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

Key Features

Essentials of Diagnosis

  • Hospital-acquired pneumonia (HAP) occurs more than 48 hours after admission to the hospital or other health care facility and excludes any infection present at the time of admission

  • Ventilator-associated pneumonia (VAP) develops more than 48 hours following endotracheal intubation and mechanical ventilation

  • At least two of the following are present

    • Fever

    • Leukocytosis

    • Purulent sputum

  • New or progressive parenchymal opacities on chest radiograph

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 extended spectrum beta-lactamase (ESBL)- producing and non–ESBL-producing organisms (eg, 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) in the setting of a new or progressive pulmonary opacity on chest radiograph were approximately 70% sensitive and 75% specific for the diagnosis of VAP in one study

  • Colonization of the pharynx and possibly the stomach with bacteria is the most important step in the pathogenesis of nosocomial pneumonia

  • See also Pneumonia, Community-Acquired

Differential Diagnosis

  • Heart failure

  • Atelectasis

  • Aspiration

  • Acute respiratory distress syndrome (ARDS)

  • Pulmonary thromboembolism

  • Pulmonary hemorrhage

  • Drug reactions


Laboratory Tests

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

  • Arterial blood gases help define illness severity and the need for assisted ventilation

  • 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

Imaging Studies

  • Radiographic findings

    • Nonspecific

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

Diagnostic Procedures

  • With suspected HAP, secretions obtained by spontaneous expectoration, sputum induction, nasotracheal suctioning and endotracheal aspiration in a patient who subsequently requires mechanical ventilation should be cultured

  • For patients with suspected VAP, endotracheal aspiration using a sterile suction catheter with semi-quantitative cultures of lower respiratory tract secretions is the recommended method of evaluation



  • 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 guidelines separate patients by disease severity

  • Duration ...

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