Management of Lower Respiratory Tract Infections
The management of lower respiratory tract infections (LRTIs) requires a structured approach based on infection type, severity, and risk factors, with appropriate antibiotic selection tailored to likely pathogens and local resistance patterns. 1
Classification and Initial Assessment
- LRTIs encompass acute bronchitis, pneumonia, and exacerbations of chronic lung diseases, with considerable overlap in clinical presentation 1
- Key assessment parameters include:
Antibiotic Selection for Specific LRTIs
Community-Managed LRTI
- Aminopenicillins (amoxicillin 500-1000 mg every 8 hours) are first-line for uncomplicated LRTIs 2
- For patients with risk factors for beta-lactamase producing organisms, amoxicillin-clavulanate is recommended 2, 3
- Alternative options for penicillin-allergic patients include:
- Macrolides (clarithromycin 250-500 mg twice daily)
- Tetracyclines (doxycycline 100 mg twice daily)
- Oral cephalosporins for non-anaphylactic penicillin allergy 2
COPD Exacerbations
- Antibiotics should be prescribed for patients with:
- Co-amoxiclav is recommended as first-line therapy, with levofloxacin and moxifloxacin as alternatives 1
- For patients with P. aeruginosa risk factors (≥2 of: recent hospitalization, frequent/recent antibiotics, severe disease with FEV1 <30%, oral steroid use >10 mg prednisolone daily), ciprofloxacin or levofloxacin is preferred 1
Hospitalized Patients (Non-ICU)
- Options include:
- Second-generation cephalosporins (IV cefuroxime 750-1500 mg every 8 hours)
- Third-generation cephalosporins (IV cefotaxime 1 g every 8 hours or IV ceftriaxone 1 g daily)
- IV benzyl penicillin or IV amoxicillin 2
- Switch from IV to oral therapy should occur by day 3 of admission if the patient is clinically stable 1
ICU Patients with Severe LRTI
- Combination therapy with a second or third-generation cephalosporin plus either a respiratory fluoroquinolone or a macrolide is recommended 2
- For suspected P. aeruginosa, ciprofloxacin or a β-lactam with antipseudomonal activity, with optional addition of aminoglycosides 1
Management of Bronchiectasis Exacerbations
- Antibiotic treatment is indicated for exacerbations 1
- Obtain sputum cultures before starting antibiotics, particularly in hospitalized patients 1
- Stratify empiric therapy based on P. aeruginosa risk 1
Non-responding Patients
- Re-evaluate for non-infectious causes of failure (inadequate treatment, pulmonary embolism, cardiac failure) 1
- Perform careful microbiological reassessment 1
- Consider changing to an antibiotic with good coverage against P. aeruginosa, resistant S. pneumoniae, and non-fermenters 1
- Adjust therapy based on microbiological results 1
Prevention Strategies
- Prophylactic antibiotics are not recommended for chronic bronchitis or COPD 1
- Inhaled steroids, long-acting beta-2-agonists, or long-acting anti-muscarinics should not be used specifically to prevent LRTIs 1
- Antiviral substances for influenza prevention should only be considered in special situations (outbreaks in closed communities) 1
Common Pitfalls and Caveats
- Many LRTIs are viral in origin and self-limiting; antibiotics should only be used when bacterial infection is suspected 2
- Fluoroquinolones should be reserved for specific indications due to resistance concerns; inappropriate use contributes to emerging resistance 2, 4
- Streptococcus pneumoniae is the most common bacterial pathogen in LRTI; antibiotic therapy should always be active against it 2
- Patients should be informed that cough may persist longer than the duration of antibiotic treatment 2
- Macrolides show only modest activity against H. influenzae due to efflux pumps in >98% of strains 1
- For CA-MRSA pneumonia, combination of a bactericidal agent with a toxin-suppressing agent (clindamycin or linezolid) may be optimal 1