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For further information, see CMDT Part 9-11: Pneumonia
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Essentials of Diagnosis
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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
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General Considerations
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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
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
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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
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Differential Diagnosis
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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
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Diagnostic Procedures
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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
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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 ...