Elisa Knudsen

Species Identification of Clinical Isolates of Anaerobic Bacteria: a Comparison of Two Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry Systems

ABSTRACT We compared two matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) systems (Shimadzu/SARAMIS and Bruker) on a collection of consecutive clinically important anaerobic bacteria (n = 290). The Bruker system had more correct identifications to the species level (67.2% versus 49.0%), but also more incorrect identifications (7.9% versus 1.4%). The system databases need to be optimized to increase identification levels. However, MALDI-TOF MS in its present version seems to be a fast and inexpensive method for identification of most clinically important anaerobic bacteria.

Performance of matrix-assisted laser desorption-time of flight mass spectrometry for identification of clinical yeast isolates

Accurate and fast yeast identification is important when treating patients with invasive fungal disease as susceptibility to antifungal agents is highly species related. Matrix‐assisted laser desorption‐time of flight mass spectrometry (MALDI‐TOF‐MS) provides a powerful tool with a clear potential to improve current diagnostic practice. Two MALDI‐TOF‐MS‐systems (BioTyper/Bruker and Saramis/AXIMA) were evaluated using: (i) A collection of 102 archived, well characterised yeast isolates representing 14 different species and (ii) Prospectively collected isolates obtained from clinical samples at two participating laboratories. Of the 102 archived isolates, 81 (79%) and 92 (90%) were correctly identified by Saramis/AXIMA and BioTyper/Bruker respectively. Saramis/AXIMA was unable to separate Candida albicans, C. africana and C. dubliniensis in 13 of 32 isolates. After manual interpretation of the mass spectra output, all 13 isolates were correctly identified, resulting in an overall identification performance of 92%. No misidentifications occurred with the two systems. Of the routine isolates one laboratory identified 99/99 (100%) and 90/99 (91%) to species level by Saramis/Axima and conventional identification, respectively, whereas the other laboratory identified 83/98 (85%) to species level by both BioTyper/Bruker and conventional identification. Both MALDI‐TOF‐MS systems are fast, have built‐in databases that cover the majority of clinically relevant Candida species, and have an accuracy that outperforms our conventional identification systems.

16S rRNA Gene Sequencing in Routine Identification of Anaerobic Bacteria Isolated from Blood Cultures

ABSTRACT A comparison between conventional identification and 16S rRNA gene sequencing of anaerobic bacteria isolated from blood cultures in a routine setting was performed (n = 127). With sequencing, 89% were identified to the species level, versus 52% with conventional identification. The times for identification were 1.5 days and 2.8 days, respectively.

Species identification of Streptococcus bovis group isolates causing bacteremia: a comparison of two MALDI-TOF MS systems

This study compared two MALDI-TOF MS systems (Biotyper and VITEK MS) on clinical Streptococcus bovis group isolates (n=66). The VITEK MS gave fewer misidentifications and a higher rate of correct identifications than the Biotyper. Only the identification of S. lutetiensis by the VITEK MS was reliable. Additional optimization of the available system databases is needed.