What antibiotics are recommended for treating lower respiratory infections?

Recommended Antibiotics for Lower Respiratory Tract Infections

For lower respiratory tract infections, antibiotic selection should be based on the specific type of infection, severity, risk factors for resistant pathogens, and local resistance patterns. 1

Community-Acquired Pneumonia (CAP)

Outpatient Treatment

• First-line options (alphabetical order):
  • Aminopenicillin (e.g., amoxicillin 500-1000 mg every 8 hours)
  • Aminopenicillin + β-lactamase inhibitor (e.g., amoxicillin-clavulanate)
  • Non-antipseudomonal cephalosporin
  • Macrolide (for suspected atypical pathogens)
  • Doxycycline (alternative for atypical pathogens) 1

Hospitalized Patients (Non-ICU)

• Recommended regimens:
  • Non-antipseudomonal cephalosporin III (ceftriaxone/cefotaxime) + macrolide
  • Levofloxacin or moxifloxacin monotherapy
  • Aminopenicillin/β-lactamase inhibitor ± macrolide 1

Severe CAP (ICU Patients)

• Without Pseudomonas risk factors:

  • Non-antipseudomonal cephalosporin III + macrolide
  • Moxifloxacin or levofloxacin ± non-antipseudomonal cephalosporin III 1

• With Pseudomonas risk factors:

  • Antipseudomonal cephalosporin OR acylureidopenicillin/β-lactamase inhibitor OR carbapenem (meropenem preferred)
  • PLUS ciprofloxacin OR macrolide + aminoglycoside 1

Exacerbations of Chronic Obstructive Pulmonary Disease (COPD)

Indications for Antibiotics

Antibiotics should be used in COPD exacerbations with:

1. All three symptoms: increased dyspnea, sputum volume, and sputum purulence (Anthonisen type I) 1
2. Two symptoms including increased sputum purulence (Anthonisen type II) 1
3. Severe exacerbation requiring mechanical ventilation 1

Antibiotic Selection

• First-line: Co-amoxiclav (amoxicillin-clavulanate) 1
• Alternatives: Levofloxacin or moxifloxacin 1

For Pseudomonas Risk

• Oral therapy: Ciprofloxacin or levofloxacin (750 mg/24h or 500 mg twice daily) 1
• Parenteral therapy: Ciprofloxacin or β-lactam with antipseudomonal activity (optional addition of aminoglycosides) 1

Exacerbations of Bronchiectasis

• Antibiotic treatment is recommended for all exacerbations 1
• Obtain sputum culture before starting antibiotics, especially in hospitalized patients 1
• Stratify patients according to Pseudomonas risk 1

Specific Pathogen-Directed Therapy

Atypical Pathogens

• Chlamydophila pneumoniae: Doxycycline, macrolide, levofloxacin, or moxifloxacin 1
• Legionella spp.: Levofloxacin, moxifloxacin, or macrolide (azithromycin preferred) ± rifampicin 1
• Coxiella burnetii: Doxycycline, levofloxacin, or moxifloxacin 1

Resistant Pathogens

• Acinetobacter baumannii: Third-generation cephalosporin + aminoglycoside or ampicillin-sulbactam 1

Treatment Duration

• For standard bacterial infections or uncomplicated CAP: 7-10 days 1
• For Mycoplasma or Chlamydia infections: 10-14 days 1
• For Legionella or S. aureus infections or severe CAP: 21 days 1
• In responding patients, treatment generally should not exceed 8 days 1

Route of Administration

• Switch from IV to oral therapy by day 3 of admission if clinically stable 1
• For ambulatory pneumonia, oral treatment can be used from the beginning 1

Important Considerations

Risk Factors for Pseudomonas aeruginosa

Consider Pseudomonas with at least two of:

1. Recent hospitalization
2. Frequent (>4 courses/year) or recent antibiotic use (last 3 months)
3. Severe disease (FEV1 <30%)
4. Oral steroid use (>10 mg prednisolone daily in last 2 weeks) 1

Non-Responding Patients

For patients not responding to initial therapy:

1. Re-evaluate for non-infectious causes (inadequate treatment, embolism, cardiac failure)
2. Perform microbiological reassessment
3. Consider changing to antibiotics with coverage against P. aeruginosa, antibiotic-resistant S. pneumoniae, and non-fermenters 1

Common Pitfalls to Avoid

• Unnecessary antibiotic use in viral bronchitis
• Failing to obtain appropriate cultures before starting antibiotics in severe cases
• Inadequate coverage for suspected resistant pathogens
• Prolonged IV therapy when oral switch is appropriate
• Not considering local resistance patterns when selecting empiric therapy

Remember that antibiotic selection should always be guided by local resistance patterns, and therapy should be de-escalated based on culture results when available.