Pneumonia
Pneumonia is an infection of the lung parenchyma that can be classified as community-acquired pneumonia (CAP) or hospital-acquired pneumonia (HAP) depending on where and when it develops.
Updated UKMLA guide to pneumonia based on the NICE 2025 guideline: CAP vs HAP, causes, symptoms, diagnosis, management, in both adult and paediatric populations.
Adult CAP is the main focus of the article, with paediatric CAP and HAP covered as separate sections below.
Community-Acquired Pneumonia (CAP) – Adults
Definition
CAP: pneumonia acquired outside the hospital, or within 48 hours of admission (includes pneumonia that develops in a nursing home resident)
Causes
Bacteria are the most common cause of pneumonia in adults
Bacterial Causes
Most common bacterial cause of CAP: Streptococcus pneumoniae [Ref]
Some classic associations between the causative organisms and specific patient populations: [Ref]
| Patient population / risk factor | Organisms |
|---|---|
| Aspiration pneumonia |
|
| COPD patients |
|
| Cystic fibrosis |
|
| Immunocompromised (e.g. HIV, post-transplant) |
|
| Post-influenza pneumonia |
|
| Cavitary pneumonia |
|
‘Atypical’ bacterial pathogens (associated with CAP): [Ref]
- Mycoplasma pneumoniae – most common atypical pathogen
- Legionella species
- Chlamydia pneumoniae
- Zoonotic bacteria – Coxiella burnetii (Q fever), Chlamydia psittaci (psittacosis), Francisella tularensis (tularemia)
Atypical pathogens share the following features:
- Lack of response to beta-lactam antibiotics, rationale:
- Mycoplasma lacks cell wall (main target of beta-lactam)
- Legionella and chlamydia pneumoniae are obligate, intracellular (beta-lactam has poor eukaryotic cell penetration)
- Characterised by negative routine gram stain and cultures, requiring alternative diagnostic methods for detection
Viral Causes
Viruses are the most common cause of pneumonia in children
Common causes: [Ref]
- Influenza viruses (A and B) – most common overall
- Severe in the elderly, those with chronic comorbidities (e.g. heart failure, COPD), pregnancy, immunocompromised
- Respiratory syncytial virus – most common cause in young children and infants
- Parainfluenza and human metapneumovirus
- Rhinoviruses
- Coronaviruses
Management of viral pneumonia is primarily supportive, with targeted antiviral treatments available mainly for influenza (using neuraminidase inhibitors such as oseltamivir) and COVID-19 (e.g., remdesivir)
Clinical Features
Typical Bacterial Pneumonia
Sudden onset of: [Ref]
- High fever
- Productive cough with purulent sputum
- Typically yellow-greenish
- Rust-coloured sputum is typical of Streptococcus pneumoniae
- Red currant sputum
The sputum is said to resemble red currant jelly due to its viscous consistency and deep red coloration, and has been historically associated with severe pneumonia caused by klebsiella pneumoniae.
The clinical significance of red currant sputum is that it may suggest a necrotizing, hemorrhagic pneumonia, most commonly seen in alcoholics or patients with significant comorbidities. However, this finding is rare and not specific.
is typical of Klebsiella (from tissue necrosis and haemorrhage) - NB its possible to have a non-productive cough in pneumonia
- Dyspnoea, tachypnoea
- Pleuritic chest pain
- Chills, rigours, malaise
Typical respiratory examination findings: [Ref]
| Examination aspect | Typical findings |
|---|---|
| Chest expansion | ↓ on the affected side (due to pain and reduced lung compliance) |
| Percussion | Focal dullness over the affected lung segment / lobe |
| Vocal/Tactile fremitus | ↑ |
| Auscultation | Focal coarse crackles +/- bronchial breath sounds |
Note that pleural effusion is a possible complication of pneumonia, which typically presents with reduced or absent breath sounds, stony dullness to percussion, and reduced tactile fremitus.
If an exam question describes pleural effusion signs in the context of a typical history of pneumonia, this is likely pneumonia complicated by pleural effusion. See the complication section below for more details.
Pneumonia Caused by Atypical Pathogens
Shared features:
- Dry cough
- Low-grade fever
- Flu-like symptoms (e.g. headache, myalgia, malaise)
- Auscultation is often unremarkable
Organism-specific features (the exam-common ones are listed):
| Atypical pathogen | Features |
|---|---|
| Mycoplasma pneumoniae | Outbreaks tend to occur in schools, institutions etc.
Clinical features:
Tests:
|
| Legionella species | Associated with contaminated water (e.g. air conditioning systems, cruises, pools)
Clinical features:
Tests:
|
| Zoonotic bacteria | Coxiella burnetii (Q fever)
Chlamydia psittaci (psittacosis)
|
While certain patterns, both clinical and radiographic, may be more frequently associated with atypical pathogens, there is significant overlap, and atypical and typical pneumonia cannot be reliably differentiated based solely on clinical presentation or radiographic findings.[Ref]
Viral Pneumonia
Similar to atypical vs typical bacterial pneumonia, viral and bacterial pneumonia cannot be reliably differentiated based solely on clinical presentation or radiographic findings.
However, certain features, as outlined in the table below, can aid differentiation. [Ref]
| Viral | Bacterial | |
|---|---|---|
| Age | Younger age Viral pathogens are the most common cause of pneumonia in children, especially in those <5 y/o. (<5 y/o) |
Adults |
| Epidemic situation | Ongoing viral epidemic | |
| Onset/History | Slow/gradual | Rapid |
| Biomarkers |
|
|
| Radiographic | Bilateral, interstitial Interstitial infiltrates are radiographic findings characterized by increased markings in the lung interstitium, often appearing as reticular or ground-glass opacities. These are classically associated, but not exclusive to, viral pneumonia, reflecting inflammation and infection primarily in the interstitial and peribronchial tissues rather than the alveolar spaces. infiltrates |
Unilateral, alveolar/lobar infiltrates Alveolar or lobar infiltrates present as dense, homogeneous opacities on imaging, often corresponding to consolidation of a lung segment or lobe. These findings are more typical of bacterial pneumonia. |
| Response to antibiotics | Slow or non-responsive | Rapid |
Complications
Main complications:
- Uncomplicated parapneumonic pleural effusion (common)
- Pleural infection (includes complicated parapneumonic effusion and empyema)
- Lung abscess
- Sepsis
- Respiratory failure
Uncomplicated parapneumonic pleural effusion vs complicated parapneumonic effusion vs empyema:
| Feature | Uncomplicated parapneumonic effusion (UPE) | Complicated parapneumonic effusion (CPPE) | Empyema |
|---|---|---|---|
| Definition | Sterile exudative effusion (no bacterial invasion of pleural space) | Infected pleural fluid without gross pus | Collection of frank pus in the pleural space |
| Pleural fluid analysis | Exudative BUT generally normal biochemistry
Gram stain/culture → negative (sterile) |
Biochemical features of infection are required to make the diagnosis:
Gram stain/culture → may be positive |
The presence of frank pus (usually visible on aspiration) is diagnostic of empyema
Biochemical features of infection (same as CPPE), are often present but not required to make the diagnosis
Gram stain/culture → frequently positive |
Assessment and Management
Step 1 – Risk Stratification and Choice of Setting
Risk stratification tools/scores such as CRB65/CURB65 are used in adults (NOT used in children) with a clinical diagnosis of CAP
Primary Care (CRB65 Score)
Calculate the CRB65 score, then use it to guide management
| Component | Score |
|---|---|
| Confusion (AMTS ≤8 / new disorientation in time, place, or person) | 1 |
| Respiratory rate ≥30 | 1 |
| Blood pressure systolic <90 mmHg or diastolic ≤60 mmHg | 1 |
| ≥65 y/o | 1 |
Interpretation:
- 0: low risk (<1% mortality risk)
- 1 or 2: intermediate risk (1-10% mortality risk)
- 3 or 4: high risk (>10% mortality risk)
CRB65 score-informed management setting:
| CRB65 score | Management setting |
|---|---|
| 0 | Primary care-led service (home management with safety netting) |
| 1 | Use clinical judgement, any of the following:
|
| 2 / 3 / 4 | Refer to hospital for inpatient care |
Secondary Care (Hospital) (CURB65 Score)
Calculate the CURB65 score, then use it to guide management
| Component | Score |
|---|---|
| Confusion (AMTS ≤8 / new disorientation in time, place, or person) | 1 |
| Blood urea >7 mmol/L | 1 |
| Respiratory rate ≥30 | 1 |
| Blood pressure systolic <90 mmHg or diastolic ≤60 mmHg | 1 |
| ≥65 y/o | 1 |
Interpretation:
- 0 or 1: low risk (<1% mortality risk)
- 2: intermediate risk (3-15% mortality risk)
- 3 or 4 or 5: high risk (>15% mortality risk)
CURB65 score-informed management setting:
| CURB65 score | Management setting |
|---|---|
| 0 / 1 | Discharge to primary care-led service (home management with safety netting) |
| 2 | Use clinical judgement, one of the following:
|
| 3 / 4 / 5 | Refer to hospital for inpatient care +/- critical care referral |
Step 2 – Investigation and Diagnosis
Primary Care
In primary care, a chest X-ray is not routinely required to diagnose CAP if the history and examination findings are typical (and given CRB65 score is low)
Secondary Care (Hospital)
1st line standard imaging: chest X-ray
Chest X-ray findings in pneumonia:
- Focal consolidation (homogenous opacity with poorly defined edges)
- Air bronchograms
Air bronchograms are defined as the radiologic appearance of air-filled bronchi made visible by the opacification of surrounding alveoli.
This sign occurs when alveolar spaces are filled with fluid, pus, blood, or cells, while the bronchi remain patent and air-filled, resulting in a branching, tubular lucency within areas of pulmonary consolidation or infiltrate.
are commonly seen within consolidation
The latest NICE guidelines emphasised the use of lung ultrasound for:
- Rapid point-of-care diagnosis in a sick or deteriorating patient, or
- Investigation for associated complications (e.g. pleural infection, parapneumonic effusion), or
- Investigation for a possible alternative diagnosis (e.g. heart failure)
Other tests to consider:
- Baseline CRP on admission
- Respiratory tract samples
- Ideally, a sputum sample for microbiological testing
- If not, nasopharyngeal swab for respiratory screen
- Blood cultures
- Pneumococcal urinary antigen test (to support use of narrow-spectrum antibiotic)
- Testing for atypical pathogens
- Legionella urinary antigen test (if there are risk factors)
- Mycoplasma pneumoniae serology (or if available, PCR of respiratory tract samples is preferred
Historically, serology is the mainstay diagnostic approach for Mycoplasma pneumoniae.
PCRs are now preferred due its superior sensitivity, specificity, and rapid turnaround time.
)
NICE recommends NOT to routinely offer microbiological tests in low-severity CAP, but consider in moderate or high-severity CAP.
Step 3 – Choosing Antibiotic Therapy
Standard course: oral antibiotics for 5 days
- Give IV antibiotics or a prolonged course of antibiotics as per clinical judgement
Choice of antibiotics is based on the severity of disease (low, moderate, high). Disease severity is determined by 1) clinical judgement AND 2) the CRB65/CURB65 score, with an emphasis placed on clinical judgement
| Severity of disease | 1st line | Penicillin allergy | Atypical pathogens suspected |
|---|---|---|---|
| Low |
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| Moderate |
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| High |
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NICE also recommends considering IV hydrocortisone (alternative: dexamethasone) for 4-7 days or until discharge, in addition to antibiotics in high-severity CAP in adults.
If the patient is not improving with antibiotics, consider non-bacterial causes of pneumonia, such as influenza.
The MHRA statement on fluoroquinolones (updated in Jan 2024) emphasises that fluoroquinolone antibiotics must only be prescribed when other commonly recommended antibiotics are inappropriate.
This restriction follows concerns over serious, disabling, long-lasting, and potentially irreversible side effects, including:
- MSK: tendonitis, tendon rupture (Achilles tendon rupture is classic), muscle pain and weakness, joint pain
- Neuro: peripheral neuropathy, altered taste / smell / hearing
- Mental health: depression, anxiety, panic attacks, memory impairment
- Psych: confusion, suicidal thoughts / attempts
A notable exception is acute bacterial prostatitis, where fluoroquinolones (ciprofloxacin / ofloxacin) remain the 1st line antibiotics despite the safety issues.
Atypical pathogens respond well to macrolides and do NOT respond to beta-lactam antibiotics (e.g. penicillins).
Step 4 – Monitoring Treatment
For those managed in hospital, consider measuring CRP or procalcitonin 3 or 4 days after starting treatment if there is a clinical concern about treatment failure:
- High levels of CRP or procalcitonin or levels that do not significantly improve with treatment are associated with treatment failure
Follow-Up
Patient Education
After starting treatment:
Explain to adults to expect the following recovery timeline (but rate of improvement will vary with the severity of the pneumonia):
- 1 week: fever should have resolved
- 4 weeks: chest pain and sputum production should have substantially reduced
- 6 weeks: cough and breathlessness should have substantially reduced
- 3 months: most symptoms should have resolved but fatigue may still be present
- 6 months: they will feel back to normal
Explain to parents or carers of children that for most children
- 3-4 days: resolution of fever (without use of antipyretics) AND dyspnoea
- Cough may persist for up to 4 weeks after discharge (despite gradual improvement), and does NOT usually require further review if the child is otherwise well
Follow-Up Chest X-Ray
Routine follow-up chest X-ray is NOT recommended
Follow-up chest X-ray at 6 weeks following discharge should be considered if:
- Risk factors for lung cancer / other underlying respiratory disease (e.g., smokers or >50 y/o, OR
- Persisting or deteriorating symptoms, OR
- Unexplained weight loss
In clinical practice, it is very common to perform a routine follow-up chest X-ray in all patients who have had a pneumonia.
Community-Acquired Pneumonia (CAP) – Paediatrics
The management of CAP in babies, children, and young people (<18 years; abbreviated as ‘BCY’ in this article) is largely similar to adult guidelines. This section highlights the key differences, particularly in diagnosis, risk stratification, and antibiotic duration.
Assessment and Risk Stratification
Risk stratification tools like CRB65 and CURB65 are NOT used in BCYBabies, children, and young people (under 18 years old) (they should only be used in adults)
Severity assessment is based solely on severity of symptoms/signs & clinical judgement. Severe signs / symptoms of CAP include:
- Difficulty breathing
- SpO2 <90%
- Raised heart rate
- Grunting
- Severe chest indrawing
- Inability to breastfeed or drink
- Lethargy / Reduced level of consciousness
Investigations
Investigations are largely the same as adults guidelines, with one minor difference:
- Urinary antigen tests are NOT routinely carried out for BCYBabies, children, and young people (under 18 years old) with severe CAP (although indicated for adults with moderate-severe CAP)
Management
Referral
On clinical diagnosis of CAP → consider hospital referral or seek specialist paediatric advice on further investigation and management
This is in contrast to adults where the decision regarding the place of care (including referral to hospital) is highly structured and primarily driven by a quantifiable mortality risk score (i.e. CURB65 or CRB65).
Antibiotic Therapy
Duration
Duration of antibiotic therapy:
- Non-severe disease: depends on age
- 3 months to 11 y/o (without complications) → 3 days
- <3 months AND 12-17 y/o → 5 days (same as adults)
- Severe disease → 5 days (same as adults)
The updated NICE guidance recommends that children aged 3 months to 11 years with non-severe, uncomplicated infection may receive a shorter 3-day antibiotic course instead of the standard 5-day regimen.
All other infants, children, and young people who do not fall within this group should continue to receive the full 5-day course, consistent with adult treatment duration.
Choice of Antibiotics
Similar to adults, with minor differences (mainly that doxycycline should NOT be used in <12 y/o)
|
Severity of disease
|
1st line
|
Penicillin allergy
|
Atypical pathogens suspected
|
|---|---|---|---|
|
Non-severe symptoms or signs
|
Amoxicillin
|
|
|
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Severe symptoms or signs
|
Co-amoxiclav
|
Consult local microbiologist
|
|
Corticosteroid Therapy
Corticosteroids (e.g., IV hydrocortisone or dexamethasone) are considered for high-severity CAP in adults, but the recommendation is NOT made for BCYBabies, children, and young people (under 18 years old) with pneumonia
Hospital-Acquired Pneumonia (HAP)
Key difference from CAP is that the causative agent is usually different, therefore different antibiotics are recommended.
Definitions
- Hospital-acquired pneumonia: defined by pneumonia onset at least 48 hours after hospital admission, or those who presented to hospital with pneumonia but were discharged (from hospital) within the last 7-10 days
Aetiology
Management
Unlike CAP, the NICE guidance for HAP is essentially the same for adults and children. The only notable differences relate to paediatric dosing and certain alternative second-line antibiotic options, which fall outside the scope of this article.
Antibiotic choice is specifically based on:
- Disease severity
- The key distinction for HAP is that, unlike CAP, there are no specific scoring systems (like CRB65 or CURB65) recommended for assessing mortality risk and severity.
- The severity of hospital-acquired pneumonia is determined primarily based on clinical judgement (as per NICE, severe disease is indicated for example by symptoms/signs of sepsis)
- Local hospital and ward-based antimicrobial resistance data
Non-Severe Disease and Not High Risk of Resistance
Offer oral antibiotics. Choice of antibiotics:
- 1st line: co-amoxiclav TDS for 5 days
- 2nd line options:
- Doxycycline
- Cephalexin
- Co-trimoxazole (off-label)
- Levofloxacin (only if switching from IV levofloxacin)
The MHRA statement on fluoroquinolones (updated in Jan 2024) emphasises that fluoroquinolone antibiotics must only be prescribed when other commonly recommended antibiotics are inappropriate.
This restriction follows concerns over serious, disabling, long-lasting, and potentially irreversible side effects, including tendonitis, tendon rupture, muscle pain and weakness, joint pain, peripheral neuropathy, and psychiatric symptoms.
Severe Disease or High Risk of Resistance
Offer IV antibiotics. Choice of antibiotics:
- Tazocin (piperacillin with tazobactam) – usually 1st line in hospital guidelines (but not explicitly stated in NICE guideline)
- Various cephalosporins (ceftazidime / ceftriaxone / cefuroxime / ceftazidime with avibactam)
- Meropenem
- Levofloxacin
The MHRA statement on fluoroquinolones (updated in Jan 2024) emphasises that fluoroquinolone antibiotics must only be prescribed when other commonly recommended antibiotics are inappropriate.
This restriction follows concerns over serious, disabling, long-lasting, and potentially irreversible side effects, including tendonitis, tendon rupture, muscle pain and weakness, joint pain, peripheral neuropathy, and psychiatric symptoms.
Suspected or Confirmed MRSA
Offer IV dual antibiotic therapy; a 1st line antibiotic PLUS one of the following:
- Vancomycin
- Teicoplanin
- Linezolid (only if vancomycin cannot be used)
References
NICE guideline Pneumonia: diagnosis and management