneumoniae, Chlamydia pneumoniae) 4, 6
• Patients with pneumonia severity index (PSI) category IV pneumonia 6

Considerations for Empirical Treatment

When selecting an empirical treatment regimen, consider the following factors:

• Local antimicrobial resistance patterns 5
• Patient comorbidities and underlying health conditions 8, 6
• Potential for adverse effects and interactions with other medications 5