characteristics of etiologic agents of pneumonia

Etiology

• Streptococcus pneumonia
  • sudden onset of rigors, fever, pleuritic chest pain
  • cough productive of rusty sputum
  • evidence of consolidation on exam
  • Gram stain: lancet-shaped diplococci
  • chest X-ray: lobar process
  • 25-50% of community-acquired pneumonia
• Haemophilus influenzae
  • increased frequency in:
    • alcoholics
    • patients with COPD
  • Gram stain: gram-negative coccobacilli
  • chest X-ray: frequently associated pleural effusion (generally sterile)
  • 4-15% of community-acquired pneumonia
• Mycoplasma pneumonia 'Atypical pneumonia'
  • mostly in children & young adults
  • insidious onset of fever, malaise, headache, non-productive cough
  • bullous myringitis
  • Gram stain: WBC's but no organisms
  • usually bronchopneumonia
• Legionella pneumophila 'Legionnaire's disease'
  • non-bloody diarrhea
  • nausea/vomiting
  • fever
  • bradycardia
  • hyponatremia (more frequently than other pneumonias)
  • obtain fluorescent antibody studies on sputum
  • Gram stain: WBC's but no organisms
• Influenzae
  • seasonal (winter months)
  • fever, chills, myalgias, malaise, anorexia 'flu symptoms'
  • non productive cough
  • dyspnea
  • hypoxia
  • complications:
    • ARDS
    • secondary bacterial pneumonia
• aspiration pneumonia
  • history is critical: look for risk factors
  • may be in any lobe or in multiple lobes
    • recumbent patients tend to aspirate into the posterior segments of the upper lobes or superior segments of the lower lobes
  • community-acquired: oral-pharyngeal flora (anaerobes)
  • hospital-acquired
    • gram-negative bacilli (including Pseudomonas)
    • Staphylococcus
  • complications
    • lung abscess

Additional terms

• pneumonia (PNA)