What is the appropriate antibiotic coverage for community-acquired pneumonia (CAP)?

Antibiotic Treatment for Community-Acquired Pneumonia

For community-acquired pneumonia (CAP), the recommended antibiotic treatment depends on the severity of illness and patient setting, with combination therapy of a β-lactam plus a macrolide or monotherapy with a respiratory fluoroquinolone being the standard of care for most hospitalized patients. 1

Outpatient Treatment

• For healthy adults without comorbidities, first-line treatment is Amoxicillin 1 g three times daily 1
• Alternative options include Doxycycline 100 mg twice daily or macrolides (azithromycin 500 mg on first day then 250 mg daily or clarithromycin 500 mg twice daily) in areas with pneumococcal macrolide resistance <25% 1
• For adults with comorbidities, use combination therapy with amoxicillin/clavulanate OR a cephalosporin PLUS a macrolide or doxycycline 1
• Recent antibiotic use within 3 months is a risk factor for drug-resistant Streptococcus pneumoniae and should guide selection away from recently used antibiotic classes 2

Non-ICU Hospitalized Patients

• Preferred regimen: β-lactam (ampicillin/sulbactam, cefotaxime, ceftriaxone, or ceftaroline) PLUS a macrolide (azithromycin or clarithromycin) 1, 3
• Alternative regimen: Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily, moxifloxacin, or gatifloxacin) 1, 3
• Levofloxacin is FDA-approved for treatment of CAP caused by methicillin-susceptible S. aureus, S. pneumoniae (including multi-drug resistant strains), H. influenzae, H. parainfluenzae, K. pneumoniae, M. catarrhalis, C. pneumoniae, L. pneumophila, or M. pneumoniae 4

Severe CAP Requiring ICU Care

• For patients without risk factors for Pseudomonas aeruginosa: Non-antipseudomonal β-lactam (ceftriaxone, cefotaxime) PLUS either a macrolide or a respiratory fluoroquinolone 2, 1
• For patients with risk factors for Pseudomonas aeruginosa: Antipseudomonal β-lactam (cefepime, ceftazidime, piperacillin-tazobactam, meropenem) PLUS either ciprofloxacin OR a macrolide plus aminoglycoside 2, 1
• Risk factors for Pseudomonas infection include severe structural lung disease (bronchiectasis), recent antibiotic therapy, or recent hospitalization (especially ICU) 2

Special Considerations

• For patients with MRSA risk factors, add vancomycin or linezolid and obtain cultures/nasal PCR to allow de-escalation 1
• For β-lactam allergic patients without Pseudomonas risk: respiratory fluoroquinolone with or without clindamycin 2
• For β-lactam allergic patients with Pseudomonas risk: aztreonam plus levofloxacin or aztreonam plus moxifloxacin/gatifloxacin, with or without an aminoglycoside 2
• Nursing home patients can be treated with a respiratory fluoroquinolone alone or amoxicillin-clavulanate plus an advanced macrolide 2

Treatment Duration

• The recommended duration is generally 5-7 days for responding patients 1
• Patients should be afebrile for 48-72 hours before discontinuing antibiotics 3
• Procalcitonin levels may guide shorter treatment duration 2
• For CAP due to S. pneumoniae, H. influenzae, H. parainfluenzae, M. pneumoniae, or C. pneumoniae, a 5-day course of levofloxacin 750 mg daily is effective 4

Microbiology and Resistance Considerations

• S. pneumoniae remains the most common causative pathogen for CAP across all disease severities 2, 5
• Macrolide resistance is reported in 20-30% of S. pneumoniae isolates 2
• Respiratory fluoroquinolones exhibit high levels of lung penetration and low levels of resistance 6
• Clinical trials show success rates >90% for fluoroquinolones in treating CAP due to S. pneumoniae 6

Common Pitfalls and Caveats

• Delayed antibiotic administration can increase mortality; prompt initiation is essential 1
• Inadequate coverage of causative pathogens is associated with worse outcomes; modifying initially inadequate therapy according to microbiological results may not improve outcomes 7
• Overuse of fluoroquinolones should be avoided to prevent development of resistance; recent use of a fluoroquinolone should dictate selection of a non-fluoroquinolone regimen 2
• For patients with influenza CAP, add oseltamivir and avoid corticosteroids 8
• Use validated severity assessment tools (PORT Severity Index, CURB-65, or CRB-65) to guide site-of-care decisions and treatment intensity 5