How small modifications in laboratory workflow of blood cultures can have a significant impact on time to results

Rapid identification and antimicrobial susceptibility testing of micro-organisms causing bloodstream infections is crucial in the management of septic patients. In this study, we compared a period of twice-daily and a period of thrice-daily reading of subculture agar plates. In 2016, 10,644 positive blood cultures bottles (bioMérieux) from 2608 patients were analyzed at UZ Leuven. Identification and antimicrobial susceptibility testing were performed by MALDI-TOF MS (Bruker Daltonics) and Vitek 2 (bioMérieux) respectively. In period 1 (January to June), subculture plates were read at 8:30 a.m. and 2:00 p.m. during the weekdays. In period 2 (August until December), reading was performed at 8:30 a.m., 2:00 p.m., and 5:00 p.m. Time to identification and time to AST results after positivity were compared. In period 1, median time to identification of all organisms was 22.8 h compared to 20.2 h in period 2 (p < 0.01). Moreover, micro-organisms were identified before 12 h in 9% of samples in period 2, a significant increase compared to 2% in period 1 (p < 0.01). In period 2, AST results were known within 36 h in 39% of samples, compared to 31% in period 1 (p < 0.01). Optimization of the reading frequency of subcultures of blood cultures significantly decreases time to results. Further optimization can be done by introducing lab automation. We will use the data of this study as a baseline to analyze the impact of introducing WASPLab (Copan Diagnostics) automation on time to results.