Comparative evaluation of the VITEK 2 Advanced Expert System (AES) in five UK hospitals

Area of Science:

• Clinical microbiology
• Antimicrobial resistance detection
• Diagnostic technology evaluation

Background:

• Accurate antimicrobial susceptibility testing (AST) is crucial for guiding patient treatment and combating antimicrobial resistance.
• Evaluating automated systems like VITEK 2 is essential to ensure their reliability and efficiency in clinical settings.
• Characterized resistance mechanisms in bacterial strains present a rigorous test for AST methodologies.

Purpose of the Study:

• To evaluate the VITEK 2 system's performance in UK laboratories.
• To compare VITEK 2 results against gold-standard agar dilution Minimum Inhibitory Concentration (MIC) data.
• To assess VITEK 2's ability to detect resistant phenotypes and compare it with routine antimicrobial susceptibility testing (AST) methods.

Main Methods:

• VITEK 2 system was evaluated in five UK laboratories.
• A collection of 82 bacterial strains with characterized resistance mechanisms were tested.
• Results were compared with agar dilution MIC data and routine AST methods.

Main Results:

• VITEK 2 demonstrated high essential agreement (96.0%) with MIC data across enterococci, staphylococci, and Gram-negative bacilli.
• Category (SIR) agreement with VITEK 2 was 95.1%, comparable to routine methods (95.0%).
• VITEK 2 Advanced Expert System (AES) detected a higher proportion of resistance mechanisms compared to routine methods across all tested bacterial groups.

Conclusions:

• VITEK 2 accurately performs susceptibility tests and appropriately detects/interprets resistance mechanisms.
• The system's use of heavy inocula in liquid media may enhance the expression of certain resistance determinants.
• VITEK 2 AES provides a rapid, standardized alternative for laboratories needing to detect resistance phenotypes effectively.