Bacterial rapid identification with matrix assisted laser desorption/ionization time-of-flight mass spectrometry: development of an ‘in-house method’ and comparison with Bruker Sepsityper^® kit

Abstract

Objective:

The objective of this study was to compare an in-house matrix-assisted laser desorption ionization with time of flight (MALDI-TOF) method and a commercial MALDI-TOF kit (Sepsityper^® kit) for direct bacterial identification in positive blood cultures. We also evaluated the time saved and the cost associated with the rapid identification techniques.

Methods:

We used the BACTEC^® automated system for detecting positive blood cultures. Direct identification using Sepsityper kit and the in-house method were compared with conventional identification by MALDI-TOF using pure bacterial culture on the solid phase. We also evaluated different cut-off scores for rapid bacterial identification.

Results:

In total, 127 positive blood vials were selected. The rate of rapid identification with the MALDI Sepsityper kit was 25.2% with the standard cut-off and 33.9% with the enlarged cut-off, while the results for the in-house method were 44.1 and 61.4%, respectively. Error rates with the enlarged cut-off were 6.98 (n = 3) and 2.56% (n = 2) for Sepsityper and the in-house method, respectively. Identification rates were higher for gram-negative bacteria.

Discussion:

Direct bacterial identification succeeded in supplying rapid identification of the causative organism in cases of sepsis. The time taken to obtain a result was nearly 24 hours shorter for the direct bacterial identification methods than for conventional MALDI-TOF on solid phase culture. Compared with the Sepsityper kit, the in-house method offered better results and fewer errors, was more cost-effective and easier to use.

• Microbiology
• MALDI-TOF
• Bacteriology
• Medical laboratory
• Rapid identification
• Matrix-assisted laser desorption ionization
• Direct identification
• Bacteria
• Bacterial
• Sepsityper