About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- CAP: most commonly caused by Streptococcus pneumoniae
- CURB-65 severity score: Confusion, Urea >7, RR ≥30, BP (systolic <90 or diastolic ≤60), age ≥65 — each scores 1
- CURB-65 0–1: mild → oral amoxicillin, home. 2: moderate → consider hospital, amoxicillin + clarithromycin. 3–5: severe → IV co-amoxiclav + clarithromycin (or tazocin)
- HAP: onset ≥48 h after hospital admission — different organisms (Gram-negatives, MRSA), different antibiotics
- CXR consolidation (air bronchograms) is the classic finding — follow up CXR at 6 weeks to ensure resolution
Overview
Pneumonia is an acute infection of the lung parenchyma causing inflammation and consolidation of the affected alveoli. It is classified by setting of acquisition: community-acquired pneumonia (CAP) develops outside hospital or within 48 hours of admission; hospital-acquired pneumonia (HAP) develops ≥48 hours after admission. Aspiration pneumonia occurs following inhalation of oropharyngeal or gastric contents. The most common causative organism for CAP is Streptococcus pneumoniae, followed by Haemophilus influenzae, Moraxella catarrhalis, and atypical organisms (Mycoplasma pneumoniae, Legionella, Chlamydophila).
Epidemiology
Pneumonia is the leading infectious cause of death in the UK and globally. CAP affects approximately 5–11 per 1,000 adults annually, with incidence highest in the very young and the elderly. Approximately 29,000 people die from pneumonia in the UK each year. Risk factors include extremes of age, smoking, COPD, immunosuppression, diabetes, chronic liver/renal disease, recent viral infection (especially influenza), aspiration risk (stroke, reduced consciousness, dysphagia), and overcrowding or institutional living.
Clinical Features
Symptoms
Productive cough — purulent or rust-coloured sputum (pneumococcal)
Fever and rigors
Dyspnoea
Pleuritic chest pain — sharp, worse on inspiration
Malaise, myalgia, headache
Confusion (especially in elderly — may be the only feature)
Signs
Tachypnoea (RR ≥30 suggests severe disease)
Fever (may be absent in elderly or immunocompromised)
Signs of consolidation: bronchial breathing, dullness to percussion, increased vocal resonance/tactile fremitus
Coarse crackles over affected area
Hypotension (systolic <90 mmHg)
Cyanosis, SpO₂ <92%
Investigations
First-line
Chest X-rayLobar consolidation (air bronchograms), patchy infiltrates, or bilateral changes. Essential to confirm diagnosis
BloodsFBC (raised WCC), CRP (elevated), U&Es (urea >7 is CURB-65 criterion), LFTs
CURB-65 scoreCalculate at presentation to guide severity and management setting
Second-line
Blood culturesBefore antibiotics if CURB-65 ≥2 — positive in ~10% of hospitalised CAP
Sputum culture and sensitivityIf productive cough — guides targeted antibiotic therapy
ABGIf SpO₂ <92% or severe pneumonia — assess for respiratory failure
Urinary antigensLegionella and pneumococcal urinary antigens in moderate-severe CAP
Specialist
CT thoraxIf CXR is inconclusive, suspected complication (empyema, abscess), or failure to respond to treatment
Pleural fluid aspirationIf significant pleural effusion — send for pH, protein, LDH, glucose, MC&S, cytology
Bronchoscopy with BALImmunocompromised patients or non-resolving pneumonia
1
Mild CAP (CURB-65 0–1) — outpatient
- Oral amoxicillin 500 mg TDS for 5 days
- If penicillin allergy: doxycycline 200 mg loading then 100 mg OD, or clarithromycin 500 mg BD
- Safety-net advice: return if worsening or no improvement at 48 h
2
Moderate CAP (CURB-65 = 2) — consider admission
- Oral amoxicillin 500 mg–1 g TDS + clarithromycin 500 mg BD (for atypical cover)
- Or doxycycline if penicillin allergic
- Duration: 5 days (extend to 7–10 if slow response)
3
Severe CAP (CURB-65 ≥3) — hospital admission
- IV co-amoxiclav 1.2 g TDS + clarithromycin 500 mg BD
- Alternative: IV piperacillin-tazobactam (Tazocin) if broader cover needed
- IV to oral switch when improving and tolerating oral intake (typically 48–72 h)
- Oxygen to target SpO₂ 94–98% (88–92% if risk of CO₂ retention)
4
Hospital-acquired pneumonia (HAP)
- Different antibiotic choice — local trust guidelines
- Typically: co-amoxiclav, piperacillin-tazobactam, or meropenem
- Consider MRSA cover (vancomycin/linezolid) if risk factors present
- Send sputum and blood cultures before starting antibiotics
5
Follow-up
- Clinical review at 6 weeks
- Repeat CXR at 6 weeks (mandatory in smokers >50 years to exclude underlying malignancy)
- If not resolving: consider empyema, abscess, underlying malignancy, or immunodeficiency
Complications
- Parapneumonic effusion/empyema: Pleural fluid pH <7.2 or purulent fluid → requires chest drain
- Lung abscess: Cavitating lesion — suspect if swinging fever despite antibiotics, especially in aspiration
- Sepsis and septic shock: Organ dysfunction from pneumonia-related bacteraemia
- ARDS: Severe bilateral infiltrates with refractory hypoxaemia
- Respiratory failure: May require NIV or invasive ventilation
UKMLA Exam Tips
- 1CURB-65: Confusion, Urea>7, RR≥30, BP<90/60, ≥65. Learn this — it appears frequently
- 2Commonest cause of CAP = Streptococcus pneumoniae. Most common atypical = Mycoplasma pneumoniae
- 3Rust-coloured sputum = pneumococcal. Currant jelly sputum = Klebsiella. Foul-smelling = anaerobes (aspiration)
- 4Legionella: think hotel/travel, air conditioning, hyponatraemia, lymphopenia, deranged LFTs — test with urinary antigen
- 5Repeat CXR at 6 weeks in smokers >50 to exclude underlying lung cancer — examiners love this
- 6Empyema: pH <7.2 = needs chest drain. pH >7.2 = may manage conservatively with antibiotics
practicetest your knowledge on pneumoniaApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — respiratory and beyond.
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