Background: Clinical resolution of ventilator-associated pneumonia (VAP) determines the duration of treatment and mechanical ventilation. The aim of this study was to evaluate the influence of organisms and their susceptibility to treatment on outcomes.
Methods: Prospective observational study in three teaching ICUs. Sixty episodes of VAP with appropriate therapy (Haemophilus influenzae, 15 episodes; methicillin-sensitive Staphylococcus aureus [MSSA], 15 episodes; Pseudomonas aeruginosa, 15 episodes; and methicillin-resistant S aureus [MRSA], 15 episodes), and 30 episodes with initial inappropriate therapy, all due to P aeruginosa, were compared. The main outcome measures were clinical resolution variables and, in survivors, length of mechanical ventilation after VAP onset.
Results: A significant delay in the resolution of hypoxemia was observed in VAP episodes due to MRSA and P aeruginosa with inappropriate antibiotic therapy (IAT) (median time to resolution, 10 and 8 days, respectively) when compared with the remaining pathogens (median time to resolution, 2 days). A multiple regression model, adjusted for disease severity, confirmed the delayed clinical resolution for MRSA and P aeruginosa with IAT. Similar associations were documented for defervescence. Among survivors, the median duration of mechanical ventilation after VAP onset was significantly longer for MRSA (17 days) and P aeruginosa IAT (11 days) when compared with episodes due to H influenzae or MSSA (6 days). Multiple regression analysis, adjusted for disease severity, confirmed that MRSA required significantly (R2 = 0.132; p < 0.01) longer respiratory support than other organisms.
Conclusions: When treated promptly, the resolution of VAP due to MSSA, H influenzae, and P aeruginosa was comparable. The resolution of MRSA VAP, regardless of the appropriateness of initial antibiotic therapy, was associated with longer respiratory support.