Improving the culture surrounding tracheal aspirates in mechanically ventilated children

Interpretation of tracheal aspirate cultures is limited by contamination with normal respiratory flora and inconsistency in collection, processing, and reporting. Our aim was to both decrease waste and improve the quality and interpretability of tracheal aspirate cultures by implementing laboratory-driven Gram stain rejection criteria. We reviewed prior tracheal aspirate specimens and cultures, examined the current literature, and gathered input from stakeholders to inform potential Gram stain rejection criteria. Rates of tracheal aspirates collected, cultured, and rejected pre-intervention (9 November 2019-2 April 2023) and post-intervention (3 April 2023-28 February 2024) were compared. We implemented culture rejection criteria and rejected specimens with Gram stains demonstrating moderate to heavy epithelial cells and/or no organisms/three or more organism morphologies. The median rate of tracheal aspirates cultured decreased from 7.7 to 2.4 per 100 ventilator days (P < 0.001) in the pre- and post-intervention periods, respectively. There was a corresponding decrease in the median proportion of cultures with no growth (15% vs 2.8%, P < 0.001) and those growing normal respiratory flora (45% vs 33% per 100 ventilator days, P < 0.001) and an increase in actionable cultures with growth of predominant organisms (39%-61%, P < 0.001). Implementation of Gram stain rejection criteria led to a 69% decrease in the rate of tracheal aspirate samples cultured and a subsequent 22% increase in cultures with actionable results. This intervention saved laboratory resources and, anecdotally, increased laboratorian satisfaction. Taken together, this initiative increased the value of care.IMPORTANCETracheal aspirate cultures are often limited by contamination with upper respiratory flora, resulting in low-yield information, unnecessary laboratory utilization, and potential misinterpretation that may influence antimicrobial use. We demonstrate that implementation of standardized, laboratory-driven Gram stain rejection criteria significantly reduces the number of cultures performed while increasing the proportion of clinically actionable results. This diagnostic stewardship intervention improved the interpretability of tracheal aspirate cultures, decreased waste, and enhanced the overall value of care. Our findings provide a practical, scalable framework for clinical microbiology laboratories to optimize tracheal aspirate culture workflows and better align testing with meaningful clinical outcomes.