Rapid tests: preliminar identification from blood culture

In the period 1 April to 30 June 2011, we compared the rapid test identification of 250 positive blood cultures with the identification by MALDI-TOF mass spectrometer (Bruker). After Gram staining and an important step in HB&L liquid culture (Alifax), rapid tests were performed according to the morphological characteristics of the sample. Pneumococcus urinary antigen test and tube coagulase test showed a concordance of 100%, the concordance rates for Pyr test and oxidase test were 91% and 89% respectively. Overall, the percentage of agreement of the rapid tests on 250 samples was found to be of 99.2%. The data obtained show that, even with their increased bacterial concentration due to the enrichment step in HB&L liquid culture, it is possible to obtain preliminary identification directly from positive blood culture with simple rapid tests

Direct identification of bacteria in blood culture by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: a new methodological approach

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has recently been demonstrated to be a powerful tool for the rapid identification of bacteria from growing colonies. In order to speed up the identification of bacteria, several authors have evaluated the usefulness of this MALDI-TOF MS technology for the direct and quick identification bacteria from positive blood cultures. The results obtained so far have been encouraging but have also shown some limitations, mainly related to the bacterial growth and to the presence of interference substances belonging to the blood cultures. In this paper, we present a new methodological approach that we have developed to overcome these limitations, based mainly on an enrichment of the sample into a growing medium before the extraction process, prior to mass spectrometric analysis. The proposed method shows important advantages for the identification of bacterial strains, yielding an increased identification score, which gives higher confidence in the results. Copyright © 2011 John Wiley & Sons, Ltd