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For further information, see CMDT Part 9-11: Pneumonia

Key Features

Essentials of Diagnosis

  • Hospital-acquired pneumonia (HAP) is diagnosed in patient with clinical features and imaging consistent with pneumonia, occurring > 48 hours after admission to the hospital, and excluding any infections present at the time of admission

  • Ventilator-associated pneumonia (VAP) requires clinical features concerning for new pneumonia with positive respiratory samples developing > 48 hours following endotracheal intubation and mechanical ventilation

General Considerations

  • Most common organisms in HAP

    • Staphylococcus aureus (both methicillin-sensitive S aureus and methicillin-resistant S aureus)

    • Pseudomonas aeruginosa

    • Gram-negative rods, including non–extended-spectrum β-lactamase (non-ESBL) producing and ESBL-producing (Enterobacter species, Klebsiella pneumoniae, and Escherichia coli)

  • Organisms seen in VAP

    • Acinetobacter species

    • Stenotrophomonas maltophilia

  • Anaerobic organisms may also cause pneumonia in the hospitalized patient

    • Bacteroides

    • Anaerobic streptococci

    • Fusobacterium

  • Uncommon causes of nosocomial pneumonias

    • Mycobacteria

    • Fungi

    • Chlamydiae

    • Viruses

    • Rickettsiae

    • Protozoal organisms

Clinical Findings

Symptoms and Signs

  • Nonspecific

  • However, two or more clinical findings (fever, leukocytosis, purulent sputum, worsening respiratory status) along with one or more new or progressive pulmonary opacities on chest imaging are characteristic features

  • See also Pneumonia, Community-Acquired

Differential Diagnosis

  • Heart failure

  • Atelectasis

  • Aspiration

  • Acute respiratory distress syndrome (ARDS)

  • Pulmonary thromboembolism

  • Pulmonary hemorrhage

  • Medication reactions


Laboratory Tests

  • Blood cultures identify the pathogen in up to 15–20% of cases

  • Complete blood count and chemistry tests

    • Not helpful in identifying the etiologic agent

    • However, can assist in determining illness severity and complications

  • Gram stains and other examinations of respiratory secretions and cultures of respiratory secretions are controversial but may be useful in guiding antibiotic therapy

  • Serum procalcitonin levels are not sufficiently sensitive to rule out HAP or VAP but may allow discontinuation of antibiotic therapy

Imaging Studies

  • Radiographic findings

    • Nonspecific

    • Range from patchy opacities to lobar consolidation to diffuse alveolar or interstitial opacities

Diagnostic Procedures

  • When HAP is suspected in a patient who subsequently requires mechanical ventilation, secretions may be obtained by

    • Spontaneous expectoration

    • Sputum induction

    • Nasotracheal suctioning

    • Endotracheal aspiration (qualitative or semiquantitative samples)

      • More likely to return nonpathogenic organisms

      • Thus, associated with higher antibiotic exposure (without improvement in mortality)

    • Bronchoscopic sampling of the lower airways secretions (quantitative samples): increases cost and patient risk

  • Invasive qualitative sampling is universally recommended when

    • The patient is not improving with initial therapy directed at the expected or isolated pathogens

    • An opportunistic pathogen is suspected in an immunocompromised person



  • See Tables 9–11 and 30–5

  • Treatment is usually empiric and should be started as soon as the diagnosis is suspected

  • No consensus regimens exist, but ...

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