Aspiration pneumonias: under-diagnosed and under-treated.

PURPOSE OF REVIEW: To examine recent advancements of the epidemiology, risk factors, bacteriology, diagnostic measures, and treatment for aspiration pneumonia.

RECENT FINDINGS: In a large prospective study, 10.3% of community-acquired pneumonia requiring hospitalization was associated with aspiration pneumonia, as opposed to 30% when patients were admitted from long-term facilities. A murine stroke model showed increased apoptosis of cell-mediated immune cells due to overactivation of the sympathetic nervous system. Subsequent nasal inoculum of low-dose Streptococcus pneumoniae caused severe pneumonia. Another murine study showed intratracheal administration of hydrochloric acid-primed lungs more susceptible to infection with Klebsiella pneumoniae. Tracheal pH monitoring demonstrated acidification of trachea in 28% of patients with acute stroke deemed to be safe for oral feeding. Various antimicrobial agents used to treat aspiration pneumonia have comparable success rates. However, clindamycin was the only agent that did not propagate emergence of methicillin-resistant Staphylococcus aureus.

SUMMARY: Aspiration pneumonia is prevalent in community-acquired pneumonia. Further studies are needed to elucidate the effects of sympathetic nervous system and aspiration pneumonitis as primers for lung infection. Predicting aspiration risk is difficult and newer diagnostic tools are necessary. Antimicrobials used in aspiration pneumonia have similar success rates although the development of resistant organisms must be monitored.