Unlike viral and/or bacterial pneumonia, aspiration pneumonia is a lung infection that starts with the inhalation/aspiration of oropharyngeal, gastric contents or foreign particles into the lower airway passages. The taking-in of the foreign particles may occur via the mouth, when partially digested contents of the stomach, tiny food particles from the mouth, mouth secretions dribble into the lower air ducts.
Once they reach the lungs, an infection slowly develops at the place where the foreign particles have lodged themselves.
Aspiration pneumonia is also known as anaerobic pneumonia or necrotizing pneumonia or chemical pneumonia. As per an article entitled Aspiration Pneumotitis and Aspiration Pneumonia by Paul E. Marik M.B, B.Ch in a publication by Stanford University Libraries (Source: N Engl J Med, Vol. 344, No. 9 • March 1, 2001. URL: http://scalpel.stanford.edu/articles/aspiration--NEJM.pdf), “Indeed, Haemophilus influenzae, Staphylococcus aureus and Streptococcus pneumoniae colonize the nasopharynx or oropharynx before they are aspirated and cause community- acquired pneumonia. The term “aspiration pneumonia,” however, refers specifically to the development of a radiographically evident infiltrate in patients who are at increased risk for oropharyngeal aspiration.”
Other pathogens are also equally culpable in causing aspiration pneumonia. They are Strptococcus milleri, oral anaerobes, non-oral anaerobes like fusobacterium, peptostreptococcus, enterobaccteria like E Coli and pseudomonas aeruginosa etc.
Symptoms of Aspiration Pneumonia are fairly similar to those of Pneumotitis or Acquired-Pneumonia such as those of high fever, tachycardia (a state of rapid heart rate), altered mental state, tachypnea (a state of rapid shallow breathing), railing, hypoxemia (condition of reduced oxygen level in the blood that results in bluish discoloration of the skin), pleural friction rub and in severe cases septic shock and hipoxia (pathological condition where the body tissues are deprived of adequate oxygen) etc.