Predicting Ventilator-associated Lower Respiratory Tract Infection Outcomes Using Sequenced-based Early Microbiological Response

Inclusion criteria

• Aged 18 years and above.
• Previously relied on mechanical ventilation (endotracheal intubation or tracheotomy) for breathing assistance, and the duration of mechanical ventilation was more than 48h.
• Lower respiratory tract infection based on at least two of the followings: abnormal temperature (body temperature greater than 38.5°C or less than 36.5°C), leucocyte count abnormality (leucocyte count greater than 12*10^9/L or less than 4*10^9/L), and the presence of purulent tracheal secretions.

Exclusion criteria

• Bronchoscopy and respiratory specimen collection were not performed at screening (Day 1) and after 3 days of treatment (Day 4).
• Refusal of patients or families to participate in the study
• After initial screening, bronchoscopy was performed to obtain BALF for bacterial culture. The results of the culture showed no evidence of infection by study-associated lower respiratory pathogens.

Note: The evidence of infection was defined as a single positive bacterial culture (pathogen quantification ≥10^4 cfu/ml or "++" and more) on Day1. And the study-associated causative pathogens are Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, and Staphylococcus aureus. Additionally, the included patient must have single infection with one of these pathogens.