Automatisation de l'identification bactérienne

The bacterial identification is essential in the process of a bacteriological examination by giving to the clinician of the important information onto the gravity, the origin or the treatment of an infection. For that purpose, it must be both reliable and fast, according to the clinical conditions. The automation of the bacterial identification was based at first on the inclusion of biochemical tests in miniaturized supports, in association with a reading and an interpretation integrated in the system. These systems are the Vitek (bioMérieux), the Phoenix (BD) and the MicroScan (Siemens then Beckman). Although these automations have acceptable performances, they are limited by strains sometimes little reactive and by database reflecting with difficulty the heterogeneity of certain species. It is in particular the case for strictly aerobic species or for species with few reference strains. Since a few years, we attend the advent of the use of the mass spectrometry Maldi-Tof for the identification based on the difference of mass of cellular proteins of which a majority of ribosomal proteins. The performances are superior to that of the phenotypic methods and globally similar between both proposed systems Microflex-Biotyper (Bruker) and Shimadsu-VitekMS (bioMérieux). Some species phylogenetically close are difficult to identify by this technology but these problems are usually well listed. The mass spectrometry Maldi-Tof can identify most of the species with only one strain in the database and the time for the result is reduced to a few minutes. This technology can be also adapted to the direct identification from positive blood cultures.