Both early-onset and late-onset ventilator-associated pneumonia are caused mainly by potentially multiresistant bacteria

Objective: To compare the causative pathogens of early-onset and late-onset ventilator-associated pneumonia (VAP) diagnosed by bronchoalveolar lavage quantitative cultures. Most previous reports have been based on endotracheal aspirate cultures and gave uncertain findings. Design: Prospective evaluation of consecutive patients with clinical suspicion for VAP. Setting: Multidisciplinary intensive care unit of a university hospital. Patients and participants: During a 3-year period 473 patients with clinical suspicion of VAP entered the study. Diagnosis of VAP was confirmed by cultures of bronchoalveolar lavage (>10(4) cfu/ml) specimens in 408 patients. Interventions: Protected bronchoalveolar lavage samples were taken. Initial antibiotic therapy was modified upon bronchoalveolar lavage culture results. Measurements and results: Among 408 patients 191 had early-onset (<7 days mechanical ventilation) and 217 late-onset (>= 7 days) VAP. Potentially multiresistant bacteria, mainly Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA), were the most commonly isolated pathogens in both types of VAP. No difference was noted in the contribution of potentially multiresistant pathogens (79% vs. 85%), P. aeruginosa (42% vs. 47%), or MRSA (33% vs. 30%) between early-onset and late-onset VAP. Initial antibiotic therapy was modified in 58% of early-onset VAP episodes and in 36% of late-onset VAP episodes. No difference in mortality was found between the two types of VAP. Conclusions: Both early-onset and late-onset VAP were mainly caused by potentially multiresistant bacteria, most commonly P. aeruginosa and MRSA. Antimicrobial agents against these pathogens should be prescribed empirically, at least in our institution.