Chapter 10: Lower Respiratory Tract Infections
Acute Bronchitis
- Common in healthy individuals
- Viral causes (most common):
- Influenza A & B, parainfluenza, coronavirus, rhinovirus, RSV, adenovirus, human metapneumovirus
- Bacterial causes (less common):
- Bordetella pertussis, Bordetella parapertussis, Mycoplasma pneumoniae, Chlamydophila pneumoniae
Treatment
- Viral: Symptomatic only ❌ No antibiotics
- B. pertussis: Antibiotics help if started early; still recommended later to prevent spread
- Mycoplasma & Chlamydophila: Azithromycin or doxycycline
Acute Exacerbation of Chronic Bronchitis (COPD)
- Defined by increased:
- Cough
- Sputum production
- Dyspnoea
- Common pathogens:
- Streptococcus pneumoniae, Moraxella catarrhalis, Haemophilus influenzae
- Severe cases: Pseudomonas aeruginosa, Enterobacteriaceae
Empiric Treatment
- Amoxicillin-clavulanate, ceftriaxone, or moxifloxacin
- Duration: 7–10 days
- Annual flu & pneumococcal vaccines recommended
Bronchiolitis
- Affects children <2 years
- Viral causes:
- RSV (most common), parainfluenza, human metapneumovirus
- Causes wheezing due to blocked bronchioles
Management
- Supportive care
- Oxygen if needed
- No antibiotics
- Ribavirin for severe RSV in immunosuppressed children
Pneumonia
Diagnosis
- Outpatients: No labs needed
- Hospitalised: Sputum MC&S, blood cultures, PCRs for viruses & atypicals
Common Pathogens
- Streptococcus pneumoniae
- Haemophilus influenzae (especially in COPD)
- Atypicals: Mycoplasma, Chlamydophila, Legionella
- Gram-negative bacilli: Klebsiella, Pseudomonas
- Staphylococcus aureus, respiratory viruses, Mycobacterium tuberculosis, Pneumocystis jirovecii
Treatment: Community-Acquired Pneumonia (CAP)
Outpatients <65 years, no comorbidities
- High-dose amoxicillin
- Optional atypical cover: Clarithromycin or azithromycin
- Alternatives: Fluoroquinolones, cefuroxime, amoxicillin-clavulanate
>65 years or with comorbidities
- High-dose amoxicillin-clavulanate
- Optional atypical cover
- Alternatives: Respiratory fluoroquinolones
- Penicillin allergy: Use fluoroquinolones
Hospitalised (Non-ICU)
- Amoxicillin-clavulanate or ceftriaxone or ceftaroline or ertapenem
- Add atypical cover: Clarithromycin or azithromycin
- Allergy: Moxifloxacin or levofloxacin
ICU Patients
- Severe illness indicators: confusion, low BP, high RR, multilobar consolidation, hypoxaemia, abnormal labs
- Treatment: β-lactam + atypical cover + aminoglycoside
- Duration: 5–7 days (14 days for S. aureus or Legionella)
- Allergy: Fluoroquinolone + atypical cover
Atypical Pneumonia
- Caused by Mycoplasma, Chlamydophila, Legionella
- Different symptoms & response to antibiotics
Treatment
- Clarithromycin, azithromycin, doxycycline, moxifloxacin, or levofloxacin
- Duration: 14 days (especially for Legionella)
Pneumonia During Influenza Epidemics
- Can be complicated by secondary bacterial infections:
- S. aureus, S. pneumoniae, S. pyogenes, H. influenzae
- Antivirals: Oseltamivir (Tamiflu®)
- Antibiotics: β-lactam + macrolide
Aspiration Pneumonia
- Common in elderly, alcoholics, epilepsy, stroke
- Caused by anaerobes ± aerobes
Treatment
- Amoxicillin-clavulanate or metronidazole + ceftriaxone
- Alternatives: Ertapenem, piperacillin-tazobactam, clindamycin
- Duration: 7–10 days
Pneumonia in Immunocompromised Patients (e.g. HIV)
- Consider Pneumocystis jirovecii, fungi, CMV
Treatment: PJP
- High-dose cotrimoxazole (oral or IV)
- Adjunctive corticosteroids for hypoxic patients
Healthcare-Associated Pneumonia (HCAP), Hospital-Acquired (HAP), Ventilator-Associated (VAP)
Pathogens
- Gram-negative bacilli: Klebsiella, Pseudomonas, Acinetobacter
- Anaerobes, MRSA
Risk Factors for MDR Pathogens
- Recent hospitalisation, nursing home, IV therapy, dialysis, wound care, prior antibiotics, structural lung disease, immunosuppression
Treatment: HCAP, HAP, VAP
No MDR Risk
- Fluoroquinolones, ceftriaxone, cefepime, piperacillin-tazobactam, ertapenem
MDR Risk Present
- Cefepime, imipenem, meropenem, doripenem, piperacillin-tazobactam, levofloxacin, ertapenem
- Optional: Aminoglycoside
MRSA Suspected
- Vancomycin or linezolid
Extended Infusions
- Optimise antimicrobial effect:
- Piperacillin-tazobactam: 4.5 g over 3 hrs, 6 hourly
- Meropenem: 1–2 g over 3 hrs, 8 hourly
- Doripenem: 1 g over 4 hrs, 8 hourly
- Cefepime: 2 g over 3 hrs, 8 hourly