Comparison of the value of initial and serial endotracheal aspirate surveillance cultures in predicting the causative pathogen of ventilator-associated pneumonia.

Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in the intensive care unit (ICU) and its outcome is affected by the adequacy and timing of initial antibiotic therapy. Recent studies have suggested that surveillance cultures of the lower airways may provide microbiological guidance for initial antibiotic prescription and increase the use of appropriate antibiotic therapy. This study aimed to compare the predictive value of initial and serial surveillance cultures of endotracheal aspirates in predicting the causative pathogen of VAP in patients receiving antibiotic therapy. This was an observational prospective cohort study. Ninety-two patients ventilated for at least 4 days were recruited into the study. Initial (IS-ETA) and serial (SS-ETA) endotracheal aspirate surveillance cultures were obtained on the day of intubation and every second day, respectively. The sensitivity, specificity, and positive and negative predictive values for the causative pathogens of VAP were calculated for each surveillance culture. Ninety-two initial and 252 serial surveillance cultures were obtained during the study period. The sensitivity of IS-ETA culture was 12% and of SS-ETA culture was 44%. The sensitivity of SS-ETA in late-onset VAP was 51%. The value of SS-ETA surveillance cultures was better than IS-ETA surveillance in predicting the causative pathogen of VAP, particularly in late-onset pneumonia.