Use CRB65 in primary care and CURB65 in hospital alongside clinical judgement; scores supplement rather than replace assessment of oxygenation, comorbidity, frailty or suspected sepsis.
Refer to hospital for severe physiological disturbance or suspected sepsis irrespective of a low score; NG250 describes SDEC, virtual-ward and hospital-at-home options for suitable patients.
In adults with community-acquired pneumonia, review treatment and usually stop antibiotics after 5 days, unless clinically unstable or microbiology indicates longer treatment. Use the current local guideline for agent, route and renal dose.
Do not send routine microbiology in low-severity adult pneumonia; consider investigations according to severity, risk factors and clinical progress.

Reference: NICE NG250 (checked 2026-10-30). This is a targeted evidence-linked teaching update; the historic article below still requires full clinical reconciliation. Follow local protocols and the current BNF for prescribing.

Community-acquired pneumonia (CAP) is an acute infection of the lung parenchyma acquired outside hospital. It causes inflammation of the alveoli and interstitium, producing consolidation, impaired gas exchange, and systemic illness. In UK practice, the priorities are to recognise CAP early, assess severity, start appropriate antibiotics promptly, and identify complications or alternative diagnoses.

📖 About CAP

CAP usually presents with acute cough, fever, breathlessness, and new focal chest signs.
It ranges from mild illness managed in the community to severe sepsis and respiratory failure requiring critical care.
Common pathogens in adults include Streptococcus pneumoniae, Haemophilus influenzae, respiratory viruses, and so-called atypical organisms such as Mycoplasma pneumoniae and Legionella.
Older age, frailty, chronic lung disease, smoking, alcohol excess, and immunocompromise increase risk of severe disease.

🧬 Pathophysiology

Micro-organisms reach the distal airways, usually by microaspiration of colonising upper-airway organisms.
Local host defences are overcome, leading to alveolar inflammation and accumulation of inflammatory exudate.
This causes consolidation, reduced ventilation of affected lung units, and V/Q mismatch with hypoxaemia.
Systemic inflammation may cause fever, tachycardia, delirium, hypotension, and sepsis.

🔎 Types of Pneumonia (Pathology)

🌑 Lobar Pneumonia: Entire lobe affected, usually S. pneumoniae. Pathological progression through 4 stages (see below).
🟡 Bronchopneumonia: Patchy, often basal consolidation spreading from bronchioles. Elderly, bedridden, aspiration-prone.
🌫️ Interstitial (Atypical): Alveolar septal inflammation; usually viral (influenza, RSV) or atypical bacteria (Mycoplasma).
🟢 Necrotising Pneumonia: Severe destruction ± abscess (e.g. S. aureus, Klebsiella).
🦠 Opportunistic: Pneumocystis jirovecii in AIDS, fungal pneumonias (Aspergillus, Cryptococcus).

📆 Classical Stages of Lobar Pneumonia

1️⃣ Congestion (Day 1–2): Heavy, red lung. Vascular engorgement, intra-alveolar fluid, few neutrophils, numerous bacteria.
2️⃣ Red Hepatization (Day 3–4): Firm, liver-like lung. Alveoli packed with neutrophils, RBCs, fibrin → red, airless tissue.
3️⃣ Gray Hepatization (Day 5–7): RBC breakdown → gray-brown tissue. Dense fibrinopurulent exudate, neutrophil dominance.
4️⃣ Resolution (Day 8+): Enzymatic digestion, macrophage clearance → lung architecture restored (or scarred if incomplete).

🧫 Histopathology

Lobar Pneumonia: Intra-alveolar neutrophilic infiltrate, fibrin, RBCs. Thickened alveolar septa. Exudate fills airspaces.
Bronchopneumonia: Suppurative inflammation centred on bronchi/bronchioles, patchy consolidation.
Interstitial Pneumonia: Mononuclear infiltrates (lymphocytes, macrophages) in alveolar walls; airspaces often clear.
Viral Pneumonia: Cytopathic effects (giant cells in RSV, inclusion bodies in CMV).
Pneumocystis jirovecii: Foamy intra-alveolar exudate, cup-shaped organisms on silver stain.

⚠️ Risk factors

Older age and frailty
Chronic respiratory disease (for example COPD or bronchiectasis)
Smoking and excess alcohol
Neurological disease, aspiration risk, poor swallow
Immunosuppression
Diabetes, heart failure, chronic kidney disease, chronic liver disease

🩺 Clinical features

Fever, rigors, sweats
Cough, with or without sputum
Breathlessness
Pleuritic chest pain
New focal chest signs such as crackles, bronchial breathing, or reduced air entry
Systemic upset, reduced exercise tolerance, anorexia
Older adults may present atypically with confusion, falls, or functional decline

🔍 Differential diagnosis

Pulmonary embolism
Acute heart failure / cardiogenic pulmonary oedema
Acute bronchitis
Exacerbation of asthma or COPD
Pneumothorax
Lung malignancy, especially in non-resolving focal change
Interstitial lung disease or organising pneumonia

📊 Severity assessment

Use clinical judgement together with a validated severity score.
In adults, CURB-65 is commonly used:

Confusion
Urea >7 mmol/L
Respiratory rate ≥30/min
Blood pressure: systolic <90 mmHg or diastolic ≤60 mmHg
Age 65 or over

Higher scores suggest greater mortality risk and are used to help decide on hospital admission and treatment intensity.
Do not rely on CURB-65 alone; oxygen requirement, frailty, comorbidity, sepsis, and social factors also matter.

🚑 When to admit

Moderate or high severity CAP
Hypoxaemia or respiratory distress
Sepsis or haemodynamic instability
Inability to take oral therapy or maintain hydration
Significant frailty, delirium, or poor support at home
Diagnostic uncertainty or concern about complications

🔎 Investigations

Observations: respiratory rate, oxygen saturation, pulse, blood pressure, temperature, mental state
Chest X-ray if CAP is suspected and the diagnosis is uncertain, symptoms are significant, or hospital assessment is needed
Blood tests: FBC, U&E, CRP, LFTs as clinically indicated in secondary care
Blood cultures in moderate/high severity CAP or if sepsis is suspected
Sputum culture if productive cough and moderate/high severity disease or failure to improve
Urinary antigen testing for pneumococcus or Legionella may be useful in selected admitted patients, especially severe CAP
Viral testing may be appropriate depending on season, outbreak setting, or severity
CT chest is not routine, but may be helpful if complications, malignancy, empyema, or alternative diagnoses are suspected

🖼️ Imaging

Lobar consolidation suggests classical bacterial CAP, especially pneumococcal disease.
Patchy or multilobar shadowing may occur in bronchopneumonia or severe disease.
Interstitial or ground-glass change may suggest viral or atypical infection, but imaging patterns are not fully specific.
Pleural effusion, cavitation, or non-resolving shadowing should prompt further review.

Lobar pneumonia

Interstitial pattern in pneumonia

💊 Management

Start antibiotics as soon as possible after diagnosis; in hospital this should be within 4 hours of presentation.
Choose antibiotic according to severity, allergy status, local antimicrobial guidance, recent antibiotic exposure, and risk factors for resistant or unusual pathogens.
Give oxygen if hypoxic, aiming for appropriate oxygen targets.
Provide fluids, analgesia, antipyretics, and venous thromboembolism prophylaxis where indicated.
Review for sepsis and escalate care early if deteriorating.
If IV antibiotics are started, review regularly and switch to oral treatment when clinically appropriate.
For adults with CAP, stop antibiotics after 5 days unless microbiology suggests otherwise or the person is not clinically stable.

💊 Community-Acquired Pneumonia (CAP) – Follow Local Antibiotic Guidance

Start antibiotics as soon as possible after diagnosis. In adults presenting to hospital, give antibiotics within 4 hours of presentation. For most adults with CAP, stop antibiotics after 5 days unless microbiology suggests a longer course or the patient is not clinically stable.

Severity	First-line	If penicillin allergy / unsuitable	Notes
Low-severity CAP	Amoxicillin 500 mg PO three times daily for 5 days	Doxycycline 200 mg PO on day 1, then 100 mg PO once daily for 4 more days OR Clarithromycin 500 mg PO twice daily for 5 days OR Erythromycin 500 mg PO four times daily for 5 days (preferred macrolide in pregnancy)	Higher doses of amoxicillin may be used in severe infection - check BNF/local policy.
Moderate-severity CAP	Amoxicillin 500 mg PO three times daily for 5 days PLUS if atypical pathogens suspected: Clarithromycin 500 mg PO twice daily for 5 days OR Erythromycin 500 mg PO four times daily for 5 days (if pregnant)	Doxycycline 200 mg PO on day 1, then 100 mg PO once daily for 4 more days OR Clarithromycin 500 mg PO twice daily for 5 days	Moderate-severity CAP often needs admission or close supervision.
High-severity CAP	Follow local hospital antimicrobial guideline urgently	Follow local hospital antimicrobial guideline urgently	Severe CAP usually requires IV antibiotics, broader cover, senior review, and sepsis / critical care assessment.

🩺 Practical prescribing notes

Use CURB-65 with clinical judgement to assess severity.
Review IV antibiotics early and switch to oral when clinically appropriate.
Check renal function, allergy history, pregnancy status, and drug interactions.
Consider local resistance patterns, recent antibiotic exposure, aspiration risk, and risk of unusual pathogens.
Do not keep antibiotics going automatically beyond 5 days without a reason.

💡 Do not hard-code antibiotic regimens without checking local antimicrobial policy. NICE gives the framework for timing, duration, review, and route, but hospitals usually specify exact antibiotic combinations locally.

⚠️ Complications

Pleural effusion and empyema
Lung abscess or necrotising pneumonia
Sepsis and septic shock
Respiratory failure
ARDS
Bronchiectatic damage after severe infection
Delirium, falls, and deconditioning in older adults

🏥 When to seek senior / ICU input

Increasing oxygen requirement or worsening work of breathing
Hypotension or sepsis despite fluids
Confusion, exhaustion, rising CO₂, or worsening acidosis
Multilobar disease, rapidly progressive infiltrates, or respiratory failure
Need for ventilatory support or vasopressors

🔁 Follow-up

Clinical review is important if symptoms worsen or fail to improve as expected.
Consider repeat chest X-ray, especially if symptoms persist, recovery is incomplete, or underlying malignancy is a concern.
People who smoke, older adults, and those with persistent focal change may need follow-up imaging to ensure resolution.

🛡️ Prevention

Smoking cessation
Influenza vaccination and pneumococcal vaccination where indicated
Optimise management of chronic lung disease and swallowing risk
Reduce alcohol excess and frailty-related aspiration risk

📚 References

Additional related clinical topics

Pneumonia 🩺 (OSCE focused)

Candidate Instructions:You are a final-year medical student in the Acute Medical Unit. A 56-year-old patient has presented with cough and fever. Take a focused history, perform a targeted examination of the chest, and explain your initial differentials and management plan to the examiner. You are not required to perform invasive procedures.

Key History Points 📝

⏱️ Onset & Duration: Sudden vs gradual; days of fever, cough.
🌬️ Symptoms: Cough (productive vs dry), sputum colour, haemoptysis, pleuritic chest pain, breathlessness.
🌡️ Systemic: Fever, rigors, malaise, anorexia, confusion in elderly.
⚠️ Risk Factors: COPD, asthma, diabetes, immunosuppression, smoking, recent viral illness, alcohol excess.
📜 PMHx & DHx: Prior pneumonia, antibiotics, drug allergies.
👪 Social: Smoking, alcohol, occupational exposures (farm, birds, air-con → atypicals).

Examination Focus 👀

🫁 Inspection: Tachypnoea, accessory muscle use, cyanosis.
🫀 Obs: Fever, tachycardia, low SpO₂, hypotension.
🩺 Chest Signs: Reduced expansion, dull percussion, bronchial breathing, coarse crepitations, increased vocal resonance.
🧠 Confusion: Check GCS (CURB-65 scoring).

Differentials ⚖️

🌬️ Viral bronchitis (often dry cough, systemic upset, diffuse wheeze).
🫀 Heart failure (bilateral crepitations, orthopnoea, raised JVP).
🫁 Pulmonary embolism (pleuritic pain, haemoptysis, sudden dyspnoea).
🧫 TB (chronic cough, weight loss, night sweats, haemoptysis).
🦠 COVID-19 (depending on context, diffuse crackles, systemic features).

Investigations 🔬

🧪 FBC (↑ WCC, neutrophilia), U&E (renal function for antibiotics).
🩸 CRP/ESR for inflammation.
🫁 CXR: lobar consolidation (classical), interstitial pattern (atypicals).
🧪 Blood cultures & sputum culture before antibiotics.
🧪 Urinary antigens (Legionella, pneumococcus) in severe cases.
🫀 ABG if hypoxic.

Severity Assessment – CURB-65 📊

C = Confusion (AMT ≤ 8)
U = Urea > 7 mmol/L
R = RR ≥ 30
B = SBP < 90 or DBP ≤ 60
65 = Age ≥ 65 years

Score 0–1 = low risk (outpatient possible), 2 = hospital admission, ≥3 = severe (consider HDU/ICU).

Management 💊

🚑 Admit if moderate/severe, hypoxia, or comorbidity.
💉 Oxygen to maintain SpO₂ > 94% (or 88–92% if CO₂ retainer).
💊 Empirical antibiotics (per local guidelines; e.g. amoxicillin, doxycycline, or macrolide for atypicals).
💧 IV fluids if hypotensive or septic.
💊 Analgesia & antipyretics.
🦠 Treat sepsis per “Sepsis Six” if features present.
📈 Monitor: obs, sats, fluid balance, repeat CXR at 6 weeks (esp. if smoker >50 → exclude underlying malignancy).

Examiner’s Marking Guide 📋

Identifies key symptoms (cough, fever, sputum, chest pain, breathlessness).
Performs structured chest exam (inspection → palpation → percussion → auscultation).
Mentions differentials & red flags (sepsis, hypoxia, confusion).
Knows CURB-65 severity scoring.
Explains empirical antibiotic choice and supportive management.
Safe plan: admit, oxygen, IV fluids, antibiotics, monitor.

🧑‍⚕️ Case Examples - Pneumonia

Case 1 (Community-Acquired Pneumonia): 🏡 A 45-year-old man presents with fever, productive cough, and pleuritic chest pain. CXR shows right lower lobe consolidation. CURB-65 = 1. Diagnosis: Mild community-acquired pneumonia (likely Streptococcus pneumoniae). Teaching point: Manage with oral amoxicillin for 5 days; review response at 48 h.
Case 2 (Atypical Pneumonia - Legionella): 💧 A 52-year-old man returns from a hotel stay with fever, dry cough, diarrhoea, and confusion. Hyponatraemia is noted. CXR shows bilateral patchy infiltrates. Diagnosis: Legionella pneumonia. Teaching point: Consider atypical pathogens if extrapulmonary features are present; treat with macrolide or fluoroquinolone.
Case 3 (Aspiration Pneumonia): 🤢 A 70-year-old woman with advanced dementia develops fever, cough, and foul-smelling sputum after choking on food. CXR shows right middle lobe consolidation. Diagnosis: Aspiration pneumonia. Teaching point: Cover anaerobes with co-amoxiclav or piperacillin-tazobactam; optimise swallowing assessment and feeding method.
Case 4 (Complication - Empyema): 🧪 A 60-year-old man initially treated for pneumonia fails to improve, develops pleuritic chest pain and swinging fevers. CXR shows persistent effusion; pleural aspiration reveals frank pus. Diagnosis: Parapneumonic effusion with empyema. Teaching point: Requires chest drain + prolonged IV antibiotics; always investigate non-resolving pneumonia for complications.
Case 5 (Complication - Lung Abscess): 🫁 A 50-year-old alcoholic man presents with 3-week history of fever, weight loss, and cough producing foul-smelling purulent sputum. CXR shows a cavitating lesion with air-fluid level. Diagnosis: Lung abscess (post-pneumonia complication). Teaching point: Prolonged antibiotics are needed; consider aspiration risk factors and exclude malignancy.

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Community Acquired Pneumonia 🫁 ✅

Current UK guidance: Community-acquired pneumonia — severity and antibiotic stewardship