Comparison of VITEK REVEAL fast antimicrobial susceptibility testing to antibiotic disk diffusion for gram-negative bloodstream infections

The VITEK REVEAL antimicrobial susceptibility testing (AST) system is a fast <i>in vitro</i> diagnostic device that determines the antimicrobial susceptibility profile of gram-negative organisms from positive blood culture after independent organism identification. The objectives of this study were to (i) compare the performance of VITEK REVEAL to disk diffusion (DD) and (ii) evaluate implementation of VITEK REVEAL into a laboratory workflow that employs matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) as the primary method for organism identification. A total of 150 monomicrobial, GN-positive blood cultures were enrolled, of which 47.3% (71/150) contained <i>Escherichia coli</i>, 17.3% (26/150) <i>Klebsiella pneumoniae</i>, and 15.3% (23/150) <i>Pseudomonas aeruginosa</i>, with the remaining comprising other <i>Enterobacterales</i> and one <i>Acinetobacter</i> spp. The time to result (TTR) from blood culture positivity to AST results was compared for DD with tiered testing for multidrug-resistant organisms and VITEK REVEAL. Overall, the standard-of-care workflow had a combined TTR for AST of 37.2-54.7 h, while the workflow of MALDI-TOF MS + VITEK REVEAL had a TTR of 14.0 h due to the time necessary to identify the organism using MALDI-TOF MS. The categorical agreement (CA) for claimed organism-antibiotic combinations was 97.0%, with a very major discrepancy (VMD) of 2.9% (8/279) and a major discrepancy (MD) of 0.3% (5/1957), following adjudication of discrepant results with broth microdilution. The CA for organisms with an extended-spectrum beta-lactamase phenotype (<i>n</i> = 29) was 93.2%, with VMD of 2.0%, and MD of 0.7%. In conclusion, the VITEK REVEAL reduced the TTR for AST by at least 23 h compared to standard-of-care DD, with a CA of 97%.IMPORTANCEBloodstream infections caused by gram-negative bacteria require effective and timely treatment. Laboratory testing informs the choice of antibiotics, but traditional methods can require multiple days for results. The VITEK REVEAL system determines antibiotic susceptibility directly from a positive blood culture within 8 h, though it requires an independent method for organism identification, such as mass spectrometry or nucleic acid amplification testing. In this study, we examined VITEK REVEAL as part of a workflow incorporating mass spectrometry for organism identification. This combined approach provided susceptibility results approximately 1 day earlier than standard disk diffusion while maintaining high accuracy for most organism-antibiotic combinations, including those active against multidrug-resistant organisms. Incorporating VITEK REVEAL into routine laboratory workflows has the potential to accelerate targeted therapy and limit unnecessary broad-spectrum use in patients with gram-negative bloodstream infections.