Pneumonia

• Pneumonia is an infection of the lung tissue, causing inflammation in the alveolar space
• Pneumonia can be seen as a consolidation on a chest x-ray
• Acute bronchitis refers to infection and inflammation in the bronchi and bronchioles
• Both pneumonia and acute bronchitis are classed as lower respiratory tract infections
• Upper respiratory tract infections (e.g., a common cold) are usually viral
• As a general rule, the lower down the respiratory tract, the higher the probability of bacterial infection, as opposed to viral
• Classification of pneumonia


  • Community-acquired pneumonia (CAP)
  • Hospital-acquired pneumonia (HAP)
  • Ventilator-acquired pneumonia (VAP)
  • Aspiration pneumonia
• Aspiration pneumonia is when the infection develops due to the aspiration of food or fluids, usually in patients with impaired swallowing (e.g., following a stroke or advanced dementia)
• Aspiration pneumonia is associated with anaerobic bacteria
• Presenting symptoms of pneumonia

  1. Cough

  2. Sputum production

  3. Shortness of breath

  4. Fever

  5. Feeling generally unwell

  6. Haemoptysis (coughing up blood)

  7. Pleuritic chest pain (sharp chest pain, worse on inspiration)

  8. Delirium (acute confusion)
• Characteristic chest signs of pneumonia

  1. Bronchial breath sounds (harsh inspiratory and expiratory breath sounds) due to consolidation around the airways

  2. Focal coarse crackles caused by air passing through sputum in the airways

  3. Dullness to percussion due to lung tissue filled with sputum or collapsed
• There may be a derangement in basic observations indicating sepsis secondary to pneumonia
• Focal coarse crackles


  Caused by air passing through sputum in the airways
• Dullness to percussion


  Due to lung tissue filled with sputum or collapsed
• Derangements indicating sepsis secondary to pneumonia

  • Tachypnoea (raised respiratory rate)
  • Tachycardia (raised heart rate)
  • Hypoxia (low oxygen)
  • Hypotension (shock)
  • Fever
  • Confusion
• The NICE guidelines on pneumonia recommend using the CRB-65 scoring system out of hospital and CURB-65 in hospital
• CRB-65 scoring system


  1. C – Confusion (new disorientation in person, place or time)

  2. U – Urea > 7 mmol/L

  3. R – Respiratory rate ≥ 30

  4. B – Blood pressure < 90 systolic or ≤ 60 diastolic

  5. 65 – Age ≥ 65
• The CURB-65 score predicts mortality. NICE state 0/1 is low risk (under 3%), 2 is intermediate risk (3-15%), and 3-5 is high risk (above 15%)
• Score 0/1 in CURB-65

  Consider treatment at home
• Score ≥ 2 in CURB-65


  Consider hospital admission
• Score ≥ 3 in CURB-65


  Consider intensive care
• Top causes of typical bacterial pneumonia

  • Streptococcus pneumoniae (most common)
  • Haemophilus influenzae
• Other causes of bacterial pneumonia

  • Moraxella catarrhalis in immunocompromised patients or those with chronic pulmonary disease
  • Pseudomonas aeruginosa in patients with cystic fibrosis or bronchiectasis
  • Staphylococcus aureus in patients with cystic fibrosis
  • Methicillin-resistant Staphylococcus aureus (MRSA) in hospital-acquired infections
• Atypical pneumonia is caused by organisms that cannot be cultured in the normal way or detected using a gram stain. Treatment includes macrolides, fluoroquinolones, and tetracyclines
• Legionella pneumophila (Legionnaires’ disease) is typically caused by inhaling infected water from infected water systems, such as air conditioning units. It can cause a syndrome of inappropriate ADH (SIADH), resulting in hyponatraemia (low sodium)
• Mycoplasma pneumoniae causes milder pneumonia and a rash called erythema multiforme, characterised by varying-sized “target lesions” formed by pink rings with pale centres. It can cause neurological symptoms in young patients
• Chlamydophila pneumoniae causes mild to moderate chronic pneumonia and wheezing in school-age children. Be cautious, as this presentation is common without chlamydophila pneumoniae infection
• Coxiella burnetii, or Q fever, is linked to exposure to the bodily fluids of animals. The typical exam patient is a farmer with a flu-like illness
• Chlamydia psittaci is typically contracted from contact with infected birds. The typical exam patient is a parrot owner
• Pneumocystis jirovecii pneumonia (PCP), a fungal pneumonia, occurs in immunocompromised patients. Patients with poorly controlled HIV and a low CD4 count are particularly at risk. It usually presents subtly with dry cough, shortness of breath on exertion, and night sweats. Co-trimoxazole treats PCP
• Patients at risk of PCP

  • Immunocompromised patients
  • Patients with poorly controlled HIV and a low CD4 count
• PCP treatment


  • Co-trimoxazole (trimethoprim/sulfamethoxazole) treats PCP (brand name Septrin)
• Prophylactic treatment for PCP

  • Patients with a low CD4 count are prescribed prophylactic co-trimoxazole to protect against PCP
• The COVID-19 virus (SARS-CoV-2) can cause pneumonia
• Anosmia (loss of smell) is a clue to the diagnosis of COVID-19
• Patients with COVID-19 may not feel particularly short of breath despite having low oxygen saturations (“silent hypoxia”)
• Vaccination has dramatically reduced the number of severe COVID-19 infections
• Treatment for COVID-19 pneumonia

  Respiratory support (e.g., oxygen), dexamethasone, and monoclonal antibodies
• Investigations for pneumonia in the community

  • Patients with CRB 0 or 1 pneumonia do not necessarily need investigations
  • A point-of-care test for the CRP level can be used in primary care to help guide diagnosis and the use of antibiotics
• Investigations for pneumonia in hospitalised patients

  • Chest x-ray
  • Full blood count (raised white cell count)
  • Renal profile (urea level for the CURB-65 score and acute kidney injury)
  • C-reactive protein (raised in inflammation and infection)
  • Sputum cultures
  • Blood cultures
  • Pneumococcal and Legionella urinary antigen tests