Use of various common isolation media to evaluate the new VITEK 2 colorimetric GN Card for identification of Burkholderia pseudomallei.

Abstract

The use of automated systems in the modern microbiology laboratory is becoming commonplace as the pressure of cost containment impacts on staff resources. With increased international travel and threats of bioterrorism, recognition and accurate identification of organisms such as Burkholderia pseudomallei is important. In areas where this organism is endemic, identification is not usually problematic. This study evaluates the performance of the new VITEK 2 colorimetric GN card for the identification of this organism. A total of 103 previously identified clinical isolates were tested with the new card with isolates taken from MacConkey agar, Columbia horse blood agar, Columbia sheep blood agar, and Trypticase soy agar in order to determine identification performance and to see if there was any variability in results due to the agar. Columbia horse blood agar produced the highest rates of identification (81%), followed by Trypticase soy agar (78%), Columbia sheep blood agar (75%), and MacConkey agar (63%). There was considerable variability in some of the reactions obtained. Seven isolates failed to identify from any of the agars used. This study highlights issues with the identification of this organism with the new VITEK 2 GN card. Enhancements of the algorithm parameters for the GN card are warranted and are in progress. Laboratory personnel need to be aware of the current limitations with this GN card and the software (version 4.02 or older for the VITEK 2 60/XL and version 1.02 or older for VITEK 2 Compact) and rely on clinical history, a high index of suspicion, and basic microbiology tests to confirm the identification of this organism.