Etiology

• Gram-positive and gram-negative aerobic bacteria predominate in community-acquired infections (e.g., S. pneumonia, S. aureus, H. influenza, Enterobacteriaceae).

• Gram-negative bacilli predominate in hospital-acquired infections (e.g., P. aeruginosa, Klebsiella spp.).

• Mixed infections with anaerobic organisms may occur (e.g., Fusobacterium, Peptostreptococcus, Bacteroides).

(predispose individuals to reduced epiglottic gag reflex and dysphagia)

• Altered consciousness: alcohol, sedation, general anesthesia, stroke

• Apoplexy and neurodegenerative conditions

• Gastroesophageal reflux disease, esophageal motility disorders

• Congenital defects (e.g., tracheoesophageal fistula)

• Use of a nasogastric feeding tube