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. The aim of this study was to catagorise patients with HAP according to these classifications and to determine the frequency of resistant pathogens and the most adequate antimicrobial regimens in each group. A total 124 patients with bacteriologically proven HAP were studied. The ATS classification categorised patients by increasing frequency of resistant pathogens from 0-30.3%. The ATS empirical antibiotic recommendations appeared valid but proposed combinations including vancomycin for 72.5% of patients. Trouillet's classification categorised patients into four groups with a frequency of resistant pathogens from 4.9-35.6%. Vancomycin was proposed for 48.5% of patients. The American Thoracic Society classification appears to be more specific than Trouillet's for predicting the absence of resistant causative pathogens in hospital-acquired pneumonia but could lead to a greater use of vancomycin. Stratification combining the two classifications is an interesting alternative.