Community-Acquired Pneumonia Treatment Recommendations
For outpatient CAP without comorbidities, start with amoxicillin 1 g every 8 hours or doxycycline 100 mg twice daily; for outpatients with comorbidities or recent antibiotic use, use a respiratory fluoroquinolone (levofloxacin or moxifloxacin) or a β-lactam plus macrolide combination; for hospitalized non-ICU patients, use a β-lactam (such as ceftriaxone) plus a macrolide (azithromycin or clarithromycin) as the preferred regimen. 1, 2
Outpatient Treatment Algorithm
Previously Healthy Patients (No Comorbidities)
Amoxicillin 1 g every 8 hours is the first-line recommendation for outpatients without comorbidities, providing robust coverage against S. pneumoniae, the most common pathogen. 1
Doxycycline 100 mg twice daily serves as an alternative first-line option, with the first dose at 200 mg to achieve adequate serum levels more rapidly. 1
Macrolide monotherapy (azithromycin 500 mg Day 1, then 250 mg Days 2-5) is appropriate for patients under 40 years old, particularly when atypical pathogens are suspected or in epidemic contexts. 1, 3
Patients with Comorbidities or Recent Antibiotic Use
A respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) is recommended due to broad-spectrum coverage of both typical and atypical organisms, excellent lung penetration, and convenience of monotherapy. 1, 2, 4
Alternatively, use a β-lactam plus macrolide combination (amoxicillin 3 g/day plus azithromycin or clarithromycin) for patients with comorbidities. 1, 2
Patients with recent exposure to one antibiotic class should receive treatment from a different class due to increased risk for bacterial resistance. 1
Critical Pitfall to Avoid
- Reserve fluoroquinolones for patients with β-lactam allergies or specific indications to prevent resistance development, despite their proven efficacy and convenience. 1 The FDA has issued warnings about increasing adverse events related to fluoroquinolone use, though they remain justified for appropriate clinical scenarios. 1
Hospitalized Non-ICU Patients
β-lactam (ceftriaxone 1-2 g every 24 hours) PLUS a macrolide (azithromycin or clarithromycin) is the standard preferred regimen for hospitalized non-ICU patients, providing coverage for both typical bacteria and atypical pathogens including Legionella. 1, 2
Respiratory fluoroquinolone monotherapy (levofloxacin or moxifloxacin) can be used as an alternative for hospitalized non-ICU patients. 1, 2, 4
Penicillin G plus a macrolide is another acceptable option for hospitalized non-ICU patients. 1
Evidence Regarding Atypical Coverage
While research shows no mortality benefit from empirical atypical coverage overall, clinical success is significantly higher for Legionella when atypical antibiotics are used. 1 This explains why combination therapy remains standard despite equivocal mortality data. 5
Consider that S. pneumoniae resistance to macrolides ranges 30-40% and often co-exists with β-lactam resistance in patients with recent hospitalization, chronic diseases, or prior antibiotic exposure. 1
Severe CAP/ICU Treatment
Without Pseudomonas Risk Factors
Use a β-lactam plus either a macrolide or a respiratory fluoroquinolone for patients without risk factors for Pseudomonas. 1, 2
Moxifloxacin or levofloxacin plus a non-antipseudomonal cephalosporin III is an alternative regimen. 1
With Pseudomonas Risk Factors
Use an antipseudomonal β-lactam plus either ciprofloxacin or levofloxacin for patients with risk factors for Pseudomonas. 1
Alternatively, use an aminoglycoside (gentamicin, tobramycin, or amikacin) plus azithromycin or an aminoglycoside plus an antipneumococcal fluoroquinolone. 1
Where Pseudomonas aeruginosa is documented or presumptive, combination therapy with an anti-pseudomonal β-lactam is recommended, as some isolates may develop resistance fairly rapidly during treatment. 4
Special Considerations for MRSA
- Add vancomycin or linezolid when community-acquired MRSA is suspected, with risk factors including prior MRSA infection, recent hospitalization, or recent antibiotic use. 1
Duration and Timing of Therapy
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, 2
For uncomplicated S. pneumoniae pneumonia, 7-10 days of treatment is typically sufficient, while severe pneumonia or specific pathogens like Legionella, staphylococcal, or Gram-negative enteric bacilli require 14-21 days. 1
Treatment should generally not exceed 8 days in a responding patient. 1
The first antibiotic dose should be administered while still in the emergency department, as early administration is associated with improved outcomes and delaying antibiotic administration increases mortality, particularly in severe pneumonia. 1
Switching to Oral Therapy
Switch from intravenous to oral therapy when patients are hemodynamically stable and improving clinically, typically when temperature has been normal for 24 hours. 1, 2
The oral route is recommended for non-severe pneumonia when there are no contraindications to oral therapy. 1
Pathogen-Directed Therapy
Once etiology is identified using reliable microbiological methods, antimicrobial therapy should be directed at that specific pathogen to avoid unnecessary prolonged therapy and reduce resistance. 1, 2
Appropriate culture and susceptibility tests should be performed before treatment to isolate and identify organisms and determine their susceptibility to antibiotics. 4
Local antimicrobial susceptibility patterns should guide the choice of empiric therapy, as resistance patterns may vary by region. 1
Common Pitfalls
Inadequate coverage for atypical pathogens should be avoided, ensuring coverage for Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila. 1
For patients who fail to improve as expected, conduct a careful review including repeat chest radiograph, CRP, white cell count, and further microbiological testing. 1