Prediction of ventilator-associated pneumonia outcomes according to the early microbiological response: a retrospective observational study.

Ventilator-associated pneumonia is a leading infectious cause of morbidity in critically ill patients; yet current guidelines offer no indications for follow-up cultures. We aimed to evaluate the role of follow-up cultures and microbiological response 3 days after diagnosing ventilator-associated pneumonia as predictors of short- and long-term outcomes. We performed a retrospective analysis of a cohort prospectively collected from 2004 to 2017. Ventilator-associated pneumonia was diagnosed based on clinical, radiographic, and microbiological criteria. For microbiological identification, a tracheobronchial aspirate was performed at diagnosis and repeated after 72 h. We defined three groups when comparing the two tracheobronchial aspirate results: persistence, superinfection, and eradication of causative pathogens. One-hundred-fifty-seven patients were enrolled in the study, among whom microbiological persistence, superinfection, and eradication was present in 67 (48%), 25 (16%), and 65 (41%), respectively, after 72hs. Those with superinfection had the highest mortalities in the intensive care unit (p=0.015) and at 90 days (p=0.036), while also having the fewest ventilation-free days (p=0.024). Multivariable analysis revealed shock at VAP diagnosis (odds ratios [OR] 3.43; 95% confidence interval [CI] 1.25 to 9.40), Staphylococcus aureus isolation at VAP diagnosis (OR 2.87; 95%CI 1.06 to 7.75), and hypothermia at VAP diagnosis (OR 0.67; 95%CI 0.48 to 0.95, per +1°C) to be associated with superinfection. Our retrospective analysis suggests that ventilator-associated pneumonia short-term and long-term outcomes may be associated with superinfection in follow-up cultures. Follow-up cultures may help guiding antibiotic therapy and its duration. Further prospective studies are necessary to verify our findings.