What is the recommended antibiotic regimen for empiric treatment of community-acquired pneumonia (CAP) in adults without risk factors for Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (P. aeruginosa)?

From the Guidelines

For adults with community-acquired pneumonia (CAP) without risk factors for MRSA or Pseudomonas aeruginosa, the recommended empiric antibiotic regimen is amoxicillin 1 g three times daily, doxycycline 100 mg twice daily, or a macrolide (azithromycin 500 mg on first day then 250 mg daily or clarithromycin 500 mg twice daily or clarithromycin extended release 1,000 mg daily) only in areas with pneumococcal resistance to macrolides, 25%. When considering the treatment of CAP in adults without risk factors for MRSA and P. aeruginosa, it is crucial to prioritize regimens that effectively target the most common pathogens, including Streptococcus pneumoniae, while minimizing the risk of promoting antibiotic resistance 1. The American Thoracic Society and Infectious Diseases Society of America guideline from 2019 provides a strong recommendation for the use of amoxicillin 1 g three times daily for healthy outpatient adults without comorbidities or risk factors for antibiotic-resistant pathogens, based on moderate quality of evidence 1. For patients with comorbidities, combination therapy with a beta-lactam (such as amoxicillin/clavulanate) and a macrolide (like azithromycin), or monotherapy with a respiratory fluoroquinolone (e.g., levofloxacin), is recommended, considering local resistance patterns and patient-specific factors 1. Key considerations in selecting an empiric antibiotic regimen include the severity of pneumonia, patient comorbidities, potential drug interactions, and local antimicrobial resistance patterns, as these factors can significantly impact morbidity, mortality, and quality of life outcomes 1. In areas with high pneumococcal resistance to macrolides, alternative treatments should be considered to ensure effective coverage against common CAP pathogens, thus optimizing patient outcomes in terms of morbidity, mortality, and quality of life.

From the FDA Drug Label

The recommended dose of Azithromycin for Injection for the treatment of adult patients with community-acquired pneumonia due to the indicated organisms is: 500 mg as a single daily dose by the intravenous route for at least two days Intravenous therapy should be followed by azithromycin by the oral route at a single, daily dose of 500 mg, administered as two 250 mg tablets to complete a 7 to 10 day course of therapy.

The recommended antibiotic regimen for empiric treatment of community-acquired pneumonia (CAP) in adults without risk factors for MRSA and P. aeruginosa is azithromycin. The dose is 500 mg intravenously for at least 2 days, followed by 500 mg orally for a total of 7-10 days 2.

• Key points:
  • Azithromycin is the recommended antibiotic
  • The dose is 500 mg intravenously for at least 2 days
  • Followed by 500 mg orally for a total of 7-10 days
  • This regimen is for adults without risk factors for MRSA and P. aeruginosa

From the Research

Antibiotic Regimen for Empiric Treatment of Community-Acquired Pneumonia

The recommended antibiotic regimen for empiric treatment of community-acquired pneumonia (CAP) in adults without risk factors for Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (P. aeruginosa) includes:

• A macrolide, doxycycline, or a respiratory fluoroquinolone for outpatients 3
• A fluoroquinolone or a combination of beta-lactam plus macrolide antibiotics for patients requiring hospitalization 3
• Dual antibiotic therapy including a third-generation cephalosporin plus a macrolide alone or in combination with a fluoroquinolone for patients with severe infection requiring admission to the intensive care unit 3

Alternative Treatment Options

Alternative treatment options for patients without risk factors for MRSA and P. aeruginosa include:

• Empiric doxycycline + β-lactam, which may be a safe empiric regimen for hospitalized CAP patients with non-severe CAP 4
• Cetaroline 600 mg (two times a day) and piperacillin 2000 mg (two times a day), which have the highest probability of being the best in terms of cure rate 5
• Ceftriaxone 2000 mg (once a day) plus levofloxacin 500 (two times a day), ertapenem 1000 mg (two times a day), and amikacin 250 mg (two times a day) plus clarithromycin 500 mg (two times a day), which have the highest probability of being the best in terms of mortality rate 5

Considerations

When choosing an antibiotic regimen, considerations should include:

• The patient's age, comorbidities, and severity of illness 6, 3
• The presence of risk factors for resistant organisms, such as MRSA and P. aeruginosa 3, 7
• The potential for antibiotic resistance and the need for broad-spectrum coverage 6, 3