Nosocomial bacterial pneumonias.

Pneumonia is the third most common nosocomial infection and the most difficult to prevent. Fifteen percent of all deaths occurring in hospitals are caused by nosocomial pneumonias. Nosocomial pneumonias prolong hospital stays over 4 days, resulting in at least $3,000 to $5,000 in extra charges per infection. Most cases of nosocomial pneumonias are caused by bacteria, especially gram-negative bacilli. The majority of nosocomial pneumonias appear to result from aspiration of bacteria that have colonized the oropharynx. Additional risk factors include colonization of the oropharynx with gram-negative bacilli, thoracic and upper abdominal surgery, continuous mechanical ventilation, extremes of age, and severity of underlying diseases. Prevention revolves around an effective infection control program, preventing colonization and aspiration, and improving host defense mechanisms. Further research is needed to clarify the role of topical antibiotics and to develop strategies to alter host defenses to prevent or eliminate colonization of gram-negative bacilli.