Lecture Notes on Pneumonia

Introduction

• Discussion on pneumonia covering:
  • Pathophysiology
  • Classification by microbes, acquisition, and location
  • Features and complications
  • Diagnostics
  • Treatment

Pathophysiology of Pneumonia

• Pneumonia: infection and inflammation of lung tissue caused by pathogens (bacterial, viral, fungal).
• Most common cause: bacterial pneumonia.

Mechanisms of Development

1. Aspiration:

   • Oropharyngeal secretion aspirated into airway (oral and gastric secretions).
   • Common in patients with compromised gag or cough reflexes (e.g., due to CNS diseases or depressants).
   • Key pathogens: Klebsiella, anaerobes, Staphylococcus aureus.

2. Inhalation of Pathogens:

   • Close contact scenarios increase exposure (e.g., crowded settings).
   • Key pathogens: Mycoplasma, Chlamydia, Influenza, Legionella (from contaminated water sources).

3. Impaired Mucociliary Clearance:

   • Conditions like cystic fibrosis, bronchiectasis, COPD lead to ineffective clearance of mucus and pathogens.
   • Key pathogens: Haemophilus influenza, Moraxella catarrhalis, Pseudomonas aeruginosa.

4. Hematogenous Spread:

   • Pathogens entering the lung from the bloodstream, particularly in IV drug users (e.g., Staphylococcus aureus).

5. Immune Response:

   • Immunocompromised patients (e.g., HIV, diabetes) have a decreased ability to clear infections.
   • Key pathogens: Pseudomonas, Legionella, PJP (Pneumocystis jirovecii).

Classification of Pneumonia

Acquisition Types

1. Community-Acquired Pneumonia (CAP)

   • Infection acquired outside of a healthcare setting.
   • Common pathogen: Streptococcus pneumoniae.

2. Hospital-Acquired Pneumonia (HAP)

   • Infection occurring 48 hours or more after hospital admission.
   • Common pathogens: MRSA, Pseudomonas.

Radiographic Types

• Lobar Pneumonia: Occupies one lobe (often Streptococcus pneumoniae).
• Bronchopneumonia: Patchy involvement (common in HAP and involves multiple pathogens).
• Interstitial Pneumonia: Involves interstitial spaces (commonly atypical pathogens like Mycoplasma).

Clinical Features and Complications

• Common symptoms: cough, fever, dyspnea, chest pain, productive cough with purulent sputum.
• Complications:
  • Pleuritic chest pain, pleural effusion, empyema, lung abscess, acute respiratory distress syndrome (ARDS), sepsis.

Diagnostics

• Laboratory tests: CBC, BMP, blood cultures, urinary antigens (Streptococcus pneumoniae, Legionella).
• Imaging: Chest X-ray (initial), CT scan for inconclusive cases or immunocompromised patients.

Treatment

Community-Acquired Pneumonia (CAP)

• Outpatient: Macrolides (e.g., azithromycin) or doxycycline.
• Inpatient, non-ICU: Respiratory fluoroquinolone or beta-lactam with macrolide.
• ICU: Macrolide or fluoroquinolone plus beta-lactam (Ceftriaxone).

Hospital-Acquired Pneumonia (HAP)

• Initial treatment: Vancomycin (for MRSA) and Piperacillin-tazobactam (for Pseudomonas).

Special Considerations for PJP

• Treat with Bactrim (Trimethoprim-sulfamethoxazole).

Prevention

• Vaccination: PCV13 for children and PPSV23 for adults 65+ or at-risk individuals.

Case Study Summary

• 72-year-old male with multiple comorbidities presenting symptoms supporting pneumonia.
• Curb-65 score assessment for hospitalization and treatment based on severity of pneumonia.