Nosocomial pneumonia: pathogenesis, diagnosis, current therapy and prophylactic approach

Pneumonia is the second most common hospital-acquired infection, occurring more frequently in mechanically-ventilated patients, and is the leading cause of death from nosocomial infections. Pathogenesis is linked with oropharyngeal flora aspiration when colonized with Gram-negative organisms either directly from the environment or retrogradely from the stomach whenever the pH is > 4. The main pathogens implicated are Enterobacteriaceae and Pseudomonas aeruginosa. Routine sputum cultures are unreliable because of contamination with oropharyngeal flora; however, a bronchoscopic protected specimen brush and bronchoalveolar lavage techniques may overcome this problem. A combination of broad-spectrum antibiotics and monotherapy with newer antimicrobial agents appear to be equally effective in treatment of nosocomial infections. The efficacy of prophylaxis after selective gut decontamination in intensive care unit patients, however, has not yet been established.