Peculiarities of Burkholderia mallei and Burkholderia pseudomallei Identification Using Microbiological Analyzer Vitek 2 Compact 30

Automated Vitek 2 system, based on comparison of a biochemical profile of the studied bacterial cultures with the existing database, is widely used for B. pseudomallei and B. mallei identification in the laboratory practice.

Objective of the study is to conduct extended phenotypic characterization of the strains of glanders and melioidosis causative agents, stored in the biobank of the Volgograd Research Anti-Plague Institute and analyze variations in their biochemical profiles, using Vitek 2 system.

Materials and methods. Using Vitek 2 device, (bioMerieux, France) analyzed have been biochemical properties of 52 collection strains of B. pseudomallei and B. mallei grown on L-agar (Difco, USA) and trypticase-soy agar – TSA (HiMedia, India).

Results and discussion. Most of the investigated strains (31 out of 40 B. pseudomallei and 8 of 12 B. mallei) have been identified with an acceptable probability for determining certain specie appurtenance, amounting to 90–99 %. The percentage of correct identification of B. pseudomallei and B. mallei is higher when strains are cultured on L-agar, than when on TSA. Due to the variability of the biochemical features, some strains have showed non-typical for its species results in certain tests (for B. pseudomallei strains – the absence of enzyme activity of β-N-acetyl-glucosaminidase, β-N-acetyl-galactosaminidase and ability to utilize D-cellobiose; for B. mallei strains – the absence of enzyme activity of L-proline-aryl-amidase and tyrosin-aryl-amidase, existence of glycin-aryl-amidase activity and ability to utilize sucrose, D-trehalose), which has led to their mal-identification. The probability of error diagnostics of microorganisms belonging to Burkholderia species necessitates up-dating of the database built into Vitek 2 analyzer as regards biochemical characteristics of the strains which have peculiar profiles.

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