Aspiration Pneumonia

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June 6, 2018 by dailybolusoflr

By: Michael Trisler, PharmD, MPH

Aspiration Pneumonia


An aspiration event is defined as the inhalation of oropharyngeal or gastric contents into the larynx and lower respiratory tract. Aspiration pneumonitis occurs in the first 4 hours following aspiration of gastric contents. However, most aspiration events do not develop into bacterial pneumonia. If it does, aspiration pneumonia generally occurs 48 hours after the aspiration event. Risk factors are PPIs, bowel obstruction, enteral feeds, poor dentition, gingival disease, loss of consciousness (e.g. overdose, seizure), older age, and esophageal motility disorder.


The results of studies evaluating the microbiology of aspiration pneumonia has changed significantly over the last 40 years. Original studies conducted in the 1970s reported isolating anaerobes in greater than 90% of cases. Whereas, studies in the last 10 years generally reported isolating anaerobes in less than 1/3 of patients.


  • Antibiotics are not indicated for most acute aspiration events involving gastric contents despite radiographic findings suggesting aspiration pneumonitis.
    • Consider antibiotics if the patient is hemodynamically unstable and may have another source of infection or if symptoms last >48 hours
  • Targeted anaerobic coverage is not routinely recommended for aspiration pneumonia
    • The most common oral anaerobes isolated are peptostreptococcus spp., which is covered by Penicillin G, amoxicillin, and parenteral cephalosporins
    • The most common abdominal anaerobes are Bacteroides spp., which may not be covered by many antibiotics commonly used for CAP/HAP. However, no significant difference exists in cure rates of necrotizing infections or lung abscesses treated with antibiotic regimens that contained and did not contain anaerobic coverage.
  • Treat as community-acquired pneumonia (CAP), without atypical coverage, if the aspiration event leading to pneumonia occurred in the community or within 72 hours of hospital admission
  • Treat as hospital-acquired pneumonia (HAP) if the aspiration event leading to pneumonia occurred > 72 hours after hospital admission or if the patient has severe illness (e.g. ICU admission)


  1. Marik PE. Aspiration pneumonitis and aspiration pneumonia. N Engl J Med. 2001;344(9):665-71.
  2. Dibardino DM, Wunderink RG. Aspiration pneumonia: a review of modern trends. J Crit Care. 2015;30(1):40-8.

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