What is the recommended treatment for lower respiratory infections, such as community-acquired pneumonia (CAP)?

Treatment of Lower Respiratory Tract Infections

For community-acquired pneumonia, antibiotic therapy must always cover Streptococcus pneumoniae, the most common pathogen, with treatment selection based on disease severity and patient comorbidities. 1

Outpatient Treatment (Non-Hospitalized Patients)

Previously Healthy Adults Without Comorbidities

• Amoxicillin 1 gram three times daily for 5-7 days is the first-line treatment (strong recommendation, moderate quality evidence) 2
• Doxycycline 100 mg twice daily for 5-7 days is the preferred alternative (conditional recommendation, low quality evidence) 2
• Macrolide monotherapy (azithromycin, clarithromycin) should only be used if local pneumococcal macrolide resistance is documented to be <25% 2
• Avoid macrolides in patients with recent antibiotic use (within 90 days) due to increased resistance risk 2

Adults With Comorbidities (COPD, diabetes, heart disease, etc.)

• Combination therapy: Amoxicillin/clavulanate 875 mg/125 mg twice daily PLUS azithromycin 500 mg day 1, then 250 mg daily for 5-7 days (strong recommendation, moderate quality evidence) 2
• Alternative monotherapy: Levofloxacin 750 mg once daily for 5 days (strong recommendation, moderate quality evidence) 2
• Fluoroquinolones should be reserved for patients who cannot tolerate combination therapy due to risks of tendinopathy, peripheral neuropathy, and QT prolongation 2, 3

Inpatient Treatment (Hospitalized Patients)

Non-ICU Patients

• β-lactam (ceftriaxone 1-2 grams IV every 24 hours, cefotaxime, or ampicillin-sulbactam) PLUS macrolide (azithromycin or clarithromycin) 1, 2
• Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) 1, 2
• First antibiotic dose should be administered while still in the emergency department 1

ICU Patients (Severe CAP)

• β-lactam (ceftriaxone 2 grams IV every 24 hours, cefotaxime, or ampicillin-sulbactam) PLUS either azithromycin OR respiratory fluoroquinolone 1, 2
• For suspected Pseudomonas infection: Antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) PLUS ciprofloxacin or levofloxacin 750 mg, OR β-lactam PLUS aminoglycoside PLUS azithromycin 1
• For suspected MRSA: Add vancomycin or linezolid 1

Treatment Duration

Standard Duration

• Minimum 5 days of treatment for uncomplicated CAP 1, 4
• Patient must be afebrile for 48-72 hours before discontinuation 1, 4
• Patient must have no more than 1 sign of clinical instability (temperature ≤37.8°C, heart rate ≤100 bpm, respiratory rate ≤24 breaths/min, systolic BP ≥90 mmHg, oxygen saturation ≥90% on room air) 1, 4
• Fever should resolve within 2-3 days of initiating appropriate antibiotics 1, 4

Extended Duration Required For:

• 10-14 days for Mycoplasma pneumoniae or Chlamydophila pneumoniae 1, 4
• 21 days for Legionella pneumophila or Staphylococcus aureus 1, 4
• Inadequate initial empirical therapy, complicated pneumonia (empyema, abscess), extrapulmonary infection (meningitis, endocarditis), or immunosuppression 1, 4

Transition to Oral Therapy

• Switch from IV to oral when patient is hemodynamically stable, improving clinically, able to ingest medications, and has normally functioning GI tract 1
• Switch when fever has resolved and clinical condition is stable 1
• Discharge as soon as clinically stable; inpatient observation while receiving oral therapy is unnecessary 1

Critical Pathogens to Consider

• Streptococcus pneumoniae is the most frequently encountered pathogen and must always be covered 1
• Other common organisms: Haemophilus influenzae, Mycoplasma pneumoniae, Moraxella catarrhalis, Chlamydophila pneumoniae 1
• Rare but serious: Legionella pneumophila, Staphylococcus aureus, Gram-negative enteric bacilli 1

Special Considerations During COVID-19 Pandemic

• Test all patients for COVID-19 and influenza when these viruses are common in the community 1, 5
• Empirical bacterial coverage is NOT required in all patients with confirmed COVID-19-related pneumonia 1
• If COVID-19/influenza tests are negative, treat empirically for bacterial pathogens using standard CAP guidelines 1
• Obtain blood and sputum cultures when concern exists for multidrug-resistant pathogens 1
• Procalcitonin may help limit antibiotic overuse in COVID-19 patients 1

Common Pitfalls to Avoid

• Never use macrolide monotherapy in patients with comorbidities, areas with ≥25% pneumococcal macrolide resistance, recent antibiotic use, or those requiring hospitalization 2
• Never use amoxicillin monotherapy in patients with comorbidities—this is insufficient coverage and risks treatment failure 2
• Do not continue antibiotics beyond necessary duration without clinical indication 4
• Do not use radiographic improvement to guide treatment duration—it lags behind clinical improvement 4
• Do not fail to assess for clinical stability criteria before discontinuing therapy 1, 4
• Recognize that fluoroquinolones carry risks of QT prolongation (potentially fatal), tendinopathy, peripheral neuropathy, and CNS effects—reserve for appropriate patients 2, 3