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A Miniaturised Semiautomated System for the Identification of Yersinia Species within the Genus Yersinia by H. Neubauer, M. Molitor, L. Rahalison, S. Aleksic, H. Backes, S. Chanteau and H. Meyer

Commercially available identifïcation systems based on biochemical reactions of bacteria are not suited for typing the species of the genus Yersinia (Y.) or the biovars (BV) of the species Y. enterocolitica. This failure is caused by the limited number of biochemical reactions applied, resulting in the absence of important discriminatory key reactions. The MICRONAUT identification system (Merlin, Bornheim-Hersel) makes use of dried substrates/enzymes reactions in the wells of a 96-well microtitration plate, reading of the results by a scanner device and typing of the isolate by the calculation of probabilities according to a data base. For this study a special identification panel was designed on which 38 substrates and enzyme reactions were configurated including 20 reactions for the identifîcation of the species of the genus and the Y. enterocolitica biovars. The database was calculated using the results obtained from a total of 250 Yersinia strains of the eleven species of the genus. Reevaluation of the results of these strains revealed an overall sensitivity of 98%, as only four strains were not identifïed satisfactorily. Considering also questionable results the sensitivity was still 85%. The system was also used to identify Y. pestis isolates, but in this case reading was done visually. The printouts usually cite species designation, identification quality and probabilities. The sealing of the plates in an aluminium bag guarantees long life and long lasting quality. However, an evaluation of the system with a considerable number of strains has to be done in a next step. The 'Yersinia identiflrcation set' can replace time-consuming tube testing in the future and is a big step forward towards a sensitive identification of Yersinia isolates in the routine laboratory .

DOI: Clin. Lab. 2000;46:561-567