VITEK 2 System: Introduction, Organisms List and Identification Cards, Principle, Identification Procedure, Result-Interpretation, and Keynotes
The image shows a front view of the bioMérieux VITEK 2 Compact, a benchtop automated system designed for rapid microbial identification and antibiotic susceptibility testing in clinical laboratorie
Introduction
Table of Contents
The VITEK 2 System is an automated microbiology platform designed for the rapid identification (ID) and antimicrobial susceptibility testing (AST) of a wide range of microorganisms. It utilizes miniaturized, closed cards that enhance lab safety and streamline workflow.
Fig. The image shows a front view of the bioMérieux VITEK 2 Compact, a benchtop automated system designed for rapid microbial identification and antibiotic susceptibility testing in clinical laboratories
The VITEK 2 cards are lightweight, credit-card-sized consumables containing 64 micro-wells pre-filled with dehydrated substrates or antibiotics. This system reduces manual labor and provides species-level results significantly faster than traditional phenotypic methods.
Fig. The main login screen of the bioMérieux VITEK 2 Release version 9 software, an automated system used for rapid microbial identification and antimicrobial susceptibility testing
Organisms List by Card Type
The system identifies hundreds of species across several specialized card types:
GN (Gram-Negative): Identifies over 150-200 taxa, including Enterobacteriaceaeand non-fermenting bacilli.
YST (Yeast): Identifies approximately 50-60 species of yeasts and yeast-like organisms.
Fig. This image shows a sealed foil package for a VITEK 2 AST-YS08 card, which is used for the automated antimicrobial susceptibility testing (AST) of yeast.
ANC (Anaerobes): Identifies anaerobes and coryneform bacteria.
NH (Neisseria/Haemophilus): Targets fastidious Gram-negative bacilli like Neisseria, Haemophilus, and HACEK organisms.
The VITEK 2 system operates on two primary technologies:
Advanced Colorimetry (Identification): Measures light transmission or fluorescence changes as organisms metabolize substrates in the card wells.
Turbidimetry (Susceptibility): Monitors organism growth in the presence of varying antibiotic concentrations to determine the Minimum Inhibitory Concentration (MIC).
Identification Procedure
Suspension Preparation: Transfer pure colonies from a culture plate into 3.0 mL of sterile saline.
Turbidity Adjustment: Use a DensiCHEK meter to ensure the inoculum density matches required standards (typically 0.50–0.63 McFarland for bacteria; 1.8–2.2 for yeast).
Loading: Place the suspension tube and the ID card into a cassette; then insert a transfer tube (straw) to connect the card to the suspension.
Filling and Sealing: The instrument uses a vacuum to fill the 64 wells, then automatically seals the card.
Incubation and Reading: Cards are incubated at 35.5°C and read every 15 minutes by the optical system.
Result Interpretation
The system compares the metabolic “fingerprint” of the sample against an extensive database. Confidence levels categorize results:
Excellent (96-99%): High probability identification.
Very Good to Acceptable (85-95%): Reliable identification.
Low Discrimination: The system cannot distinguish between 2-3 organisms and may suggest “off-line” supplemental tests (e.g., Gram stain, oxidase).
Inconsistent/Unidentified: Results do not match known phenotypes, often due to mixed cultures or technical issues.
Keynotes
Advanced Expert System (AES): A critical software component that validates MIC results against known resistance mechanisms to ensure clinical accuracy.
Pure Culture Requirement: Only use well-isolated, pure colonies; mixed cultures will lead to “Inconsistent” or “Qualified” results.
Time Savings: Identifications are typically completed within 2–10 hours, significantly shorter than overnight manual methods.
Safety: The closed-card design minimizes aerosolization and personal contamination risks.
PDF: VITEK 2 SYTEM IDENTIFICATION CARDS ORGANISM LIST