Annika Schmidt (Tübingen / DE), Johannes Zens (Tübingen / DE), Paul D'Alvise (Tübingen / DE), Muriel Bauer (Tübingen / DE), Leonie Gouvernoy (Tübingen / DE), Judith Mack (Tübingen / DE), Silke Peter (Tübingen / DE), Matthias Marschal (Tübingen / DE)
Introduction
One of the most important and timely critical procedures in microbiology diagnostics is the detection, ID and AST of microbes from blood stream infections. A delay in appropriate antibiotic therapy is detrimental to patients" outcome.
Goals
We aimed to compare two systems which promise to reduce the time to result for ID and AST directly from blood culture bottles with our routine diagnostic methods.
Materials & Methods
The study was conducted on consecutive positive blood cultures from March to May 2023. We included in total 100 monomicrobial samples with 55 gram-positive cocci and 45 gram-negative rods. For ID we compared the liquid colony from the FAST™ system (Qvella Corporation Europe) with our routine method of short-term culture analyzed by MALDI-TOF (Bruker). The AST was conducted for both by VITEK2 and compared with the AST by the dRAST (Quantamatrix).
Results
Overall, we identified 24 different bacterial species. The FAST™ system reduces the mean time to ID significantly. On a species level 95.6% of gram-negative and 85.5% of gram-positive bacteria were identified by the FAST™ system with consecutive MALDI-TOF. In 5 samples the direct ID failed, all other samples were at least identified on genus level. The mean time to AST was 9:43 h for the gram-negative and 10:48 h for the gram-positive bacteria for the FAST™ system. The dRAST takes in average 6:19 h for gram-negative and 6:45 h for the included gram-positive bacteria. 20 different antibiotics were available in all systems and were incorporated in the analyses. The rate of VME was 0.2% for the FAST™ system and 1.7% for the dRAST system.
Summary
In our study the FAST™ system reduces the time to ID considerably. It identified 95 % of the bacteria on genus level independently of restricted panel. Both systems showed satisfying and comparable performance for AST and speed up the diagnostic procedure. For the FAST™ system the usual procedure can be maintained after getting the liquid colony. The dRAST has in total a shorter hands-on time but needs a separate ID. Depending on the workflow and opening hours of the laboratory the adequate system can be chosen.