Potential Impact of Flow Cytometry Antimicrobial Susceptibility Testing on the Clinical Management of Gram-Negative Bacteremia Using the FASTinov Kit.

Laboratory assessment of antimicrobial susceptibility is a prerequisite for adequate management of infections. The aim of this research was to evaluate the performance of the novel FASTinov kit for antimicrobial susceptibility testing (AST) of Gram negative bacilli directly on positive blood cultures. One hundred and two positive blood cultures from patients of a Portuguese University Hospital were included. AST were performed with routine method, Vitek2, with FASTinov kit, and with the gold standard microdilution. Bacteria directly extracted from blood cultures were used to inoculate the FASTinov kit. Time-to-result as well as the number of patients receiving initially inappropriate therapy (and those in whom de-escalation would have been done) and length of stay (LOS) was recorded. Seventy percent of patients were over 70 years old and 18.6% were admitted in intensive care units. Regarding the isolates, 88.2% were Enterobacteriaceae, 9.8% spp. and 1% spp. Extended spectrum β-lactamases producing-Enterobacteriaceae were found in 7.8% of cases and 10.8% were multi-drug resistant. Fifty-one hours was the mean of time-to-result for routine test (Vitek2) vs. 2 h response regarding Fastinov test. The overall agreement between FASTinov and the reference microdilution method was 98%. According to the susceptibility phenotype, 16.7% of patients received initially inappropriate therapy and the mean hospital LOS of these patients was significantly higher. FASTinov kit revealed an excellent correlation with the AST standard method and provided much earlier results than Vitek2.