Pneumonia

Common LRT infection characterized by inflammation of the lung tissue

Aetiology

  • Streptococcus pneumoniae (70%) - most common, community acquired
  • Haemophilus influenza (5%) - usually the elderly and patients with COPD
  • Staph. aureus (4%) - common in PWIDs, often following influenza
notion image

Atypicals

  • Legionella - inhalation of contaminated water droplets
  • Mycoplasma pneumonia - children and young adults, peaks every 4 years
  • Coxiella burneti (Q fever) - farming
  • Chlamydia psittaci - birds (pets)
  • Klebsiella - aspiration (e.g. from alcoholism)
  • Pneumocytis jiroveci - immunocompromised e.g. AIDS patients

Pathophysiology

  • Infection → inflammatory exudation → consolidation

Lobar pneumonia

  • Confluent consolidation involving a complete lung lobe
  • Most commonly Streptococcus pneumoniae (community acquired), classically in otherwise healthy young adults

Bronchopneumonia

  • Infection starting in the airways and spreading to adjacent alveolar lung
  • Most often seen in the context of pre-existing disease

Clinical presentation

Symptoms

  • Fever, chills
  • Cough ± sputum (purulent, rusty)
  • Dyspnea
  • Pleuritic chest pain
  • Fatigue, myalgia
  • Elderly: confusion, falls

Signs

  • Tachypnea, tachycardia
  • Reduced chest expansion
  • Bronchial breath sounds
  • Crackles
  • Dullness to percussion
  • ↑ vocal fremitus

Investigations

  • General investigations are not necessary for the majority of patients who are managed in the community
  • When a patient is admitted to hospital:
    • FBCs, CRP, U+Es
    • CXR
    • If moderate/severe - sputum examination and culture, blood culture, legionella and pneumococcal urinary antigens

CURB 65 - Risk Score

  • Confusion
  • Urea ≳ 7 mmol
  • Resp. rate > 30
  • BP - systolic < 90, diastolic ≲ 60
  • ≳65 years
Interpretation
  • 0–1: Outpatient
  • 2: Inpatient
  • ≥3: Severe → ICU

Sputum

  • Sterptococcus pneumonia - rust coloured sputum
  • Pseudomonas, Haemophilus - green sputum
  • Klebsiella - red currant-jelly sputum
  • Anaerobes - foul smelling and bad-tasting sputum

Management

CAP (pneumococcal)

Outpatient (No Comorbidities)
  • Amoxicillin 1 g PO 3x1
  • Doxycycline 100 mg PO 2x1
  • Azithromycin 500 mg PO (day 1) → 250 mg PO 1x1
Outpatient (With Comorbidities)
  • Amoxicillin-clavulanate / Cephalosporin + Macrolide or Doxycycline
  • Respiratory fluoroquinolone
Inpatient
  • β-lactam / Cephalosporin + Macrolide
  • Respiratory fluoroquinolone
  • β-lactam / Cephalosporin + Doxycycline
📄 Empiric Antibiotic Options (Respiratory Infections)
Drug Class
Drug
Dose
Frequency
β-lactam / β-lactamase inhibitor
Amoxicillin–clavulanate
500 mg / 125 mg
3×1
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875 mg / 125 mg
2×1
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2000 mg / 125 mg
2×1
Macrolide
Azithromycin
500 mg (Day 1)
1x1
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250 mg (Day 2–5)
1x1
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Clarithromycin
500 mg
2x1
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Clarithromycin XR
1000 mg
1x1
Cephalosporin (oral)
Cefpodoxime
200 mg
2x1
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Cefuroxime
500 mg
2x1
Respiratory Fluoroquinolone
Levofloxacin
750 mg
1x1
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Moxifloxacin
400 mg
1x1
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Gemifloxacin
320 mg
1x1

Hospital acquired (extended gram-negative cover)

  • Non-severe - PO amoxicillin (if penicillin allergic: PO doxycycline)
  • Severe - IV amoxicillin + gentamicin (if penicillin allergic: PO doxycycline + gentamicin)

Aspiration pneumonia (anaerobic cover)

  • Non-severe - PO amoxicillin + metronidazole (if penicillin allergic: doxycycline + metronidazole)
  • Severe - IV amoxicillin + gentamicin + metronidazole (if penicillin allergic: PO doxycycline + IV gentamicin + metronidazole)

Atypicals

  • Doxycycline
  • Except Legionella - clarithromycin/erythromycin or levofloxin