Pneumonia Overview

Pneumonia Overview

• Inflammation of lung parenchyma caused by infectious agents.
• Leading infectious cause of death globally in children under 5 years.
• Over 99% of pneumonia-related deaths occur in low- and middle-income countries.
• Significant 97% decline in mortality in developed countries (e.g., USA) from 1939 to 1996 due to vaccines and antibiotics.

Etiology of Pneumonia

• Microorganisms are primary causes; however, noninfectious factors can also contribute.
• Noninfectious causes include:
  • Aspiration of food, gastric acid, foreign bodies, hydrocarbons, and lipoid substances (common in practice).
  • Hypersensitivity reactions.
  • Drug- or radiation-induced pneumonitis (e.g., Bleomycin).
• Determining the specific cause in patients can be challenging without invasive procedures.
• Bacterial cultures of sputum or upper respiratory samples often do not accurately diagnose lower respiratory infections.

Common Etiologic Agents

• Streptococcus pneumoniae (pneumococcus): Most common bacterial pathogen in children aged 3 weeks to 4 years.
• Mycoplasma pneumoniae: Frequent pathogen in older children.
• Chlamydophila pneumoniae: Notable in children aged 5 and older.
• Staphylococcus aureus: Often complicates pneumonia linked to influenza.

Pediatric Considerations

• Major bacterial pathogens for hospitalization and pneumonia deaths in developing countries: S. pneumoniae, H. influenzae, S. aureus.
• In HIV-infected children, consider M. tuberculosis, non-TB mycobacteria, Salmonella, E. coli, P. jiroveci, and CMV.
• Viral pathogens are prevalent in infants and children aged 1 month to 5 years.
• Common viral pathogens: Respiratory syncytial virus and rhinoviruses, especially in children under 2 years.

Pathogenesis

• Lower respiratory tract defenses include:
  • Mucociliary clearance.
  • Macrophages and secretory immunoglobulin A.
  • Coughing to clear airways.
• The lower respiratory tract may contain diverse microbial communities, contradicting previous beliefs of sterility.
• Pneumonia may stem from disruptions in a complex ecosystem involving:
  • Potential pneumonia pathogens.
  • Resident microbial communities.
  • Host immune defenses.
• Inhalation of contaminated air or droplets containing pathogens leads to infection and inflammatory response.

This quiz covers essential information about pneumonia, including its definition, causes, and impact on global health, especially among children. It highlights the disparities in pneumonia mortality rates between low- and middle-income countries and developed nations. Test your knowledge on this critical health issue.