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Source: Blackford MG, Glover ML, Reed MD. Lower Respiratory Tract Infections. In: DiPiro, JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic Approach. 8th ed. Accessed July 12, 2012.

  • Lung inflammation caused by bacterial or viral infection

  • Majority of cases in otherwise healthy adults caused byS. pneumoniae (pneumococcus)
  • Aypical pathogens include:
    • M. pneumoniae
    • Legionella
    • C. pneumoniae
  • Staphylococcus aureus and Gram-negative rods causative agents in elderly nursing home patients and in association with alcoholism and other debilitating conditions.

  • Microorganisms gain access to lower respiratory tract by 3 routes:
    • Inhaled as aerosolized particles
    • Via bloodstream from extrapulmonary site of infection
    • Aspiration of oropharyngeal contents
  • Viral lung infections suppress bacterial clearing activity of lung by impairing alveolar macrophage function and mucociliary clearance, setting stage for secondary bacterial pneumonia.

  • Most common infectious cause of death in United States.
  • Occurs in persons of all ages, although clinical manifestations most severe in very young, elderly, and chronically ill.

  • Polyvalent polysaccharide vaccines available for S. pneumoniae and H. influenzae.
  • Influenza vaccine
    • To prevent primary influenza pneumonia and secondary bacterial pneumonia
      • Annual administration to those ≥65 years, residents of long-term care facilities, or underlying cardiopulmonary disease

  • Age ≥65 years
  • Underlying cardiopulmonary disease

  • Clinical appearance similar regardless of etiology

Signs and Symptoms

  • Abrupt onset of:
    • Fever
    • Chills
    • Dyspnea
    • Productive cough
  • Rust-colored sputum or hemoptysis
  • Pleuritic chest pain
  • Tachypnea
  • Tachycardia
  • Dullness to percussion
  • Increased tactile fremitus, whispered pectoriloquy, and egophony
  • Chest wall retractions and grunting respirations
  • Diminished breath sounds
  • Inspiratory crackles during lung expansion

Means of Confirmation and Diagnosis

  • Chest radiograph
  • Sputum examination and culture
    • Gram stain

Laboratory Tests

  • Sputum Gram stain and culture
  • Complete blood count (CBC)
    • Leukocytosis with predominance of polymorphonuclear cells
  • Arterial blood gas
    • Low oxygen saturation


  • Chest radiograph: dense lobar or segmental infiltrate

Diagnostic Procedures

  • Sputum induction and bronchoscopy for patients who cannot provide expectorated samples

Differential Diagnosis

  • Eradicate offending organism.
  • Achieve complete clinical cure.
  • Minimize associated morbidity (e.g., renal, pulmonary, or hepatic dysfunction)

  • Evaluate adequacy of respiratory function.
  • Determine signs of systemic illness, specifically dehydration, or sepsis with resulting circulatory collapse.

  • Oxygen
  • Mechanical ventilation
  • Fluid resuscitation
  • Nutritional support
  • Fever control
  • Chest physiotherapy with postural drainage if secretions retained

  • Administer bronchodilators (albuterol) if bronchospasm present.
  • Antibiotics
    • Antibiotic concentrations in respiratory secretions in excess of pathogen minimum inhibitory concentration (MIC) are necessary.
    • Initial empiric treatment with broad-spectrum antibiotic(s)
    • Narrow therapy based on culture results
    • Adult recommendations in Table 1
    • Pediatric recommendations in Table 2
    • Doses to treat pneumonia in Table 3

Table 1. Evidence-Based Empiric Antimicrobial Therapy for Pneumonia in Adultsa

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