Assessment of VITEK® MS IVD database V3.0 for identification of Nocardia spp. using two culture media and comparing direct smear and protein extraction procedures.
T Durand, F Vautrin, E Bergeron, V Girard, S Polsinelli, V Monnin, G Durand, O Dauwalder, O Dumitrescu, F Laurent, V Rodríguez-Nava
Author Information
T Durand: Institut des Agents infectieux, Centre de Biologie et Pathologies Nord, Hôpital de la Croix Rousse, Lyon, France.
F Vautrin: UMR CNRS 5557, Ecologie Microbienne - Groupe de Recherche "Pathogènes Opportunistes et Environnement" - ISPB-Faculté de Pharmacie, Université Lyon 1, Lyon, France.
E Bergeron: UMR CNRS 5557, Ecologie Microbienne - Groupe de Recherche "Pathogènes Opportunistes et Environnement" - ISPB-Faculté de Pharmacie, Université Lyon 1, Lyon, France.
V Girard: bioMérieux France, Microbiology R&D, La Balme-les-Grottes, France.
S Polsinelli: bioMérieux France, Microbiology R&D, La Balme-les-Grottes, France.
V Monnin: bioMérieux France, Microbiology R&D, La Balme-les-Grottes, France.
G Durand: bioMérieux France, Microbiology R&D, La Balme-les-Grottes, France.
O Dauwalder: Institut des Agents infectieux, Centre de Biologie et Pathologies Nord, Hôpital de la Croix Rousse, Lyon, France.
O Dumitrescu: Institut des Agents infectieux, Centre de Biologie et Pathologies Nord, Hôpital de la Croix Rousse, Lyon, France.
F Laurent: Institut des Agents infectieux, Centre de Biologie et Pathologies Nord, Hôpital de la Croix Rousse, Lyon, France.
V Rodríguez-Nava: Institut des Agents infectieux, Centre de Biologie et Pathologies Nord, Hôpital de la Croix Rousse, Lyon, France. veronica.rodriguez-nava@univ-lyon1.fr.
We assessed the performance of the VITEK® MS IVD V3.0 matrix-assisted laser desorption ionization - time of flight mass spectrometry (MALDI-ToF MS) V3.0 database for the identification of Nocardia spp. as compared with targeted DNA sequencing. A collection of 222 DNA sequence-defined Nocardia spp. strains encompassing 18 different species present or not in the database was tested. Bromocresol purple agar (BCP) and Columbia agar +5% sheep's blood (COS) culture media were used together with two different preparation steps: direct smear and a "3 attempts" procedure that covered (1) spotting of an extract, (2) new spotting of the same extract, and (3) spotting of a new extract. The direct smear protocol yielded low correct identification rates (≤ 15% for both media) whereas protein extraction yielded correct identification results (> 67% regardless of the media used.). The use of 2 additional attempts using repeat or new extracts increased correct identification rates to 87% and 91% for BCP and COS, respectively. When using the 3 attempts procedure, the best identification results, independent of media types, were obtained for N. farcinica and N. cyriacigeorgica (100%). Identification attempts 2 and 3 allowed to increase the number of correct identifications (BCP, +20%; COS, +13%). The enhancement in performance during attempts 2 and 3 was remarkable for N. abscessus (81% for both media) and low prevalence species (BCP, 70%; COS, 85%). Up to 3.4% and 2.4% of the strains belonging to species present in the database were misidentified with BCP and COS media, respectively. In 1.9% of the cases for BCP and 1.4% for COS, these misidentifications concerned a species belonging to the same phylogenetic complex. Concerning strains that are not claimed in the V3.0 database, N. puris and N. goodfellowi generated "No identification" results and 100% of the strains belonging to N. arthritidis, N.cerradoensis, and N. altamirensis yielded a misidentification within the same phylogenetic complex. Vitek® MS IVD V3.0 is an accurate and useful tool for identification of Nocardia spp.
