Hospital-acquired pneumonia: microbiological data and potential adequacy of antimicrobial regimens.

Adequate antimicrobial therapy is a main approach employed to decrease the mortality associated with hospital-acquired pneumonia (HAP). All methods that optimise empirical treatment without increasing antibiotic selective pressure are relevant. Categorisation of patients according to HAP time of onset, severity and risk factors (American Thoracic Society (ATS) classification) or duration of mechanical ventilation and prior antibiotics (Trouillet's classification) are two such methods.