Hospital acquired pneumonia

Hospital-acquired pneumonia (often abbreviated as HAP) or nosocomial pneumonia is defined by the American Thoracic Society (ATS) guidelines as pneumonias that occur more than 48 hours after hospital administration but were not present at the time of admission.

It can be a common cause of pneumonia in patients admitted to intensive care units (ICU) and those on mechanical ventilation (ventilator-associated pneumonia). While all ages and both sexes can be affected, elderly patients are more prone.

Hospital acquired pneumonia is divided into:

  • early onset: within 4 days of admission
  • late onset: after day 5 of admission

Hospital acquired pneumonia commonly results from colonised upper respiratory tract infections being aspirated into the lower respiratory tract and ascending infection from the stomach (i.e. ingested oropharyngeal secretions).

Common organisms for early onset type are Streptococcus pneumoniae and Haemophilus influenzae.

For late onset type, Staphylococcus aureus, Pseudomonas aeruginosaKlebsiella species and Acinetobacter are common.

Intubation and ventilatory support bypass normal defence mechanism predisposing patients to infection.

It is essentially a clinical diagnosis with no specific features.

Areas of consolidation in unilateral or bilateral lung fields may be seen depending on severity. 

The early onset type has a better prognosis. High morbidity and mortality are seen patients with Hospital acquired pneumonia as they are already hospitalised for another condition. 

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Article information

rID: 26829
System: Chest
Synonyms or Alternate Spellings:
  • Health-care associated pneumonia
  • Hospital acquired pneumonias
  • Nosocominal pneumonia
  • Nosocominal pneumonias
  • Health-care associated pneumonias
  • Health-care associated pneumonia (HCAP)
  • Hospital acquired pneumonia (HAP)

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