Evaluation of the VITEK 2 Gram-negative (GN) microbial identification test card: collaborative study

Area of Science:

• Clinical Microbiology
• Bacteriology
• Diagnostic Technology

Background:

• Accurate identification of Gram-negative bacilli is crucial for effective patient treatment and public health.
• The VITEK 2 system offers automated microbial identification.
• The VITEK 2 Gram-negative (GN) Identification card utilizes biochemical tests for bacterial characterization.

Purpose of the Study:

• To evaluate the performance of the VITEK 2 GN Identification card for identifying Gram-negative bacteria.
• To assess the accuracy of the VITEK 2 GN card, including its ability to identify select agent organisms.
• To compare the VITEK 2 GN card's performance with traditional Gram stain methods.

Main Methods:

• A collaborative study involving 20 laboratories across the United States.
• Analysis of 720 Gram-negative inclusivity isolates using the VITEK 2 GN Identification card.
• Screening of 120 exclusive isolates using Gram stain procedures to assess false exclusions.

Main Results:

• The VITEK 2 GN card correctly identified 707 out of 720 Gram-negative isolates.
• No misidentifications or unidentified results were reported for the inclusivity set.
• Gram stain errors led to misidentification in 3 instances, highlighting the importance of accurate initial sample preparation.

Conclusions:

• The VITEK 2 GN Identification card is an acceptable automated method for the rapid identification of Gram-negative bacteria.
• The system demonstrates high accuracy for identifying a broad range of Gram-negative bacilli, including challenging select agents.
• Accurate Gram staining is essential for optimal performance of automated identification systems like VITEK 2 GN.