Aspiration pneumonia
Aspiration pneumonia is bronchopneumonia
Bronchopneumonia or bronchial pneumonia or "Bronchogenic pneumonia" is the acute inflammation of the walls of the bronchioles...

 that develops due to the entrance of foreign materials into the bronchial tree, usually oral or gastric contents (including food, saliva, or nasal secretions). Depending on the acidity of the aspirate, a chemical pneumonitis can develop, and bacterial pathogens (particularly anaerobic bacteria) may add to the inflammation.


Aspiration pneumonia is often caused by an incompetent swallowing
Swallowing, known scientifically as deglutition, is the process in the human or animal body that makes something pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. If this fails and the object goes through the trachea, then choking or pulmonary aspiration...

 mechanism, such as occurs in some forms of neurological disease including disease like MS, Multiple sclerosis (a common cause being strokes) or while a person is intoxicated
Alcohol intoxication is a physiological state that occurs when a person has a high level of ethanol in his or her blood....

. An iatrogenic cause is during general anaesthesia
General anaesthesia
General anaesthesia is a state of unconsciousness and loss of protective reflexes resulting from the administration of one or more general anaesthetic agents...

 for an operation
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...

 and patients are therefore instructed to be nil per os
Nil per os
Nil per os is a medical instruction meaning to withhold oral food and fluids from a patient for various reasons. It is a Latin phrase which translates as "nothing through the mouth". In the United Kingdom it is translated as nil by mouth .Typical reasons for NPO instructions are the prevention...

 (NPO) (aka Nothing By Mouth) for at least four hours before surgery.

Whether aspiration pneumonia represents a true bacterial infection or a chemical inflammatory process remains the subject of significant controversy. Both causes may present with similar symptoms.

Implicated bacteria

When bacteria are implicated, they are usually of the anaerobic oral flora:
  • Bacteroides
    Bacteroides is a genus of Gram-negative, bacillus bacteria. Bacteroides species are non-endospore-forming, anaerobes, and may be either motile or non-motile, depending on the species. The DNA base composition is 40-48% GC. Unusual in bacterial organisms, Bacteroides membranes contain sphingolipids...

  • Prevotella
    Prevotella is a genus of bacteria.Bacteroides melaninogenicus has recently been reclassified and split into Prevotella melaninogenica and Prevotella intermedia....

  • Fusobacterium
    Fusobacterium is a genus of filamentous, anaerobic, Gram-negative bacteria, similar to Bacteroides.Fusobacterium contribute to several human diseases, including periodontal diseases, Lemierre's syndrome, and topical skin ulcers...

  • Peptostreptococcus
    Peptostreptococcus is a genus of anaerobic, Gram-positive, non-spore forming bacteria. The cells are small, spherical, and can occur in short chains, in pairs or individually. Peptostreptococcus are slow-growing bacteria with increasing resistance to antimicrobial drugs.The most frequently...

They may also be admixed with aerobic bacteria:
  • Streptococcus pneumoniae
    Streptococcus pneumoniae
    Streptococcus pneumoniae, or pneumococcus, is Gram-positive, alpha-hemolytic, aerotolerant anaerobic member of the genus Streptococcus. A significant human pathogenic bacterium, S...

  • Staphylococcus aureus
    Staphylococcus aureus
    Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...

  • Haemophilus influenzae
    Haemophilus influenzae
    Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...

  • Pseudomonas aeruginosa
    Pseudomonas aeruginosa
    Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...


The location is often gravity dependent, and depends on the patient position. Generally the right middle and lower lung lobes are the most common sites of infiltrate formation due to the larger caliber and more vertical orientation of the right mainstem bronchus. Patients who aspirate while standing can have bilateral lower lung lobe infiltrates. The right upper lobe is a common area of consolidation in alcoholics who aspirate in the prone position.


Aspiration pneumonia is typically diagnosed by a combination of clinical circumstances (debilitated or neurologically impaired patient), radiologic findings (right lower lobe pneumonia) and microbiologic cultures. Some cases of aspiration pneumonia are caused by aspiration of food particles or other particulate substances like pill fragments; these can be diagnosed by pathologists on lung biopsy specimens .

See also

  • Dysphagia
    Dysphagia is the medical term for the symptom of difficulty in swallowing. Although classified under "symptoms and signs" in ICD-10, the term is sometimes used as a condition in its own right. Sufferers are sometimes unaware of their dysphagia....

  • Meconium aspiration syndrome
    Meconium aspiration syndrome
    Meconium aspiration syndrome is a medical condition affecting newborn infants. It occurs when meconium is present in their lungs during or before delivery...

  • Nosocomial pneumonia
  • Superior mesenteric artery syndrome
    Superior mesenteric artery syndrome
    Superior mesenteric artery syndrome is a very rare, life-threatening gastro-vascular disorder characterized by a compression of the third portion of the duodenum by the abdominal aorta and the overlying superior mesenteric artery...

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