Automated antimicrobial susceptibility testing in gram-negative bacteremia: A comparative study of VITEK® REVEAL™ and BD phoenix™.

Bloodstream infections (BSIs) due to Gram-negative bacteria can rapidly escalate to life-threatening conditions, making the early selection of the appropriate antibiotics crucial for saving lives. Current conventional laboratory antimicrobial susceptibility tests for identifying effective antibiotics typically require 16-24 hours in addition to the sub-culture time, prolonging time-to-result (TTR) and delaying appropriate therapy. In this study, we compared the fast antimicrobial susceptibility test (AST) system VITEK® REVEALTM (VITEK REVEAL) with BD PhoenixTM (BD Phoenix) on 192 prospectively collected blood cultures positive for Gram-negative organisms (n = 184 after exclusions) from two U.S. study sites. A total of 12 Gram-negative species were evaluated against a panel of 20 antimicrobials. Performance was assessed by essential agreement (EA), categorical agreement (CA), and rates of very major (VMD), major (MD), and minor discrepancies (miD). BD Phoenix served as the reference comparator, whereas broth microdilution (BMD) was applied for isolates with VMD or MD discordant results between the two systems. TTRs were recorded for both systems. VITEK REVEAL achieved EA 98.74% (95% CI: 98.26-99.12%) and CA 97.58% (95% CI: 96.95-98.11%) in 2,854 microorganism-antimicrobial combinations. Rates of discrepancies between the systems were 4.24% for VMD, 0.23% for MD and 1.96% for miD. Median instrument TTR was 8.0 hours for VITEK REVEAL versus 13.8 hours for BD Phoenix (p < 0.001), noting that BD Phoenix TTR values did not include the required 18-24 hours pre-AST subculture time. On the VITEK REVEAL, resistant isolates were reported earlier than susceptible ones (5.0 h vs 6.5 h; p < 0.001). Overall, VITEK REVEAL showed high concordance with BD Phoenix and demonstrated faster TTR, which can potentially facilitate Gram-negative BSI therapy optimization.