Gram Negative Bloodstream Infections / Gram Negative Bacterial Infections · Journal article

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

Diagnostic Microbiology and Infectious Disease · August 14, 2026

Strong Evidence Why this matters to you Expert discussion

Well-designed and adequately powered for the question it asks.

AI Summary

VITEK REVEAL demonstrated high concordance with BD Phoenix reference system (98.74% essential agreement, 97.58% categorical agreement) across 2,854 test combinations from 184 Gram-negative blood culture isolates. Median time-to-result was substantially shorter for VITEK REVEAL (8.0 hours vs 13.8 hours, p<0.001), potentially enabling faster clinical decision-making in bacteremia. This is a diagnostic accuracy comparison, not a clinical outcome study; the clinical utility of the shorter TTR remains to be validated in prospective clinical management trials.

What was studied

Prospective comparative diagnostic accuracy study. Blood cultures positive for Gram-negative organisms from two U.S. clinical laboratory sites; 12 Gram-negative species represented. Intervention: VITEK REVEAL automated antimicrobial susceptibility testing system. Compared with: BD Phoenix automated system (primary reference); broth microdilution (reference standard for discordant results). n = 184. Two U.S. study sites.

Key findings

VITEK REVEAL achieved essential agreement of 98.74% (95% CI: 98.26-99.12%) and categorical agreement of 97.58% (95% CI: 96.95-98.11%) versus BD Phoenix on 2,854 microorganism-antimicrobial combinations Discrepancy rates: 4.24% very major discrepancies, 0.23% major discrepancies, 1.96% minor discrepancies between systems Median instrument time-to-result: VITEK REVEAL 8.0 hours versus BD Phoenix 13.8 hours (p<0.001)

Safety

Safety was not reported in the material analysed. Check the source before drawing any conclusion about harm.

Who this may help

Clinicians interpreting results should recognize that VITEK REVEAL provides faster antimicrobial susceptibility results than BD Phoenix, potentially shortening time-to-appropriate therapy in Gram-negative bacteremia. However, the clinical benefit of this 5.8-hour median reduction requires validation in prospective studies measuring impact on patient outcomes, antibiotic selection timing, and clinical course.

Plain-language summary

Rigorous comparative diagnostic study with large sample size, pre-specified endpoints (essential and categorical agreement), and clear superiority in time-to-result; well-designed but a diagnostic accuracy study rather than a clinical outcome trial.

Study design

As stated by the source record.

MethodsBlood cultures positive for Gram-negative bacteria were prospectively collected from two U.S. sites. Isolates were tested using both VITEK REVEAL and BD Phoenix systems (reference comparator) against a panel of 20 antimicrobials. For discordant results (very major or major discrepancies), broth microdilution was performed as gold standard. Performance was assessed by essential agreement, categorical agreement, and discrepancy rates. Time-to-result was recorded for both systems.

DesignProspective comparative diagnostic accuracy study

PopulationBlood cultures positive for Gram-negative organisms from two U.S. clinical laboratory sites; 12 Gram-negative species represented

Sample size184

InterventionVITEK REVEAL automated antimicrobial susceptibility testing system

ComparatorBD Phoenix automated system (primary reference); broth microdilution (reference standard for discordant results)

SettingTwo U.S. study sites

Reported figures

Quoted from the source exactly as published.

Essential agreement98.74%

Essential agreement 95% CI98.26-99.12%

Categorical agreement97.58%

Categorical agreement 95% CI96.95-98.11%

Very major discrepancy rate4.24%

Major discrepancy rate0.23%

Minor discrepancy rate1.96%

Median TTR VITEK REVEAL8.0 hours

Clinical bottom line

Caveats

Study did not measure clinical outcomes or patient-level impact of faster reporting; diagnostic accuracy alone does not prove clinical utility
Only two U.S. sites; generalizability to other geographic regions or laboratory settings unclear
BD Phoenix TTR did not include mandatory 18-24 hour pre-AST subculture time, so absolute difference in clinical practice may be smaller than reported
Very major discrepancy rate of 4.24% is non-trivial and source does not report whether these were clinically significant misclassifications

Evidence assessment

Graded across the dimensions that decide whether you should act, each from what the source actually supports. There is no single score, and where a dimension was not assessed it says so.

Study design

strong

Prospective, comparative evaluation of two automated AST systems with reference standard validation

Directness

strong

Directly evaluates clinical specimens (blood cultures) with clinically relevant outcomes (antimicrobial susceptibility reporting)

Consistency

moderate

High agreement metrics reported; discrepancy rates provided but no external replication cited

Risk of bias

moderate

Prospective collection, but only two U.S. sites; BD Phoenix as reference may introduce bias favouring comparator

Sample adequacy

strong

184 isolates, 12 Gram-negative species, 2,854 organism-antimicrobial combinations evaluated

Source abstract

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.

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Gram Negative Bloodstream InfectionsGram Negative Bacterial InfectionsSiu-Kei ChowL Erin ArmsDooil HoMatthew WeverSusanna ReedShivaramu Keelara