Respiratory

Question 1

What organisms commonly cause community acquired pneumonia? How do atypical pneumonia differ from classical bacterial pneumonia? What are the potential consequences of pneumonia?

Answer 1

1. Organisms causing CAP
   - Bacterial typical: Staph aureus, strep pneumoniae, haemophilus influenzae, Klebsiella, pseudomonas, moraxella catarrhalis
   - Bacterial atypical: Mycoplasma, chlamydia, legionella
   - Viral: Influenza A+B, RSV, adenovirus
2. Atypical pneumonias compared to typical pneumonia
   A. Clinical features
   - More non-specific symptoms: Fever, myalgia, headache, cough may or may not be present, moderate amount of sputum
   B. Blood findings
   - Moderate elevation of WCC
   C. Chest findings
   - No confluent consolidation
   - No alveolar infiltrates
   - Patchy inflammatory changes in alveolar septa and pulmonary interstitium
   D. Mortality
   - Lower mortality than typical pneumonia
3. Potential consequences of pneumonia
   - Resolution of infection
   - Abscess formation
   - Emphysema
   - Pleural effusion
   - Bacterial dissemination -> sepsis, endocarditis, pericarditis, meningitis

Question 2

What factors predispose patients to the development of acute bacterial pneumonia? How is legionella pneumonia contracted? How is legionella pneumonia diagnosed?

Answer 2

1. Risk factors for pneumonia
   - Extremes of age: Elderly, young children
   - Presence of chronic disease: Emphysema, COPD, heart failure, diabetes
   - Immunocompromised states: Malignancy, HIV, asplenia, chemotherapy
2. Legionella
   - Spread through aquatic environment
   - Inhalation of aerolised droplets
   - Aspiration of contaminated drinking water
3. Legionella diagnosed via
   - Urinary antigens
   - Sputum culture

Question 3

Describe the pathogenesis of aspiration pneumonia. How is community acquired pneumonia different to aspiration pneumonia?

Answer 3

1. Aspiration pneumonia
   - Aspiration of gastric contents into lungs
   - Usually seen in debilitated patients
   - Risk factors are low GCS, profuse vomiting, impaired gag/cough reflex, impaired swallowing
   - Can be caused by chemicals or bacteria
   - Usually > 1 organism involved, aerobes and anaerobes
   - Causes pneumonitis
   - Complications are necrotizing infections, abscess formation
   - Higher mortality
2. Community acquired pneumonia compared to aspiration pneumonia
   - Infection of lungs caused by pathogens found in the community
   - Risk factors: Extremes of age, underlying chronic disease, immunocompromised
   - Bacterial causes: Strep pneumoniae, staph aureus, haemophilus
   - Viral causes: Influenzae A + B, RSV
   - Confluent consolidation
   - Complications are empyema, abscess formation, bacterial dissemination
   - Lower mortality rate compared to aspiration pneumonia

Question 4

What is atypical pneumonia? What organisms are usually involved? Describe the clinical features

Answer 4

1. Atypical pneumonia is interstitial pneumonitis with lack of exudate
   - Patchy inflammation in alveolar septa and pulmonary interstitium
   - No consolidation
2. Organisms involved
   - Bacterial: Mycoplasma, Chlamydia, Legionella
   - Viral: Influenza A + B, RSV
3. Clinical features are more non-specific
   - Fever
   - Myalgias
   - Headache
   - Cough may or may not be present
   - Moderate amount of sputum