Pneumonia: Causes, CURB-65 and Antibiotic Principles

Pneumonia is an infection of the lung tissue (alveoli) that causes inflammation and consolidation. It is one of the most common reasons for hospital admission and a major cause of death, particularly in young children and older adults.

Types

• Community-acquired pneumonia (CAP) — acquired outside hospital.
• Hospital-acquired pneumonia — developing 48 hours or more after admission.
• Ventilator-associated pneumonia.
• Aspiration pneumonia — after inhaling stomach or oral contents, for example in reduced consciousness or swallowing problems.
• Pneumonia in immunocompromised patients (for example Pneumocystis jirovecii in advanced HIV).

Common organisms in CAP

• Streptococcus pneumoniae — the most common bacterial cause.
• Haemophilus influenzae (especially in COPD).
• "Atypical" organisms: Mycoplasma pneumoniae, Legionella and Chlamydophila.
• Staphylococcus aureus (including after influenza).
• Respiratory viruses.
• Klebsiella in people with alcohol dependence or diabetes.

Always consider tuberculosis in high-burden areas, especially if the illness is prolonged.

Clinical features

Fever, cough with sputum, breathlessness and pleuritic chest pain. Older patients may present only with confusion or falls. Signs of consolidation:

• reduced chest expansion on the affected side
• dullness to percussion
• bronchial breathing
• increased vocal resonance
• coarse crackles

Investigations

• Chest X-ray: consolidation confirms the diagnosis. Repeat after about 6 weeks in smokers and older patients to exclude an underlying cancer, if symptoms or signs persist.
• Blood tests:
  • full blood count
  • CRP
  • urea and electrolytes
  • liver function
  • blood cultures in moderate or severe cases
• Sputum culture.
• Urinary antigens for pneumococcus and Legionella in severe cases.
• Pulse oximetry, and arterial blood gases if saturation is low.

Assessing severity: CURB-65

Score 1 point for each:

• Confusion (new).
• Urea above 7 mmol/L.
• Respiratory rate 30/min or more.
• Blood pressure: systolic below 90 mmHg or diastolic 60 mmHg or less.
• Age 65 or more.

Interpreting the score:

• 0–1: low risk, usually home treatment.
• 2: moderate risk, consider hospital treatment.
• 3 or more: high risk, hospital admission and consider critical care.

Clinical judgement always applies.

Management

• Antibiotics according to severity and local guidelines, started promptly. Low-severity CAP is often treated with amoxicillin. Higher severity usually needs a beta-lactam plus a macrolide to cover atypical organisms.
• Oxygen to target saturations.
• Fluids.
• Analgesia for pleuritic pain.
• Early mobilisation.
• Monitoring for deterioration and sepsis.

Complications

• Sepsis and septic shock.
• Respiratory failure.
• Parapneumonic effusion and empyema (needs drainage).
• Lung abscess.
• Acute kidney injury.

Exam pearls

• Legionella: think of it with hyponatraemia, deranged liver tests, diarrhoea, and recent travel or exposure to air-conditioning or water systems.
• Mycoplasma: young patients, headache, a dry cough, erythema multiforme and cold agglutinins (haemolysis).
• Klebsiella: upper lobe cavitation with "redcurrant jelly" sputum.

For more, see Exam Night Notes 1.0: Pulmonology and X-Ray Interpretation Simplified.

Test yourself

5 exam-style single-best-answer questions. Choose your answer, then tap “Show answer”.

1. Which is NOT part of CURB-65?

   1. Age 65 or more
   2. Respiratory rate 30/min or more
   3. Urea above 7 mmol/L
   4. Heart rate above 100/min
   5. New confusion
   Show answer

   Answer: D. Heart rate above 100/min
   CURB-65: Confusion, Urea >7, RR ≥30, low BP, age ≥65. Heart rate is not included.

2. Pneumonia with hyponatraemia, deranged LFTs and diarrhoea after a hotel stay suggests:

   1. Legionella
   2. Staphylococcus aureus
   3. Mycoplasma
   4. Klebsiella
   5. Streptococcus pneumoniae
   Show answer

   Answer: A. Legionella
   Legionella classically causes hyponatraemia, abnormal liver tests and GI symptoms, linked to water systems.

3. Upper lobe cavitation with 'redcurrant jelly' sputum in a patient with alcohol dependence suggests:

   1. Legionella
   2. Chlamydophila
   3. Klebsiella pneumoniae
   4. Haemophilus
   5. Pneumocystis
   Show answer

   Answer: C. Klebsiella pneumoniae
   Klebsiella classically causes upper lobe cavitating pneumonia with redcurrant jelly sputum.

4. CURB-65 score of 3 or more means:

   1. Score is not useful
   2. No antibiotics needed
   3. Discharge with follow-up
   4. Treat at home
   5. High risk: hospital admission and consider critical care
   Show answer

   Answer: E. High risk: hospital admission and consider critical care
   A score of 3 or more indicates severe pneumonia with high mortality.

5. Which sign suggests consolidation?

   1. Reduced vocal resonance
   2. Absent breath sounds with resonance
   3. Tracheal deviation away from the side
   4. Hyper-resonant percussion
   5. Bronchial breathing
   Show answer

   Answer: E. Bronchial breathing
   Consolidation: dullness, bronchial breathing, increased vocal resonance and crackles.

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Disclaimer

For education and exam preparation only. This is not medical advice and must not be used to diagnose or treat patients. Always follow current clinical guidelines and the advice of qualified senior colleagues.